MDS PREP
Which vitamin is the most important antioxidant in the body, acting in the lipid phase of membranes?
1) Vitamin C
2) Vitamin A
3) Vitamin E (tocopherol)
4) Vitamin B
Physiology
Answer: 3
Vitamin E is the most important antioxidant in the body, acting in the lipid phase of membranes and protecting against the effects of free radicals. It is crucial for maintaining the integrity and function of cellular organelles and the cell membrane by preventing the oxidation of unsaturated fats.
What is the mechanism of action of umami taste substances?
1) Activation of sodium-dependent glucose transporters
2) Stimulation of bitter G-protein coupled receptors
3) Activation of amiloride-sensitive sodium channels
4) Activation of glutamate taste sensors (glutamate receptors)
Umami taste is triggered by the activation of glutamate receptors present in taste cells, which leads to the perception of savoriness.
What is the primary function of type A? fibers?
1) Proprioception and motor function in muscle spindles
2) Pain and temperature sensation
3) Touch and pressure sensation
4) Autonomic regulation of smooth muscles
Type A? fibers are thinly myelinated and conduct pain and temperature signals rapidly. They are involved in the transmission of the initial sharp pain sensation, often in response to noxious stimuli such as pinpricks or intense heat.
What is the primary mechanism responsible for the reabsorption of sodium in the distal tubules and collecting ducts of the nephron?
1) Sodium-hydrogen exchange
2) Sodium-glucose cotransport
3) Sodium-potassium-2-chloride cotransport
4) Sodium-phosphate cotransport
E) Sodium-chloride symport
The primary mechanism for sodium reabsorption in the distal tubules and collecting ducts is sodium-hydrogen exchange, which occurs through the NHE3 transporter. This allows for the reclamation of sodium while maintaining the acid-base balance by exchanging sodium for hydrogen ions, which are then secreted into the tubular lumen.
What is the primary function of the pharyngeal stage of deglutition?
1) Voluntary contraction of the pharyngeal muscles to move food into the esophagus
2) Relaxation of the upper esophageal sphincter
3) Closure of the epiglottis to prevent aspiration of food into the trachea
4) Involuntary contraction of the pharyngeal muscles to propel the food bolus into the esophagus
E) Stimulation of salivary glands to secrete saliva
The pharyngeal stage of deglutition involves involuntary contraction of the pharyngeal muscles and is responsible for the rapid passage of the food bolus from the oral cavity to the upper esophagus. It is primarily a reflex act triggered by the voluntary movement of food into the back of the mouth.
What is the osmolarity of the tubular fluid leaving the ascending limb of the loop of Henle?
1) 300mOsm/L
2) 100mOsm/L
3) 1200mOsm/L
4) 50mOsm/L
The osmolarity of the tubular fluid leaving the ascending limb of the loop of Henle is 100mOsm/L, as it is impermeable to water and reabsorbs solutes.
MCQ: The pancreas has which of the following cell types?
1) Alpha cells
2) Beta cells
3) Delta cells
4) All of the above
The pancreas has all of the following cell types: alpha cells (which produce glucagon), beta cells (which produce insulin), and delta cells (which produce somatostatin).
How does the cerebellum contribute to motor coordination?
1) By timing and comparing the duration of agonist muscle activity and latency of antagonist activity
2) By directly controlling the force of muscle contraction
3 ) By regulating the rate of nerve impulse conduction in motor neurons
4) By initiating voluntary movement
The cerebellum is crucial for the coordination of movement. It receives signals from the motor cortex about the intended movement and the actual position of the limb through climbing fibers. By timing these signals, it helps to stop the movement at the correct point by inhibiting the agonist muscles and stimulating the antagonist muscles.