MDS PREP
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 primary role of pancreatic amylase in the digestive process?
1) Breaking down fats into fatty acids and glycerol
2) Degrading proteins into peptides and amino acids
3) Hydrolyzing polysaccharides into maltose and isomaltose
4) Neutralizing gastric acid in the duodenum
E) Converting bile salts into bile acids
Pancreatic amylase is an enzyme that plays a key role in the digestion of carbohydrates. It is secreted into the duodenum in response to food and breaks down complex starches into simpler disaccharides like maltose and isomaltose. These disaccharides are then further hydrolyzed by other enzymes into glucose for absorption.
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.
Which of the following structures is associated with the control of voluntary eye movement?
1) Occipital lobe
2) Temporal lobe
3) Frontal eye field
4) Parietal lobe
The frontal eye field, located in the dorsolateral part of the frontal lobe, is involved in the control of voluntary eye movement. It is part of the motor system and helps in the planning and execution of saccadic movements.
What is the primary mechanism of bicarbonate reabsorption in the proximal convoluted tubule?
1) Passive diffusion
2) Active transport
3) Combination with hydrogen ions
4) Co-transport with sodium
The primary mechanism of bicarbonate reabsorption in the proximal convoluted tubule involves combination with hydrogen ions, forming carbonic acid, which is then converted to water and carbon dioxide.
What is the primary effect of acetylcholine on the cardiac muscles?
1) Decreased heart rate
2) Increased heart rate
3) No effect on heart rate
4) Increased force of contraction
Answer: 1) Decreased heart rateExplanation: In the heart, acetylcholine acts on muscarinic receptors, which are present on the sinoatrial (SA) and atrioventricular (AV) nodes. This leads to a decrease in heart rate by slowing the sinoatrial (SA) node's automaticity and increasing the time it takes for an electrical impulse to pass through the AV node.
The release of which hormone is triggered by the macula densa cells during tubulo-glomerular feedback?
1) Renin
2) Angiotensin II
3) Atrial Natriuretic Peptide (ANP)
4) Aldosterone
The macula densa cells respond to decreases in sodium chloride concentration in the tubular fluid by releasing renin, which initiates the renin-angiotensin-aldosterone system (RAAS). This leads to increased sodium reabsorption and water retention, thereby restoring the sodium chloride balance and blood volume.
What is the significance of the pre-to-post ganglionic fiber ratio in the sympathetic nervous system?
1) It indicates the speed of nerve impulse transmission.
2) It reflects the number of synapses involved in the pathway.
3) It is unrelated to the function of the sympathetic nervous system.
4) It indicates the level of sympathetic nervous system activity.
In the sympathetic nervous system, the pre-to-post ganglionic fiber ratio of 1:20 to 1:100 indicates that there are fewer postganglionic fibers than preganglionic fibers. This ratio suggests that each preganglionic neuron synapses with multiple postganglionic neurons, thereby amplifying the sympathetic response to a given input.