Question

Which of the following may result in an increase in mean arterial pressure (MAP) explain:

W) increased heart rate

X) decreased venous return.

Y) increased peripheral resistance.

Z) increased radius of systemic arterioles.

Select one:

a. if only W, X and Y are correct

b. if only W and Y are correct

c. if only X and Z are correct

d. if only Z is correct

e. if all are correct

COULD YOU EXPLAIN NOT JUST THE CORRECT ANSWER BUT THE REASONS FOR ALL PLS

Answer 1

Mean Arterial Pressure (MAP) is the average pressure in an individual's artery during a cardiac cycle.

MAP = ( CO × SVR ) + CVP

where, CO = cardiac output

SVP = Systemic Vascular Resistance

CVP = Central Venous Pressure

We know that Cardiac output determined by stroke volume and heart rate.

CO = Heart rate × Stroke Volume

So increase in Heart will increase Cardiac output which in turn increase MAP. Statement (W) is correct.

Statement (Y) is also Correct since increase in peripheral resistance increases the Mean arterial pressure.

Statement (Z) is incorrect. We know that resistance is inversely proportional to fourth power of radius of the arterioles. So if the radius is increased the resistance will decrease by four times. If the resistance decreases then the MAP will also decrease.

where a = any constant

R= resistance and r = radius of the vessel.

Central Venous Pressure has minimal role in mean arterial pressure. But if venous return is decreased then central venous pressure will also decrease which decreases the mean arterial pressure. Also decrease in venous return decreases the cardiac output which in turn decreases Mean Arterial Pressure. So statement (X) is also incorrect.

So the correct statements are :- (W) and (Y).

Thus the correct answer is (b) Only W and Y are correct.