D.2

Question 1

State the reasons why humans require water to survive

Answer 1

Water:

• the basic substance for all metabolic processes

-regulation of body temperature

-enables transport of substances essential for growth

Question 2

State where extracellular fluid can be located throughout the body

Answer 2

Extracellular fluid includes:

• the blood plasma and lymph
• saliva
• fluid secreted by (glands & digestive tract), (skin & kidneys) respectively

Question 3

Explain that Homeostasis involves monitoring and correcting changes in levels by negative feedback mechanisms

Question 4

Explain the role of the loop oh Henlé, medulla, collecting duct and ADH in maintaining the water balance of the blood.

Answer 4

When body fluid levels are low, receptors in the hypothalamus are stimulated. The hypothalamus stimulates the pituitary gland to release ADH. ADH acts on the kidneys, increasing water permeability of the renal tubules and collecting ducts, leading to increased re-absorption of water.