MDS PREP
What is the role of the vagus nerve in the parasympathetic system?
1) Control of heart rate and gastric motility
2) Control of pupil dilation and salivation
3) Control of skeletal muscle contraction
4) Control of pituitary hormone secretion
The vagus nerve, as part of the parasympathetic system, innervates various organs in the thoracic and abdominal cavities, influencing heart rate and gastric motility among other functions.
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.
What is the threshold for glucose excretion in the urine in a healthy individual?
1) 100 mg/100 ml
2) 180 mg/100 ml
3) 200 mg/100 ml
4) 250 mg/100 ml
The threshold for glucose excretion in the urine in a healthy individual is approximately 180 mg/100 ml, above which glucose appears in the urine.
What is the primary effect of norepinephrine on the pupillary muscles during the fight-or-flight response?
1) Dilatation (mydriasis)
2) Constriction (miosis)
3) No effect on pupil size
4) It depends on the presence of other neurotransmitters
Answer: 1) Dilatation (mydriasis)Explanation: Norepinephrine acts on alpha-adrenergic receptors in the pupillary dilator muscles, leading to pupil dilation. This is a component of the sympathetic nervous system's response to stress, which also includes pupil dilatation mediated by epinephrine.
What is the primary site of bilirubin deposition in tissues during jaundice?
1) The liver
2) The spleen
3) The skin and sclera
4) The pancreas
The primary site of bilirubin deposition in tissues during jaundice is the skin and sclera, leading to yellowing.
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 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.
What happens when the estrogen level crosses a certain threshold during the menstrual cycle?
1) It inhibits the release of LH and FSH
2) It stimulates the release of LH and FSH
3) It has no effect on pituitary hormone secretion
4) It triggers ovulation
When estrogen levels cross a certain threshold during the menstrual cycle, it triggers ovulation by stimulating the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH).