BIO 222 Lecture6.Homeostasis Review
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BIO 222 Anatomy & Physiology 2
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51 Terms
Any of the body’s water-based liquids.
Water is the main component.
body fluid
Maintaining the appropriate volume and concentration of the body fluids
fluid balance
cytosol = inside cells.
~2/3 of the body’s fluids.
intracellular (ICF)
Outside the cells.
Variety of fluids.
extracellular (ECF)
Ingestion of liquids and moist foods.
Metabolic synthesis of water during cellular respiration and dehydration synthesis.
fluid intake
The kidneys.
In the feces.
Evaporation from the skin.
Exhalation from the lungs.
fluid loss
The kidneys.
In the feces.
sensible
Evaporation from the skin.
Exhalation from the lungs.
insensible
Main Regulators of fluid balance
fluid input = fluid output
4 main hormones
angiotensin II
aldosterone
ADH
ANP
aka vasopressin
ADH
Hormonal Regulation by
angiotensin II
aldosterone
Angiotensin II also stimulates thirst center in the hypothalamus
increases fluid intake
Neurons in the hypothalamus
Osmoreceptors in hypothalamus
Controlled by the hypothalamus
thirst mechanism
Baroreceptors detect change in BP (not as sensitive as osmoreceptors to change in osmolarity)
decrease blood pressure
Measure of the osmotic pressure gradient between two fluid compartments
tonicity
Cytosol (ICF) & ECF are isotonic
normal condition
Net movement of water into the cell; cells swell ; overhydration/hypotonic hydration
Hypotonic ECF
Net movement of water out of the cell; cell “shrinks” ; dehydration
Hypertonic ECF
Osmotic pressure increases in extracellular fluids.
Water moves out of cells (crenate).
Osmoreceptors in hypothalamus stimulated.
Hypothalamus signals posterior pituitary to release ADH.
Urine output decreases.
Severe thirst, wrinkling of skin, fall in plasma volume and decreased blood pressure, circulator shock, death.
dehydration
water moves out of cells
crenate
Osmotic pressure decreases in extracellular fluids.
Water moves into cells
Osmoreceptors inhibited in hypothalamus.
Hypothalamus signals posterior pituitary to decrease ADH output.
Urine output increases.
Overhydration
Osmotic pressure decreases in extracellular fluids
aka hypotonic hydration
Water moves into cells
cells lyse
‘Drunken’ behavior.
Confusion, hallucinations, convulsions, coma, death
water intoxication
Eliminated via respiratory or urinary
volatile acids
Biggest source of metabolic acids
carbon dioxide
Eliminated via urinary only.
Lactic acid, uric acid, intermediate products of citric acid cycle, ketone bodies.
fixed acids (nonvolatile)
Chemicals to buffer the fluids in the body & resist pH changes
protein
carbonic acid
phosphate
Slowest; only way to eliminate acids other than carbonic acid
urinary
Can change the rate/depth f breathing to adjust CO2 levels
respiratory
Carbonic Acid.
Important to ECF.
bicarbonate buffer system
Most abundant in ICF and blood plasma
protein buffer system
Protein’s monomer
amino acid
Important to ICF.
Important in kidney filtrate.
phosphate buffer system
H2PO4- (dihydrogen phosphate).
Will donate a H+ when excess OH- to form H20 & HPO4-
weak acid
HPO4-.
Will accept a H+ when excess H+ to form H2PO4 (dihydrogen phosphate)
weak base
CO2 out
metabolic CO2
Body fluid pH < 7.35.
More H+ than the buffers can bind.
Decrease in HCO3- & other buffer molecules.
acidosis
Body fluid pH >7.45.
More base ions than buffers can bind.
Decreases in H+ ions.
alkalosis
Creates resting potential of nerves and muscles.
Drives many secondary active transport mechanisms (symporters; antiporters).
Principal cation of ECF, strongly affecting osmolarity.
sodium (Na+) functions
Sodium (Na+) influencers
ANP (high BP)
aldosterone (low BP)
Most abundant cation in ICF (recall Na+/K+ pump).
Plays key role in creating resting membrane potential for muscle and nerves.
potassium (K+) functions
Potassium (K+) influencers
aldosterone
Calcium (Ca2+) influencers
PTH
calcitriol
The hormone levels affect whether it is withdrawn or deposited in bones, if it’s excreted by kidneys, & if it’s absorbed in the intestines
PTH
calcitriol
Can make nerves & muscles over-excitable
hypocalcemia
Can inhibit depolarization of muscles and nerves
hypercalcemia
Linked to ATP → ADP reaction.
Linked to ATP, GTP, nucleic acid, & phospholipid structure.
phosphate (PO43-) functions
Phosphate (PO43-) influencers
Ca2+ homeostasis
