anatomy ch 26--fluids, electrolytes and pH balance

body fluid content

depends on age, body mass, sex, ad body fat

skeletal muscle is 75% water

fat tissue is 50% water

total body water in adults averages 40L

age body fluid content

infants are 70% or more water

male adults are 60% water

female adults are 50% water

older adults are 45-50% water

fluid regulation

regulated by kidneys with renin and angiotensin

intracellular and extracellular

intracellular fluid

inside the cell

accounts for 67% of total body fluid

plasma and interstitial fluid

extracellular fluid

outside the cell

33% of total body fluid

body fluid composition

water, solutes (nonelectrolytes and electrolytes)

nonelectrolytes

most are organic molecules, dont carry an electric charge

do not dissociate in water

glucose, lipids, creatinine, and urea

low osmotic power

electrolytes

have electrical charges (ions)

mostly inorganic molecules

conduct electrical current

greater osmotic power

ECF major cation

sodium

ECF major anion

Chloride

ICF major cation

potassium

ICF major anion

hydrogen phosphate

osmolarity

total solute concentration in solution

osmosis

movement of water from low osmolarity (high water) to high osmolarity (low water)

osmotic power

degree of solute concentration to cause osmosis

tonicity

the capability of a solution to modify the volume of cells by altering their water content

what happens with increased ECF solute concentration

water leaves the cell

what happens with decreased ECF solute concentration

water centers the cell

hypotonic solution

solute concentration lower out and higher in

hypertonic solution

solute concentration higher out and lower in

water intake

mostly from eating/drinking

thirst mechanism from the hypothalamus sensing detects ECF increases in osmolaity

water output

from urine (60%) and lungs (25-30%), kidneys regulate output

uncontrollable water loss due to metabolism

ADH controls water reabsorption

increase in ECF concentration activates ADH

sodium balancing

water follows sodium, controls ECF volume and water distribution

changes in sodium levels affect plasma volume, blood pressure, and ECF and IF volumes

sodium balancing controls

renin-angiotensin-aldosterone mechanism for sodium retention

kidneys secrete renin when low sodium concentration/low blood pressure (causes the adrenal glands to release aldosterone, which triggers sodium reabsorption); raises BP

ANP inhibits ADH, renin, and aldosterone production, decreases sodium absorption, water absorption,reduces blood volume and pressure

ADH

promotes vasodilation, inhibits the renin pathway

ANP and aldosterone

balance the salt levels in the body

hypernatremia vs hyponatremia

potassium balancing

affects resting membrane potential in neurons and muscle cells

the DCT and collecting duct regulate the amoutn secreted into filtrate

regulated by aldosterone

hyperkalemia vs hypokalemia

calcium

99% found in bones

controlled by PTH (raises in blood) and calcitonin (lowers in blood)

hypercalcemia vs hypocalcemia

regulated in distal tubes

Chloride balancing

regulated by kidneys and aldosterone

99% is reabsorbed

acid-base balance

chemical buffers and respiratory regulation

outside the right pH, proteins are denatured and digested, enzymes lose their ability to function and death my occur

arterial blood is 7.4

venous blood 7.35

ICF is 7.0

most acid is produced as a by-product of metabolism

kidneys and cardiovascular and respiratory system removes acid

alkalosis/alkemia

blood pH is greater than 7.45

acidosis/acidemia

blood pH less than 7.35

strong blood acid vs weak

strong acid completely break down and change pH more

weak acids do not completely breakdown, changing pH less

hydrogen ion concentration regulation systems

chemical buffer system

brain stem respiratory centers

renal mechanisms

chemical buffer system

rapid response

bicarbonate buffer system and phosphate buffer system

bicarbonate buffer system

best for buffering ECF compartment

bicarbonate regulated by kidneys and CO2 by respiratory

if CO2 increases, elevated respiratory rate
if CO2 decreases, shallow respiratory rate

phosphate buffer system

best buffering for ICF compartment and urine

phosphate concetrations are high in the ICF

protein buffer system

brain stem respiratory centers

takes 1-3 minutes

renal mechanisms

takes hours to days

ultimate long term rgulation of acid-base balance

beside bicarbonate, it is the main/strongest

kidneys adjust amount of bicarbonate in blood by either reabsorbing or generating new HCO3 (to increase pH) or be excreting HCO3 (lowering pH)

what do A cells do

reabsorbe HCO3 into the blood

detects acidosis

what do B cells do

secrete HCO3

detects alkalosis

abnormalities of acid-base balance

classified as either respiratory or metabolic

respiratory abnormality

from poor CO2 exchange

metabolic abnomality

bicarbonate change

usually a kidney problem

respiratory acidosis

CO2 not eliminated fast enough, so blood pH is acidic

due to a decrease in ventilation or gas exchange

causes medulla to elevate breathing rates

respiratory alkalosis

CO2 is eliminated faster than produced, blood pH is basic

common result of hyperventilation

slower breathing rates