MDS PREP
What is the role of Secretin in pancreatic enzyme secretion?
1) It directly stimulates the release of pancreatic enzymes.
2) It inhibits the release of pancreatic enzymes.
3) It has no effect on pancreatic enzyme secretion.
4) It augments the action of CCK in producing pancreatic enzyme secretion.
Secretin augments the action of CCK (cholecystokinin) in producing pancreatic enzyme secretion, facilitating digestion.
What is the primary mechanism of the fight-or-flight response in the regulation of glycogenolysis?
1) Activation of glycogen phosphorylase by epinephrine
2) Inhibition of glycogen synthase by cortisol
3) Stimulation of glucose-6-phosphatase by thyroid hormones
4) Activation of hexokinase by norepinephrine
Answer: 1) Activation of glycogen phosphorylase by epinephrineExplanation: Epinephrine acts on the beta-adrenergic receptors of liver and muscle cells, which activate protein kinase. This kinase then phosphorylates and activates glycogen phosphorylase, an enzyme that breaks down glycogen into glucose-1-phosphate, which is rapidly converted to glucose-6-phosphate for use in glycolysis or for release into the bloodstream to maintain glucose levels during stress.
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.
What is the significance of the transport maximum for substances like glucose and phosphate?
1) It indicates the maximum amount that can be filtered by the glomerulus
2) It represents the maximum amount that can be actively reabsorbed by the tubules
3) It is the point at which the substance begins to be excreted in the urine
4) It is the point at which the substance becomes toxic to the body
Physiology
Answer: 2
Transport maximum indicates the maximum rate at which an active transport system can reabsorb a substance from the glomerular filtrate.
What is the primary visual area of the occipital lobe also known as?
1) Brodmann area 17
2) V1
3) Calcarine cortex
4) Striate cortex
The primary visual area is Brodmann area 17, which is located in the occipital lobe's medial side of the calcarine sulcus. It is also commonly referred to as the striate cortex due to the distinctive myelinated strip, the stria of Gennari.
What is the function of the thick ascending limb of the loop of Henle?
1) Reabsorption of water
2) Secretion of hydrogen ions
3) Reabsorption of sodium, chloride, and bicarbonate
4) Reabsorption of urea
The thick ascending limb of the loop of Henle is responsible for the reabsorption of sodium, chloride, and bicarbonate, contributing to urine concentration.
Which of the following is NOT an action of bile salts?
1) Emulsification of fat
2) Facilitation of fat absorption
3) Neutralization of stomach acid
4) Conjugation of bile acids
Physiology
Answer: 3
Bile salts are involved in the emulsification and absorption of fat, not in neutralizing stomach acid.
What is the function of titin in muscle contraction?
1) It provides the structural framework for the sarcomere
2) It acts as a bridge between actin and myosin filaments
3) It is the primary contractile protein in muscle fibers
4) It regulates muscle length during contraction and relaxation
Titin acts as a scaffold that supports the alignment of the thick and thin myofilaments in muscle cells, maintaining the integrity of the sarcomere structure during contraction.