MDS PREP
What is the normal plasma concentration of glucose that does not lead to its excretion in the urine?
1) 100 mg/100 ml
2) 180 mg/100 ml
3) 200 mg/100 ml
4) 250 mg/100 ml
The normal plasma concentration of glucose that does not lead to its excretion in the urine is approximately 100 mg/100 ml, below which glucose is typically reabsorbed completely.
Which vitamin is the most important antioxidant in the body, acting in the lipid phase of membranes?
1) Vitamin C
2) Vitamin A
3) Vitamin E (tocopherol)
4) Vitamin B
Vitamin E (tocopherol) is the most important antioxidant in the body, acting in the lipid phase of membranes to protect against oxidative damage.
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.
What is the transport maximum for glucose reabsorption in the kidneys?
1) 125 mg/min
2) 250 mg/min
3) 375 mg/min
4) 500 mg/min
The transport maximum for glucose reabsorption in the kidneys is about 375 mg/min, which indicates the maximum amount of glucose that can be reabsorbed before it appears in the urine.
In which part of the nephron is bicarbonate primarily reabsorbed?
1) Loop of Henle
2) Distal convoluted tubule
3) Proximal convoluted tubule
4) Collecting duct
Bicarbonate is primarily reabsorbed in the proximal convoluted tubule, where it plays a crucial role in maintaining acid-base balance in the body.
What is the primary neurotransmitter involved in the sympathetic nervous system's response at the neuromuscular junction?
1) Acetylcholine
2) Norepinephrine
3) Epinephrine
4) Dopamine
Answer: 2) The primary neurotransmitter involved in the sympathetic nervous system's response at the neuromuscular junction is norepinephrine, which acts on alpha and beta-adrenergic receptors.
What is the primary mechanism by which the pancreas regulates the activity of its own enzymes in the small intestine?
1) By secreting specific enzyme inhibitors
2) By controlling the pH of pancreatic juice
3) By altering the concentration of bile salts
4) Through the action of the sphincter of Oddi
E) By regulating the flow of pancreatic juice into the intestine
The pancreas secretes specific enzyme inhibitors, such as trypsin inhibitor, to prevent the premature activation of pancreatic enzymes in the pancreas itself. These inhibitors are degraded in the duodenum when the enzymes encounter the higher pH, allowing the enzymes to become active and participate in the digestion of food. Additionally, the presence of food in the intestine triggers the release of secretin, which stimulates the pancreas to secrete bicarbonate to neutralize acidic chyme and create an optimal environment for enzyme activity.
In the proximal convoluted tubule (PCT), which of the following substances is NOT reabsorbed?
1) Sodium
2) Chloride
3) Glucose
4) Water
In the proximal convoluted tubule (PCT), water is reabsorbed along with sodium, chloride, and glucose; however, not all substances are reabsorbed equally.