water and electrolytes

water properties

• universal solvent

• highly polar

water sources

• beverages

• water from food

• small amount from metabolism (<10%)

• total of abt 2500 ml of fluid

water absorption

• most absorbed in gut

  • most of this in small intestine

• rest absorbed in large intestine

• absorbed thru osmosis

water and metabolism

• needed for metabolic and electrochemical rxns in body

• maintain blood pressure and circulation

• needed for proper solute concentration

kidney’s role

• glomerular filtrate

• urine formation

  • filtration

  • reabsorption

  • secretion

renin

• juxtaglomerular apparatus

• released in response to low blood pressure or reduced blood volume

• enzymes released from kidneys which can cleave angiotensinogen to antiotensinogen 1

angiotensinogen

• liver protein'

• converted to angiotensinogen 1 by renin in live

angiotensinogen 1

• enters blood

• converted by angiotensinogen 2 by angiotensinogen converted enzyme (ACE)

angiotensinogen 2

• increases blood pressure by causing release of aldosterone (from adrenal cortex) and vasopressin (by pituitary gland)

angiotensinogen converting enzyme (ACE)

cleave and activate angiotensinogen 1 to angiotensinogen 2

aldosterone

hormone that increase sodium retention and potassium excretion

vasopressin

• hormone that enhances reabsorption of water and sodium in kidney

• enhances water retention

electrolytes

• chemicals that have positive or neg charge and conduct electrical impulses in body

• are distributed in way which electrical neutrality is always maintained

  • anion conc balances cation conc

3 main electrolytes

sodium, potassium, chloride

sodium fact

most abundant extracellular cation

sodium sources

• canned, processed and frozen foods/meals

• major source is table salt

sodium range

1500 mg/day
DV food labels: 2400 mg

sodium absorption

• 95-100% absorbed

• three basic pathways

  • Na+/glucose co transport system functions thru small intestine

  • electro neutral Na+ and Cl- co transport system is active in small intestine and proximal portion of colon

  • electrogenic Na+ absorption

sodium deficiency

rare, associated with excessive sweating

sodium toxicities

• dietary sodium intake increases urinary calcium excretion

• linked to high blood pressure

potassium fact

major intracellular cation (>95% in cells)

potassium sources

• widespread in foods

• good sources are fruits, veggies, beans, nuts, seeds

potassium absorption

• >85% of potassium thought to be absorbed by passive diffusion or by K+/H+ -ATPpase pump

• decreases urinary excretion of calcium

potassium deficiency

rare

• too little or too much can neg affect heart rhythms

• increased intake linked to lower blood pressure

chloride fact

most abundant anion in extracellular fluid

chloride source

main source table salt

chloride range

similar to sodium

chloride absorption

in Na+/glucose co transport system, follows actively absorbed Na+

chloride function

maintain fluid balance, blood volume, blood pressure

chloride deficiency

rare, usually with dehydration, diarrhea, vomiting

distribution of water in body

intracellular > extracellular > interstitial fluid > plasma