MDS PREP
In the presence of which substance does vitamin B12 combine in the stomach to prevent its degradation by gastric acid?
1) Intrinsic factor
2) Pepsin
3) Gastric acid
4) Pancreatic amylase
Physiology
Answer: 1
Vitamin B12 combines with intrinsic factor to form a complex that is protected from degradation by gastric acid.
Which of the following is the primary active transport mechanism for calcium absorption in the intestine?
1) Vitamin D dependent calcium binding protein (calbindin)
2) Sodium-calcium exchanger (NCX)
3) Calcium-dependent ATPase
4) All of the above
Physiology
Answer: 4
Calcium is absorbed mainly in the duodenum and jejunum by an active transport mechanism regulated by 1,25 (OH)2 D3 (calcitriol). It is transported across the brush border of intestinal epithelial cells via TRPV6 channels and binds to calbindin. The absorbed calcium is then delivered to the basolateral membrane by calbindin, and from there it is transported into the bloodstream by either the sodium-calcium exchanger (NCX) or calcium-dependent ATPase.
What is the primary inhibitory neurotransmitter in the central nervous system?
1) Dopamine
2) GABA (gamma-aminobutyric acid)
3) Glutamate
4) Acetylcholine
GABA is the main inhibitory neurotransmitter in the central nervous system, playing a crucial role in reducing the excitability of neurons and contributing to the regulation of neural circuits and synaptic plasticity.
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 are the primary metabolic effects of GH?
1) Lipolysis and protein anabolism
2) Lipolysis and gluconeogenesis
3) Lipolysis and increased peripheral utilization of glucose
4) Lipolysis and increased uptake of glucose by muscles
Answer: 2) The primary metabolic effects of GH are lipolysis and gluconeogenesis, which result in increased plasma fatty acids and glucose levels.
The reticular formation gives rise to which of the following extrapyramidal tracts?
1) Corticospinal tract
2) Reticulospinal tract
3) Vestibulospinal tract
4) Rubrospinal tract
E. Tectospinal tract
The reticulospinal tract arises from neurons in the reticular formation of the brainstem and projects to the spinal cord. It influences both voluntary and involuntary motor activities, modulating the excitability of motor neurons. The corticospinal tract arises from the cerebral cortex, the vestibulospinal tract from the vestibular nuclei, the rubrospinal tract from the red nucleus, and the tectospinal tract from the superior colliculus.
How does the skin color change in light-skinned patients with high serum bilirubin levels?
1) The skin turns yellow.
2) The skin turns green.
3) The skin turns blue.
4) The skin turns red.
In light-skinned patients with high serum bilirubin levels, the skin turns yellow due to the deposition of bilirubin.
In which part of the nephron is bicarbonate primarily reabsorbed?
1) Loop of Henle
2) Distal convoluted tubule
3) Proximal convoluted tubule
4) Collecting duct
Bicarbonate is primarily reabsorbed in the proximal convoluted tubule, where it plays a crucial role in maintaining acid-base balance in the body.