MDS PREP
What is the role of gastrin in the gastric phase of acid secretion?
1) It is released by the pancreas and stimulates acid secretion in the stomach
2) It is released by the duodenum and inhibits acid secretion
3) It is released by the stomach and stimulates acid secretion in response to food
4) It has no role in gastric acid secretion
Gastrin is released by the stomach and stimulates acid secretion in response to food, playing a key role in the gastric phase of digestion.
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 significance of the latch effect in smooth muscle contraction?
1) It allows for rapid contraction and relaxation
2) It prevents the muscle from fully relaxing between contractions
3) It is responsible for the generation of the resting membrane potential
4) It is not relevant to the function of smooth muscles
Answer: 2) It prevents the muscle from fully relaxing between contractionsExplanation: The latch effect in smooth muscles refers to the ability of phosphorylated myosin heads to maintain their attachment to actin filaments even after calcium levels decrease, thus preventing full relaxation without further calcium influx. This sustained contraction with minimal energy expenditure is a characteristic feature of smooth muscles.
What is the most common cause of vitamin D deficiency?
1) Inadequate sunlight exposure
2) Poor dietary intake of vitamin D
3) Impaired liver function
4) Impaired kidney function
Inadequate sunlight exposure is the most common cause of vitamin D deficiency, as sunlight is necessary for the skin to produce vitamin D.
In the somatosensory area-I of the cerebral cortex, which of the following statements is true?
1) The body is represented in a distorted manner, with the face and hands having a disproportionately larger representation than the rest of the body.
2) The body is represented in a manner proportional to its size, with no distortion in the representation of different body parts.
3) The body is represented in a reversed order, with the feet at the top and the face at the bottom of the postcentral gyrus.
4) Each side of the cortex receives sensory information from the same side of the body.
Answer: 1) The body is represented in a distorted manner in the somatosensory area-I, with the face and hands having a disproportionately larger representation due to their higher innervation density.
What is the condition characterized by the lack of intrinsic factor, leading to vitamin B12 malabsorption?
1) Pernicious anemia
2) Celiac disease
3) Lactose intolerance
4) Crohn's disease
Pernicious anemia is characterized by the lack of intrinsic factor, leading to vitamin B12 malabsorption and subsequent anemia.
What is the primary mechanism of H+ secretion by parietal cells?
1) Active transport via the sodium-hydrogen exchanger (NHE3)
2) Secretion through H+-K+ ATPase pump
3) Secretion through a chloride-bicarbonate antiporter
4) Secretion through a sodium-bicarbonate cotransporter
E) Secretion through a sodium-hydrogen antiporter
The primary mechanism of H+ secretion by parietal cells is through the action of the H+-K+ ATPase pump, also known as the proton pump. This enzyme is responsible for actively transporting H+ ions into the gastric lumen while moving K+ ions into the cells, thereby acidifying the gastric content.
The average time required for spermatogenesis in humans is:
1) 30 days
2) 42 days
3) 74 days
4) 120 days
Spermatogenesis, the process of producing mature sperm cells from spermatogonia, takes approximately 74 days in humans. This includes the development of spermatids and their subsequent transformation into spermatozoa.