MDS PREP
What is the primary function of the cholinergic system in the gastrointestinal tract?
1) Decreases peristalsis and relaxes sphincters
2) Increases peristalsis and relaxes sphincters
3) Increases peristalsis and constricts sphincters
4) Decreases peristalsis and constricts sphincters
The cholinergic system, acting via muscarinic receptors, increases peristalsis and relaxes the sphincters in the gastrointestinal tract to facilitate the movement of food and waste through the digestive system.
Which of the following is NOT a direct component of the corticospinal tract's termination?
1) Alpha-motor neurons (anterior or ventral horn cells)
2) Interneurons in the intermediate gray matter
3) Delta-motor neurons in the ventral horn
4) Gamma-motor neurons in the ventral horn
The corticospinal tract primarily terminates on alpha-motor neurons and interneurons, not directly on delta-motor neurons, which are involved in the control of muscle spindles and not in direct motor control.
What type of receptors are found in the heart that are stimulated by the parasympathetic nervous system?
1) Adrenergic receptors
2) Muscarinic receptors
3) Nicotinic receptors
4) GABAergic receptors
The parasympathetic nervous system acts on muscarinic receptors (specifically M2 receptors) in the heart to decrease the heart rate and atrial contractility, thereby contributing to a resting state and energy conservation.
What is the primary mechanism by which acid secretion is regulated in the stomach?
1) By the pH of the stomach content
2) By the amount of food present
3) By the time of day
4) By the type of food consumed
The primary mechanism by which acid secretion is regulated in the stomach is by the pH of the stomach content, which influences gastric secretions.
What is the primary effect of norepinephrine on blood vessels during the fight-or-flight response?
1) Vasodilatation in most vessels
2) Vasoconstriction in most vessels
3) Vasodilatation in arterioles of skeletal muscles and the heart
4) Vasoconstriction in arterioles of skeletal muscles and the heart
Answer: 2) Vasoconstriction in most vesselsExplanation: Norepinephrine acts on alpha-adrenergic receptors in the vascular smooth muscles, causing vasoconstriction in most blood vessels. This diverts blood flow to critical organs like the brain and muscles, preparing the body for physical exertion.
Which of the following is NOT a hormone secreted by the kidney?
1) 1,25 Dihydrocholecalciferol
2) Renin
3) Erythropoietin
4) Angiotensin I
Angiotensin I is NOT a hormone secreted by the kidney; it is produced from angiotensinogen in the liver and converted to angiotensin II by the kidneys.
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.
What is the primary mechanism of the inhibitory postsynaptic potential (IPSP) in the nervous system?
1) Activation of sodium channels causing depolarization
2) Activation of potassium channels causing hyperpolarization
3) Activation of chloride channels causing depolarization
4) Activation of calcium channels causing hyperpolarization
Answer: 2) Activation of potassium channels causing hyperpolarizationExplanation: IPSPs are typically generated when a neurotransmitter binds to GABA receptors on the postsynaptic membrane of a neuron, causing potassium channels to open and leading to efflux of K+ ions. This hyperpolarizes the neuron, reducing the likelihood of an action potential.