MDS PREP
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 effect of thyroid hormones on the peripheral vascular resistance during the fight-or-flight response?
1) Increases peripheral vascular resistance
2) Decreases peripheral vascular resistance
3) No effect on peripheral vascular resistance
4) Variable effect on peripheral vascular resistance
Answer: 2) Decreases peripheral vascular resistanceExplanation: Thyroid hormones cause vasodilatation in several vascular beds, which decreases peripheral vascular resistance. This, along with increased cardiac output, leads to an overall increase in systolic blood pressure despite the diastolic BP possibly decreasing due to reduced resistance.
In which part of the male reproductive system does spermatogenesis occur?
1) Seminal vesicles
2) Epididymis
3) Prostate gland
4) Seminiferous tubules
Spermatogenesis occurs in the seminiferous tubules of the male reproductive system, where sperm cells are produced and matured.
What is the typical osmolality of intestinal chyme?
1) Isotonic with blood (~300 mOsm/L)
2) Hypotonic (<300 mOsm/L)
3) Hypertonic (>300 mOsm/L)
4) Varies greatly depending on the composition of ingested food
E) Is not relevant for nutrient absorption
The osmolality of intestinal chyme can vary widely depending on the type and quantity of food consumed. It can range from isotonic to hypertonic or hypotonic relative to blood. The intestinal mucosa plays a critical role in adjusting water and ion transport to maintain the osmolality of the blood and facilitate the absorption of nutrients.
Which of the following is NOT a primary bile acid synthesized in the liver from cholesterol?
1) Cholic acid
2) Chenodeoxycholic acid
3) Deoxycholic acid
4) Lithocholic acid
Physiology
Answer: 3
Deoxycholic acid is a secondary bile acid formed by bacterial conversion of cholic acid in the colon.
Which of the following is a characteristic of the absolute refractory period during an action potential?
1) The membrane is fully depolarized.
2) The membrane is fully repolarized.
3) The membrane is inexcitable regardless of the strength of the stimulus.
4) The membrane is hyperpolarized.
E. The membrane is depolarized.
The absolute refractory period occurs during the initial phase of repolarization after an action potential. During this period, the membrane is inactivated and cannot be depolarized to generate another action potential, regardless of the stimulus strength. This ensures that action potentials are unidirectional and do not propagate backward along the axon.
What happens when the transport maximum for glucose is exceeded?
1) All excess glucose is reabsorbed
2) Some glucose is reabsorbed and some is excreted
3) All excess glucose is excreted in the urine
4) No glucose is excreted regardless of the amount
Physiology
Answer: 2
When the transport maximum for glucose is exceeded, the excess glucose is not reabsorbed and appears in the urine, known as glucosuria.
Which of the following statements about the neuronal circuit of the cerebellum is true?
1) Climbing fibers originate from the cerebral cortex and terminate on purkinje cells.
2) Mossy fibers establish excitatory synapses with interneurons in the molecular layer.
3) Stellate and basket cells are stimulated by inhibitory inputs from purkinje cells.
4) Golgi cells are inhibited by mossy fiber inputs.
E. All of the above.
Mossy fibers originate from various sources in the brain and spinal cord and terminate on granule cells in the granular layer of the cerebellum. The axons of granule cells, called parallel fibers, stimulate the purkinje cells and also synapse with interneurons such as stellate and basket cells in the molecular layer and Golgi cells in the granular layer. Climbing fibers originate from the inferior olivary nuclei and synapse directly on purkinje cells. The statement that stellate and basket cells are stimulated by inhibitory inputs from purkinje cells is incorrect; they are stimulated by parallel fibers and inhibit purkinje cells. Golgi cells are also stimulated by mossy fibers and help in the regulation of the overall output of the cerebellum.