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  • Question 1 - Which statement about steroid receptors is accurate? ...

    Incorrect

    • Which statement about steroid receptors is accurate?

      Your Answer: The oestrogen receptor is an example of a steroid receptor that can be found in the cytoplasm

      Correct Answer: Receptors have a DNA binding domain

      Explanation:

      Steroid Receptors

      Steroid receptors are composed of three main domains: ligand binding, DNA binding, and transcription activation. These receptors are typically found in the cytoplasm and are only translocated to the nucleus after binding with a ligand. However, the oestrogen receptor is an exception to this rule, as it is constitutively found in the nucleus.

      In summary, steroid receptors are essential for the regulation of gene expression. They are composed of three domains and are typically found in the cytoplasm. However, the oestrogen receptor is an exception to this rule, as it is always found in the nucleus. the function of steroid receptors is crucial for developing treatments for various diseases.

    • This question is part of the following fields:

      • Pharmacology
      23
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  • Question 2 - A 50-year-old male is brought to the trauma unit following a car accident,...

    Incorrect

    • A 50-year-old male is brought to the trauma unit following a car accident, with an estimated blood loss of 1200ml. His vital signs are as follows: heart rate of 125 beats per minute, blood pressure of 125/100 mmHg, and he feels cold to the touch.

      Which component of his cardiovascular system has played the biggest role in maintaining his blood pressure stability?

      Your Answer: Veins

      Correct Answer: Arterioles

      Explanation:

      The highest resistance in the cardiovascular system is found in the arterioles, which means they contribute the most to the total peripheral resistance. In cases of compensated hypovolaemic shock, such as in this relatively young patient, the body compensates by increasing heart rate and causing peripheral vasoconstriction to maintain blood pressure.

      Arteriole vasoconstriction in hypovolaemic shock patients leads to an increase in total peripheral resistance, which in turn increases mean arterial blood pressure. This has a greater effect on diastolic blood pressure, resulting in a narrowing of pulse pressure and clinical symptoms such as cold peripheries and delayed capillary refill time.

      Capillaries are microscopic channels that provide blood supply to the tissues and are the primary site for gas and nutrient exchange. Venules, on the other hand, are small veins with diameters ranging from 8-100 micrometers and join multiple capillaries exiting from a capillary bed.

      The heart has four chambers and generates pressures of 0-25 mmHg on the right side and 0-120 mmHg on the left. The cardiac output is the product of heart rate and stroke volume, typically 5-6L per minute. The cardiac impulse is generated in the sino atrial node and conveyed to the ventricles via the atrioventricular node. Parasympathetic and sympathetic fibers project to the heart via the vagus and release acetylcholine and noradrenaline, respectively. The cardiac cycle includes mid diastole, late diastole, early systole, late systole, and early diastole. Preload is the end diastolic volume and afterload is the aortic pressure. Laplace’s law explains the rise in ventricular pressure during the ejection phase and why a dilated diseased heart will have impaired systolic function. Starling’s law states that an increase in end-diastolic volume will produce a larger stroke volume up to a point beyond which stroke volume will fall. Baroreceptor reflexes and atrial stretch receptors are involved in regulating cardiac output.

    • This question is part of the following fields:

      • Cardiovascular System
      55.3
      Seconds
  • Question 3 - A 35-year-old man is in a car crash and is brought to the...

    Incorrect

    • A 35-year-old man is in a car crash and is brought to the emergency department. He is stable at first and a catheter is inserted. However, one minute later he experiences hypotension and develops angioedema around his penis. What is the probable cause of this occurrence?

      Your Answer:

      Correct Answer: Type I latex hypersensitivity reaction

      Explanation:

      Classification of Hypersensitivity Reactions

      Hypersensitivity reactions are classified into four types according to the Gell and Coombs classification. Type I, also known as anaphylactic hypersensitivity, occurs when an antigen reacts with IgE bound to mast cells. This type of reaction is commonly seen in atopic conditions such as asthma, eczema, and hay fever. Type II hypersensitivity occurs when cell-bound IgG or IgM binds to an antigen on the cell surface, leading to autoimmune conditions such as autoimmune hemolytic anemia, ITP, and Goodpasture’s syndrome. Type III hypersensitivity occurs when free antigen and antibody (IgG, IgA) combine to form immune complexes, leading to conditions such as serum sickness, systemic lupus erythematosus, and post-streptococcal glomerulonephritis. Type IV hypersensitivity is T-cell mediated and includes conditions such as tuberculosis, graft versus host disease, and allergic contact dermatitis.

      In recent times, a fifth category has been added to the classification of hypersensitivity reactions. Type V hypersensitivity occurs when antibodies recognize and bind to cell surface receptors, either stimulating them or blocking ligand binding. This type of reaction is seen in conditions such as Graves’ disease and myasthenia gravis. Understanding the classification of hypersensitivity reactions is important in the diagnosis and management of these conditions.

    • This question is part of the following fields:

      • General Principles
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  • Question 4 - A 3-year-old girl is brought to the emergency department due to severe abdominal...

    Incorrect

    • A 3-year-old girl is brought to the emergency department due to severe abdominal pain. She has tenderness throughout her abdomen, but it is especially painful in the right iliac fossa. Her parents are concerned because they noticed blood in her stool earlier today.

      The patient is admitted and receives appropriate treatment. Further investigations reveal the presence of ectopic ileal mucosa.

      What is the probable underlying condition?

      Your Answer:

      Correct Answer: Meckel's diverticulum

      Explanation:

      Meckel’s diverticulum is the most likely diagnosis for this child’s symptoms. It is a congenital condition that affects about 2% of the population and typically presents with symptoms around the age of 2. Some children with Meckel’s diverticulum may develop diverticulitis, which can be mistaken for appendicitis. The presence of ectopic ileal mucosa is a key factor in diagnosing Meckel’s diverticulum.

      Appendicitis is an unlikely diagnosis as it would not explain the presence of ectopic ileal mucosa. Duodenal atresia is also unlikely as it typically presents in newborns and is associated with Down’s syndrome. Necrotising enterocolitis is another unlikely diagnosis as it primarily affects premature infants and would not explain the ectopic ileal mucosa.

      Meckel’s diverticulum is a congenital diverticulum of the small intestine that is a remnant of the omphalomesenteric duct. It occurs in 2% of the population, is 2 feet from the ileocaecal valve, and is 2 inches long. It is usually asymptomatic but can present with abdominal pain, rectal bleeding, or intestinal obstruction. Investigation includes a Meckel’s scan or mesenteric arteriography. Management involves removal if narrow neck or symptomatic, with options between wedge excision or formal small bowel resection and anastomosis. Meckel’s diverticulum is typically lined by ileal mucosa but ectopic gastric, pancreatic, and jejunal mucosa can also occur.

    • This question is part of the following fields:

      • Gastrointestinal System
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  • Question 5 - A 72-year-old male is admitted with central chest pain. He reports that the...

    Incorrect

    • A 72-year-old male is admitted with central chest pain. He reports that the pain occurs during physical activity and subsides with rest. He has a medical history of hypertension.

      ECG results:

      ECG T wave inversion in V4-V6

      Blood results:

      Troponin I 0.02 ng/ml (normal <0.07)

      What is the molecule that troponin I attaches to?

      Your Answer:

      Correct Answer: Actin

      Explanation:

      Troponin I functions by binding to actin and securing the troponin-tropomyosin complex in place.

      The clinical presentation suggests stable angina, with further evidence of ischemic heart disease seen in the T wave inversion in the lateral leads. The absence of elevated troponin I levels rules out a myocardial infarction.

      Cardiac myocytes lack a neuromuscular junction and instead communicate with each other through gap junctions.

      Calcium ions bind to troponin C.

      Myosin constitutes the thick filament in muscle fibers, while actin slides along myosin to generate muscle contraction.

      The sarcoplasmic reticulum plays a crucial role in regulating the concentration of calcium ions in the cytoplasm of striated muscle cells.

      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
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  • Question 6 - A 50-year-old man visits the clinic with a complaint of gradual hearing loss...

    Incorrect

    • A 50-year-old man visits the clinic with a complaint of gradual hearing loss over the past nine months. He works in construction and initially attributed it to the use of loud power tools, despite always wearing ear protection. He also reports experiencing a high-pitched ringing in his ears for the same duration. Recently, he has been experiencing episodes of dizziness where he feels like the room is spinning. Otoscopy reveals no abnormalities. During the Rinne and Weber tests, the Rinne test is positive bilaterally, and the sound is louder on the left. What conclusions can be drawn from these findings?

      Your Answer:

      Correct Answer: Sensorineural hearing loss on the right.

      Explanation:

      The patient in the question has a sensorineural hearing loss on the right side. The Rinne and Weber tests were used to determine the type and affected side of the hearing loss. The Rinne test was positive bilaterally, indicating normal hearing or a sensorineural deficit on one or both sides. The Weber test was heard better on the left, indicating a conductive hearing loss on the left or a sensorineural hearing loss on the right. As a conductive hearing loss was ruled out with the Rinne test, the patient must have a right-sided sensorineural deficit. This is suggestive of a vestibular schwannoma, a benign tumor of the vestibulocochlear nerve, which can cause gradual unilateral hearing loss, tinnitus, and vertigo.

      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 7 - A 10-year-old boy is rushed to the emergency department following a seizure. According...

    Incorrect

    • A 10-year-old boy is rushed to the emergency department following a seizure. According to his mother, the twitching started in his right hand while he was having breakfast, then spread to his arm and face, and eventually affected his entire body. The seizure lasted for a few minutes, and afterward, he felt groggy and had no recollection of what happened.

      Which part of the boy's brain was impacted by the seizure?

      Your Answer:

      Correct Answer: Frontal lobe

      Explanation:

      The correct location for a seizure with progressive clonic movements travelling from a distal site (fingers) proximally, known as a Jacksonian march, is the frontal lobe. Seizures in the occipital lobe present with visual disturbances, while seizures in the parietal lobe result in sensory changes and seizures in the temporal lobe present with hallucinations and automatisms. Absence seizures are associated with the thalamus and are characterized by brief losses of consciousness without postictal fatigue or grogginess.

      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 8 - A 19-year-old male is hospitalized due to haemoptysis and reports a recent change...

    Incorrect

    • A 19-year-old male is hospitalized due to haemoptysis and reports a recent change in urine color to brown. Upon examination, his blood pressure is found to be 170/110. A kidney biopsy confirms the diagnosis of Goodpasture's syndrome through positive staining for autoantibodies. What type of collagen is targeted by the patient's autoantibodies?

      Your Answer:

      Correct Answer: Collagen type 4

      Explanation:

      Autoantibodies against collagen type IV are responsible for the development of Goodpasture’s syndrome, which is characterized by defective collagen IV. Meanwhile, Ehlers-Danlos syndrome is primarily caused by a genetic defect in collagen type III, with a less common variant affecting collagen type V. Osteogenesis imperfecta, on the other hand, is characterized by defective collagen type I.

      Understanding Collagen and its Associated Disorders

      Collagen is a vital protein found in connective tissue and is the most abundant protein in the human body. Although there are over 20 types of collagen, the most important ones are types I, II, III, IV, and V. Collagen is composed of three polypeptide strands that are woven into a helix, with numerous hydrogen bonds providing additional strength. Vitamin C plays a crucial role in establishing cross-links, and fibroblasts synthesize collagen.

      Disorders of collagen can range from acquired defects due to aging to rare congenital disorders. Osteogenesis imperfecta is a congenital disorder that has eight subtypes and is caused by a defect in type I collagen. Patients with this disorder have bones that fracture easily, loose joints, and other defects depending on the subtype. Ehlers Danlos syndrome is another congenital disorder that has multiple subtypes and is caused by an abnormality in types 1 and 3 collagen. Patients with this disorder have features of hypermobility and are prone to joint dislocations and pelvic organ prolapse, among other connective tissue defects.

    • This question is part of the following fields:

      • General Principles
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  • Question 9 - A 32-year-old woman arrives at the emergency department feeling ill with pain in...

    Incorrect

    • A 32-year-old woman arrives at the emergency department feeling ill with pain in her upper abdomen that spreads to her back, but is relieved when she leans forward. Her blood test shows elevated levels of serum amylase and lipase. She had been diagnosed with a viral infection a week ago.

      What type of viral infection is linked to an increased likelihood of her current symptoms?

      Your Answer:

      Correct Answer: Mumps virus

      Explanation:

      Acute pancreatitis can be caused by mumps virus.

      The symptoms described in the scenario are consistent with acute pancreatitis. The mnemonic ‘I GET SMASHED’ is a helpful tool for identifying risk factors for this condition, and mumps virus is included in this list.

      While hepatitis B and C viruses have been associated with cases of pancreatitis, they are not known to directly cause the condition. influenzae virus is also not a known cause of acute pancreatitis.

      However, mumps virus is a known cause of acute pancreatitis. In addition to symptoms of pancreatitis, patients may also experience other symptoms of mumps virus. The severity of the pancreatitis is typically mild in these cases.

      Acute pancreatitis is a condition that is primarily caused by gallstones and alcohol consumption in the UK. However, there are other factors that can contribute to the development of this condition. A popular mnemonic used to remember these factors is GET SMASHED, which stands for gallstones, ethanol, trauma, steroids, mumps, autoimmune diseases, scorpion venom, hypertriglyceridaemia, hyperchylomicronaemia, hypercalcaemia, hypothermia, ERCP, and certain drugs. It is important to note that pancreatitis is seven times more common in patients taking mesalazine than sulfasalazine. CT scans can show diffuse parenchymal enlargement with oedema and indistinct margins in patients with acute pancreatitis.

    • This question is part of the following fields:

      • Gastrointestinal System
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  • Question 10 - A 23-year-old man is hit in the head while playing rugby. He experiences...

    Incorrect

    • A 23-year-old man is hit in the head while playing rugby. He experiences a temporary concussion but later regains consciousness. After thirty minutes, he begins to exhibit slurred speech, ataxia, and eventually loses consciousness. Upon arrival at the hospital, he is intubated and put on a ventilator. A CT scan reveals the presence of an extradural hematoma. What is the probable cause of this condition?

      Your Answer:

      Correct Answer: Middle meningeal artery laceration

      Explanation:

      The middle meningeal artery is the vessel most likely to result in an acute Extradural haemorrhage, while the anterior and middle cerebral arteries may cause acute Subdural haemorrhage. It is worth noting that acute Subdural haemorrhages tend to take a bit longer to develop compared to acute Extradural haemorrhages.

      The Middle Meningeal Artery: Anatomy and Clinical Significance

      The middle meningeal artery is a branch of the maxillary artery, which is one of the two terminal branches of the external carotid artery. It is the largest of the three arteries that supply the meninges, the outermost layer of the brain. The artery runs through the foramen spinosum and supplies the dura mater. It is located beneath the pterion, where the skull is thin, making it vulnerable to injury. Rupture of the artery can lead to an Extradural hematoma.

      In the dry cranium, the middle meningeal artery creates a deep indentation in the calvarium. It is intimately associated with the auriculotemporal nerve, which wraps around the artery. This makes the two structures easily identifiable in the dissection of human cadavers and also easily damaged in surgery.

      Overall, understanding the anatomy and clinical significance of the middle meningeal artery is important for medical professionals, particularly those involved in neurosurgery.

    • This question is part of the following fields:

      • Neurological System
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  • Question 11 - A 36-year-old woman presents to her general practitioner with sudden-onset painful red-eye and...

    Incorrect

    • A 36-year-old woman presents to her general practitioner with sudden-onset painful red-eye and blurred vision in her left eye. She reports that the pain started suddenly while she was out for lunch with her friends. On examination, a hypopyon is present in the left eye, which is also red and has a small and irregularly shaped pupil. Ophthalmoscopy cannot be performed due to photophobia. The patient is diagnosed with anterior uveitis. What medical history might be observed in this patient's past?

      Your Answer:

      Correct Answer: Ankylosing spondylitis

      Explanation:

      The patient in this scenario is likely suffering from anterior uveitis, which is characterized by inflammation of the ciliary body and iris. Symptoms include a red and painful eye, irregularly shaped pupil, and the presence of a hypopyon. Anterior uveitis is commonly associated with the HLA-B27 haplotype. The correct answer to the question about conditions associated with anterior uveitis is ankylosing spondylitis, which is the only condition mentioned that has a known association with HLA-B27. Coeliac disease, Goodpasture’s syndrome, and haemochromatosis are all incorrect answers as they do not have an association with HLA-B27.

      Anterior uveitis, also known as iritis, is a type of inflammation that affects the iris and ciliary body in the front part of the uvea. This condition is often associated with HLA-B27 and may be linked to other conditions such as ankylosing spondylitis, reactive arthritis, ulcerative colitis, Crohn’s disease, Behcet’s disease, and sarcoidosis. Symptoms of anterior uveitis include sudden onset of eye discomfort and pain, small and irregular pupils, intense sensitivity to light, blurred vision, redness in the eye, tearing, and a ring of redness around the cornea. In severe cases, pus and inflammatory cells may accumulate in the front chamber of the eye, leading to a visible fluid level. Treatment for anterior uveitis involves urgent evaluation by an ophthalmologist, cycloplegic agents to relieve pain and photophobia, and steroid eye drops to reduce inflammation.

    • This question is part of the following fields:

      • Neurological System
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  • Question 12 - A 25-year-old female presents to her primary care physician complaining of fatigue and...

    Incorrect

    • A 25-year-old female presents to her primary care physician complaining of fatigue and dizziness. She has a medical history of anxiety, binge-drinking, bulimia nervosa, and self-harm.

      During the examination, the patient appears pale, and mild organomegaly is detected upon palpation of her abdomen.

      The following laboratory results were obtained:
      - Hemoglobin (Hb): 78 g/l
      - Platelets: 200 * 109/l
      - White blood cells (WBC): 5 * 109/l
      - Mean corpuscular volume (MCV): 76
      - Bone marrow aspirate: Sideroblasts present

      What could be the underlying cause of her symptoms?

      Your Answer:

      Correct Answer: Vitamin B6 deficiency

      Explanation:

      Sideroblastic anaemia can be caused by a deficiency in Vitamin B6. Other deficiencies and their associated features include muscle weakness and anergia for Vitamin B1 (thiamine), bleeding gums and prolonged wound healing for Vitamin C, alopecia and dermatitis for Vitamin B7 (biotin), and pellagra, diarrhoea, and dermatitis for Vitamin B3 (niacin). Additionally, a deficiency in Vitamin B6 can lead to seizures due to its role as a cofactor in the synthesis of GABA, as well as peripheral neuropathy.

      The Importance of Vitamin B6 in the Body

      Vitamin B6 is a type of water-soluble vitamin that belongs to the B complex group. Once it enters the body, it is converted into pyridoxal phosphate (PLP), which acts as a cofactor for various biochemical reactions such as transamination, deamination, and decarboxylation. These reactions are essential for the proper functioning of the body.

      However, a deficiency in vitamin B6 can lead to various health problems such as peripheral neuropathy and sideroblastic anemia. One of the common causes of vitamin B6 deficiency is isoniazid therapy, which is used to treat tuberculosis. Therefore, it is important to ensure that the body receives an adequate amount of vitamin B6 to maintain optimal health.

    • This question is part of the following fields:

      • General Principles
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  • Question 13 - A 7-year-old boy is diagnosed by his pediatrician with a condition characterized by...

    Incorrect

    • A 7-year-old boy is diagnosed by his pediatrician with a condition characterized by a slightly low mean corpuscular volume (MCV) and a haemoglobin at the lower end of normal. Upon full investigation, it is discovered that he is missing a gene for one of his four alpha globin alleles. The doctor explains the condition to the boy and his parents, writing (aa/a-) to describe it. What is the name of this condition?

      Your Answer:

      Correct Answer: Silent carrier (alpha(+) heterozygous)

      Explanation:

      There are five potential disease phenotypes of alpha thalassaemia based on the number of faulty or missing globin alleles in a patient’s genotype. These include silent carrier (alpha(+) heterozygous) for one missing allele, alpha thalassaemia trait: alpha(0) heterozygous for two missing alleles, alpha thalassaemia trait: alpha(+) homozygous for two missing alleles, haemoglobin H disease for three missing alleles, and (–/–) for four missing alleles.

      Understanding Alpha-Thalassaemia

      Alpha-thalassaemia is a genetic disorder that results from a deficiency of alpha chains in haemoglobin. The condition is caused by a mutation in the alpha-globulin genes located on chromosome 16. The severity of the disease depends on the number of alpha globulin alleles affected. If one or two alleles are affected, the blood picture would be hypochromic and microcytic, but the haemoglobin level would typically be normal. However, if three alleles are affected, it results in a hypochromic microcytic anaemia with splenomegaly, which is known as Hb H disease. In the case of all four alleles being affected, which is known as homozygote, it can lead to death in utero, also known as hydrops fetalis or Bart’s hydrops. Understanding the different levels of severity of alpha-thalassaemia is crucial in diagnosing and managing the condition.

    • This question is part of the following fields:

      • Haematology And Oncology
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  • Question 14 - You have been tasked with exploring the feasibility of establishing a program to...

    Incorrect

    • You have been tasked with exploring the feasibility of establishing a program to assist elderly patients with multiple sclerosis in the community. What is the primary consideration in determining the amount of resources needed?

      Your Answer:

      Correct Answer: Prevalence

      Explanation:

      Understanding Incidence and Prevalence

      Incidence and prevalence are two terms used to describe the frequency of a condition in a population. The incidence refers to the number of new cases per population in a given time period, while the prevalence refers to the total number of cases per population at a particular point in time. Prevalence can be further divided into point prevalence and period prevalence, depending on the time frame used to measure it.

      To calculate prevalence, one can use the formula prevalence = incidence * duration of condition. This means that in chronic diseases, the prevalence is much greater than the incidence, while in acute diseases, the prevalence and incidence are similar. For example, the incidence of the common cold may be greater than its prevalence.

      Understanding the difference between incidence and prevalence is important in epidemiology and public health, as it helps to identify the burden of a disease in a population and inform healthcare policies and interventions. By measuring both incidence and prevalence, researchers can track the spread of a disease over time and assess the effectiveness of prevention and treatment strategies.

    • This question is part of the following fields:

      • General Principles
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  • Question 15 - By what means do viruses enter human cells? ...

    Incorrect

    • By what means do viruses enter human cells?

      Your Answer:

      Correct Answer: Specific surface protein-protein interaction

      Explanation:

      How Viruses Enter Cells

      Viruses have specific proteins on their surface that bind to cell surface proteins, allowing them to enter the cell and release their genomic material. Sometimes, the viral genomic material is injected through a protein channel, while the capsid remains outside the cell. In other cases, the entire virus enters the cell. Viruses only cause membrane lysis when they have multiplied inside cells and kill them to release viral particles.

      The viral envelope is formed when virus particles bud off from cells, taking some membrane with them. While it can play a role in permitting viral entry, a protein-protein interaction must still occur for the capsid and genome to enter. Viruses are too large to pass through cell membrane pores.

    • This question is part of the following fields:

      • Microbiology
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  • Question 16 - A 68-year-old woman comes into the emergency department with her daughter after experiencing...

    Incorrect

    • A 68-year-old woman comes into the emergency department with her daughter after experiencing shortness of breath for 2 hours. She is in poor condition with a heart rate of 128/min, blood pressure of 90/66 mmHg, O2 saturation of 94% on air, respiratory rate of 29/min, and temperature of 36.3ºC. Her legs are swollen up to her knees, and her JVP is visible at her ear lobe. She has a history of myocardial infarction 4 years ago, angina, and a smoking history of 20 packs per year.

      What is the underlying cause of her presentation?

      Your Answer:

      Correct Answer: Reduced cardiac output

      Explanation:

      The cause of the patient’s acute heart failure is a decrease in cardiac output, which may be due to biventricular failure. This is evidenced by peripheral edema and respiratory distress, including shortness of breath, high respiratory rate, and low oxygen saturation. These symptoms are likely caused by inadequate heart filling, leading to peripheral congestion and pulmonary edema or pleural effusion.

      The pathophysiology of myocardial infarction is not relevant to the patient’s condition, as it is not explained by her peripheral edema and elevated JVP.

      While shortness of breath in heart failure may be caused by reduced ventilation/perfusion due to pulmonary edema, this is only one symptom and not the underlying mechanism of the condition.

      The overactivity of the renin-angiotensin system is a physiological response to decreased blood pressure or increased renal sympathetic firing, but it is not necessarily related to the patient’s current condition.

      Understanding Acute Heart Failure: Symptoms and Diagnosis

      Acute heart failure (AHF) is a medical emergency that can occur suddenly or worsen over time. It can affect individuals with or without a history of pre-existing heart failure. Decompensated AHF is more common and is characterized by a background history of HF. AHF is typically caused by a reduced cardiac output resulting from a functional or structural abnormality. De-novo heart failure, on the other hand, is caused by increased cardiac filling pressures and myocardial dysfunction, usually due to ischaemia.

      The most common precipitating causes of acute AHF are acute coronary syndrome, hypertensive crisis, acute arrhythmia, and valvular disease. Patients with heart failure may present with signs of fluid congestion, weight gain, orthopnoea, and breathlessness. They are broadly classified into four groups based on whether they present with or without hypoperfusion and fluid congestion. This classification is clinically useful in determining the therapeutic approach.

      The symptoms of AHF include breathlessness, reduced exercise tolerance, oedema, fatigue, chest signs, and an S3-heart sound. Signs of AHF include cyanosis, tachycardia, elevated jugular venous pressure, and a displaced apex beat. Over 90% of patients with AHF have a normal or increased blood pressure.

      The diagnostic workup for patients with AHF includes blood tests, chest X-ray, echocardiogram, and B-type natriuretic peptide. Blood tests are used to identify any underlying abnormalities, while chest X-ray findings include pulmonary venous congestion, interstitial oedema, and cardiomegaly. Echocardiogram is used to identify pericardial effusion and cardiac tamponade, while raised levels of B-type natriuretic peptide (>100mg/litre) indicate myocardial damage and support the diagnosis.

    • This question is part of the following fields:

      • Cardiovascular System
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  • Question 17 - A 25-year-old male is at the doctor's office with his girlfriend, reporting that...

    Incorrect

    • A 25-year-old male is at the doctor's office with his girlfriend, reporting that she sleepwalks at night. During which stage of the sleep cycle is this most likely to happen?

      Your Answer:

      Correct Answer: Non-REM stage 3 (N3)

      Explanation:

      Understanding Sleep Stages: The Sleep Doctor’s Brain

      Sleep is a complex process that involves different stages, each with its own unique characteristics. The Sleep Doctor’s Brain provides a simplified explanation of the four main sleep stages: N1, N2, N3, and REM.

      N1 is the lightest stage of sleep, characterized by theta waves and often associated with hypnic jerks. N2 is a deeper stage of sleep, marked by sleep spindles and K-complexes. This stage represents around 50% of total sleep. N3 is the deepest stage of sleep, characterized by delta waves. Parasomnias such as night terrors, nocturnal enuresis, and sleepwalking can occur during this stage.

      REM, or rapid eye movement, is the stage where dreaming occurs. It is characterized by beta-waves and a loss of muscle tone, including erections. The sleep cycle typically follows a pattern of N1 → N2 → N3 → REM, with each stage lasting for different durations throughout the night.

      Understanding the different sleep stages is important for maintaining healthy sleep habits and identifying potential sleep disorders. By monitoring brain activity during sleep, the Sleep Doctor’s Brain can provide valuable insights into the complex process of sleep.

    • This question is part of the following fields:

      • Neurological System
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  • Question 18 - A baby girl is born at 38 weeks gestation. She is healthy at...

    Incorrect

    • A baby girl is born at 38 weeks gestation. She is healthy at birth with no issues noted and no concerns from the obstetrics team.

      Fifteen days later, the mother notices that the baby's eye is stuck closed with discharge, along with a reddening of the sclera and swelling of the eyelids. The baby is taken to the Pediatrician's office. A diagnosis of ophthalmia neonatorum is suspected and tests are done to confirm this.

      What are the two bacteria that are most likely to be identified by the tests?

      Your Answer:

      Correct Answer: Chlamydia trachomatis and Neisseria gonorrhoeae

      Explanation:

      The most frequent culprits behind ophthalmia neonatorum are Chlamydia trachomatis and Neisseria gonorrhoeae, with the former being more prevalent. Typically, these two organisms manifest at different stages and necessitate distinct antibiotic treatments. Although less frequent, mixed infections can also occur. While the remaining choices may cause ophthalmia neonatorum, they are not as commonly observed.

      Understanding Ophthalmia Neonatorum

      Ophthalmia neonatorum is a term used to describe an infection that affects the eyes of newborn babies. This condition is caused by two main organisms, namely Chlamydia trachomatis and Neisseria gonorrhoeae. It is important to note that suspected cases of ophthalmia neonatorum should be referred for immediate ophthalmology or paediatric assessment.

      To prevent complications, it is crucial to identify and treat ophthalmia neonatorum as soon as possible. This condition can cause severe damage to the eyes and even lead to blindness if left untreated. Therefore, parents and healthcare providers should be vigilant and seek medical attention if they notice any signs of eye infection in newborns. With prompt diagnosis and treatment, the prognosis for ophthalmia neonatorum is generally good.

    • This question is part of the following fields:

      • General Principles
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  • Question 19 - A 20-year-old female presents with frequent bruising and bleeding gums, prompting concern for...

    Incorrect

    • A 20-year-old female presents with frequent bruising and bleeding gums, prompting concern for the extrinsic pathway of coagulation. What tests would you order to investigate this?

      Your Answer:

      Correct Answer: Prothrombin time (PT)

      Explanation:

      The prothrombin time (PT) is used to assess the extrinsic pathway of the clotting cascade, while the activated partial thromboplastin time (aPTT) is used to assess the intrinsic pathway. The thrombin time is used to assess fibrin formation. A 50:50 mixing study is used to determine if a prolonged PT or aPTT is due to factor deficiency or a factor inhibitor.

      The Coagulation Cascade: Two Pathways to Fibrin Formation

      The coagulation cascade is a complex process that leads to the formation of a blood clot. There are two pathways that can lead to fibrin formation: the intrinsic pathway and the extrinsic pathway. The intrinsic pathway involves components that are already present in the blood and has a minor role in clotting. It is initiated by subendothelial damage, such as collagen, which leads to the formation of the primary complex on collagen by high-molecular-weight kininogen (HMWK), prekallikrein, and Factor 12. This complex activates Factor 11, which in turn activates Factor 9. Factor 9, along with its co-factor Factor 8a, forms the tenase complex, which activates Factor 10.

      The extrinsic pathway, on the other hand, requires tissue factor released by damaged tissue. This pathway is initiated by tissue damage, which leads to the binding of Factor 7 to tissue factor. This complex activates Factor 9, which works with Factor 8 to activate Factor 10. Both pathways converge at the common pathway, where activated Factor 10 causes the conversion of prothrombin to thrombin. Thrombin hydrolyses fibrinogen peptide bonds to form fibrin and also activates factor 8 to form links between fibrin molecules.

      Finally, fibrinolysis occurs, which is the process of clot resorption. Plasminogen is converted to plasmin to facilitate this process. It is important to note that certain factors are involved in both pathways, such as Factor 10, and that some factors are vitamin K dependent, such as Factors 2, 7, 9, and 10. The intrinsic pathway can be assessed by measuring the activated partial thromboplastin time (APTT), while the extrinsic pathway can be assessed by measuring the prothrombin time (PT).

    • This question is part of the following fields:

      • Haematology And Oncology
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  • Question 20 - A 87-year-old male with chronic untreated hypertension arrives at the emergency department complaining...

    Incorrect

    • A 87-year-old male with chronic untreated hypertension arrives at the emergency department complaining of chest pain. Upon examination of his ECG, it is observed that there are tall QRS complexes throughout the entire ECG with elevated R-waves in the left-sided leads. What condition does this suggest?

      Your Answer:

      Correct Answer: Left ventricular hypertrophy (LVF)

      Explanation:

      ST elevation is expected in the leads corresponding to the affected part of the heart in an STEMI, while ST depression, T wave inversion, or no change is expected in an NSTEMI or angina. Dilated cardiomyopathy does not have any classical ECG changes, and it is not commonly associated with hypertension as LVF. LVF, on the other hand, causes left ventricular hypertrophy due to prolonged hypertension, resulting in an increase in R-wave amplitude in leads 1, aVL, and V4-6, as well as an increase in S wave depth in leads III, aVR, and V1-3 on the right side.

      ECG Indicators of Atrial and Ventricular Hypertrophy

      Left ventricular hypertrophy is indicated on an ECG when the sum of the S wave in V1 and the R wave in V5 or V6 exceeds 40 mm. Meanwhile, right ventricular hypertrophy is characterized by a dominant R wave in V1 and a deep S wave in V6. In terms of atrial hypertrophy, left atrial enlargement is indicated by a bifid P wave in lead II with a duration of more than 120 ms, as well as a negative terminal portion in the P wave in V1. On the other hand, right atrial enlargement is characterized by tall P waves in both II and V1 that exceed 0.25 mV. These ECG indicators can help diagnose and monitor patients with atrial and ventricular hypertrophy.

    • This question is part of the following fields:

      • Cardiovascular System
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  • Question 21 - A 79-year-old male arrives at the emergency department with sudden onset right sided...

    Incorrect

    • A 79-year-old male arrives at the emergency department with sudden onset right sided hemiparesis. He has a medical history of hypertension and reports no changes to his vision, speech or hearing.

      What is the probable diagnosis?

      Your Answer:

      Correct Answer: Lacunar infarct

      Explanation:

      A lacunar stroke can lead to isolated hemiparesis, hemisensory loss, or hemiparesis with limb ataxia. In this case, the patient is experiencing isolated hemiparesis, which is likely caused by a lacunar infarct. Hypertension is strongly linked to this type of stroke.

      Weber’s syndrome results in CN III palsy on the same side as the stroke and weakness in the opposite limb.

      Nystagmus is a common symptom of Wallenberg syndrome.

      Ipsilateral deafness is a common symptom of lateral pontine syndrome.

      Stroke can affect different parts of the brain depending on which artery is affected. If the anterior cerebral artery is affected, the person may experience weakness and loss of sensation on the opposite side of the body, with the lower extremities being more affected than the upper. If the middle cerebral artery is affected, the person may experience weakness and loss of sensation on the opposite side of the body, with the upper extremities being more affected than the lower. They may also experience vision loss and difficulty with language. If the posterior cerebral artery is affected, the person may experience vision loss and difficulty recognizing objects.

      Lacunar strokes are a type of stroke that are strongly associated with hypertension. They typically present with isolated weakness or loss of sensation on one side of the body, or weakness with difficulty coordinating movements. They often occur in the basal ganglia, thalamus, or internal capsule.

    • This question is part of the following fields:

      • Neurological System
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  • Question 22 - Regarding the placebo effect, which of the following is true? ...

    Incorrect

    • Regarding the placebo effect, which of the following is true?

      Your Answer:

      Correct Answer: The effects of placebos tend to be short lived

      Explanation:

      Understanding the Placebo Effect

      The placebo effect refers to the phenomenon where a patient experiences an improvement in their condition after receiving an inert substance or treatment that has no inherent pharmacological activity. This can include a sugar pill or a sham procedure that mimics a real medical intervention. The placebo effect is influenced by various factors, such as the perceived strength of the treatment, the status of the treating professional, and the patient’s expectations.

      It is important to note that the placebo effect is not the same as receiving no care, as patients who maintain contact with medical services tend to have better outcomes. The placebo response is also greater in mild illnesses and can be difficult to separate from spontaneous remission. Patients who enter randomized controlled trials (RCTs) are often acutely unwell, and their symptoms may improve regardless of the intervention.

      The placebo effect has been extensively studied in depression, where it tends to be abrupt and early in treatment, and less likely to persist compared to improvement from antidepressants. Placebo sag refers to a situation where the placebo effect is diminished with repeated use.

      Overall, the placebo effect is a complex phenomenon that is influenced by various factors and can have significant implications for medical research and treatment. Understanding the placebo effect can help healthcare professionals provide better care and improve patient outcomes.

    • This question is part of the following fields:

      • General Principles
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  • Question 23 - A young man presents with polyuria, polydipsia and weight loss. He is subsequently...

    Incorrect

    • A young man presents with polyuria, polydipsia and weight loss. He is subsequently diagnosed with type 1 diabetes mellitus. What is he at an increased risk of developing?

      Your Answer:

      Correct Answer: Addison's disease, Grave's disease, coeliac disease

      Explanation:

      Type 1 diabetes is linked to other autoimmune disorders like Addison’s disease, Grave’s disease, and coeliac disease, due to its own autoimmune nature. The other choices are incorrect as they contain a non-autoimmune disorder.

      Understanding Diabetes Mellitus: A Basic Overview

      Diabetes mellitus is a chronic condition characterized by abnormally raised levels of blood glucose. It is one of the most common conditions encountered in clinical practice and represents a significant burden on the health systems of the developed world. The management of diabetes mellitus is crucial as untreated type 1 diabetes would usually result in death. Poorly treated type 1 diabetes mellitus can still result in significant morbidity and mortality. The main focus of diabetes management now is reducing the incidence of macrovascular and microvascular complications.

      There are different types of diabetes mellitus, including type 1 diabetes mellitus, type 2 diabetes mellitus, prediabetes, gestational diabetes, maturity onset diabetes of the young, latent autoimmune diabetes of adults, and other types. The presentation of diabetes mellitus depends on the type, with type 1 diabetes mellitus often presenting with weight loss, polydipsia, polyuria, and diabetic ketoacidosis. On the other hand, type 2 diabetes mellitus is often picked up incidentally on routine blood tests and presents with polydipsia and polyuria.

      There are four main ways to check blood glucose, including a finger-prick bedside glucose monitor, a one-off blood glucose, a HbA1c, and a glucose tolerance test. The diagnostic criteria are determined by WHO, with a fasting glucose greater than or equal to 7.0 mmol/l and random glucose greater than or equal to 11.1 mmol/l being diagnostic of diabetes mellitus. Management of diabetes mellitus involves drug therapy to normalize blood glucose levels, monitoring for and treating any complications related to diabetes, and modifying any other risk factors for other conditions such as cardiovascular disease. The first-line drug for the vast majority of patients with type 2 diabetes mellitus is metformin, with second-line drugs including sulfonylureas, gliptins, and pioglitazone. Insulin is used if oral medication is not controlling the blood glucose to a sufficient degree.

    • This question is part of the following fields:

      • Endocrine System
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  • Question 24 - A 35-year-old female who has previously had a colectomy for familial adenomatous polyposis...

    Incorrect

    • A 35-year-old female who has previously had a colectomy for familial adenomatous polyposis coli complains of a solid mass located at the lower part of her rectus abdominis muscle. What type of cell is commonly linked with these types of tumors?

      Your Answer:

      Correct Answer: Myofibroblasts

      Explanation:

      The most probable differential diagnosis in this case would be desmoid tumors, which involve the abnormal growth of myofibroblast cells.

      Desmoid tumours are growths that arise from musculoaponeurotic structures and are made up of clonal proliferations of myofibroblasts. They are typically firm and have a tendency to infiltrate surrounding tissue. These tumours are often seen in patients with familial adenomatous polyposis coli, and are most commonly found in women after childbirth in the rectus abdominis muscle. Bi allelic APC mutations are usually present in desmoid tumours.

      The preferred treatment for desmoid tumours is radical surgical resection, although radiotherapy and chemotherapy may be considered in some cases. Non-surgical therapy is generally less effective than surgical resection. In certain cases of abdominal desmoids, observation may be preferred as some tumours may spontaneously regress. However, desmoids have a high likelihood of local recurrence. These tumours consist of sheets of differentiated fibroblasts.

    • This question is part of the following fields:

      • Gastrointestinal System
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  • Question 25 - What is the most accurate definition of evidence-based medicine (EBM)? ...

    Incorrect

    • What is the most accurate definition of evidence-based medicine (EBM)?

      Your Answer:

      Correct Answer: EBM is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients

      Explanation:

      Evidence-Based Medicine

      Evidence-based medicine (EBM) is a widely accepted approach to healthcare decision-making that involves the conscientious, explicit, and judicious use of current best evidence. This approach integrates the best available evidence with individual patient preferences to make informed decisions about patient care. While economic analyses can help allocate resources in a cost-effective manner, critical appraisal of clinical research is also an essential element of EBM.

      EBM recognizes that high-quality randomized controlled trials and systematic reviews are valuable sources of evidence, but they are not the only sources. Practicing according to guidelines can be beneficial if the guidelines are evidence-based, but this is not always the case. Ultimately, the goal of EBM is to provide patients with the best possible care by using the most current and reliable evidence available while taking into account individual patient preferences and characteristics. By doing so, healthcare providers can make informed decisions that lead to better patient outcomes.

    • This question is part of the following fields:

      • Clinical Sciences
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  • Question 26 - A 35-year-old female presents with recurrent episodes of severe vertigo that have been...

    Incorrect

    • A 35-year-old female presents with recurrent episodes of severe vertigo that have been disabling. She experiences these episodes multiple times a day, with each one lasting for about 10-20 minutes. Along with the vertigo, she also experiences ringing in both ears, nausea, and vomiting. She has noticed a change in her hearing in both ears, with difficulty hearing at times and normal hearing at other times. Additionally, she reports increased pressure in her ears. During the examination, you notice a painless rash behind her ear that has been present for many years.

      What is the most likely diagnosis?

      Your Answer:

      Correct Answer: Meniere’s disease

      Explanation:

      Suspect Meniere’s disease in a patient presenting with vertigo, tinnitus, and fluctuating sensorineural hearing loss. Acoustic neuroma would present with additional symptoms such as facial numbness and loss of corneal reflex. Herpes Zoster Oticus (Ramsey Hunt syndrome) would present with facial palsy and a painless rash. Vestibular neuronitis would have longer episodes of vertigo, nausea, and vomiting, but no hearing loss. Benign paroxysmal positional vertigo would have brief episodes of vertigo after sudden head movements.

      Meniere’s disease is a condition that affects the inner ear and its cause is unknown. It is more commonly seen in middle-aged adults but can occur at any age and affects both men and women equally. The condition is characterized by the excessive pressure and progressive dilation of the endolymphatic system. The main symptoms of Meniere’s disease are recurrent episodes of vertigo, tinnitus, and sensorineural hearing loss. Vertigo is usually the most prominent symptom, but patients may also experience a sensation of aural fullness or pressure, nystagmus, and a positive Romberg test. These episodes can last from minutes to hours and are typically unilateral, but bilateral symptoms may develop over time.

      The natural history of Meniere’s disease is that symptoms usually resolve in the majority of patients after 5-10 years. However, most patients will be left with some degree of hearing loss, and psychological distress is common. ENT assessment is required to confirm the diagnosis, and patients should inform the DVLA as the current advice is to cease driving until satisfactory control of symptoms is achieved. Acute attacks can be managed with buccal or intramuscular prochlorperazine, and admission to the hospital may be required. Prevention strategies include the use of betahistine and vestibular rehabilitation exercises, which may be beneficial.

    • This question is part of the following fields:

      • Respiratory System
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  • Question 27 - A 30-year-old male comes to your clinic with a three-month history of abdominal...

    Incorrect

    • A 30-year-old male comes to your clinic with a three-month history of abdominal pain that is relieved by eating. You suspect a duodenal ulcer and plan to test for Helicobacter pylori infection using a urea breath test. He has no history of NSAID use and lives in a city where the prevalence of H. pylori is 40%. The sensitivity of the test is 96%, and the specificity is 92%. What is the likelihood ratio for a positive test result?

      Your Answer:

      Correct Answer: 12

      Explanation:

      The positive likelihood ratio of a test can be calculated using the formula: sensitivity divided by (1 minus specificity). This ratio is not affected by the prevalence of the disease. For example, if the sensitivity of a test is 0.96 and the specificity is 0.92, the positive likelihood ratio would be 12.

      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 28 - Which of the structures listed below are not located within the mediastinum? ...

    Incorrect

    • Which of the structures listed below are not located within the mediastinum?

      Your Answer:

      Correct Answer: Vertebral bodies

      Explanation:

      Both the lungs and vertebral bodies are located outside of the mediastinum.

      The mediastinum is the area located between the two pulmonary cavities and is covered by the mediastinal pleura. It extends from the thoracic inlet at the top to the diaphragm at the bottom. The mediastinum is divided into four regions: the superior mediastinum, middle mediastinum, posterior mediastinum, and anterior mediastinum.

      The superior mediastinum is the area between the manubriosternal angle and T4/5. It contains important structures such as the superior vena cava, brachiocephalic veins, arch of aorta, thoracic duct, trachea, oesophagus, thymus, vagus nerve, left recurrent laryngeal nerve, and phrenic nerve. The anterior mediastinum contains thymic remnants, lymph nodes, and fat. The middle mediastinum contains the pericardium, heart, aortic root, arch of azygos vein, and main bronchi. The posterior mediastinum contains the oesophagus, thoracic aorta, azygos vein, thoracic duct, vagus nerve, sympathetic nerve trunks, and splanchnic nerves.

      In summary, the mediastinum is a crucial area in the thorax that contains many important structures and is divided into four regions. Each region contains different structures that are essential for the proper functioning of the body.

    • This question is part of the following fields:

      • Respiratory System
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  • Question 29 - A saturation curve is created to demonstrate the impact of cyanide on the...

    Incorrect

    • A saturation curve is created to demonstrate the impact of cyanide on the function of cytochrome oxidase. As a non-competitive inhibitor of cytochrome oxidase, what will be the effect of cyanide on the enzyme's Km value?

      Your Answer:

      Correct Answer: No effect on Km

      Explanation:

      Enzyme kinetics is the study of how enzymes catalyze chemical reactions. Catalysts increase the rate of a chemical reaction without being consumed or altering the position of equilibrium between substrates and products. Enzyme-catalyzed reactions display saturation kinetics, meaning that there is not a linear response to increasing levels of substrate. Vmax is the maximum rate of the catalyzed reaction, while Km is the concentration of substrate that leads to half-maximal velocity. Enzymes with a low Km have a high affinity for their substrate. The Michaelis-Menten model of a single substrate reaction demonstrates the saturation curve for an enzyme, showing the relationship between substrate concentration and reaction rate. Linear plots of the Michaelis-Menten model are used to estimate Vmax. The Lineweaver-Burk plot of kinetic data shows how the y-intercept equals 1/Vmax, and as the y-intercept increases, Vmax decreases. There are three types of inhibitors: competitive, non-competitive, and uncompetitive. Each type has a different effect on Vmax and Km. Competitive inhibitors compete with the substrate for the enzyme’s active binding site, while non-competitive inhibitors bind outside the enzyme’s active binding site. Uncompetitive inhibitors are rare and bind to the enzyme, enhancing the binding of substrate.

    • This question is part of the following fields:

      • General Principles
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  • Question 30 - A 16-year-old female was admitted to the paediatric unit with a history of...

    Incorrect

    • A 16-year-old female was admitted to the paediatric unit with a history of anorexia nervosa and a body mass index of 16kg/m². Despite being uncooperative initially, she has shown improvement in her willingness to participate with the team. However, she now presents with complaints of abdominal pain and weakness. Upon blood testing, the following results were obtained:

      Hb 125 g/L Male: (135-180) Female: (115 - 160)
      Platelets 180 * 109/L (150 - 400)
      WBC 4.5 * 109/L (4.0 - 11.0)

      Na+ 138 mmol/L (135 - 145)
      K+ 3.2 mmol/L (3.5 - 5.0)
      Bicarbonate 26 mmol/L (22 - 29)
      Urea 5 mmol/L (2.0 - 7.0)
      Creatinine 70 µmol/L (55 - 120)

      Calcium 2.1 mmol/L (2.1-2.6)
      Phosphate 0.5 mmol/L (0.8-1.4)
      Magnesium 0.6 mmol/L (0.7-1.0)

      What is the likely cause of the patient's abnormal blood results?

      Your Answer:

      Correct Answer: Extended period of low calories then high carbohydrate intake

      Explanation:

      Refeeding syndrome can occur in patients who have experienced prolonged catabolism and then suddenly switch to carbohydrate metabolism. This can lead to a rapid uptake of phosphate, potassium, and magnesium into the cells, caused by spikes in insulin and glucose. Patients with low BMI and poor nutritional intake over a long period of time are at a higher risk. Taking vitamin tablets would not affect blood results, but excessive intake can result in hypervitaminosis. While exogenous insulin could also cause this syndrome, there is no indication that the patient has taken it. To reduce the risk of refeeding syndrome, some patients may be advised to follow initial high-fat, low-carbohydrate diets.

      Understanding Refeeding Syndrome

      Refeeding syndrome is a condition that occurs when a person who has been starved for an extended period suddenly begins to eat again. This metabolic abnormality is caused by the abrupt switch from catabolism to carbohydrate metabolism. The consequences of refeeding syndrome include hypophosphataemia, hypokalaemia, hypomagnesaemia, and abnormal fluid balance, which can lead to organ failure.

      To prevent refeeding syndrome, it is important to identify patients who are at high risk of developing the condition. According to guidelines produced by NICE in 2006, patients are considered high-risk if they have a BMI of less than 16 kg/m2, have experienced unintentional weight loss of more than 15% over 3-6 months, have had little nutritional intake for more than 10 days, or have hypokalaemia, hypophosphataemia, or hypomagnesaemia prior to feeding (unless high).

      If a patient has two or more of the following risk factors, they are also considered high-risk: a BMI of less than 18.5 kg/m2, unintentional weight loss of more than 10% over 3-6 months, little nutritional intake for more than 5 days, or a history of alcohol abuse, drug therapy (including insulin, chemotherapy, diuretics, and antacids).

      To prevent refeeding syndrome, NICE recommends that patients who haven’t eaten for more than 5 days should be re-fed at no more than 50% of their requirements for the first 2 days. By following these guidelines, healthcare professionals can help prevent the potentially life-threatening consequences of refeeding syndrome.

    • This question is part of the following fields:

      • Gastrointestinal System
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