Regulation of ECF Volume and NaCl Balance Flashcards
What is the Effecting Circulating Volume?
Portion of ECF under pressure thats perfusing tissues.
Triangle
ECF Salt balance influences ECF volume
ECF Water balance influences ECF osmolarity
Approximately how much of the vascular volume forms the ECV?
0.7L
What impact does congestive heart failure have on ECV?
ECV is decreased in patients with congestive heart failure due to decreased cardiac output.
How does edema occur in patients with CHF?
Patients start retaining more sodium and fluid, which increases ECF
What are the 4 ways that a low ECV is counteracted?
- Activation of RAAS pathway
- Baroreceptor reflex via sympathetic stimulation
- ADH secretion
- Fluid Retention via Starlings forces
What are the two functions of osmoreceptors?
- Increase Thirst
2. Stimulate ADH secretion
Where are osmoreceptors located?
Supraoptic and paraventricular areas of the hypothalamus
SON and PVN
What two receptor types control ADH secretion?
What do they each detect?
Osmoreceptors: detect changes in body osmolarity
Baroreceptors: detect changes in body volume
Of the two receptors that control ADH secretion, which receptor type is more sensitive?
Osmoreceptors
What changes in blood pressure and blood volume stimulate ADH secretion?
Decreased blood pressure
Decreased blood volume
What is the most important non-osmotic stimulus of ADH release?
A decrease in sensed body volume
What is the impact of sensed volume on osmolarity and ADH release?
Volume contraction: smaller change in osmolarity leads to a larger amount of ADH release.
Volume expansion: Higher threshold for ADH secretion needs to be met.
Where do arterial baroreceptors send afferent information to?
Brainstem vasomotor center
Where do cardiopulmonary baroreceptors send afferent information to?
Brainstem vasomotor center
Hypothalamus
What do the intrarenal baroreceptors influence?
RAAS system, GFR, NaCl/Water reabsorption
What do the Cardiopulmonary baroreceptors influence?
ADH!!! (via Hypothalamus)
- Brainstem vasomotor center
What does the brainstem vasomotor center impact?
TPR
Cardiac performance
Sympathetic drive to kidney
Venous compliance
What receptor senses changes in ECV as a result of changes in sodium balance?
Arterial and Cardiac baroreceptors
Sodium balance changes –> ECF change —> ECV change
What receptor senses changes in Plasma osmolarity as a result of changes in water balance?
Hypothalmic osmoreceptors
(Water balance changes –> Plasma osmolarity changes_
What are the effectors involved in the baroreceptor response to changed ECV?
AGT II
Aldosterone
SNS
ANP
What are the effectors involved in the osmoreceptor response to changed plasma osmolarity?
ADH
What are the steps involved in maintaining homeostasis after a change in sodium balance?
Increased sodium
- Increase in Na-> leads to INCREASED plasma osmolarity
- Osmoreceptors sense the change in plasma osmolarity
- Stimulate release of ADH
- ADH increases fluid reabsorption
- Fluid moves into the ECF from the ICF
- Na concentration in the ECF falls —> osmolarity is maintained and ECF volume increases
What are the steps involved in maintaining homeostasis after a change in sodium balance?
Decreased sodium
- Decreased Na –> DECREASED osmolarity
- Osmoreceptors are decreased
- ADH is inhibited -> Thirst decreases, and fluid retention decreases
- Water loss = reduced ECF
- Homostasis maintained, ECF decreases
