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Question 1
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Linda, a 68-year-old female, visits a shoulder clinic for a routine follow-up appointment after undergoing a right shoulder replacement surgery for osteoarthritis. During the consultation, she reports limited movement in bending her elbow and shoulder.
Upon examining her upper limb, the surgeon observes decreased flexion at the elbow and suspects nerve damage during the operation.
Which nerve is most likely to have been affected based on the patient's symptoms and signs?Your Answer: Musculocutaneous nerve
Explanation:When the musculocutaneous nerve is injured, it can result in weakness when flexing the upper arm at the shoulder and elbow. This nerve is responsible for innervating the brachialis, biceps brachii, and coracobrachialis muscles. Other nerves, such as the axillary nerve, median nerve, and radial nerve, also play a role in muscle innervation and movement. The axillary nerve innervates the teres minor and deltoid muscles, while the median nerve innervates the majority of the flexor muscles in the forearm, the thenar muscles, and the two lateral lumbricals. The radial nerve innervates the triceps brachii and the muscles in the posterior compartment of the forearm, which generally cause extension of the wrist and fingers.
The Musculocutaneous Nerve: Function and Pathway
The musculocutaneous nerve is a nerve branch that originates from the lateral cord of the brachial plexus. Its pathway involves penetrating the coracobrachialis muscle and passing obliquely between the biceps brachii and the brachialis to the lateral side of the arm. Above the elbow, it pierces the deep fascia lateral to the tendon of the biceps brachii and continues into the forearm as the lateral cutaneous nerve of the forearm.
The musculocutaneous nerve innervates the coracobrachialis, biceps brachii, and brachialis muscles. Injury to this nerve can cause weakness in flexion at the shoulder and elbow. Understanding the function and pathway of the musculocutaneous nerve is important in diagnosing and treating injuries or conditions that affect this nerve.
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This question is part of the following fields:
- Neurological System
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Question 2
Incorrect
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A 22-year-old man presents to the emergency department with complaints of weakness in his right wrist. He reports heavy drinking the previous night and falling asleep with his arm hanging over a chair's armrest. Upon examination, there is weakness in the extensor muscles of the forearm, and a radial nerve palsy is diagnosed. A neurologist later uses an electromyogram, which indicates the presence of axonotmesis in the radial nerve.
What is a reasonable expectation for the patient's recovery?Your Answer: Full recovery of function in 4 days
Correct Answer: Full recovery of function in 12 months
Explanation:When a nerve is crushed, it can lead to axonotmesis, which is a serious injury. However, in most cases, patients can fully recover from this type of injury, but the process is slow.
The radial nerve of the patient in this case was compressed for a long time due to falling asleep on an armrest, resulting in axonotmesis. Although complete recovery is probable, it can take up to a year for the axons to regenerate.
Nerve injuries can be classified into three types: neuropraxia, axonotmesis, and neurotmesis. Neuropraxia occurs when the nerve is intact but its electrical conduction is affected. However, full recovery is possible, and autonomic function is preserved. Wallerian degeneration, which is the degeneration of axons distal to the site of injury, does not occur. Axonotmesis, on the other hand, happens when the axon is damaged, but the myelin sheath is preserved, and the connective tissue framework is not affected. Wallerian degeneration occurs in this type of injury. Lastly, neurotmesis is the most severe type of nerve injury, where there is a disruption of the axon, myelin sheath, and surrounding connective tissue. Wallerian degeneration also occurs in this type of injury.
Wallerian degeneration typically begins 24-36 hours following the injury. Axons are excitable before degeneration occurs, and the myelin sheath degenerates and is phagocytosed by tissue macrophages. Neuronal repair may only occur physiologically where nerves are in direct contact. However, nerve regeneration may be hampered when a large defect is present, and it may not occur at all or result in the formation of a neuroma. If nerve regrowth occurs, it typically happens at a rate of 1mm per day.
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This question is part of the following fields:
- Neurological System
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Question 3
Incorrect
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A 75-year-old man with Alzheimer's disease visits his doctor for a medication review, accompanied by his son. The son reports that his father is struggling to perform daily tasks and requests an increase in his care package.
During the examination, the patient appears disoriented to time and place. A mini-mental state examination is conducted, revealing a score of 14/30, indicating moderate dementia.
Which histological finding would be the most specific for this patient's diagnosis?Your Answer: Extraneuronal amyloid plaques, intraneuronal Lewy bodies
Correct Answer: Extraneuronal amyloid plaques, intraneuronal neurofibrillary tangles
Explanation:In Alzheimer’s disease, the pathology involves extraneuronal amyloid plaques and intraneuronal neurofibrillary tangles. Amyloid plaques are clumps of beta-amyloid that are found in the extracellular matrix, while neurofibrillary tangles are made up of hyperphosphorylated tau and are located within the neurons. The exact role of beta-amyloid and tau in the development of Alzheimer’s disease is still not fully understood.
Alzheimer’s disease is a type of dementia that gradually worsens over time and is caused by the degeneration of the brain. There are several risk factors associated with Alzheimer’s disease, including increasing age, family history, and certain genetic mutations. The disease is also more common in individuals of Caucasian ethnicity and those with Down’s syndrome.
The pathological changes associated with Alzheimer’s disease include widespread cerebral atrophy, particularly in the cortex and hippocampus. Microscopically, there are cortical plaques caused by the deposition of type A-Beta-amyloid protein and intraneuronal neurofibrillary tangles caused by abnormal aggregation of the tau protein. The hyperphosphorylation of the tau protein has been linked to Alzheimer’s disease. Additionally, there is a deficit of acetylcholine due to damage to an ascending forebrain projection.
Neurofibrillary tangles are a hallmark of Alzheimer’s disease and are partly made from a protein called tau. Tau is a protein that interacts with tubulin to stabilize microtubules and promote tubulin assembly into microtubules. In Alzheimer’s disease, tau proteins are excessively phosphorylated, impairing their function.
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This question is part of the following fields:
- Neurological System
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Question 4
Correct
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A 72-year-old woman presents to the emergency department with right hip pain following a fall at home. She is unable to bear weight and her right leg appears externally rotated and shorter. Her medical history includes osteoarthritis in her knee, type 2 diabetes mellitus, and hypertension. She is currently being tapered off prednisolone for polymyalgia rheumatica which was diagnosed 2 years ago. Which medication in her regimen may have contributed to her increased risk?
Your Answer: Prednisolone
Explanation:Patients who take systemic corticosteroids over a long period of time are at a higher risk of developing osteoporosis and experiencing fractures. In this case, the patient’s hip fracture may have been caused by her pre-existing osteoporosis.
Corticosteroids are commonly prescribed medications that can be taken orally or intravenously, or applied topically. They mimic the effects of natural steroids in the body and can be used to replace or supplement them. However, the use of corticosteroids is limited by their numerous side effects, which are more common with prolonged and systemic use. These side effects can affect various systems in the body, including the endocrine, musculoskeletal, gastrointestinal, ophthalmic, and psychiatric systems. Some of the most common side effects include impaired glucose regulation, weight gain, osteoporosis, and increased susceptibility to infections. Patients on long-term corticosteroids should have their doses adjusted during intercurrent illness, and the medication should not be abruptly withdrawn to avoid an Addisonian crisis. Gradual withdrawal is recommended for patients who have received high doses or prolonged treatment.
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This question is part of the following fields:
- Endocrine System
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Question 5
Correct
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In a 70 Kg person, what percentage of the entire body fluid will be provided by plasma?
Your Answer: 5%
Explanation:Understanding the Physiology of Body Fluid Compartments
Body fluid compartments are essential components of the human body, consisting of intracellular and extracellular compartments. The extracellular compartment is further divided into interstitial fluid, plasma, and transcellular fluid. In a typical 70 Kg male, the intracellular compartment comprises 60-65% of the total body fluid volume, while the extracellular compartment comprises 35-40%. The plasma volume is approximately 5%, while the interstitial fluid volume is 24%. The transcellular fluid volume is approximately 3%. These figures are only approximate and may vary depending on the individual’s weight and other factors. Understanding the physiology of body fluid compartments is crucial in maintaining proper fluid balance and overall health.
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This question is part of the following fields:
- Renal System
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Question 6
Correct
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A woman presents to the GP after taking a home pregnancy test, which revealed that she is 10 weeks pregnant. She has come to ask whether she should start taking folic acid supplements, as she has heard that this can help the baby develop.
Folic acid helps to prevent neural tube defects. The GP explains that folic acid is only advised during the first trimester of pregnancy, as the neural tube closes around 28 days after conception.Your Answer: Week 4
Explanation:The process of neural tube closure takes place during the fourth week of development. Prior to this, during week 3, gastrulation occurs and the neural plate is formed. Primary neurulation, which involves the folding and fusion of the lateral edges of the neural plate to form the neural tube, occurs during week 4. Folic acid is believed to play a role in this process. From week 5 onwards, the central nervous system continues to develop and expand through secondary neurulation and axon guidance.
Embryology is the study of the development of an organism from the moment of fertilization to birth. During the first week of embryonic development, the fertilized egg implants itself into the uterine wall. By the second week, the bilaminar disk is formed, consisting of two layers of cells. The primitive streak appears in the third week, marking the beginning of gastrulation and the formation of the notochord.
As the embryo enters its fourth week, limb buds begin to form, and the neural tube closes. The heart also begins to beat during this time. By week 10, the genitals are differentiated, and the embryo exhibits intermittent breathing movements. These early events in embryonic development are crucial for the formation of the body’s major organs and structures. Understanding the timeline of these events can provide insight into the complex process of human development.
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This question is part of the following fields:
- General Principles
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Question 7
Incorrect
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A 78-year-old man is admitted to the care of the elderly ward with urosepsis and an acute kidney injury stage 2. His medical history includes type 2 diabetes, ischaemic heart disease and prostate cancer.
Assessing his risk of venous thromboembolism (VTE), you determine that he is at high risk. To prevent VTE, you initiate subcutaneous enoxaparin, a low molecular weight heparin. What is the mechanism of action of this medication?Your Answer: Directly inhibits factor Xa
Correct Answer: Activates antithrombin III and forms a complex that inhibits factor Xa
Explanation:The activation of antithrombin III (ATIII) is the mechanism by which low-molecular weight heparins (LMWH) produce an anti-coagulant effect. ATIII is a glycoprotein that inhibits several enzymes involved in the clotting cascade, including thrombin, factor Xa, and factor IXa. All heparins work to enhance the effect of ATIII, but LMWH specifically binds to ATIII and produces a conformational change that accelerates its inhibition of factor Xa.
In contrast, unfractionated heparin also produces a conformational change in ATIII, but due to its larger size, it can also inhibit other clotting factors such as thrombin, factors IXa, XIa, and XIIa.
Direct oral anticoagulants such as apixaban and rivaroxaban directly inhibit factor Xa, while dabigatran is a direct thrombin inhibitor. Aspirin, on the other hand, inhibits the production of thromboxane A2 by inhibiting COX-1 and COX-2, resulting in reduced platelet aggregation.
Heparin is a type of anticoagulant medication that comes in two main forms: unfractionated heparin and low molecular weight heparin (LMWH). Both types work by activating antithrombin III, but unfractionated heparin forms a complex that inhibits thrombin, factors Xa, IXa, XIa, and XIIa, while LMWH only increases the action of antithrombin III on factor Xa. Adverse effects of heparins include bleeding, thrombocytopenia, osteoporosis, and hyperkalemia. LMWH has a lower risk of causing heparin-induced thrombocytopenia (HIT) and osteoporosis compared to unfractionated heparin. HIT is an immune-mediated condition where antibodies form against complexes of platelet factor 4 (PF4) and heparin, leading to platelet activation and a prothrombotic state. Treatment for HIT includes direct thrombin inhibitors or danaparoid. Heparin overdose can be partially reversed by protamine sulfate.
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This question is part of the following fields:
- General Principles
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Question 8
Incorrect
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What type of hallucination is Lillian experiencing while being unwell in bed with pneumonia and seeing a tiny marching band on her bedclothes?
Your Answer: Visual hallucination - elementary hallucination
Correct Answer: Visual hallucination - Lilliputian hallucinations
Explanation:Types of Hallucinations
Hallucinations are false perceptions that occur simultaneously with real perceptions. There are different types of hallucinations, including visual hallucinations associated with micropsia, which are known as Lilliputian hallucinations. These hallucinations often occur in patients suffering from delirium. Another type of visual hallucination is elementary hallucinations, which appear as flashes of light.
Extracampine hallucinations occur when an individual experiences a hallucination outside their sensory field, such as seeing someone standing behind them while looking straight ahead. Reflex hallucinations happen when a true sensory stimulus causes a hallucination in another sensory modality. Lastly, autoscopy is the experience of seeing oneself and knowing it is oneself, also known as the phantom mirror-image. the different types of hallucinations can help in identifying and treating them appropriately.
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This question is part of the following fields:
- Psychiatry
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Question 9
Correct
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A 42-year-old woman comes to the clinic for a follow-up on her ambulatory blood pressure test results. The test shows an average blood pressure of 150/92 mmHg. You suggest starting antihypertensive medication and recommend ACE inhibitors as the first-line treatment for her age group. These medications work by inhibiting the action of angiotensin-converting-enzyme, which converts angiotensin I to angiotensin II. Renin catalyzes the hydrolysis of angiotensinogen to produce angiotensin I. Where in the body is renin produced?
Your Answer: Kidneys
Explanation:Renin, which is produced in the kidneys’ juxtaglomerular cells, plays a crucial role in the renin-angiotensin-aldosterone system by converting angiotensinogen into angiotensin I. Angiotensin-converting-enzyme, which is primarily located in the lungs, converts angiotensin I to angiotensin II. The adrenal cortex produces aldosterone, a vital compound in the system, while the liver produces angiotensinogen. The pancreas, on the other hand, has no involvement in this system and produces insulin, glucagon, and other hormones and enzymes. Based on the World Health Organisation’s hypertension classification, the patient in question has mild hypertension, and according to current NICE guidelines, individuals under 55 years old with mild hypertension should receive lifestyle advice and be prescribed ACE inhibitors.
The renin-angiotensin-aldosterone system is a complex system that regulates blood pressure and fluid balance in the body. The adrenal cortex is divided into three zones, each producing different hormones. The zona glomerulosa produces mineralocorticoids, mainly aldosterone, which helps regulate sodium and potassium levels in the body. Renin is an enzyme released by the renal juxtaglomerular cells in response to reduced renal perfusion, hyponatremia, and sympathetic nerve stimulation. It hydrolyses angiotensinogen to form angiotensin I, which is then converted to angiotensin II by angiotensin-converting enzyme in the lungs. Angiotensin II has various actions, including causing vasoconstriction, stimulating thirst, and increasing proximal tubule Na+/H+ activity. It also stimulates aldosterone and ADH release, which causes retention of Na+ in exchange for K+/H+ in the distal tubule.
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This question is part of the following fields:
- Renal System
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Question 10
Incorrect
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What distinguishes articular cartilage from other types of hyaline cartilage?
Your Answer: More type IV collagen
Correct Answer: Regular arrangement of collagen fibres
Explanation:Types of Cartilage
Hyaline cartilage is a type of cartilage that is firm and is composed of type II collagen. It is found in various parts of the body such as the nose, the cartilaginous rings of the trachea, the foetal skeleton, and lines synovial joints in a specialized form known as articular cartilage. Articular cartilage has a more regular arrangement of collagen fibers and slightly more elastin, which makes it less frictional and facilitates the movement of synovial joints.
Fibrocartilage, on the other hand, is made up of type I collagen and is much more solid. It is used to hold bones together, such as in the pubic symphysis. Lastly, elastic cartilage has a rich elastin content and forms the pinna of the ear.
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This question is part of the following fields:
- Histology
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