MDS PREP
What is the primary function of the C-peptide after it is cleaved from proinsulin during the synthesis of insulin?
1) It has no significant role
2) It acts as a regulator of insulin secretion
3) It serves as a precursor for other pancreatic hormones
4) It is involved in the maintenance of islet cell structure
The C-peptide is removed during the conversion of proinsulin to insulin and does not have a known biological function. Its primary purpose is to hold the A and B chains of proinsulin together during synthesis.
MCQ: The primary site of absorption for:
1) Calcium - Jejunum
2) Iron - Jejunum
3) Vitamin B12 - Duodenum
4) All of the above
The primary site of absorption for calcium, iron, and vitamin B12 is the jejunum, making the answer "All of the above" correct.
What are the main characteristics of type I (slow twitch) muscle fibers?
1) High myoglobin content and oxidative metabolism
2) Low myoglobin content and oxidative metabolism
3) High actin and myosin content for rapid contraction
4) Large diameter and high glycolytic enzyme activity
Type I fibers are also called slow-twitch fibers due to their high myoglobin content, which supports aerobic metabolism and allows for sustained contractions over time.
Which hormone is primarily responsible for increasing the force and frequency of uterine contractions during parturition?
1) Oxytocin
2) Estrogen
3) Progesterone
4) Prolactin
E. Cortisol
Oxytocin is synthesized in the paraventricular nucleus of the hypothalamus and acts on the uterus to increase the force and frequency of contractions during childbirth. It is released during labor and stimulated by the stretching of the cervix and vagina as the baby descends. Estrogens increase the sensitivity of the uterus to oxytocin, while progesterone decreases it. Prolactin is involved in milk production and let-down reflex. Cortisol is a stress hormone that prepares the body for parturition but does not directly increase uterine contractions.
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 primary function of the myenteric plexus in the gastrointestinal tract?
1) Control of gastrointestinal motility
2) Regulation of intestinal secretion
3) Blood flow regulation in the gut wall
4) Nutrient absorption from the intestinal lumen
E) Maintenance of the mucosal barrier function
The myenteric plexus, or Auerbach's plexus, is located between the longitudinal and circular muscle layers of the gut wall. Its primary function is to regulate the motility of the gastrointestinal tract. It does so by coordinating the contractions of the smooth muscles, which are responsible for peristalsis and the propulsion of food through the digestive system. The myenteric plexus works in conjunction with the submucosal plexus and can be influenced by both the sympathetic and parasympathetic nervous systems.
What is the significance of the increased pulse rate and blood pressure during REM sleep?
1) It indicates the body is preparing for wakefulness
2) It is a byproduct of increased brain activity during dreaming
3) It is not significant and does not reflect any physiological changes
4) It indicates a pathological condition
The increased pulse rate and blood pressure during REM sleep are associated with the heightened brain activity and autonomic system arousal that occurs during this phase of sleep, despite the presence of muscular atonia.
What is the primary function of the reticular activating system during wakefulness?
1) It initiates REM sleep
2) It suppresses sensory input
3) It filters and modulates sensory information
4) It maintains the overall level of arousal and alertness
The reticular activating system (RAS) is involved in the regulation of wakefulness and arousal by modulating the transmission of sensory information to the thalamus and cortex and by influencing the release of neurotransmitters that promote alertness.