Water and Electrolyte Homeostasis

Question 1

THE INTERNAL ENVIRONMENT

Answer 1

• The constancy of the internal environment is the prerequisite for life
• The internal environment is made up of the body fluids (intracellular fluid and extracellular fluid)
• Exchange between the fluid compartments is occurring continuously

Question 2

ALDOSTERONE

Answer 2

• Corticosteroid hormone synthesised in and secreted from the adrenal glands cortex
• Secretion increases in response to either;
• A decrease in blood pressure (renin- angiotensin- aldosterone system)
• An increase in blood K+ levels
• Aldosterone drives Na+ reabsorption in exchange for K+
• Water re-uptake will also occur along an established osmotic gradient

Question 3

ELECTROLYTE: SODIUM

Answer 3

• Regulation linked with water balance
• High blood sodium= lower body water
• Low blood sodium= high body water

Question 4

ELECTROLYTE: POTASSIUM

Answer 4

Regulation by removal of excess blood potassium by renal secretion

Question 5

ELECTROLYTE: PHOSPHATES

Answer 5

“Overflow mechanism” if blood phosphorus level is higher than the capacity of the kidneys to reabsorb phosphate→ the excess is lost in the urine