You are running late for physiology class, and instead of cutting through a yard

Question

You are running late for physiology class, and instead of cutting through a yard where there is a dangerous cat, you go the long way and run all the way to school. It is very hot and you sweat excessively and become dehydrated. You lose proportionately more water than salts.

a. What happens to your mean arterial pressure as a direct result of dehydration? b. Will your heart rate be elevated or extra slow as a result of dehydration?

c. Will your stroke volume be elevated or lower than normal as a result of dehydration?

d. What happens to the osmolarity of your blood?

e. What hormone is released as direct response to this change in osmolarity?

f. On what region of the nephron does this hormone act?

g. What enzyme is released as a direct result of the change in renal blood pressure?

h. What non-‘roid hormone is produced as the end result of activation of the pathway in g.?

i. Name 3 hormones that will be affecting the state of contraction of your arterioles and peripheral vasculature.

j. Will your levels of aldosterone increase or decrease in response to dehydration? Explain.

k. What is the direct stimulus for increased release of aldosterone when MAP is low?

l. How specifically does aldosterone cause increased absorption of water?

m. You drink 2 L of water to replace the fluids that you lost, and restore normal mean arterial pressure. What happens to the osmolarity of your blood?

n. You start to experience muscle weakness due to low plasma potassium levels. What condition are you suffering from?

Explanation / Answer

A. Dehydration will cause decrease in mean arterial pressure due to decrease in volume of blood as a result of dehydration.

b. Heart rate will be elevated as a result of dehydration due to the fact that loss of fluids results in decrease in arterial pressure and stroke volume in the heart. In order to maintain homeostatic cardiac output at lower pressure, heart rate increases.

C. Stroke volume means amount of blood pumped per beat by the heart. Stroke volume decreases due to dehydration.

D. Due to loss of fluids from blood,its osmolarity increases and blood will become more hypertonic.

E. Hormone vassopressin is released due to change in blood osmolarity.

F. This hormone will causes absorption of water from DCT,CT and CD of nephron of kidneys.

G. Enzyme renin is produced by juxtaglomerular cells of renal cortex in response to fall in arterial blood pressure.

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