Water balance part 2 Flashcards
True/False: Hormones can regulate water balance
True
What is antidiuretic hormone (ADH)?
It is a small peptide molecule that is made in the hypothalamus and released by pituitary gland in the brain. ADH binds to receptor cells in the collecting ducts of the kidneys which promote the reabsorption of water into circulation instead of leaving in the urine. the urine osmolarity increases and the plasma osmolarity decreases. ADH promotes water reabsorption by stimulating the synthesis of Aquaporins. Reabsorption dilutes bodily fluids decreasing sodium concentration
ADH stimulates the synthesis of what?
Aquaporins.
It also sorts aquaporins to the apical membrane of collecting ducts so water can pass through and get reabsorbed. Otherwise collecting ducts in kidneys are impermeable to water.
ADH lowers osmolarity, what other mechanism does the kidney have to keep osmolarity from going too low?
Aldosterone
What does Aldosterone do?
Aldosterone reabsorbs sodium (and water) in the kidney
Where is the thirst center located?
the CNS
Where is aldosterone released from?
adrenal cortex
What happens if there is a decrease in arterial blood pressure? (hint angiotensin)
kidney receptors tell renin to increase. which tells angiotensinogen to increase in liver. which tells angiotensin I and II to increase. which increases Aldosterone, ADH, thirst. which intern increases Na+ reabsorption, water reabsorption, and fluid intake. arterial pressure returns to normal.
how to regulate body fluid gain (when in dehyrdation)?
by adjusting preformed water intake (DRINK MORE WATER)
What controls electrolyte balance?
HORMONES
What three hormones regulate fluid loss?
1) Antidiuretic hormone (ADH)
2) Aldosterone
3) Atrial natriuretic peptide (ANP)
What two factors stimulate the release of ADH?
1) Increased blood osmolarity
2) decrease in blood volume (same thing)
What stimulates the release of Aldosterone
An increase in angiotensin II
What is the opposite of ADH?
ANP
When is ANP (atrial natriuretic peptide) released? In response to what?
When blood volume or blood pressure is increased, by the stretching of the walls of the atrium (heart), ANP is released to decrease it.
What releases ANP (atrial natriuretic peptide)?
the cardiac muscle cells
Does ANP increase or decrease urine flow?
ANP increases urine flow rate, which increases the excretion of water, which decreases the volume of water in the blood
ADH and Aldosterone do what to urine flow rate?
ADH and Aldosterone decrease urine flow rate, which increases fluid absorption, and blood volume
What cells monitor osmotic concentrations of the ECF?
osmoreceptors
What cells are sensitive to subtle changes in osmolarity?
osmoreceptors
Where are osmoreceptors located?
in the hypothalamus
What are osmoreceptors?
are neurons in the anterior hypothalamus and their axons release ADH into the posterior pituitary gland
What two effects does releasing ADH have?
1) it stimulates water conservation in the kidneys which reduces water loss, and concentrates the urine
2) it stimulates thirst to promote drinking of fluid
what happens when there is a water deficit?
1) Plasma Osmolarity increases
2) activated Osmoreceptors release ADH from anterior hypothalamus into posterior pituitary gland
3) Thirst is stimulated
4) water permeability is increased in Collecting Ducts
5) Water is reabsorbed
6) plasma osmolality decreases to normal
What determines the osmolality of the excreted urine?
The collecting ducts (because of its permeability of water)
When is diluted urine produced?
when ADH is absent, the collecting ducts become impermeable to water (increasing urination and diluting the urine)
When osmotic pressure of interstiital fluid goes down, ADH secretion stops. True or false
True
During over-hydration what happens to interstitial osmotic pressure? ADH?
it decreases, it stops
In normally functioning kidneys, what happens to the urine, and tonicity if ADH secretion STOPS.
If ADH secretion stops, excess water will be excreted into the urine, and hypotonicity will not occur
If kidney function is poor (renal failure), what happens if ADH secretion STOPS
Excess urine will not be excreted:
1) water intoxication
2) Circulatory shock
aldosterone release occurs in response to what?
the activation of the renin-angiotensin system not directly by sodium ion concentration
what does the renin-angiotensin system do to blood volume and pressure
it increases blood volume and pressure
what is erythropoietin?
it enhances red blood cell production
What is the most abundant cation in the ICF
Potassium (K+)
What does potassium play a key role in?
1) establishes resting membrane potential
2) establishes repolarization phase of action in nervous and muscle cells
What hormone controls the plasma level of Potassium?
Aldosterone
Which organ regulates K+?
kidneys
How does ANP reduce blood pressure and volume? (4 things)
1) Increases water lose in the kidneys
2) Reducing thirst
3) Blocks the release of ADH
4) Stimulates vasodilation
What opposes the actions of angiotensin II?
Atrial Natriuretic Peptide (ANP)
