MDS PREP
What is the function of the enteric nervous system?
1) Controls the heart rate and rhythm
2) Regulates the contraction of skeletal muscles
3) Regulates the function of the gastrointestinal tract
4) Controls the pupillary response to light
The enteric nervous system is the intrinsic nervous system of the gastrointestinal tract and is responsible for the regulation of digestion and other gastrointestinal functions. It can operate independently of the central nervous system and consists of a network of neurons and glial cells that are embedded within the wall of the gut, coordinating local reflexes and influencing the muscle and secretory activities of the digestive system.
What is the role of the cholinergic system in the regulation of urinary bladder function?
1) Contraction of the detrusor muscle and relaxation of the trigone
2) Relaxation of the detrusor muscle and contraction of the trigone
3) Contraction of the urethral sphincter
4) Contraction of the urethral sphincter and relaxation of the detrusor muscle
The parasympathetic nervous system, which is cholinergic, stimulates the detrusor muscle of the urinary bladder to contract and the trigone muscle to relax, facilitating micturition (urination). This is mediated by the activation of muscarinic M3 receptors.
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 primary role of the cephalic phase of gastric acid secretion?
1) Stimulation of gastrin release in the stomach
2) Secretion of gastric juices in response to the thought or smell of food
3) Increase in gastric motility
4) Secretion of gastric juices in response to food entering the duodenum
Physiology
Answer: 2
The cephalic phase of gastric acid secretion is initiated by the parasympathetic system and is triggered by the sight, smell, or thought of food. It accounts for approximately 20% of total acid secretion and prepares the stomach for digestion even before food arrives.
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
Deoxycholic acid is NOT a primary bile acid synthesized in the liver from cholesterol; it is a secondary bile acid formed from the bacterial action on primary bile acids in the intestine.
What is the primary action of antidiuretic hormone (ADH) in the kidneys?
1) Increases the permeability of water in the proximal tubules
2) Increases the permeability of water in the collecting tubules and ducts
3) Stimulates glomerular filtration rate
4) Inhibits sodium reabsorption
Physiology
Answer: 2
ADH acts on the distal tubules and collecting ducts of the kidney to increase the permeability of the tubular epithelium to water. This results in the reabsorption of water and the concentration of urine, thereby reducing urine volume and increasing blood pressure.
What happens when the estrogen level crosses a certain threshold during the menstrual cycle?
1) It inhibits the release of LH and FSH
2) It stimulates the release of LH and FSH
3) It has no effect on pituitary hormone secretion
4) It triggers ovulation
Physiology
Answer: 4
Around day 11 of the menstrual cycle, the rising estrogen level reaches a threshold that has a positive feedback effect on LH secretion, leading to the LH surge. This LH surge is essential for ovulation to occur.
The macula densa is found in:
1) The proximal convoluted tubule
2) The loop of Henle
3) The distal convoluted tubule
4) The collecting duct
The macula densa is a specialized group of epithelial cells located in the distal convoluted tubule at the junction with the afferent and efferent arterioles. It plays a role in the tubulo-glomerular feedback mechanism to regulate renal blood flow and glomerular filtration rate.