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.
Which of the following is the correct sequence of enzyme activation in the pancreatic juice?
1) Trypsinogen -> Chymotrypsinogen -> Procarboxypeptidase A -> Proelastase
2) Enterokinase -> Trypsinogen -> Trypsin -> Chymotrypsinogen -> Chymotrypsin
3) Procarboxypeptidase B -> Chymotrypsinogen -> Trypsin -> Procarboxypeptidase A
4) Proelastase -> Chymotrypsinogen -> Chymotrypsin -> Trypsinogen
E) Trypsin -> Chymotrypsinogen -> Chymotrypsin -> Procarboxypeptidase A
The activation of pancreatic enzymes involves a cascade. Enterokinase, an enzyme present in the brush border of the small intestinal epithelial cells, first cleaves trypsinogen into active trypsin. Trypsin then cleaves chymotrypsinogen into chymotrypsin. This process continues with chymotrypsin activating proelastase and procarboxypeptidase A and B into their respective active forms, which are essential for the complete breakdown of proteins in the small intestine.
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
Pernicious anemia is characterized by the lack of intrinsic factor, leading to vitamin B12 malabsorption and subsequent anemia.
What is the effect of vitamin E deficiency on cell membranes?
1) Increased fluidity
2) Decreased fluidity
3) No change in fluidity
4) Unknown
Physiology
Answer: 2
Vitamin E is an important antioxidant that protects unsaturated fats in cell membranes from oxidation. Without vitamin E, these fats can become oxidized, leading to decreased fluidity and altered function of membranes.
What is the effect of acetylcholine on the heart's sinoatrial (S1) node?
1) It increases the heart rate
2) It decreases the heart rate
3) It has no effect on the SA node
4) It causes arrhythmias in the SA node
Acetylcholine, released by the vagus nerve, acts on the SA node to slow down the heart rate by hyperpolarizing the membranes of the SA node cells and decreasing their automaticity.
Angiotensin I is formed by the action of which enzyme on Angiotensinogen?
1) Renin
2) ACE
3) Aldosterone
4) Erythropoietin
Angiotensin I is formed by the action of renin on Angiotensinogen, which is produced by the liver and released into the bloodstream.
MCQ: The macula densa is found in:
1) The proximal convoluted tubule
2) The loop of Henle
3) The distal convoluted tubule
4) The collecting duct
The macula densa is found in the distal convoluted tubule, where it senses sodium chloride concentration and helps regulate glomerular filtration rate.
What is the function of the macula densa in the regulation of the nephron's function?
1) It secretes ADH to regulate water reabsorption.
2) It monitors sodium chloride concentration in the tubular fluid.
3) It produces erythropoietin to stimulate RBC production.
4) It is involved in the conversion of vitamin D to its active form.
The macula densa monitors sodium chloride concentration in the tubular fluid, playing a crucial role in regulating kidney function.