MDS PREP
What is the main difference between endopeptidases and exopeptidases?
1) Endopeptidases cleave internal peptide bonds, while exopeptidases act on the terminal peptide bonds.
2) Endopeptidases are inactive in the stomach, whereas exopeptidases are active in the stomach.
3) Endopeptidases are exclusively found in the pancreas, whereas exopeptidases are exclusively found in the intestinal mucosa.
4) Endopeptidases are exclusively activated by enterokinase, whereas exopeptidases are activated by other enzymes.
E) Endopeptidases are inhibited by acidic pH, while exopeptidases function best at acidic pH.
Endopeptidases, also known as endoproteinases, are enzymes that hydrolyze peptide bonds within the polypeptide chain, breaking down proteins into smaller peptides. Examples include pepsin, trypsin, and chymotrypsin. In contrast, exopeptidases, or exoproteinases, cleave peptide bonds at the ends of the polypeptide chain, either at the N-terminal (aminopeptidases) or C-terminal (carboxypeptidases). These enzymes are involved in the final steps of protein digestion and the degradation of small peptides into individual amino acids.
What is the primary mechanism of H+ secretion by parietal cells?
1) Active transport via the sodium-hydrogen exchanger (NHE3)
2) Secretion through H+-K+ ATPase pump
3) Secretion through a chloride-bicarbonate antiporter
4) Secretion through a sodium-bicarbonate cotransporter
E) Secretion through a sodium-hydrogen antiporter
The primary mechanism of H+ secretion by parietal cells is through the action of the H+-K+ ATPase pump, also known as the proton pump. This enzyme is responsible for actively transporting H+ ions into the gastric lumen while moving K+ ions into the cells, thereby acidifying the gastric content.
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.
Which of the following is not a type of action potential propagation?
1) Autocrine
2) Paracrine
3) Endocrine
4) Synaptic
E. All of the above are types of action potential propagation.
The question contains an error. The terms autocrine, paracrine, endocrine, and synaptic are not types of action potential propagation. Instead, they describe different modes of hormonal or neuronal signaling. Action potentials are propagated along axons without any of these specific types of interactions.
In the presence of antidiuretic hormone (ADH), which part of the nephron becomes highly permeable to water?
1) Proximal Convoluted Tubule (PCT)
2) Loop of Henle
3) Collecting Duct
4) Afferent Arteriole
In the presence of antidiuretic hormone (ADH), the collecting duct becomes highly permeable to water, allowing for increased water reabsorption and concentrated urine.
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 main stimulation for production of A.D.H. is
1. Increase in plasma potassium.
2. Decrease in blood volume
3. Increase in extracellular fluid
4. Decrease inextracellularosmotic pressure
Physiology
Answer: 2
The main stimulation for production of A.D.H. is Decrease in blood volume
- A.D.H. secretion increases during osmotic diuresis
The primary site of absorption for:
1) Calcium - Jejunum
2) Iron - Jejunum
3) Vitamin B12 - Duodenum
4) All of the above
The small intestine, particularly the duodenum and jejunum, are responsible for the absorption of various nutrients. Calcium and iron are mainly absorbed in the duodenum, while vitamin B12 absorption primarily occurs in the ileum with the help of intrinsic factor.