MDS PREP
What is the role of intrinsic factor in vitamin B12 absorption?
1) It protects vitamin B12 from gastric digestion
2) It facilitates binding of vitamin B12 to intestinal receptors
3) It synthesizes vitamin B12 in the gastrointestinal tract
4) It increases the production of gastric acid
Intrinsic factor facilitates the binding of vitamin B12 to intestinal receptors, which is essential for its absorption in the ileum.
Which of the following is not a type of action potential propagation?
1) Autocrine
2) Paracrine
3) Endocrine
4) Synaptic
E. All of the above are types of action potential propagation.
The question contains an error. The terms autocrine, paracrine, endocrine, and synaptic are not types of action potential propagation. Instead, they describe different modes of hormonal or neuronal signaling. Action potentials are propagated along axons without any of these specific types of interactions.
What is the role of the post-prandial alkaline tide in the regulation of gastric pH?
1) It increases gastric acidity
2) It decreases gastric acidity
3) It has no effect on gastric acidity
4) It neutralizes gastric acid
E) It promotes the secretion of bicarbonate into the gastric lumen
The post-prandial alkaline tide refers to the increase in blood bicarbonate levels that occurs after a meal due to the secretion of bicarbonate by the pancreas and duodenal mucosa to neutralize the acidic chyme entering the small intestine. This temporary rise in blood pH reduces the secretion of gastrin and therefore decreases gastric acidity.
What is the primary mechanism of the fight-or-flight response mediated by cortisol?
1) Increases heart rate and blood pressure
2) Facilitates gluconeogenesis and lipolysis
3) Relaxes smooth muscles of the gastrointestinal tract
4) Increases the sensitivity of the heart to catecholamines
Answer: 2) Facilitates gluconeogenesis and lipolysisExplanation: Cortisol, a glucocorticoid hormone, plays a key role in the fight-or-flight response by mobilizing energy stores. It stimulates gluconeogenesis in the liver and promotes lipolysis in adipose tissue, increasing the availability of glucose and fatty acids for energy production during stressful situations.
What happens to lithocholic acid in the enterohepatic circulation?
1) It is reabsorbed in the terminal ileum and returned to the liver
2) It is metabolized into chenodeoxycholic acid
3) It is converted into deoxycholic acid
4) It is excreted in feces due to its insolubility
Physiology
Answer: 4
Lithocholic acid is insoluble and not efficiently reabsorbed, leading to its excretion in the feces.
What is the function of the hypothalamus in the regulation of spermatogenesis?
1) It produces gonadotropin-releasing hormone (GnRH) which stimulates the release of LH and FSH from the pituitary
2) It produces androgens such as testosterone
3) It directly controls the maturation of spermatids
4) It has no role in spermatogenesis
The hypothalamus produces gonadotropin-releasing hormone (GnRH), which stimulates the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary, playing a crucial role in spermatogenesis.
The glomerular filtration barrier consists of:
1) Endothelial cells
2) Basement membrane
3) Podocytes
4) All of the above
The glomerular filtration barrier is a three-layered structure composed of endothelial cells of the glomerular capillaries, the basement membrane, and the podocytes (visceral epithelial cells of Bowman's capsule). These layers work together to filter blood, allowing small molecules to pass into the nephron while retaining larger ones.
What is the primary effect of excitatory postsynaptic potentials (EPSPs) on the excitability of a neuron?
1) Depolarization
2) Hyperpolarization
3) No change in excitability
4) Initiation of an action potential
Answer: 1) DepolarizationExplanation: EPSPs occur when the neurotransmitter binds to postsynaptic receptors that open sodium channels, allowing sodium ions to flow into the neuron and causing the membrane to depolarize. This increases the excitability of the neuron, bringing the membrane potential closer to the threshold for action potential firing.