Water

Question 1

Describe the body’s water distribution?

Answer 1

2/3 of the bodys water is intracellular

The rest is extracellular in the interstitial and intravascular spaces. This increases in obesity

Distribution changes with growth and age

Question 2

What are the function of water in the body?

Answer 2

• blood volume
• precursor to bodily fluids (e.g. saliva)
• solvent to metabolic processes
• temperature regulation
• waste product removal

Question 3

What are the body’s water needs?

Answer 3

Varies greatly depending on temperature and activity

AI:

• men: 15 cups
• women: 11 cups

This is based on 80% fluid intake and 20% through food

Question 4

What occurs when water is deficient?

Answer 4

Dehydration gives responses from anti-diuretic hormone, renin-angiotensin system and aldosterone

Question 5

What occurs in water toxicity?

Answer 5

• hyponatremia: concentration of electrolytes decreases
• water is pulled into cells by osmosis
• diluted blood and swollen cells can cause headaches, blurry vision and muscle cramps

Question 6

Explain the mechanisms involved in the regulation of water balance

Answer 6

Decreased blood pressure is sensed by the kidneys

Kidneys increase Na+ absorption, and thus increases water reabsorption

The kidneys also trigger the release of the enzyme renin which converts angiotensinogen to angiotensin I

Angiotension I is then converted to angiotensin II in the lungs

Angiotensin II then acts on the adrenal glands, which triggers the release of aldosterone

Angiotensin II also causes blood vessels to constrict

All of these cause blood pressure to increase

Question 7

How does ADH effect water balance?

Answer 7

Receptors in the brain sense high osmolarity and signal the posterior pituitary gland to release ADH

ADH acts on the aquaporins of the nephrons within the kidneys to increase water retention and increase blood pressure