MDS PREP
What is the role of the acrosome in sperm?
1) Provides energy for sperm motility
2) Contains enzymes that help in the penetration of the ovum
3) Protects the sperm DNA
4) Involved in the fertilization process by fusing with the egg membrane
Physiology
Answer: 2
The acrosome is a cap-like structure located on the head of a spermatozoon. It contains lysosome-like organelles rich in enzymes that are essential for penetrating the egg's outer layers during fertilization.
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.
The increased venous return to the heart causes:
1. End diastolic volume increase
2. End systolic volume decrease
3. Decrease stroke volume
4. Decreased isovolumetric ventricular contraction.
Physiology
Answer: 1
The increased venous return to the heart causes End diastolic volume increase
What is the function of the enteric nervous system?
1) Controls the heart rate and rhythm
2) Regulates the contraction of skeletal muscles
3) Regulates the function of the gastrointestinal tract
4) Controls the pupillary response to light
The enteric nervous system is the intrinsic nervous system of the gastrointestinal tract and is responsible for the regulation of digestion and other gastrointestinal functions. It can operate independently of the central nervous system and consists of a network of neurons and glial cells that are embedded within the wall of the gut, coordinating local reflexes and influencing the muscle and secretory activities of the digestive system.
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 role of the cholinergic system in the regulation of urinary bladder function?
1) Contraction of the detrusor muscle and relaxation of the trigone
2) Relaxation of the detrusor muscle and contraction of the trigone
3) Contraction of the urethral sphincter
4) Contraction of the urethral sphincter and relaxation of the detrusor muscle
The parasympathetic nervous system, which is cholinergic, stimulates the detrusor muscle of the urinary bladder to contract and the trigone muscle to relax, facilitating micturition (urination). This is mediated by the activation of muscarinic M3 receptors.
What is the role of gastrin in the gastric phase of acid secretion?
1) It is released by the pancreas and stimulates acid secretion in the stomach
2) It is released by the duodenum and inhibits acid secretion
3) It is released by the stomach and stimulates acid secretion in response to food
4) It has no role in gastric acid secretion
Physiology
Answer: 3
Gastrin is released from G cells in the antral mucosa of the stomach in response to the presence of food. It stimulates the parietal cells of the stomach to secrete hydrochloric acid and intrinsic factor, contributing to the gastric phase of acid secretion.
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).