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.
What is the primary neurotransmitter of the sympathetic nervous system?
1) Acetylcholine
2) Norepinephrine
3) Dopamine
4) Epinephrine
The sympathetic nervous system primarily uses norepinephrine (also known as noradrenaline) as its neurotransmitter. It is released from the synaptic terminals of postganglionic sympathetic fibers and acts on adrenergic receptors, which are found on various target cells throughout the body. This neurotransmitter is essential for the body's "fight or flight" response, contributing to increased heart rate, dilated pupils, and other physiological changes associated with stress or emergency situations.
What is the primary function of chymotrypsin in the digestive process?
1) Converting chymotrypsinogen into chymotrypsin
2) Breaking down proteins into peptides
3) Catalyzing the hydrolysis of disulfide bonds in proteins
4) Activating pepsinogen into pepsin
E) Releasing gastrin from gastric mucosa
Chymotrypsin is an endopeptidase enzyme that plays a crucial role in the digestive system by breaking down proteins into smaller peptides. It is activated from its precursor chymotrypsinogen by the enzyme trypsin. Once active, chymotrypsin hydrolyzes the peptide bonds at the carboxyl side of aromatic and bulky amino acids, such as phenylalanine, tryptophan, and tyrosine. This process is essential for the further digestion and absorption of dietary proteins.
What is the condition characterized by the lack of intrinsic factor, leading to vitamin B12 malabsorption?
1) Pernicious anemia
2) Celiac disease
3) Lactose intolerance
4) Crohn's disease
Physiology
Answer: 1
Pernicious anemia is caused by the lack of intrinsic factor, which leads to impaired vitamin B12 absorption and subsequent megaloblastic anemia.
Which of the following statements is true about the regulation of the sympathetic nervous system?
1) The sympathetic nervous system is primarily regulated by the parasympathetic nervous system.
2) The sympathetic nervous system is mainly controlled by the hypothalamus.
3) The sympathetic nervous system is regulated by the spinal cord through the sympathetic chain ganglia.
4) The sympathetic nervous system is primarily regulated by the sympathetic chain ganglia.
Answer: 3) The sympathetic nervous system is regulated by the spinal cord through the sympathetic chain ganglia, which receive input from the hypothalamus and other higher centers.
In which part of the male reproductive system does spermatogenesis occur?
1) Seminal vesicles
2) Epididymis
3) Prostate gland
4) Seminiferous tubules
Physiology
Answer: 4
Spermatogenesis is the process of sperm cell development. It takes place in the seminiferous tubules within the testes. These tubules are lined with spermatogonia, which mature into primary spermatocytes, then secondary spermatocytes, and finally into spermatids, which mature into spermatozoa.
What is the primary function of the theophylline?
1) It acts as a muscle relaxant
2) It increases intracellular cAMP levels
3) It inhibits acetylcholine receptors
4) It stimulates the release of insulin
Theophylline is a methylxanthine derivative that acts as a phosphodiesterase inhibitor, leading to increased intracellular cyclic AMP (cAMP) levels. This can stimulate various cellular processes, including smooth muscle relaxation and bronchodilation in the respiratory system. It also enhances insulin secretion.
What is the primary effect of acetylcholine on the cardiac muscles?
1) Decreased heart rate
2) Increased heart rate
3) No effect on heart rate
4) Increased force of contraction
Answer: 1) Decreased heart rateExplanation: In the heart, acetylcholine acts on muscarinic receptors, which are present on the sinoatrial (SA) and atrioventricular (AV) nodes. This leads to a decrease in heart rate by slowing the sinoatrial (SA) node's automaticity and increasing the time it takes for an electrical impulse to pass through the AV node.