MDS PREP
What is the primary mechanism by which the stomach protects itself from self-digestion by its own enzymes?
1) Mucus secretion by gastric mucosal cells
2) Presence of intrinsic factor in the gastric juice
3) High concentration of bicarbonate in gastric juice
4) Low pH of gastric juice inhibiting its own enzymes
E) The mucosal lining is impermeable to H+ ions
The stomach protects itself from the harsh acidic environment and its own digestive enzymes through the secretion of a thick layer of mucus by mucosal cells. This mucus barrier forms a physical and chemical barrier that shields the underlying tissue from the acid and pepsin. Additionally, the stomach lining has a high turnover rate and is continuously regenerated, and the enzymes in the gastric juice are inactive until they come into contact with food.
What is the primary function of the enteric nervous system in the gastrointestinal tract?
1) Controlling digestive enzyme secretion
2) Regulating the absorption of nutrients
3) Coordinating muscular contractions and peristalsis
4) Secreting hormones that regulate digestion
E) Controlling blood flow to the GI tract
The enteric nervous system, also known as the gut-brain, is a network of neurons that controls the muscular activity of the gastrointestinal tract. It is capable of operating independently of the central nervous system but can be modulated by it. Its main function is to regulate motility and secretion within the GI tract, which includes coordinating peristaltic contractions that propel food and facilitate mixing and absorption.
What is the effect of increased parathyroid hormone during pregnancy?
1) Decreased calcium ion liberation from maternal bones
2) Increased calcium ion absorption in the gut
3) Increased calcium ion excretion in the urine
4) Increased calcium ion mobilization from maternal bones for fetal use
Answer: 4) Increased parathyroid hormone during pregnancy stimulates liberation of calcium ions from maternal bones for the fetus's calcium needs.
What hormone is secreted by the kidneys that stimulates red blood cell production?
1) Renin
2) Erythropoietin
3) Aldosterone
4) Cortisol
Erythropoietin is the hormone secreted by the kidneys that stimulates red blood cell production in response to low oxygen levels in the blood.
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
The primary action of antidiuretic hormone (ADH) in the kidneys is to increase the permeability of water in the collecting tubules and ducts, promoting water reabsorption.
Which area of the brain is associated with the comprehension of speech?
1) Wernicke’s area
2) Broca’s area
3) Primary auditory cortex
4) Angular gyrus
E. Occipital lobe
Wernicke's area, located in the posterior part of the superior temporal gyrus, is involved in language comprehension. It receives input from the secondary somatic, auditory, and visual association areas and is critical for understanding spoken and written language.
What is the role of antidiuretic hormone (ADH) in the nephron?
1) Increases sodium reabsorption
2) Increases water reabsorption
3) Decreases potassium secretion
4) Inhibits renin secretion
Antidiuretic hormone (ADH) increases water reabsorption in the nephron, particularly in the collecting ducts, by making them more permeable to water.
Which of the following is the correct statement regarding mammalian nerve fibers?
1) A-alpha fibers have the lowest conduction velocity and are responsible for pain and temperature sensation.
2) A-beta fibers have the highest conduction velocity and are responsible for motor supply to skeletal muscles.
3) A-gamma fibers are heavily myelinated and have the fastest conduction velocity.
4) C fibers have a large diameter and are responsible for fine motor control.
Answer: 2) A-beta fibers have the second highest conduction velocity after A-alpha fibers and are responsible for touch, kinesthetic sense, and pressure sensation, not motor supply to skeletal muscles. A-alpha fibers have the highest conduction velocity and are indeed responsible for motor supply to skeletal muscles.