Fluid Balance

fluid balance

taking in and eliminating equal amounts of fluid

factors affecting total body water content

age, sex, body mass and body fat

infants

group with highest water content

males

sex with higher water content: 60%; females 50%

elderly female

group with the lowest water content

ECF (extracellular fluid)

fluid found outside the cells of the body; interstitial fluid and plasma (also some transcellular fluids)

ICF (intracellular fluid)

fluid within cells; 2/3rds of all water content

ECF (extracellular fluid)

compartment with the highest sodium ion Na+ concentration

ICF (intracellular fluid)

compartment with the highest potassium ion K+ concentration

sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell

2.5 L

average daily intake and output of water

water intake sources

ingested fluid (60%) and solid food (30%); metabolic water or water of oxidation (10%)

water output

urine (60%), insensible water loss (lost through skin and lungs), perspiration, and feces

thirst center

region in hypothalamus that monitors osmolarity and dehydration to regulate fluid intake

osmolality

reflects the number, not the type, of particles (solute) in a solution

hypothalamus

location of thirst center; captain - makes ADH stored in posterior pituitary

ADH effect

reduces urine output = low volume of concentrated urine; increases water retention - you pee less

No ADH present

distal and collecting tubules impermeable to water; water excess excreted = high volume of dilute urine - you pee more

high specific gravity

urinalysis result that shows urine is concentrated; possibly due to dehydration or other causes

low specific gravity

urinalysis result that shows urine is dilute; possibly due to high fluid intake or diabetes insipidus

diuresis

increased output of urine

dehydration

an abnormally low amount of water in the body; condition where water loss is greater than water intake

dehydration

infants and elderly exhibit the greatest risk for ___?

water intoxication

a dangerous dilution of the body's fluids resulting from excessive ingestion of plain water; hypotonic hydration - get brain swelling

edema

abnormal accumulation of fluid in interstitial spaces of tissues

electrolytes

a substance that dissociates in water into cations and anions: Na+, Cl-, Ca+2, K+

electrolyte balance

condition when the quantities of electrolytes entering the body equal those leaving it

foods

main electrolyte input is through ___

pica

an abnormal craving or appetite for abnormal substances, such as dirt, paint, or ice; may indicate severe electrolyte deficiency

urine

greatest electrolyte output is through ______

general causes for electrolyte deficiency

poor diet or poor absorption of nutrients and loss from the GI tract: vomiting, diarrhea or gastric suction, renal disease

Image: general causes for electrolyte deficiency

hypertension

high sodium diets are associated with what health conditions? Increased blood volume = ?

aldosterone

hormone that increases sodium reabsorption and potassium excretion; increases blood volume and blood pressure

aldosterone

hormone released when blood pressure is low, potassium is high or during times of stress

ANP (atrial natriuretic peptide)

hormone released by the heart when blood pressure is high - kidneys excrete more Na+ and water, thus decreasing blood pressure and blood volume - it makes you pee

parathyroid hormone (PTH)

increases blood calcium by increasing absorption of calcium from DCT, stimulating osteoclasts and increasing calcium absorption from the small intestine

kidney disease, dietary intake (high or low), loss from GI tract

sources of electrolyte imbalance

neurological & muscular dysfunction

what electrolyte imbalances of Na+, K+ and Ca+2 will cause

hypernatremia

excessive sodium in the blood; hypertonic ECF - cells shrivel - usually caused by low water volume

hypernatremia

electrolyte imbalance caused by dehydration, diabetes insipidus (too little ADH) or hyperaldosteronism (Cushings)

hyponatremia

low sodium in the blood; hypotonic ECF - brain swells

hyponatremia

electrolyte imbalance caused by water intoxication or SIADH (too much ADH)

potassium

most abundant intracellular cation - most important in setting resting membrane potential

sodium

most abundant extracellular cation - controls ECF volume and water distribution

Image: sodium

hyperkalemia

excessive potassium in the blood

hyperkalemia

electrolyte imbalance caused by hypoaldosteronism (Addison's) or kidneys' failure to excrete potassium

hypokalemia

deficient potassium in the blood

hypokalemia

electrolyte imbalance caused by hyperaldosteronism or kidneys over-secretion of potassium

hypercalcemia

excessive calcium in the blood

hypercalcemia

electrolyte imbalance caused by hyperparathyroidism

hypercalcemia

electrolyte imbalance that decreases neuromuscular excitability, increases the risk of kidney stones and in some cases causes osteoporosis and increased risk of fractures

hypocalcemia

low calcium in the blood

hypocalcemia

electrolyte imbalance caused by hypoparathyroidism and diet low in vitamin D resulting in poor absorption

hypocalcemia

electrolyte imbalance that increases neuromuscular excitability and can lead to muscle cramps and tetany; osteomalacia with possible fractures and bruising

acidosis

condition with low blood pH <7.35

alkalosis

condition with high blood pH >7.45

acidosis

condition caused by high CO2 or low HCO3- (bicarbonate)

alkalosis

condition caused by low CO2 or high HCO3- (bicarbonate)

acid

what most metabolic processes make

Image: acid

3 buffers in the body

bicarbonate, phosphate and proteins

bicarbonate buffer

maintains pH of extracellular fluid; HCO3- and H2CO3

protein buffer

most plentiful buffer in body cells including RBCs

increased rate and depth of breathing

respiratory response to low pH/acid

decrease rate and depth of breathing

respiratory response to high pH/alkaline

excretion of H+ and reabsorption of HCO3-

renal response to low pH/acid

reabsorption of H+ and excretion of HCO3-

renal response to high pH/alkaline

renal compensation

kidney varies acid (H+) secretion and bicarbonate (HCO3-) reabsorption depending on pH of ECF; e.g. kidney removes excess acid from plasma

respiratory compensation

changes in ventilation change pH by increasing or decreasing CO2 levels; e.g. lungs exhale plasma acid as CO2

buffers

weak acid-base pairs that resist changes in pH; in place and FASTEST acting

renal excretion of hydrogen ions

active hours to days; SLOWEST but MOST POWERFUL; only way to rid body of metabolic acids

respiratory acidosis

a drop in blood pH due to hypoventilation (too little breathing) and a resulting accumulation of CO2

respiratory alkalosis

rise in blood pH due to hyperventilation (excessive breathing) and a resulting decrease in CO2

metabolic acidosis

decreased pH in blood due to an increase in non-respiratory acids or excessive loss of bases through GI tract

metabolic alkalosis

increased pH in blood due to loss of hydrogen ions H+ by emptying of stomach or overdose of anti-acids

ECF (extracellular fluid)

plasma and interstitial fluid are part of ____?

female

group with 50% water content

hypercapnea

high amounts of CO2 in the blood

hypocapnea

condition of deficient carbon dioxide in the blood

potassium

levels controlled by aldosterone; imbalances of this ion are easily seen on an ECG (echocardiogram)

Image: potassium

sodium

reabsorption controlled by aldosterone

calcium

levels controlled by parathyroid hormone PTH

1.5 L

average amount of urine that is excreted each day

diabetes insipidus

low ADH, antidiuretic hormone; high urine output and intense thirst; may lead to dehydration

SIADH

syndrome of inappropriate antidiuretic hormone; too much ADH - water retention leads to hyponatremia and brain swelling