2.78B - Role of ADH

what is osmoregulation?

* process of maintaining water and salt concentrations across membranes within body
* example of homeostasis

why is maintaining water levels important?

* prevent harmful changes occurring to cells of the body as a result of osmosis
* too much water in the blood - causes cell swelling as water moves into them, can lead to cell lysis (bursting)
* too little water in the blood - cells lose water by osmosis, dehydrating effect, possible cell death

what are the two sources of water in the body

* product of aerobic respiration
* diet

how is water lost from the body?

* via the lungs during exhalation
* sweating
* urine

can water loss controlled?

* water lost through lungs/skin cannot be controlled
* volume of water lost in urine can be controlled by the kidney

is water reabsorption negative or positive feedback?

negative feedback

* when feedback causes corrective measures to be turned ‘off’ so system returns to normal level

how is water reabsorpiton controlled?

by ADH

where is ADH released?

pituitary gland

how much ADH is released?

depends on how much water the kidneys need to reabsorb

what does ADH affect?

permeability of the tubules (collecting duct) to water

if water content of blood is too high…

* **less** ADH released
* **less** water reabsorbed in collectign ducts
* kidneys produce **large** volume of **dilute** urine

if water content of blood is too low…

* pituitary gland releases **more** ADH
* **more** water reabsorbed
* kidneys produce **small** volume of **concentrated** urine