MDS PREP
What happens to lithocholic acid in the enterohepatic circulation?
1) It is reabsorbed in the terminal ileum and returned to the liver
2) It is metabolized into chenodeoxycholic acid
3) It is converted into deoxycholic acid
4) It is excreted in feces due to its insolubility
Physiology
Answer: 4
Lithocholic acid is insoluble and not efficiently reabsorbed, leading to its excretion in the feces.
What is the role of the sodium-calcium exchanger (NCX) in calcium homeostasis?
1) It transports calcium into cells
2) It transports sodium into cells and calcium out of cells
3) It transports sodium out of cells and calcium into cells
4) It has no role in calcium homeostasis
The sodium-calcium exchanger (NCX) transports sodium into cells and calcium out of cells, playing a crucial role in calcium homeostasis.
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 primary function of bile acids in the intestine?
1) Emulsification of dietary fat
2) Neutralization of intestinal pH
3) Digestion of proteins
4) Absorption of water and electrolytes
The primary function of bile acids in the intestine is the emulsification of dietary fat, which aids in fat digestion and absorption.
What is the primary function of vitamin D in the body?
1) Blood clotting
2) Bone formation and maintenance
3) Vision
4) Immune system function
The primary function of vitamin D in the body is bone formation and maintenance, as it helps regulate calcium and phosphate levels.
Which hypothalamic nucleus is considered the satiety center?
1) Venteromedial nucleus
2) Lateral nucleus
3) Arcuate nucleus
4) Dorsomedial nucleus
Answer: 1) The venteromedial nucleus of the hypothalamus is considered the satiety center.
What is the effect of muscarinic stimulation on the pupil of the eye?
1) Dilation (mydriasis)
2) Constriction (miosis)
3) No effect on pupil size
4) Paralysis of the pupil
The pupillary light reflex is under the control of the parasympathetic nervous system, which stimulates muscarinic receptors in the iris sphincter muscle. This leads to pupil constriction (miosis) in response to light, as part of the body's attempt to regulate the amount of light entering the eye.
What is the primary effect of excitatory postsynaptic potentials (EPSPs) on the excitability of a neuron?
1) Depolarization
2) Hyperpolarization
3) No change in excitability
4) Initiation of an action potential
Answer: 1) DepolarizationExplanation: EPSPs occur when the neurotransmitter binds to postsynaptic receptors that open sodium channels, allowing sodium ions to flow into the neuron and causing the membrane to depolarize. This increases the excitability of the neuron, bringing the membrane potential closer to the threshold for action potential firing.