Chapter 26 Fluid, electrolyte and acid-base balances

Question 1

Define nonelectrolytes

Answer 1

does not dissociate at all in solution and therefore does not produce any ions. They are typically polar covalent substance that do dissolve in water as molecules instead of ions. Sugar is a good example of a nonelectrolyte

Question 2

Define electrolyte

Answer 2

a liquid or gel that contains ions and can be decomposed by electrolysis.

Question 3

Describe feedback mechanisms that regulate water intake

Answer 3

feedback mechanisms
•The thirst mechanism is triggered by a decrease in plasma osmolarity, which results in a dry mouth and excites the hypothalamic thirst center.
•Thirst is quenched as the mucosa of the mouth is moistened, and continues with distention of the stomach and intestines, resulting in inhibition of the hypothalamic thirst center.

Question 4

Describe possible causes and consequences of dehydration, hypotonic hydration and edema

Answer 4

Dehydration occurs when water loss exceeds water intake over time, can lead to hypovolemic shock; Hypotonic hydration occurs when body fluids are excessively diluted & cells become swollen by water entry, cerebral edema; Edema is abnormal accumulation of fluid in the IF which may impair blood circulation

Question 5

describe mechanisms involved in regulating sodium balance, blood volume, and blood pressure

Answer 5

•When aldosterone secretion is high, nearly all the filtered sodium is reabsorbed in the distal convoluted tubule and the collecting duct.
oThe most important trigger for the release of aldosterone is the renin-angiotensin mechanism, initiated in response to sympathetic stimulation, decrease in filtrate osmolality, or decreased blood pressure.

• Angiotensin II, produced by the renin-angiotensin mechanism, causes the adrenal cortex to release aldosterone, and also directly causes kidney tubules to increase Na+ retention as part of a mechanism regulating systemic blood pressure.
• Cardiovascular baroreceptors monitor blood volume so that blood pressure remains stable.
• Atrial natriuretic peptide reduces blood pressure and blood volume by inhibiting release of ADH, renin, and aldosterone, and directly causing vasodilation.
• Estrogens are chemically similar to aldosterone, and enhance reabsorption of salt by the renal tubules.
• Glucocorticoids enhance tubular reabsorption of sodium, but increase glomerular filtration.

Question 6

List the three major chemical buffer systems of the body and describe how they resist pH changes

Answer 6

Bicarbonate buffer system - Extracellular fluid, respiration based
Phosphate buffer system - Urine/Intracellular fluid, similar to bicarbonate, Sodium dihydrogen phosphate: weak acid, monohydrogen phosphate: weak base
Protein buffer system - Uses organic acids with carboxyl groups. Dissociate to release an H+ when pH is higher, or bind H+ when pH is too low

Question 7

describe the influence of the respiratory system on acid-base balance

Answer 7

CO2+H2O -> Carbonic Anhydrase ->H2CO3 -> H+ +HCO3-
Increased breathing rate if pH drops by modulating the respiratory center
Decrease breathing rate if pH is high by modulating the respiratory center