Please answer ALL questions A-G! You are running late for physiology class, and

Question

Please answer ALL questions A-G!

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?

Explanation / Answer

A. As a direct result of dehydration due to running, the cardiac output increases and the total resistance decrease.Mean arterial pressure will decrease due to low blood volume.

B. Dehydration elevates the heart rate. If you are dehydrated, your blood volume decreases, so vessel walls do not stretch as much as they should. Baroreceptors relay this information to the brain, which boosts your heart rate to compensate for the reduced blood volume.

C. Stroke volume refers to the amount of blood that is ejected with each systolic beat. Both stroke volume and heart rate are interrelated, and an increase in one often results in a decrease in the other. Dehydration elevates heart rate, hence stroke volume will be lower than the normal.

D. Osmolarity is an estimation of the osmolar concentration of plasma and is proportional to the number of particles per litre of solution. Osmolarity of blood increases with dehydration and decreases with overhydration

E. In normal people, increased osmolarity in the blood will stimulate secretion of Vasopressin/ Antidiuretic hormone (ADH). This will result in increased water reabsorption, more concentrated urine, and less concentrated blood plasma.

F. Antidiuretic hormone binds to receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into the circulation. The parts of the nephron where the receptors are specifically located are on the distal convoluted tubule (DCT) and collecting duct (CD).

G. Renin is an enzyme that is synthesised and stored in Juxta Glomerular Apparatus(JGA) of Kidney. This enzyme is thought to be released in response to a decrease in renal blood flow

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