April 5, 2016 - Water Metabolism

Question 1

Aquaporin Channels

Answer 1

AQP1 and AQP4 are always expressed

Water is always free to flow in and out of cells through these channels.

Question 2

Water and the Brain

Answer 2

Too much water can lead to cerebral edema

Too little water can lead to cerebral hemorrhage

Because of this, the brain has adapted and can self-regulate itself. If there is too much water, the brain can pump out osmoles. This also has consequences though, because the cells are losing vital material.

Question 3

Sensing and Regulating Total Body Water

Answer 3

Sensed by osmoreceptors in the hypothalamus. This determines whether or not you are thirsty, as well as to get rid of less water by sending signals to the kidneys and making ADH.

If your body has too much water, you lower the amount of ADH produced.

* ADH can respond very rapidly *

Question 4

Renin Angiotensin System

Answer 4

Depends on the stretch of the arterioles in the kidneys. If the arteries become less stretched, it will produce renin which will ultimately retain salt and increase blood pressure.

Interestingly, the hormonal system that regulates sodium concentration is not influenced by the sodium concentration.

RAS only cares about volume, not [Na].

Question 5

Abnormal Serum [Na⁺ ]

Answer 5

Implies an abnormal amount of water.