MDS PREP
What is the function of titin in muscle contraction?
1) It provides the structural framework for the sarcomere
2) It acts as a bridge between actin and myosin filaments
3) It is the primary contractile protein in muscle fibers
4) It regulates muscle length during contraction and relaxation
Titin acts as a scaffold that supports the alignment of the thick and thin myofilaments in muscle cells, maintaining the integrity of the sarcomere structure during contraction.
What is the primary mechanism responsible for the reclamation of bile acids in the enterohepatic circulation?
1) Active transport in the ileum
2) Facilitated diffusion in the colon
3) Passive diffusion in the small intestine
4) Bacterial synthesis in the liver
The primary mechanism responsible for the reclamation of bile acids in the enterohepatic circulation is active transport in the ileum, allowing for recycling of bile acids.
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 function of calcidiol in the body?
1) It is the active form of vitamin D
2) It is the precursor to calcitriol (active vitamin D)
3) It has no known function
4) It inhibits calcium absorption
Physiology
Answer: 2
Calcidiol (25 hydroxy cholecalciferol) is a precursor to calcitriol (1,25 dihydroxy vitamin D3), which is the active form of vitamin D. Calcitriol is formed in the kidneys by the action of 1-? hydroxylase and plays a critical role in calcium homeostasis.
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.
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.
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.
What is the normal ratio of glycine to taurine conjugates of bile acids in the bile?
1) 1:1
2) 2:1
3) 3:1
4) 4:1
Physiology
Answer: 3
The ratio of glycine to taurine conjugates of bile acids is normally 3:1.