Exam 3 Lecture: Body Fluid and Osmolarity Flashcards
What is the main ECF ion?
Na
What is the main determinant of ECF osmolarity?
Na
What will an increase in the amount of ECF Na do to the ECF volume?
it will increase it
What will a decrease in the amount of ECF Na do to the ECF volume?
it will decrease it
Where is the only site of ECF Na regulation?
the kidney
What is osmolarity?
the concentration of osmotically active things
How does the kidney regulate ECF osmolarity?
by changing ECF Na concentration
How does the kidney regulate ECF volume?
by changing ECF Na amount
What does high Na concentration in the ECF lead to?
an increase in ECF osmolarity and cause water movement out of cells; cells will shrink
What does low Na concentration in the ECF lead to?
a decrease in ECF osmolarity and cause water to move into the cells; cells will swell
What do the terms hypo- and hypernatremia define?
the ECF Na concentration
What is hyponatremia?
low Na concentration in the ECF
What is hypernatremia?
high Na concentration in the ECF
What are some symptoms of hypernatremia?
rupture of cerebral vessels/hemorrhage, muscle weakness, behavioral changes/ataxia, coma leading to death
What are some conditions that lead to hypernatremia?
- limited access to water supply
- diabetes insipidus
- loss of hypotonic fluids
- salt poisoning
What are some symptoms of hyponatremia?
cerebral/pulmonary edema, muscle weakness, uncoordination and seizures
What are some conditions that lead to hyponatremia?
- hyperglycemia
- GI fluid loss/third space fluid loss
- congestive heart failure
- liver failure
- psychogenic polydispia
How is ECF Na concentration controlled?
by adjusting ECF water levels
What does adding or subtracting Na into the ECF do?
it affects the ECF volume because water will ultimately follow it
What is the mechanism used for adding water to the ECF?
a combination of increased ADH release and thirst
What are ECF osmolarity changes detected by and what do the detectors due?
sensed by osmoreceptors that either shrink or swell the hypothalmus which triggers or prevents ADH realease from the posterior pituitary
What do osmoreceptors stimuulate aside from the swelling and shrinking of the hypothalmus?
stimulate the thirst center
What do the osmoreceptors do if the ECF osmolarity is high?
They shrink, increasing ADH release (to bring water into the extracellular space), and the animal becomes thirsty and drinks
What do the osmoreceptors do if the ECF osmolarity is low?
They swell, reducing the amount ADH release and inhibiting the thirst response
What is hypervolemia?
high ECF volume
What is hypovolemia?
low ECF volume
What are symptoms of hypervolemia?
ascites, pulmonary edema
What are symptoms of hypovolemia?
directly related to the low circulating volume - hypovolemic shock, organ damage
What does changing the amount of Na in the ECF do?
changes the ECF volume
Why do kidneys change ECF Na amount?
to regulate imbalances in ECF volume
What does salt poisoning lead to?
hypervolemia
What do low aldosterone levels lead to?
impaired renal Na retention leading to low
What senses ECF volume change?
baroreceptors in the left atria and pulmonary vessels
What senses change in ECF pressure?
baroreceptors located in the aortic arch and sinus
If baroreceptors stretch, what happens?
no ADH is released
If baroreceptors do not stretch, what happens?
ADH is released
What do JG cells do in response to stretch in afferent arterioles?
release renin
When baroreceptors sense decreased volume, what do they do?
they relay a signal to the brain to increase sympathetic flow to the kidney
What is the main neurotransmitter of the sympathetic nervous system?
norepinephrine
What does norepinephrine do?
it is a vasoconstrictor that constricts efferent more than efferent and increases GFR
True or False: Starling forces only effect the glomerulus
False: they effect the paritubular capillaries too
What do Starling’s forces contribute to?
regulating movement of ions and water from the tubular fluid to the capillary
What happens to hydrostatic pressure in the peritubular capillary if GFR goes up?
It goes down, because a greater amount of the plasma has been filtered less is making its way to the peritubular capillaries
What happens to oncotic pressure in the peritubular capillary if the GFR goes up?
it goes up because elevated filtration will increase protein concentration in the peritubular capillaries
How does norepinephrin work in the proximal tubule?
it stimulates Na reabsorption
When baroreceptors sense high volume, what happens?
they release natriuretic peptide release
How does the renin-angiotensin system increase ECF volume?
- constricts efferent arterioles to increase GFR and change Starling’s forces to increase Na and water uptake
- stimulates NaH antiporter to increase Na uptake
- stimulates ADH release to increase water uptake
- Stimulates aldosterone release to increase Na uptake
How do natriuretic peptides fix high volume?
- increase Na and water load entering tubules
- inhibits renin release from juxtaglomerular apparatus to inhibit RAS
- inhibits ADH release by inhibiting RAS
- Inhibits aldosterone release by inhibiting RAS
- inhibits NaCl reabsorption in the collecting duct by inhibiting Na channels
What does increased natriuretic peptide lead to?
decreases Na reabsorption which reduces water reabsorption and decreases ECF volume
What must happen in regards to Na in the case of hypovalemia?
Na absorption must increase
What must happen in regards to Na in the case of hypervalemia?
Na excretion must increase
What mechanisms work to increase Na absorption in the case of hypovalemia?
baroreceptors that increase sympathetic flow and the juxtaglomerular apparatus
What does the juxtaglomerular apparatus stimulate?
the RAS system which leads to the production of angiotensin
What mechanisms work to increase Na excretion in the case of hypervalemia?
baroreceptors that release natriuretic peptides
