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  • Question 1 - A 65-year-old man with a history of hypertension, diabetes and high cholesterol arrives...

    Incorrect

    • A 65-year-old man with a history of hypertension, diabetes and high cholesterol arrives at the hospital complaining of severe chest pain that spreads to his jaw. He has vomited twice and feels lightheaded.

      An electrocardiogram (ECG) reveals widespread ST elevation with reciprocal ST-segment depression. A troponin T serum level is obtained and confirms an elevated reading.

      What is the target of this cardiac biomarker?

      Your Answer: Calcium ions

      Correct Answer: Tropomyosin

      Explanation:

      The troponin-tropomyosin complex is formed when troponin T binds to tropomyosin. In cases of ST-elevation myocardial infarction (STEMI), elevated levels of troponin T in the bloodstream can confirm the presence of cardiac tissue damage. This biomarker plays a role in regulating muscle contraction by binding to tropomyosin. However, troponin I, not troponin T, binds to actin to hold the troponin-tropomyosin complex in place. While troponin T is released in cases of cardiac cell damage, it is considered less sensitive and specific than troponin I in diagnosing myocardial infarction.

      Understanding Troponin: The Proteins Involved in Muscle Contraction

      Troponin is a group of three proteins that play a crucial role in the contraction of skeletal and cardiac muscles. These proteins work together to regulate the interaction between actin and myosin, which is essential for muscle contraction. The three subunits of troponin are troponin C, troponin T, and troponin I.

      Troponin C is responsible for binding to calcium ions, which triggers the contraction of muscle fibers. Troponin T binds to tropomyosin, forming a complex that helps regulate the interaction between actin and myosin. Finally, troponin I binds to actin, holding the troponin-tropomyosin complex in place and preventing muscle contraction when it is not needed.

      Understanding the role of troponin is essential for understanding how muscles work and how they can be affected by various diseases and conditions. By regulating the interaction between actin and myosin, troponin plays a critical role in muscle contraction and is a key target for drugs used to treat conditions such as heart failure and skeletal muscle disorders.

    • This question is part of the following fields:

      • Cardiovascular System
      19.2
      Seconds
  • Question 2 - A 45-year-old businessman comes to his GP complaining of fever, headache, and diarrhoea....

    Correct

    • A 45-year-old businessman comes to his GP complaining of fever, headache, and diarrhoea. He denies having any coughs, nausea, or vomiting. He has a good health history. However, he recently returned from a business trip to India three weeks ago. He has been consuming the same food and drinks as his family since his return, and they are all healthy. During the examination, the man seems dehydrated and has tenderness in the right upper quadrant.

      What do you think is the probable diagnosis?

      Your Answer: Hepatitis A

      Explanation:

      Understanding Hepatitis A: Symptoms, Transmission, and Prevention

      Hepatitis A is a viral infection that affects the liver. It is usually a mild illness that resolves on its own, with serious complications being rare. The virus is transmitted through the faecal-oral route, often in institutions. The incubation period is typically 2-4 weeks, and symptoms include a flu-like prodrome, abdominal pain (usually in the right upper quadrant), tender hepatomegaly, jaundice, and deranged liver function tests.

      While complications are rare, there is no increased risk of hepatocellular cancer. An effective vaccine is available, and it is recommended for people travelling to or residing in areas of high or intermediate prevalence, those with chronic liver disease, patients with haemophilia, men who have sex with men, injecting drug users, and individuals at occupational risk (such as laboratory workers, staff of large residential institutions, sewage workers, and people who work with primates).

      It is important to note that the vaccine requires a booster dose 6-12 months after the initial dose. By understanding the symptoms, transmission, and prevention of hepatitis A, individuals can take steps to protect themselves and others from this viral infection.

    • This question is part of the following fields:

      • General Principles
      482.5
      Seconds
  • Question 3 - A 78-year-old man reports experiencing discomfort behind his breastbone and occasional backflow of...

    Correct

    • A 78-year-old man reports experiencing discomfort behind his breastbone and occasional backflow of stomach acid into his mouth, especially after meals and at bedtime, causing sleep disturbance. What is a potential risk factor for GORD?

      Your Answer: Smoking

      Explanation:

      Gastro-Oesophageal Reflux Disease (GORD)

      Gastro-oesophageal reflux disease (GORD) is a chronic condition where stomach acid flows back up into the oesophagus, causing discomfort and increasing the risk of oesophageal cancer. Obesity is a known risk factor for GORD, as excess weight around the abdomen increases pressure in the stomach. Hiatus hernia, which also results from increased intra-abdominal pressure, is also associated with GORD. This is because the widening of the diaphragmatic hiatus in hiatus hernia reduces the effectiveness of the lower oesophageal sphincter in preventing acid reflux.

      Smoking is another risk factor for GORD, although the exact mechanism by which it weakens the lower oesophageal sphincter is not fully understood. Interestingly, male sex does not appear to be associated with GORD. Overall, the risk factors for GORD can help individuals take steps to prevent or manage this chronic condition.

    • This question is part of the following fields:

      • Gastrointestinal System
      424.9
      Seconds
  • Question 4 - A 70-year-old individual presents to the ophthalmology clinic with a gradual decline in...

    Correct

    • A 70-year-old individual presents to the ophthalmology clinic with a gradual decline in visual acuity, difficulty seeing at night, and occasional floaters. Upon fundoscopy, yellow pigment deposits are observed in the macular region, along with demarcated red patches indicating fluid leakage and bleeding. The patient has no significant medical history. The ophthalmologist recommends a treatment that directly inhibits vascular endothelial growth factors. What is the appropriate management for this patient?

      Your Answer: Bevacizumab

      Explanation:

      Bevacizumab is a monoclonal antibody that targets vascular endothelial growth factor (VEGF) and is used as a first-line treatment for the neovascular or exudative form of age-related macular degeneration (AMD). This form of AMD is characterized by the proliferation of abnormal blood vessels in the eye that leak blood and protein below the macula, causing damage to the photoreceptors. Bevacizumab blocks VEGF, which stimulates the growth of these abnormal vessels.

      Fluocinolone is a corticosteroid that is used as an anti-inflammatory via intraocular injection in some eye conditions, but it does not affect VEGF. Laser photocoagulation is used to cauterize ocular blood vessels in several eye conditions, but it also does not affect VEGF. Verteporfin is a medication used as a photosensitizer prior to photodynamic therapy, which can be used in eye conditions with ocular vessel proliferation, but it is not an anti-VEGF drug.

      Age-related macular degeneration (ARMD) is a common cause of blindness in the UK, characterized by degeneration of the central retina (macula) and the formation of drusen. The risk of ARMD increases with age, smoking, family history, and conditions associated with an increased risk of ischaemic cardiovascular disease. ARMD is classified into dry and wet forms, with the latter carrying the worst prognosis. Clinical features include subacute onset of visual loss, difficulties in dark adaptation, and visual hallucinations. Signs include distortion of line perception, the presence of drusen, and well-demarcated red patches in wet ARMD. Investigations include slit-lamp microscopy, colour fundus photography, fluorescein angiography, indocyanine green angiography, and ocular coherence tomography. Treatment options include a combination of zinc with anti-oxidant vitamins for dry ARMD and anti-VEGF agents for wet ARMD. Laser photocoagulation is also an option, but anti-VEGF therapies are usually preferred.

    • This question is part of the following fields:

      • Neurological System
      39.9
      Seconds
  • Question 5 - A 43-year-old female comes to the ENT clinic with a history of constant...

    Incorrect

    • A 43-year-old female comes to the ENT clinic with a history of constant vertigo and right-sided deafness for the past year. She has no significant medical history. Upon conducting an audiogram, it is discovered that her right ear has reduced hearing to both bone and air conduction. During a cranial nerve exam, an absent corneal reflex is observed on the right side, and she has poor balance. Otoscopy of both ears is normal. What is the probable underlying pathology responsible for this patient's symptoms and signs?

      Your Answer:

      Correct Answer: Vestibular schwannoma (acoustic neuroma)

      Explanation:

      If a patient presents with loss of the corneal reflex, the likely diagnosis is vestibular schwannoma (acoustic neuroma). This is a noncancerous tumor that affects the vestibular portion of the 8th cranial nerve, leading to sensorineural deafness, tinnitus, and vertigo. As the tumor grows, it can also press on other cranial nerves. Loss of the corneal reflex is a classic sign of early trigeminal (cranial nerve 5) involvement, which is unlikely in any of the other listed conditions.

      Meniere’s disease is not the correct answer. This is a disorder of the middle ear that causes episodic vertigo, sensorineural hearing loss, and a sensation of aural fullness or pressure.

      Otosclerosis is also incorrect. This is an inherited condition that causes conductive deafness and tinnitus, typically presenting in patients aged 20-40 years.

      Vestibular mononeuritis is not the correct answer either. This condition is caused by inflammation of the vestibular nerve following a recent viral infection and presents with vertigo, but hearing is not affected.

      Vestibular schwannomas, also known as acoustic neuromas, make up about 5% of intracranial tumors and 90% of cerebellopontine angle tumors. These tumors typically present with a combination of vertigo, hearing loss, tinnitus, and an absent corneal reflex. The specific symptoms can be predicted based on which cranial nerves are affected. For example, cranial nerve VIII involvement can cause vertigo, unilateral sensorineural hearing loss, and unilateral tinnitus. Bilateral vestibular schwannomas are associated with neurofibromatosis type 2.

      If a vestibular schwannoma is suspected, it is important to refer the patient to an ear, nose, and throat specialist urgently. However, it is worth noting that these tumors are often benign and slow-growing, so observation may be appropriate initially. The diagnosis is typically confirmed with an MRI of the cerebellopontine angle, and audiometry is also important as most patients will have some degree of hearing loss. Treatment options include surgery, radiotherapy, or continued observation.

    • This question is part of the following fields:

      • Neurological System
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  • Question 6 - A 35-year-old woman visits her doctor for a routine cervical smear. She has...

    Incorrect

    • A 35-year-old woman visits her doctor for a routine cervical smear. She has a history of generalised anxiety disorder and is concerned about the possibility of having an undiagnosed malignancy due to her family's history of cervical cancer. She wants to know the likelihood of not having cervical cancer if the cervical screening test is negative.

      Which statistical measure would be most appropriate to address this patient's worries?

      Your Answer:

      Correct Answer: Test negative predictive value

      Explanation:

      Precision refers to the consistency of a test in producing the same results when repeated multiple times. It is an important aspect of test reliability and can impact the accuracy of the results. In order to assess precision, multiple tests are performed on the same sample and the results are compared. A test with high precision will produce similar results each time it is performed, while a test with low precision will produce inconsistent results. It is important to consider precision when interpreting test results and making clinical decisions.

    • This question is part of the following fields:

      • General Principles
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  • Question 7 - Where is the highest percentage of musculi pectinati located? ...

    Incorrect

    • Where is the highest percentage of musculi pectinati located?

      Your Answer:

      Correct Answer: Right atrium

      Explanation:

      The irregular anterior walls of the right atrium are due to the presence of musculi pectinati, which are located in the atria. These internal muscular ridges are found on the anterolateral surface of the chambers and are limited to the area that originates from the embryological true atrium.

      The walls of each cardiac chamber are made up of the epicardium, myocardium, and endocardium. The heart and roots of the great vessels are related anteriorly to the sternum and the left ribs. The coronary sinus receives blood from the cardiac veins, and the aortic sinus gives rise to the right and left coronary arteries. The left ventricle has a thicker wall and more numerous trabeculae carnae than the right ventricle. The heart is innervated by autonomic nerve fibers from the cardiac plexus, and the parasympathetic supply comes from the vagus nerves. The heart has four valves: the mitral, aortic, pulmonary, and tricuspid valves.

    • This question is part of the following fields:

      • Cardiovascular System
      0
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  • Question 8 - What characteristic might indicate the presence of high-grade dysplasia? ...

    Incorrect

    • What characteristic might indicate the presence of high-grade dysplasia?

      Your Answer:

      Correct Answer: High Ki67 index

      Explanation:

      Dysplasia and its Association with Malignancy

      Dysplasia refers to the cellular changes that occur during the development of malignancy. The degree of dysplasia in a cell is directly proportional to its likelihood of being found in an invasive cancer. Cells with higher-grade dysplasia have more genetic abnormalities than those with low-grade dysplasia.

      Progressive dysplasia is characterized by variations in the appearance of cells and their nuclei, which is not typical in most tissues where cells appear similar. The nuclei of dysplastic cells are larger, and there is an increase in the number of nucleoli. The Ki67 index is a marker of proliferation, and a higher Ki67 index indicates a higher rate of cell turnover.

      In most tissues, mitoses are rare, but malignant tissues made up of dysplastic cells show visible mitoses. dysplasia and its association with malignancy is crucial in the early detection and treatment of cancer.

    • This question is part of the following fields:

      • Histology
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  • Question 9 - An elderly man, aged 72, visits his family doctor with complaints of a...

    Incorrect

    • An elderly man, aged 72, visits his family doctor with complaints of a vague abdominal pain that has been bothering him for the past few months. He is unable to pinpoint the exact location of the pain but mentions that it is more severe around the epigastric region. The pain worsens after meals and has resulted in a loss of appetite and recent weight loss. The man denies experiencing any nausea or vomiting and reports only mild constipation. He has a long-standing history of type 2 diabetes mellitus, hypertension, and dyslipidemia and is currently taking glipizide, insulin injections, atorvastatin, candesartan, and metoprolol as regular medications. Additionally, he is a current smoker with a 25 pack-year history. On examination, the abdomen is soft and non-tender. The man’s vital signs include a heart rate of 62 beats per minute, respiratory rate of 13 breaths per minute, and blood pressure of 147/91 mmHg. What is the most likely mechanism responsible for this patient’s symptoms?

      Your Answer:

      Correct Answer: Fatty accumulation, foam cell formation and fibrous plaque formation in the wall of blood vessels

      Explanation:

      The patient’s symptoms suggest that he may have chronic mesenteric ischemia, which is often caused by atherosclerosis in the arteries supplying the splanchnic circulatory vessels. There is no indication of recent abdominal surgery or an underlying inflammatory process. Constipation is a common issue in elderly individuals, but it is not typically associated with abdominal pain. Meckel diverticulum is a congenital defect that can cause symptoms such as melaena, acute appendicitis, and acute abdominal pain due to ectopic acid secretion. Diverticulitis is characterized by inflammation in the colon, often due to a lack of dietary fiber. Small bowel obstruction due to adhesions is a surgical emergency. Chronic mesenteric ischemia, also known as intestinal angina, is common in individuals with atherosclerotic diseases such as diabetics, smokers, hypertensive patients, and those with dyslipidemia. As the population ages and chronic diseases become more prevalent, the incidence and prevalence of chronic mesenteric ischemia are expected to increase.

      Ischaemia to the lower gastrointestinal tract can result in acute mesenteric ischaemia, chronic mesenteric ischaemia, and ischaemic colitis. Common predisposing factors include increasing age, atrial fibrillation, other causes of emboli, cardiovascular disease risk factors, and cocaine use. Common features include abdominal pain, rectal bleeding, diarrhea, fever, and elevated white blood cell count with lactic acidosis. CT is the investigation of choice. Acute mesenteric ischaemia is typically caused by an embolism and requires urgent surgery. Chronic mesenteric ischaemia presents with intermittent abdominal pain. Ischaemic colitis is an acute but transient compromise in blood flow to the large bowel and may require surgery in a minority of cases.

    • This question is part of the following fields:

      • Gastrointestinal System
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  • Question 10 - A 20-year-old woman is undergoing evaluation by a psychiatrist for her eating patterns....

    Incorrect

    • A 20-year-old woman is undergoing evaluation by a psychiatrist for her eating patterns. She confesses to engaging in binge eating and then inducing vomiting for the last half-year. During the physical examination, her BMI is measured at 20 kg/m², and enamel erosion is observed.

      What acid-base and electrolyte imbalances are commonly linked to her eating disorder?

      Your Answer:

      Correct Answer: Metabolic alkalosis, hypochloraemia, hypokalaemia

      Explanation:

      Metabolic alkalosis, hypokalemia, and hypochloremia are commonly observed in individuals with bulimia nervosa, even if their BMI falls within a normal range. This is due to the excessive self-induced vomiting, which results in the loss of stomach acid (HCl) and potassium.

      Understanding Bulimia Nervosa

      Bulimia nervosa is an eating disorder that is characterized by recurrent episodes of binge eating followed by purging behaviors such as self-induced vomiting, misuse of laxatives, diuretics, or other medications, fasting, or excessive exercise. According to the DSM 5 diagnostic criteria, individuals with bulimia nervosa experience a sense of lack of control over eating during the episode, and the binge eating and compensatory behaviors occur at least once a week for three months. Recurrent vomiting may lead to erosion of teeth and Russell’s sign – calluses on the knuckles or back of the hand due to repeated self-induced vomiting.

      Individuals with bulimia nervosa are unduly influenced by body shape and weight, and their self-evaluation is often based on these factors. It is important to note that the disturbance does not occur exclusively during episodes of anorexia nervosa. Referral for specialist care is appropriate in all cases, and NICE recommends bulimia-nervosa-focused guided self-help for adults. If this approach is not effective, individual eating-disorder-focused cognitive behavioral therapy (CBT-ED) may be considered. Children should be offered bulimia-nervosa-focused family therapy (FT-BN). While pharmacological treatments have a limited role, a trial of high-dose fluoxetine is currently licensed for bulimia, but long-term data is lacking.

      In summary, bulimia nervosa is a serious eating disorder that requires specialized care. Early intervention and treatment can help individuals recover and improve their quality of life.

    • This question is part of the following fields:

      • Psychiatry
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  • Question 11 - A man in his early 50s comes to the hospital with a fever...

    Incorrect

    • A man in his early 50s comes to the hospital with a fever and cough. An X-ray shows pneumonia in his left lower lobe. Upon arrival at the emergency department, his blood pressure is 83/60mmHg and his heart rate is 112/min. The doctor prescribes antibiotics and IV fluids.

      What is the primary way the body reacts to a drop in blood pressure?

      Your Answer:

      Correct Answer: Insertion of AQP-2 channels in collecting ducts

      Explanation:

      When blood pressure drops, the body initiates several physiological responses, one of which is the activation of the renin-angiotensin aldosterone system (RAAS). This system breaks down bradykinin, a potent vasodilator, through the action of angiotensin-converting enzyme (ACE).

      RAAS activation results in increased aldosterone levels, which in turn increases the number of epithelial sodium channels (ENAC) to enhance sodium reabsorption.

      Another response to low blood pressure is the release of antidiuretic hormone, which promotes the insertion of aquaporin-2 channels in the collecting duct. This mechanism increases water reabsorption to help maintain fluid balance in the body.

      Understanding Antidiuretic Hormone (ADH)

      Antidiuretic hormone (ADH) is a hormone that is produced in the supraoptic nuclei of the hypothalamus and released by the posterior pituitary gland. Its primary function is to conserve body water by promoting water reabsorption in the collecting ducts of the kidneys through the insertion of aquaporin-2 channels.

      ADH secretion is regulated by various factors. An increase in extracellular fluid osmolality, a decrease in volume or pressure, and the presence of angiotensin II can all increase ADH secretion. Conversely, a decrease in extracellular fluid osmolality, an increase in volume, a decrease in temperature, or the absence of ADH can decrease its secretion.

      Diabetes insipidus (DI) is a condition that occurs when there is either a deficiency of ADH (cranial DI) or an insensitivity to ADH (nephrogenic DI). Cranial DI can be treated with desmopressin, which is an analog of ADH.

      Overall, understanding the role of ADH in regulating water balance in the body is crucial for maintaining proper hydration and preventing conditions like DI.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 12 - Which of the following nerves is responsible for the motor innervation of the...

    Incorrect

    • Which of the following nerves is responsible for the motor innervation of the sternocleidomastoid muscle?

      Your Answer:

      Correct Answer: Accessory nerve

      Explanation:

      The accessory nerve provides the motor supply to the sternocleidomastoid, while the ansa cervicalis is responsible for supplying sensory information from the muscle.

      The Sternocleidomastoid Muscle: Anatomy and Function

      The sternocleidomastoid muscle is a large muscle located in the neck that plays an important role in head and neck movement. It is named after its origin and insertion points, which are the sternum, clavicle, mastoid process, and occipital bone. The muscle is innervated by the spinal part of the accessory nerve and the anterior rami of C2 and C3, which provide proprioceptive feedback.

      The sternocleidomastoid muscle has several actions, including extending the head at the atlanto-occipital joint and flexing the cervical vertebral column. It also serves as an accessory muscle of inspiration. When only one side of the muscle contracts, it can laterally flex the neck and rotate the head so that the face looks upward to the opposite side.

      The sternocleidomastoid muscle divides the neck into anterior and posterior triangles, which are important landmarks for medical professionals. The anterior triangle contains several important structures, including the carotid artery, jugular vein, and thyroid gland. The posterior triangle contains the brachial plexus, accessory nerve, and several lymph nodes.

      Overall, the sternocleidomastoid muscle is a crucial muscle for head and neck movement and plays an important role in the anatomy of the neck.

    • This question is part of the following fields:

      • Musculoskeletal System And Skin
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  • Question 13 - A 9-year-old girl has recently been diagnosed with focal seizures. She reports feeling...

    Incorrect

    • A 9-year-old girl has recently been diagnosed with focal seizures. She reports feeling tingling in her left leg before an episode, but has no other symptoms. Upon examination, her upper limbs, lower limbs, and cranial nerves appear normal. She does not experience postictal dysphasia and is fully oriented to time, place, and person.

      Which specific region of her brain is impacted by the focal seizures?

      Your Answer:

      Correct Answer: Posterior to the central gyrus

      Explanation:

      Paraesthesia is a symptom that can help localize a seizure in the parietal lobe.

      The correct location for paraesthesia is posterior to the central gyrus, which is part of the parietal lobe. This area is responsible for integrating sensory information, including touch, and damage to this region can cause abnormal sensations like tingling.

      Anterior to the central gyrus is not the correct location for paraesthesia. This area is part of the frontal lobe and seizures here can cause motor disturbances like hand twitches that spread to the face.

      The medial temporal gyrus is also not the correct location for paraesthesia. Seizures in this area can cause symptoms like lip-smacking and tugging at clothes.

      Occipital lobe seizures can cause visual disturbances like flashes and floaters, but not paraesthesia.

      Finally, the prefrontal cortex, which is also located in the frontal lobe, is not associated with paraesthesia.

      Localising Features of Focal Seizures in Epilepsy

      Focal seizures in epilepsy can be localised based on the specific location of the brain where they occur. Temporal lobe seizures are common and may occur with or without impairment of consciousness or awareness. Most patients experience an aura, which is typically a rising epigastric sensation, along with psychic or experiential phenomena such as déjà vu or jamais vu. Less commonly, hallucinations may occur, such as auditory, gustatory, or olfactory hallucinations. These seizures typically last around one minute and are often accompanied by automatisms, such as lip smacking, grabbing, or plucking.

      On the other hand, frontal lobe seizures are characterised by motor symptoms such as head or leg movements, posturing, postictal weakness, and Jacksonian march. Parietal lobe seizures, on the other hand, are sensory in nature and may cause paraesthesia. Finally, occipital lobe seizures may cause visual symptoms such as floaters or flashes. By identifying the specific location and type of seizure, doctors can better diagnose and treat epilepsy in patients.

    • This question is part of the following fields:

      • Neurological System
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  • Question 14 - During a hand examination of a 75-year-old woman, it was observed that her...

    Incorrect

    • During a hand examination of a 75-year-old woman, it was observed that her fingers had a swan-neck deformity and her thumbs had a Z-shape deformity on both hands. After conducting blood tests, the rheumatologist confirmed the presence of anti-CCP antibodies, indicating a diagnosis of rheumatoid arthritis. Which cells, originating from pluripotent hematopoietic stem cells, are responsible for producing antigen-specific immunoglobulins?

      Your Answer:

      Correct Answer: B cells

      Explanation:

      B cells produce antibodies, which are essential in fighting off new pathogens. T helper cells assist B cells by promoting the production of targeted antibodies.

      Mast cells release inflammatory mediators, contributing to the body’s immune response.

      Dendritic cells present antigens to help recruit white blood cells.

      T cells are responsible for immunological memory and the adaptive immune response.

      Immunoglobulins, also known as antibodies, are proteins produced by the immune system to help fight off infections and diseases. There are five types of immunoglobulins found in the body, each with their own unique characteristics.

      IgG is the most abundant type of immunoglobulin in blood serum and plays a crucial role in enhancing phagocytosis of bacteria and viruses. It also fixes complement and can be passed to the fetal circulation.

      IgA is the most commonly produced immunoglobulin in the body and is found in the secretions of digestive, respiratory, and urogenital tracts and systems. It provides localized protection on mucous membranes and is transported across the interior of the cell via transcytosis.

      IgM is the first immunoglobulin to be secreted in response to an infection and fixes complement, but does not pass to the fetal circulation. It is also responsible for producing anti-A, B blood antibodies.

      IgD’s role in the immune system is largely unknown, but it is involved in the activation of B cells.

      IgE is the least abundant type of immunoglobulin in blood serum and is responsible for mediating type 1 hypersensitivity reactions. It provides immunity to parasites such as helminths and binds to Fc receptors found on the surface of mast cells and basophils.

    • This question is part of the following fields:

      • General Principles
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  • Question 15 - A 49-year-old woman visits her GP complaining of low mood, fatigue, constipation, and...

    Incorrect

    • A 49-year-old woman visits her GP complaining of low mood, fatigue, constipation, and urinary frequency. The doctor orders a standard blood test to investigate the possible cause. After reviewing the results, the GP diagnosis the woman with primary hyperparathyroidism.

      What blood test results are expected for this patient?

      Your Answer:

      Correct Answer: Raised calcium, low phosphate

      Explanation:

      Parathyroid hormone (PTH) is responsible for increasing plasma calcium levels and decreasing plasma phosphate levels. Hyperparathyroidism is a condition where there is an excess of PTH, either due to an overactive parathyroid gland (primary) or a low serum calcium level (secondary). Primary hyperparathyroidism results in raised calcium levels and low phosphate levels, while secondary hyperparathyroidism is typically seen in chronic kidney disease. PTH acts by increasing calcium reabsorption in the kidneys and digestive tract, as well as increasing bone resorption. This helps to prevent the formation of calcium phosphate crystals, which can cause renal stones. Symptoms of hyperparathyroidism include constipation and low mood, which are typical of hypercalcaemia.

      Hormones Controlling Calcium Metabolism

      Calcium metabolism is primarily controlled by two hormones, parathyroid hormone (PTH) and 1,25-dihydroxycholecalciferol (calcitriol). Other hormones such as calcitonin, thyroxine, and growth hormone also play a role. PTH increases plasma calcium levels and decreases plasma phosphate levels. It also increases renal tubular reabsorption of calcium, osteoclastic activity, and renal conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol. On the other hand, 1,25-dihydroxycholecalciferol increases plasma calcium and plasma phosphate levels, renal tubular reabsorption and gut absorption of calcium, osteoclastic activity, and renal phosphate reabsorption. It is important to note that osteoclastic activity is increased indirectly by PTH as osteoclasts do not have PTH receptors. Understanding the actions of these hormones is crucial in maintaining proper calcium metabolism in the body.

    • This question is part of the following fields:

      • General Principles
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  • Question 16 - A 65-year-old man presents to the Emergency Department with a 60-minute history of...

    Incorrect

    • A 65-year-old man presents to the Emergency Department with a 60-minute history of central chest pain that extends to his jaw. An ECG reveals an inferior ST-segment elevation myocardial infarction (STEMI). The QRS is positive in leads I and aVL but negative in leads II and aVF. What type of axis deviation is indicated by this finding?

      Your Answer:

      Correct Answer: Left

      Explanation:

      To estimate the heart’s axis, one method is the quadrant method, which involves analyzing leads I and aVF. If lead I is positive and lead aVF is negative, this suggests a possible left axis deviation. To confirm left axis deviation, a second method using lead II can be used. If lead II is also negative, then left axis deviation is confirmed. Other types of axis deviation can be determined by analyzing the polarity of leads I and aVF.

      ECG Axis Deviation: Causes of Left and Right Deviation

      Electrocardiogram (ECG) axis deviation refers to the direction of the electrical activity of the heart. A normal axis is between -30 and +90 degrees. Deviation from this range can indicate underlying cardiac or pulmonary conditions.

      Left axis deviation (LAD) can be caused by left anterior hemiblock, left bundle branch block, inferior myocardial infarction, Wolff-Parkinson-White syndrome with a right-sided accessory pathway, hyperkalaemia, congenital heart defects such as ostium primum atrial septal defect (ASD) and tricuspid atresia, and minor LAD in obese individuals.

      On the other hand, right axis deviation (RAD) can be caused by right ventricular hypertrophy, left posterior hemiblock, lateral myocardial infarction, chronic lung disease leading to cor pulmonale, pulmonary embolism, ostium secundum ASD, Wolff-Parkinson-White syndrome with a left-sided accessory pathway, and minor RAD in tall individuals. It is also normal in infants less than one year old.

      It is important to note that Wolff-Parkinson-White syndrome is a common cause of both LAD and RAD, depending on the location of the accessory pathway. Understanding the causes of ECG axis deviation can aid in the diagnosis and management of underlying conditions.

    • This question is part of the following fields:

      • Cardiovascular System
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  • Question 17 - A 67-year-old man visits his GP complaining of alterations in his vision. In...

    Incorrect

    • A 67-year-old man visits his GP complaining of alterations in his vision. In addition to decreased sharpness, he describes object distortion, difficulty discerning colors, and occasional flashes of light. He has a history of smoking (40-pack-year) and a high BMI. Based on these symptoms, what is the most probable diagnosis?

      Your Answer:

      Correct Answer: Age-related macular degeneration

      Explanation:

      Age-related macular degeneration (AMD) is characterized by a decrease in visual acuity, altered perception of colors and shades, and photopsia (flashing lights). The risk of developing AMD is higher in individuals who are older and have a history of smoking.

      As a natural part of the aging process, presbyopia can cause difficulty with near vision. Smoking increases the likelihood of developing cataracts, which can result in poor visual acuity and reduced contrast sensitivity. However, symptoms such as distortion and flashing lights are not typically associated with cataracts. Similarly, retinal detachment is unlikely given the patient’s risk factors and lack of distortion and perception issues. Since there is no mention of diabetes mellitus in the patient’s history, diabetic retinopathy is not a plausible explanation.

      Age-related macular degeneration (ARMD) is a common cause of blindness in the UK, characterized by degeneration of the central retina (macula) and the formation of drusen. The risk of ARMD increases with age, smoking, family history, and conditions associated with an increased risk of ischaemic cardiovascular disease. ARMD is classified into dry and wet forms, with the latter carrying the worst prognosis. Clinical features include subacute onset of visual loss, difficulties in dark adaptation, and visual hallucinations. Signs include distortion of line perception, the presence of drusen, and well-demarcated red patches in wet ARMD. Investigations include slit-lamp microscopy, colour fundus photography, fluorescein angiography, indocyanine green angiography, and ocular coherence tomography. Treatment options include a combination of zinc with anti-oxidant vitamins for dry ARMD and anti-VEGF agents for wet ARMD. Laser photocoagulation is also an option, but anti-VEGF therapies are usually preferred.

    • This question is part of the following fields:

      • Neurological System
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  • Question 18 - A 29-year-old man attempts suicide by cutting the posterolateral aspect of his wrist...

    Incorrect

    • A 29-year-old man attempts suicide by cutting the posterolateral aspect of his wrist with a knife. Upon arrival at the emergency department, examination reveals a wound situated over the lateral aspect of the extensor retinaculum, which remains intact. What structure is most vulnerable to injury in this scenario?

      Your Answer:

      Correct Answer: Superficial branch of the radial nerve

      Explanation:

      The extensor retinaculum laceration site poses the highest risk of injury to the superficial branch of the radial nerve, which runs above it. Meanwhile, the dorsal branch of the ulnar nerve and artery are situated medially but also pass above the extensor retinaculum.

      The Extensor Retinaculum and its Related Structures

      The extensor retinaculum is a thick layer of deep fascia that runs across the back of the wrist, holding the long extensor tendons in place. It attaches to the pisiform and triquetral bones medially and the end of the radius laterally. The retinaculum has six compartments that contain the extensor muscle tendons, each with its own synovial sheath.

      Several structures are related to the extensor retinaculum. Superficial to the retinaculum are the basilic and cephalic veins, the dorsal cutaneous branch of the ulnar nerve, and the superficial branch of the radial nerve. Deep to the retinaculum are the tendons of the extensor carpi ulnaris, extensor digiti minimi, extensor digitorum, extensor indicis, extensor pollicis longus, extensor carpi radialis longus, extensor carpi radialis brevis, abductor pollicis longus, and extensor pollicis brevis.

      The radial artery also passes between the lateral collateral ligament of the wrist joint and the tendons of the abductor pollicis longus and extensor pollicis brevis. Understanding the topography of these structures is important for diagnosing and treating wrist injuries and conditions.

    • This question is part of the following fields:

      • Neurological System
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  • Question 19 - Which electrolyte imbalance is frequently observed in individuals suffering from malnutrition? ...

    Incorrect

    • Which electrolyte imbalance is frequently observed in individuals suffering from malnutrition?

      Your Answer:

      Correct Answer: Hypokalaemia

      Explanation:

      Electrolyte Abnormalities in Malnourished Individuals

      Malnutrition can lead to various changes in the body’s systems and physiology, particularly in the levels of electrolytes. The most common electrolyte abnormalities in malnourished individuals are hypokalaemia, hypocalcaemia, hypophosphataemia, and hypomagnesaemia. Prolonged malnutrition can cause the body to adapt to a reduced dietary supply of minerals, resulting in changes in renal physiology such as increased aldosterone secretion and reduced glomerular filtration rate. This leads to increased urinary excretion of potassium, calcium, magnesium, and phosphate, which can cause a tendency towards electrolyte imbalances over time.

      Moreover, severe malnutrition can cause reduced muscle bulk, resulting in low levels of production of urea and creatinine. However, reduced excretion can cause plasma levels to be normal or slightly reduced. As muscle breaks down to provide substrates for gluconeogenesis, a negative nitrogen balance ensues. Therefore, patients with severe malnutrition are at risk of refeeding syndrome once they start eating again or are treated with parenteral nutrition. To prevent this, prophylaxis with B vitamins, folic acid, and minerals is recommended.

    • This question is part of the following fields:

      • Clinical Sciences
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  • Question 20 - A 38-year-old woman is diagnosed with hyperthyroidism and started on carbimazole. What is...

    Incorrect

    • A 38-year-old woman is diagnosed with hyperthyroidism and started on carbimazole. What is the mechanism of action of this medication?

      Your Answer:

      Correct Answer: Prevents iodination of the tyrosine residue on thyroglobulin

      Explanation:

      Carbimazole is a medication used to treat thyrotoxicosis, a condition where the thyroid gland produces too much thyroid hormone. It is usually given in high doses for six weeks until the patient’s thyroid hormone levels become normal, after which the dosage is reduced. The drug works by blocking thyroid peroxidase, an enzyme that is responsible for coupling and iodinating the tyrosine residues on thyroglobulin, which ultimately leads to a reduction in thyroid hormone production. In contrast, propylthiouracil has a dual mechanism of action, inhibiting both thyroid peroxidase and 5′-deiodinase, which reduces the peripheral conversion of T4 to T3.

      However, carbimazole is not without its adverse effects. One of the most serious side effects is agranulocytosis, a condition where the body’s white blood cell count drops significantly, making the patient more susceptible to infections. Additionally, carbimazole can cross the placenta and affect the developing fetus, although it may be used in low doses during pregnancy under close medical supervision. Overall, carbimazole is an effective medication for managing thyrotoxicosis, but its potential side effects should be carefully monitored.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 21 - A 35-year-old female arrives at the emergency department with an 8-hour history of...

    Incorrect

    • A 35-year-old female arrives at the emergency department with an 8-hour history of headache and altered mental status. Upon examination, her vital signs are as follows: blood pressure 194/128 mmHg, oxygen saturation 97%, heart rate 88/min, respiratory rate 22/min, and temperature 36.6ºC. What other clinical manifestation would you anticipate based on the probable diagnosis of this patient?

      Your Answer:

      Correct Answer: Papilloedema

      Explanation:

      Papilloedema can be caused by malignant hypertension.

      The patient’s symptoms, including a severe headache and altered mental status, indicate a diagnosis of malignant hypertension due to their extremely high blood pressure.

      Excessive sweating is not a typical symptom of malignant hypertension and may suggest a different condition such as acromegaly.

      Consolidation on an X-ray is typically associated with pneumonia and would not present with the symptoms described.

      While raised neutrophils may indicate a bacterial infection, the presence of a headache, altered mental state, and high blood pressure suggest meningitis, although a fever would also be expected in this case.

      Understanding Papilloedema

      Papilloedema is a condition characterized by swelling of the optic disc due to increased pressure within the skull. This condition typically affects both eyes. During a fundoscopy, several signs may be observed, including venous engorgement, loss of venous pulsation, blurring of the optic disc margin, elevation of the optic disc, loss of the optic cup, and Paton’s lines.

      There are several potential causes of papilloedema, including space-occupying lesions such as tumors or vascular abnormalities, malignant hypertension, idiopathic intracranial hypertension, hydrocephalus, and hypercapnia. In rare cases, papilloedema may be caused by hypoparathyroidism and hypocalcaemia or vitamin A toxicity.

      It is important to diagnose and treat papilloedema promptly, as it can lead to permanent vision loss if left untreated. Treatment typically involves addressing the underlying cause of the increased intracranial pressure, such as surgery to remove a tumor or medication to manage hypertension.

    • This question is part of the following fields:

      • Neurological System
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  • Question 22 - A 67-year-old man arrives at the emergency department following a car crash with...

    Incorrect

    • A 67-year-old man arrives at the emergency department following a car crash with significant injuries. To address his decreasing heart rate, the medical team administers adrenaline. Which set of receptors does adrenaline primarily act upon in this scenario?

      Your Answer:

      Correct Answer: β1

      Explanation:

      The adrenoceptors, also known as adrenergic receptors, are a type of G protein-coupled receptors that respond to catecholamines, particularly norepinephrine and epinephrine.

      These receptors are present in various cells, and when a catecholamine binds to them, it typically activates the sympathetic nervous system. This system triggers the fight-or-flight response, which involves widening the pupils, accelerating the heart rate, releasing energy, and redirecting blood flow from non-essential organs to skeletal muscles. Adrenaline is used to enhance cardiac muscle function by targeting β1 adrenergic receptors.

      Inotropes are drugs that primarily increase cardiac output and are different from vasoconstrictor drugs that are used for peripheral vasodilation. Catecholamine type agents are commonly used in inotropes and work by increasing cAMP levels through adenylate cyclase stimulation. This leads to intracellular calcium ion mobilisation and an increase in the force of contraction. Adrenaline works as a beta adrenergic receptor agonist at lower doses and an alpha receptor agonist at higher doses. Dopamine causes dopamine receptor-mediated renal and mesenteric vascular dilatation and beta 1 receptor agonism at higher doses, resulting in increased cardiac output. Dobutamine is a predominantly beta 1 receptor agonist with weak beta 2 and alpha receptor agonist properties. Noradrenaline is a catecholamine type agent and predominantly acts as an alpha receptor agonist and serves as a peripheral vasoconstrictor. Milrinone is a phosphodiesterase inhibitor that acts specifically on the cardiac phosphodiesterase and increases cardiac output.

      The cardiovascular receptor action of inotropes varies depending on the drug. Adrenaline and noradrenaline act on alpha and beta receptors, with adrenaline acting as a beta adrenergic receptor agonist at lower doses and an alpha receptor agonist at higher doses. Dobutamine acts predominantly on beta 1 receptors with weak beta 2 and alpha receptor agonist properties. Dopamine acts on dopamine receptors, causing renal and spleen vasodilation and beta 1 receptor agonism at higher doses. The minor receptor effects are shown in brackets. The effects of receptor binding include vasoconstriction for alpha-1 and alpha-2 receptors, increased cardiac contractility and heart rate for beta-1 receptors, and vasodilation for beta-2 receptors. D-1 receptors cause renal and spleen vasodilation, while D-2 receptors inhibit the release of noradrenaline. Overall, inotropes are a class of drugs that increase cardiac output through various receptor actions.

    • This question is part of the following fields:

      • General Principles
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  • Question 23 - A 75-year-old man has been experiencing illness for several years and after his...

    Incorrect

    • A 75-year-old man has been experiencing illness for several years and after his passing, an autopsy is conducted. Microscopic examination of tissue samples reveals the presence of apple green birefringence under polarised light in sections of the myocardium. What is the probable diagnosis?

      Your Answer:

      Correct Answer: Amyloidosis

      Explanation:

      When viewed under polarised light, amyloidosis exhibits a distinctive apple green birefringence.

      Understanding Amyloid: Protein Deposits that Affect Tissue Structure and Function

      Amyloid refers to the accumulation of insoluble protein deposits outside of cells. These deposits can disrupt the normal structure of tissues and, if excessive, can impair their function. Amyloid is composed of a major fibrillar protein that defines its type, along with various minor components. The different types of amyloid are classified with the prefix A and a suffix that corresponds to the fibrillary protein present. The two main clinical types are AA and AL amyloidosis.

      Systemic AA amyloidosis is a long-term complication of several chronic inflammatory disorders, such as rheumatoid arthritis, ankylosing spondylitis, Crohn’s disease, malignancies, and conditions that predispose individuals to recurrent infections. On the other hand, AL amyloidosis results from the deposition of fibril-forming monoclonal immunoglobulin light chains, most commonly of lambda isotype, outside of cells. Most patients with AL amyloidosis have evidence of isolated monoclonal gammopathy or asymptomatic myeloma, and the occurrence of AL amyloidosis in patients with symptomatic multiple myeloma or other B-cell lymphoproliferative disorders is unusual. The kidney and heart are two of the most commonly affected sites.

      Diagnosis of amyloidosis is based on surgical biopsy and characteristic histological features, which consist of birefringence under polarised light. Immunohistochemistry is used to determine the subtype. Treatment is usually targeted at the underlying cause. Understanding amyloid and its different types is crucial in the diagnosis and management of patients with amyloidosis.

    • This question is part of the following fields:

      • Cardiovascular System
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  • Question 24 - A 69-year-old man is admitted to the medical assessment unit with reduced urine...

    Incorrect

    • A 69-year-old man is admitted to the medical assessment unit with reduced urine output and nausea. He has a complex medical history, including heart failure, hypercholesterolemia, hypertension, type 1 diabetes mellitus, and hypothyroidism. Among his regular medications are bisoprolol, furosemide, simvastatin, insulin, and levothyroxine. The medical team suspects that he is currently experiencing an acute kidney injury.

      Which of his usual medications should be discontinued?

      Your Answer:

      Correct Answer: Furosemide

      Explanation:

      In cases of AKI, it is advisable to discontinue the use of diuretics as they may aggravate renal function. Loop diuretics like Furosemide should be stopped. Additionally, drugs that have the potential to harm the kidneys, such as aminoglycoside antibiotics (e.g. gentamicin), non-steroidal anti-inflammatory drugs, angiotensin-converting enzyme inhibitors (e.g. ramipril), angiotensin II receptor antagonists (e.g. losartan), and diuretics, should also be discontinued.

      Fortunately, the remaining drugs are generally safe to continue as they are not typically considered nephrotoxic. Insulin, a peptide hormone drug used in treating type 1 and type 2 diabetes mellitus, is cleared from the body through enzymatic breakdown in the liver and kidneys and is not usually harmful to the kidneys.

      Acute kidney injury (AKI) is a condition where there is a reduction in renal function following an insult to the kidneys. It was previously known as acute renal failure and can result in long-term impaired kidney function or even death. AKI can be caused by prerenal, intrinsic, or postrenal factors. Patients with chronic kidney disease, other organ failure/chronic disease, a history of AKI, or who have used drugs with nephrotoxic potential are at an increased risk of developing AKI. To prevent AKI, patients at risk may be given IV fluids or have certain medications temporarily stopped.

      The kidneys are responsible for maintaining fluid balance and homeostasis, so a reduced urine output or fluid overload may indicate AKI. Symptoms may not be present in early stages, but as renal failure progresses, patients may experience arrhythmias, pulmonary and peripheral edema, or features of uraemia. Blood tests such as urea and electrolytes can be used to detect AKI, and urinalysis and imaging may also be necessary.

      Management of AKI is largely supportive, with careful fluid balance and medication review. Loop diuretics and low-dose dopamine are not recommended, but hyperkalaemia needs prompt treatment to avoid life-threatening arrhythmias. Renal replacement therapy may be necessary in severe cases. Patients with suspected AKI secondary to urinary obstruction require prompt review by a urologist, and specialist input from a nephrologist is required for cases where the cause is unknown or the AKI is severe.

    • This question is part of the following fields:

      • Renal System
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  • Question 25 - A 50-year-old woman visits her general practitioner with a complaint of severe facial...

    Incorrect

    • A 50-year-old woman visits her general practitioner with a complaint of severe facial pain. The pain occurs several times a day and is described as the worst she has ever experienced. It is sudden in onset and termination and is felt in the right ophthalmic and maxillary regions of her face.

      During the examination, the cranial nerves appear normal except for the absence of a blink reflex in the patient's right eye when cotton wool is rubbed against it. However, the patient blinks when cotton wool is rubbed against her left eye.

      Which efferent pathway of this reflex is responsible for this nerve?

      Your Answer:

      Correct Answer: CN VII

      Explanation:

      Cranial nerves are a set of 12 nerves that emerge from the brain and control various functions of the head and neck. Each nerve has a specific function, such as smell, sight, eye movement, facial sensation, and tongue movement. Some nerves are sensory, some are motor, and some are both. A useful mnemonic to remember the order of the nerves is Some Say Marry Money But My Brother Says Big Brains Matter Most, with S representing sensory, M representing motor, and B representing both.

      In addition to their specific functions, cranial nerves also play a role in various reflexes. These reflexes involve an afferent limb, which carries sensory information to the brain, and an efferent limb, which carries motor information from the brain to the muscles. Examples of cranial nerve reflexes include the corneal reflex, jaw jerk, gag reflex, carotid sinus reflex, pupillary light reflex, and lacrimation reflex. Understanding the functions and reflexes of the cranial nerves is important in diagnosing and treating neurological disorders.

    • This question is part of the following fields:

      • Neurological System
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  • Question 26 - A 68-year-old man visits his GP complaining of an 8-week cough and an...

    Incorrect

    • A 68-year-old man visits his GP complaining of an 8-week cough and an unintentional weight loss of 7kg. He has a smoking history of 35 pack-years. The GP observes some alterations in his left eye, which are indicative of Horner's syndrome.

      The man is referred to the suspected cancer pathway and is subsequently diagnosed with a Pancoast tumour.

      What symptom is this individual most likely to exhibit?

      Your Answer:

      Correct Answer: Anhidrosis

      Explanation:

      Horner’s syndrome is characterized by meiosis, ptosis, and enophthalmos, and may also present with anhidrosis. Anhidrosis is a common symptom in preganglionic and central causes of Horner’s syndrome, while postganglionic causes do not typically result in anhidrosis. Exophthalmos is not associated with Horner’s syndrome, but rather with other conditions. Hypopyon and mydriasis are also not symptoms of Horner’s syndrome.

      Horner’s syndrome is a condition characterized by several features, including a small pupil (miosis), drooping of the upper eyelid (ptosis), a sunken eye (enophthalmos), and loss of sweating on one side of the face (anhidrosis). The cause of Horner’s syndrome can be determined by examining additional symptoms. For example, congenital Horner’s syndrome may be identified by a difference in iris color (heterochromia), while anhidrosis may be present in central or preganglionic lesions. Pharmacologic tests, such as the use of apraclonidine drops, can also be helpful in confirming the diagnosis and identifying the location of the lesion. Central lesions may be caused by conditions such as stroke or multiple sclerosis, while postganglionic lesions may be due to factors like carotid artery dissection or cluster headaches. It is important to note that the appearance of enophthalmos in Horner’s syndrome is actually due to a narrow palpebral aperture rather than true enophthalmos.

    • This question is part of the following fields:

      • Neurological System
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  • Question 27 - A 40-year-old man comes to the clinic complaining of headaches, dizziness, and a...

    Incorrect

    • A 40-year-old man comes to the clinic complaining of headaches, dizziness, and a pinkish tint to his skin. He discloses that he is homeless and currently squatting in an abandoned house with some companions who are also experiencing similar symptoms. He reports purchasing a paraffin heater to keep the house warm.

      The physician suspects that the patient's oxygen saturation is being affected by a blood gas disturbance.

      Considering the probable cause of this manifestation, how would his oxygen dissociation curve vary from prior to his exposure to the gas?

      Your Answer:

      Correct Answer: Lower plateau

      Explanation:

      In cases of carbon monoxide poisoning, the binding of carbon monoxide to haemoglobin results in a decrease in oxygen saturation, causing the oxygen dissociation curve to plateau at a lower saturation point. This is often caused by incomplete combustion from sources such as paraffin heaters. Clinicians should be aware of vague symptoms such as headaches in all household members, which may indicate exposure to carbon monoxide. The sigmoid shape of the oxygen dissociation curve is retained in carbon monoxide poisoning, although it is shifted left and tops out at a lower level than normal. A more staggered curve is not seen in any pathology and is a distractor.

      Carbon monoxide poisoning occurs when carbon monoxide binds to haemoglobin and myoglobin, leading to tissue hypoxia. Symptoms include headache, nausea, vomiting, vertigo, confusion, and in severe cases, pink skin and mucosae, hyperpyrexia, arrhythmias, extrapyramidal features, coma, and death. Diagnosis is made through measuring carboxyhaemoglobin levels in arterial or venous blood gas. Treatment involves administering 100% high-flow oxygen via a non-rebreather mask for at least six hours, with hyperbaric oxygen therapy considered for more severe cases.

    • This question is part of the following fields:

      • General Principles
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  • Question 28 - Which one of the following statements regarding drug metabolism is incorrect? ...

    Incorrect

    • Which one of the following statements regarding drug metabolism is incorrect?

      Your Answer:

      Correct Answer: Products of phase I reactions are typically more lipid soluble

      Explanation:

      Understanding Drug Metabolism: Phase I and Phase II Reactions

      Drug metabolism involves two types of biochemical reactions, namely phase I and phase II reactions. Phase I reactions include oxidation, reduction, and hydrolysis, which are mainly performed by P450 enzymes. However, some drugs are metabolized by specific enzymes such as alcohol dehydrogenase and xanthine oxidase. The products of phase I reactions are typically more active and potentially toxic. On the other hand, phase II reactions involve conjugation, where glucuronyl, acetyl, methyl, sulphate, and other groups are typically involved. The products of phase II reactions are typically inactive and excreted in urine or bile. The majority of phase I and phase II reactions take place in the liver.

      First-Pass Metabolism and Drugs Affected by Zero-Order Kinetics and Acetylator Status

      First-pass metabolism is a phenomenon where the concentration of a drug is greatly reduced before it reaches the systemic circulation due to hepatic metabolism. This effect is seen in many drugs, including aspirin, isosorbide dinitrate, glyceryl trinitrate, lignocaine, propranolol, verapamil, isoprenaline, testosterone, and hydrocortisone.

      Zero-order kinetics describe metabolism that is independent of the concentration of the reactant. This is due to metabolic pathways becoming saturated, resulting in a constant amount of drug being eliminated per unit time. Drugs exhibiting zero-order kinetics include phenytoin, salicylates (e.g. high-dose aspirin), heparin, and ethanol.

      Acetylator status is also an important consideration in drug metabolism. Approximately 50% of the UK population are deficient in hepatic N-acetyltransferase. Drugs affected by acetylator status include isoniazid, procainamide, hydralazine, dapsone, and sulfasalazine. Understanding these concepts is important in predicting drug efficacy and toxicity, as well as in optimizing drug dosing.

    • This question is part of the following fields:

      • General Principles
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  • Question 29 - A 49-year-old man with a history of uncontrolled HIV presents with dyspnea and...

    Incorrect

    • A 49-year-old man with a history of uncontrolled HIV presents with dyspnea and hemoptysis. Diagnostic tests reveal invasive aspergillosis, and he is prescribed amphotericin B. What is the mode of action of amphotericin B?

      Your Answer:

      Correct Answer: Binds with ergosterol

      Explanation:

      The mechanism of action of Amphotericin B involves binding with ergosterol, a key component of fungal cell membranes. This binding results in the formation of pores that cause the cell wall to lyse, ultimately leading to fungal cell death.

      Flucytosine, on the other hand, is converted by cytosine deaminase to 5-fluorouracil. This compound inhibits thymidylate synthase, which in turn disrupts fungal protein synthesis.

      Caspofungin works by inhibiting the synthesis of beta-glucan, a major component of the fungal cell wall.

      Griseofulvin interacts with microtubules, leading to the disruption of the mitotic spindle.

      Anti-viral agents like acyclovir function by inhibiting viral DNA polymerase.

      Antifungal agents are drugs used to treat fungal infections. There are several types of antifungal agents, each with a unique mechanism of action and potential adverse effects. Azoles work by inhibiting 14α-demethylase, an enzyme that produces ergosterol, a component of fungal cell membranes. However, they can also inhibit the P450 system in the liver, leading to potential liver toxicity. Amphotericin B binds with ergosterol to form a transmembrane channel that causes leakage of monovalent ions, but it can also cause nephrotoxicity and flu-like symptoms. Terbinafine inhibits squalene epoxidase, while griseofulvin interacts with microtubules to disrupt mitotic spindle. However, griseofulvin can induce the P450 system and is teratogenic. Flucytosine is converted by cytosine deaminase to 5-fluorouracil, which inhibits thymidylate synthase and disrupts fungal protein synthesis, but it can cause vomiting. Caspofungin inhibits the synthesis of beta-glucan, a major fungal cell wall component, and can cause flushing. Nystatin binds with ergosterol to form a transmembrane channel that causes leakage of monovalent ions, but it is very toxic and can only be used topically, such as for oral thrush.

    • This question is part of the following fields:

      • General Principles
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  • Question 30 - Which vessel contributes the most to the arterial supply of the breast? ...

    Incorrect

    • Which vessel contributes the most to the arterial supply of the breast?

      Your Answer:

      Correct Answer: Internal mammary artery

      Explanation:

      The internal mammary artery is the primary source of arterial supply to the breast, with the external mammary and lateral thoracic arteries playing a smaller role. This information is relevant for surgeons performing reduction mammoplasty surgeries.

      The breast is situated on a layer of pectoral fascia and is surrounded by the pectoralis major, serratus anterior, and external oblique muscles. The nerve supply to the breast comes from branches of intercostal nerves from T4-T6, while the arterial supply comes from the internal mammary (thoracic) artery, external mammary artery (laterally), anterior intercostal arteries, and thoraco-acromial artery. The breast’s venous drainage is through a superficial venous plexus to subclavian, axillary, and intercostal veins. Lymphatic drainage occurs through the axillary nodes, internal mammary chain, and other lymphatic sites such as deep cervical and supraclavicular fossa (later in disease).

      The preparation for lactation involves the hormones oestrogen, progesterone, and human placental lactogen. Oestrogen promotes duct development in high concentrations, while high levels of progesterone stimulate the formation of lobules. Human placental lactogen prepares the mammary glands for lactation. The two hormones involved in stimulating lactation are prolactin and oxytocin. Prolactin causes milk secretion, while oxytocin causes contraction of the myoepithelial cells surrounding the mammary alveoli to result in milk ejection from the breast. Suckling of the baby stimulates the mechanoreceptors in the nipple, resulting in the release of both prolactin and oxytocin from the pituitary gland (anterior and posterior parts respectively).

    • This question is part of the following fields:

      • Reproductive System
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SESSION STATS - PERFORMANCE PER SPECIALTY

Cardiovascular System (0/1) 0%
General Principles (1/1) 100%
Gastrointestinal System (1/1) 100%
Neurological System (1/1) 100%
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