MDS PREP
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
Lithocholic acid is excreted in feces due to its insolubility, as it is not efficiently reabsorbed in the enterohepatic circulation.
In the presence of antidiuretic hormone (ADH), which part of the nephron becomes highly permeable to water?
1) Proximal Convoluted Tubule (PCT)
2) Loop of Henle
3) Collecting Duct
4) Afferent Arteriole
In the presence of antidiuretic hormone (ADH), the collecting duct becomes highly permeable to water, allowing for increased water reabsorption and concentrated urine.
What are the main stimuli that increase the secretion of growth hormone (GH)?
1) High blood glucose levels and physical inactivity
2) Hypoglycemia, exercise, protein meals, and stress
3) REM sleep and increased IGF-1 levels
4) High cortisol and fatty acid levels
Answer: 2) Main stimuli that increase GH secretion include hypoglycemia, exercise, protein meals, and stress.
Which of the following is NOT a direct component of the corticospinal tract's termination?
1) Alpha-motor neurons (anterior or ventral horn cells)
2) Interneurons in the intermediate gray matter
3) Delta-motor neurons in the ventral horn
4) Gamma-motor neurons in the ventral horn
The corticospinal tract primarily terminates on alpha-motor neurons and interneurons, not directly on delta-motor neurons, which are involved in the control of muscle spindles and not in direct motor control.
Which type of receptors are involved in the contraction of the detrusor muscle during micturition?
1) Muscarinic receptors
2) Adrenergic receptors
3) Dopaminergic receptors
4) Serotonergic receptors
The contraction of the detrusor muscle during micturition is mediated by the activation of muscarinic receptors (specifically M3 receptors) on the smooth muscle cells of the detrusor. This leads to increased muscle tone and the expulsion of urine from the bladder.
What primarily determines the Glomerular Filtration Rate (GFR)?
1) Blood volume
2) Net filtration pressure and Kf
3) Renal blood flow
4) Urine output
The Glomerular Filtration Rate (GFR) is primarily determined by net filtration pressure and the glomerular capillary filtration coefficient (Kf), which reflects the permeability of the glomerular membrane.
What is the primary function of the macula densa?
1) Filtration of blood
2) Regulation of glomerular filtration rate
3) Secretion of renin
4) Reabsorption of glucose
The primary function of the macula densa is to regulate glomerular filtration rate by sensing sodium chloride concentration in the tubular fluid.
What is the function of cholecystokinin (CCK) in the digestive system?
1) Stimulates the release of bile from the liver
2) Increases the secretion of water in the collecting tubules of the kidney
3) Relaxes the lower esophageal sphincter
4) Decreases the motility of the small intestine
Physiology
Answer: 3
Cholecystokinin is a hormone secreted by the mucosa of the upper intestine in response to the presence of food, particularly proteins and fats. One of its key functions is to stimulate the contraction of the gallbladder and relax the sphincter of Oddi, facilitating the release of bile and pancreatic enzymes into the duodenum to aid in digestion.