Chapter 25 Fluid, Electrolyte, and Acid-Base Balance Flashcards

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What percentage of our bodies is composed of water? Do men or women have higher percent body water?

A healthy young man is 60% water. A healthy young women is 50% water. Females have more body and less muscle. Of all tissues adipose tissue is least hydrated.


Fluid in the body is in two main compartments. Name them!

Intracellular Fluid: 2/3 of total water.

Extraceullular Fluid: 1/3 outside cells. 1.) plasma 2.) interstitial fluid

42L= 28L of Intra and 14L of Extra. Of the 14L only 3L is plasma the other 11L is interstitial


What is edema and what can cause it?

a typical accumulation of fluid n the interstitial space leading to tissue swelling. Increased blood pressure, capillary permeability, incompetent venous valves, localized blood vessel blockage, congestive heart failure

Hindered fluid return usually reflect an imbalance in colloid osmotic pressure.


Extracellular fluid classified as either ___________ or ___________ fluid.

Plasma or interstitial fluid (fluid in spaces bw cells)


Body fluids are considered to be electrolytes or _________

Electrolytes: inorganic salts, all acids and bases and some proteins

Nonelectrolytes: glucose, lipids, creatinine and urea

Electrolytes have greater osmotic power and water moves according to osmotic gradients.


What are some differences between electrolytes and nonelectrolytes? Anions and Cations?

Nonelectrolytes have bond that prevent them from dissociating in solution.

Electrolytes do dissociate into ions in water. Ions are charged.


How do we obtain water? How do we lose water? What is insensible water loss? What is metabolic water?

Most water enters the body through ingested liquids and solid foods. Body water produced by cellular metabolism is called metabolic water. Water that vaporizes out of the lungs in expired air or diffuses through the skin is called insensible water loss.


What triggers thirst?

The thirst mechanism. It is governed by the hypothalamus thirst center which is activated by:

1.) Osmoreceptors

2.) Dry mouth

3.) A decrease in blood volume



pertaining to a process by which net charge is transferred to a differentlocation so that hyperpolarization occurs.

Sodium-potassium pump: against concentration gradient.


How is water balance regulated by the hypothalamus & ADH?

Hypothalamic osmo-receptors detect ECF osmolality through changes in plasma membrane stretch that result from gaining or losing water. An increase of only 1-2% activates this.

ADH is low = water not reabsorbed. The results is dilute urine.

ADH is high = water is reabsorbed. small volume of concentrated urine is excreted.


Influence of the renin-angiotensin-aldosterone system?

The most important trigger for aldosterone release from adrenal cortex is renin - angio 2 - aldosterone mechanism.

When aldosterone concentrations are high all remaining filtered Na+ is actively reabsorbed in the DCT. Water always follows Na+. One way or another aldosterone increase ECF.

If aldosterone is inhibited. Large amounts of Na+ is excreted along with large amounts of water.


What does ANP do? Where is it produced?

It reduces blood pressure and blood volume by inhibiting all events that promote vasoconstriction, Na+ and water retention. ANP has diuretic effects. Inhibits ability of collecting duct to reabsorb Na+ by suppressing release of ADH


How is sodium regulated?

Linked to blood volume and blood pressure. Neural and hormonal controls that regulate total body Na+ content.

1.) Aldosterone and Angio 2

2.) ANP


How is potassium regulated?

Chiefly by renal mechanisms. PCT reabsorb about 60-80% of K+ and thick ascending loop absorbs another 10-20%. The responsibility for K+ balance falls chiefly on the collecting ducts. Achieve balance by changing the amount of K+ secreted into filtrate.

The single most important factor influencing K+ secretion into the filtrate is the K+ concentration in ECF.

2nd factor is aldosterone.


How is calcium regulated?

99% of calcium is found in bones. The bony skeleton provides a reservoir from which calcium can be withdrawn or deposited to maintain the balance.

PTH activates bone digesting osteoclasts which break down the bone releasing calcium.


How is chloride regulated?

Chloride is the major anion accompanying Na+ in ECF. It helps maintain osmotic pressure.

Alkaline- 99% of filtered chloride is reabsorbed

Acidosis- less chloride accompanies Na+ bc Bicarbonate (HCO3-) reabsorption is stepped up.


What do calcitonin and parathyroid hormone (parathormone) do?

Calcitonin is involved in helping to regulate levels of calcium and phosphate in the blood, opposing the action of parathyroid hormone. This means that it acts to reduce calcium levels in the blood

The parathyroid hormone (PTH), secreted by the parathyroid glands, is responsible for regulating blood calcium levels; it is released whenever blood calcium levels are low.

PTH increases blood calcium levels by stimulating osteoclasts, which break down bone to release calcium into the blood stream.

PTH increases blood calcium levels by increasing the amount of calcium resorbed by the kidneys before it can be excreted in the urine.



whenever the pH of a person rises above 7.45.



whenever the pH of a person drops below 7.35


The three major chemical buffer systems are?

Resist changes in pH

1.) Bicarbonate

2.) Phosphate

3.) Protein buffer system


Bicarbonate Buffer System:

If strong acid is added- pH of solution decreases only slightly

If strong base is added- pH of solution increases only slightly


Strong Acids

all their H+ is dissociated completely in water


Weak acids

dissociate partially in water and are efficient at preventing change in pH


Strong bases

dissociate easily in water and quickly tie up H+


Weak bases

accept H+ more slowly


Phosphate Buffer System

Nearly identical to Bicarbonate.

Effective buffer in urine and ICF


Protein Buffer System

Proteins in plasma and in cells.


Respiratory regulation of H+