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Question 1
Incorrect
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Regarding the formation of CSF, which of the following is true?
Your Answer: The rate of formation fluctuates depending on CSF lumbar/outflow pressure
Correct Answer: Its composition resembles that of brain ECF
Explanation:In normal adults CSF volume is around 125ml to 150ml. Turnover of entire volume of cerebrospinal fluid a day is about 3 to 4 times a day. Composition of CSF is similar to that of plasma except that CSF is nearly protein-free compared with plasma and has a different electrolyte level. About 80% of CSF is produced by the choroid plexus. It is also produced by a single layer of column shaped ependymal cells. The composition and rate of CSF generation depends on several factors and is influenced by hormones and the content and pressure of blood and CSF.
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This question is part of the following fields:
- Medicine
- Neurology
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Question 2
Incorrect
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The production of bile is increased by: Stimulation of the ____ nerve and the hormone ____.
Your Answer: Glossopharyngeal, secretin
Correct Answer: Vagus, CCK
Explanation:Cholecystokinin is synthesized and secreted by enteroendocrine cells in the duodenum, the first segment of the small intestine, and causes the release of digestive enzymes and bile from the pancreas and gallbladder, respectively. It also acts as a hunger suppressant. Release of CCK is stimulated by monitor peptide released by pancreatic acinar cells as well as CCK-releasing protein, a paracrine factor secreted by enterocytes in the gastrointestinal mucosa. In addition, release of acetylcholine by the parasympathetic nerve fibers of the vagus nerve also stimulate its secretion.
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This question is part of the following fields:
- Hepatobiliary
- Medicine
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Question 3
Correct
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Which protein in the HIV genome is responsible for binding to the host CD4 cells?
Your Answer: gp120
Explanation:HIV can infect a variety of immune cells such as CD4+ T cells, macrophages, and microglial cells. HIV-1 entry to macrophages and CD4+ T cells is mediated through interaction of the virion envelope glycoproteins (gp120) with the CD4 molecule on the target cells and also with chemokine coreceptors.
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This question is part of the following fields:
- Infectious Diseases
- Medicine
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Question 4
Correct
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Erythropoietin is synthesized by which cells of the nephron?
Your Answer: Tubular interstitial cells
Explanation:Erythropoietin is produced by interstitial fibroblasts in the kidney in close association with peritubular capillary and proximal convoluted tubule. It is also produced in perisinusoidal cells in the liver. While liver production predominates in the fetal and perinatal period, renal production is predominant during adulthood.
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This question is part of the following fields:
- Medicine
- Renal
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Question 5
Incorrect
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Which of the following regulates the calcium release channels?
Your Answer: Phospholambin
Correct Answer: Calstabin 2
Explanation:Ca2+ is released from the SR through a Ca2+ release channel, a cardiac isoform of the ryanodine receptor (RyR2), which controls intracytoplasmic [Ca2+] and, as in vascular smooth-muscle cells, leads to the local changes in intracellular [Ca2+] called calcium sparks. A number of regulatory proteins, including calstabin 2, inhibit RyR2 and, thereby, the release of Ca2+ from the SR.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 6
Correct
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A 47-year-old woman diagnosed with oestrogen receptor positive breast cancer three months ago was started on treatment with tamoxifen. Which of the following is most likely a complaint of this patient during her review today?
Your Answer: Hot flushes
Explanation:The most likely complaint of this patient would be hot flushes.
Alopecia and cataracts are listed as possible side-effects, however they are not as prevalent as hot flushes, which are very common in pre-menopausal women.
Tamoxifen is a Selective Oestrogen Receptor Modulator (SERM) which acts as an oestrogen receptor antagonist and partial agonist. It is used in the management of oestrogen receptor-positive breast cancer
Adverse effects:
- Menstrual disturbance: vaginal bleeding, amenorrhoea
- Hot flushes – 3% of patients stop taking tamoxifen due to climacteric side-effects.
- Venous thromboembolism.
- Endometrial cancer (although antagonistic with respects to breast tissue, tamoxifen may serve as an agonist at other sites. Therefore the risk of endometrial cancer is increased). Raloxifene is a pure oestrogen receptor antagonist and carries a lower risk of endometrial cancer.
Tamoxifen is typically used for 5 years following the removal of the tumour.
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This question is part of the following fields:
- Medicine
- Pharmacology
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Question 7
Correct
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What type of intercellular connection found between cardiac muscle fibers allow for the spread of excitation from one cell to another?
Your Answer: Gap junctions
Explanation:The cardiac muscles have gap junctions in-between the cells. They form low resistance passages, which allow ions to diffuse through every muscle fiber rapidly and result in the cardiac muscles functioning as a syncytium, without any protoplasmic bridges involved.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 8
Incorrect
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What happens first during depolarisation of the membrane potential?
Your Answer: Gated Na channels open allowing the efflux of Na
Correct Answer: Gated Na channels open allowing the influx of Na
Explanation:Generation of an action potential in response to a stimulus is a result of a previously maintained resting membrane potential (RMP). Generation of resting membrane potential is mediated mainly by potassium ions. Several membrane proteins maintain RMP by transport of ions in and out of cell. Na+/K+ ATPase pump maintains a concentration gradient of Na+ and K+ ions. Na+ concentration in extracellular fluid is higher compared to intracellular fluid and K+ ion concentration is higher intracellularly. Generation of an action potential facilitates opening of Na+ ion channels which allow for Na+ to diffuse inside the cell according to the concentration gradient.
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This question is part of the following fields:
- Medicine
- Neurology
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Question 9
Correct
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Select the correct statement regarding the macro anatomy of the thyroid gland.
Your Answer: It surrounds the trachea at the front of the neck.
Explanation:The thyroid is located around the trachea, in the anterior portion of the neck. It is formed by two lobes which are connected by an isthmus. The presence of a pyramidal lobe, or third lobe, is considered to be a normal anatomical variant. It originates from the primitive pharynx and the neural crest and has a rich vascular supply.
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This question is part of the following fields:
- Endocrinology
- Medicine
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Question 10
Correct
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Which are the main hormones secreted by the posterior pituitary gland.
Your Answer: Oxytocin and vasopressin
Explanation:The posterior pituitary gland secretes oxytocin and vasopressin (antidiuretic hormone). These hormones are stored in Herring bodies before being secreted into the bloodstream.
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This question is part of the following fields:
- Endocrinology
- Medicine
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