BIOL 1051H Lecture Notes - Lecture 3: Resting Potential, Efferent Arteriole, Posterior Pituitary
Fluid, Electrolyte and Acid-Base Balance
The great percentage of the body’s water is in
●The intracellular fluid
Regulation of Fluid Intake
●Governed mainly by thirst
●Osmoreceptors respond to Angll and rise osmolarity of ECF
Renin- Angiotensin- Aldosterone (RAAS) System
●A system of hormones that helps control BP and filtration in the kidneys
●Angiotensin
○Potent vasoconstrictor raising BP
○Constricts efferent arteriole raising kidney filtration
○Stimulates adrenal cortex to secrete aldosterone, which promotes Na and H2O
reabsorption
○Stimulates posterior pituitary to secrete ADH which promotes H2O reabsorption
○Stimulates thirst
Aldosterone - the “salt-retaining hormone”
●Steroid hormone secreted by the adrenal cortex
●Functions of aldosterone
○Acts on thick segment of nephron loop, DCT, and cortical portion of collecting
duct
■Stimulates reabsorption of Na and secretion of K
Fluid Deficiency
●Volume Depletion (hypovolemia)
○Proportionate loss of water and sodium without replacement
○Osmolarity remains normal
●Dehydration (negative water balance)
○Body eliminates more water than sodium
○Osmolarity of ECF rises
Sodium Balance
●One of principal ions responsible for resting membrane potential
○Na inflow essential to depolarization that underlies nerve and muscle function
Document Summary
The great percentage of the body"s water is in. Osmoreceptors respond to angll and rise osmolarity of ecf. A system of hormones that helps control bp and filtration in the kidneys. Stimulates adrenal cortex to secrete aldosterone, which promotes na and h2o. Stimulates posterior pituitary to secrete adh which promotes h2o reabsorption. Steroid hormone secreted by the adrenal cortex. Acts on thick segment of nephron loop, dct, and cortical portion of collecting duct. Stimulates reabsorption of na and secretion of k. Proportionate loss of water and sodium without replacement. One of principal ions responsible for resting membrane potential. Na inflow essential to depolarization that underlies nerve and muscle function. Most significant solute in determining total body water and distribution. Usually accompanied by changes in water volume. Hypernatremia = plasma sodium > 145 meq/l. Greatest determination of intracellular osmolarity and cell volume. Produce the resting membrane potentials and action potentials of nerve and muscle cells.
