Water and Electrolytes

Question 1

Regulation of Water

Answer 1

Amount of water lost by the body is regulated by increasing or decreasing the amount of water excreted by the kidneys
When concentrations of salutes in the blood increases, the brain senses this and releases antidiuretic hormone
ADH signals the kidneys to reabsorb water
When solute concentration is low, ADH level decreases, and more water is excreted into the urine

Question 2

Dehydration

Answer 2

Drop in body water reduces the blood volume, reducing the ability to deliver oxygen and nutrients to cells and to remove waste products

Question 3

Overhydration

Answer 3

Too much water relative to the amount of sodium in the body results in a drop of sodium levels –> hyponatremia
Hyponatremia causes water to move out of the blood vessels by osmosis, causing tissues to swell

Question 4

Potassium

Answer 4

The principal positively charged ion inside cells - 30x more concentrated inside than outside

Question 5

Sodium

Answer 5

Most abundant positively charged ion outside the cell

Question 6

Chloride

Answer 6

The principal negatively charged extracellular ion

Question 7

Sodium-Potassium ATPase Pump

Answer 7

Maintains the concentration gradient by pumping Na out of the cell and K into the cell
Concentration gradient important for nerve conduction and muscle contraction
Also linked to nutrient transport
Requires energy

Question 8

Regulation of Electrolyte Balance

Answer 8

Na plays a critical role in regulating extracellular blood volume, which can change blood pressure
When BP decreases, kidneys release renin, which eventually leads to the production of angiotensin II
Angiotensin II stimulates released of aldosterone and ADH
Aldosterone acts on the kidneys by increasing the number of Na/K pumps, leading to increased Na reabsorption
Water follows the reabsorbed Na to help maintain blood volume (increased water retention –> increased BP)