ECF volume regulation Flashcards
major ECF osmoles
Na+
Cl=
major ICF osmoles
K+
regulation of ECF volume =
regulation of body Na+
what will changes in Na+ content of ECF cause
change in ECF volume and so affects volume of blood perfusing tissues - effecting circulating volume and so BP
what is regulation of Na+ basically dependent on
high and low p baroreceptors
low ECF and so sympathetic discharge from baroreceptors: effects on kidney
- renal arteriolar constriction and inc renin
- renin causes angiotensin II
- angiotensin II causes inc Na+ reabsorption from proximal tubule
- Angiotensin II leads to aldosterone which leads to more distal tubule Na+ reabsrptin
regulation of distal tubule Na+ reabsorption is controlled by
adrenal cortical steroid hormone - aldosteron
what does angiotensin II do
vasoconstriction
inc ADH
inc thirst
inc aldosterone - Na+ reabsorption
where is ACE found
found throughou vascular endothelium but most of conversion occurs as blood passes through pulmonary circuit
what is the rate limiting step in aldosterone secretion
release of renin since angiotensinogen is always present in plasma
factors that increase renin release
- low pressure in afferent arteriole at level of JG cells
- inc sympathetic nerve activity (via B1 effect)
- less NaCl being delivered to macula densa
factors that inhibit renin release
- angiotensin II feeds back to inhibit renin
2. ADH inhibits renin release
what is most important if both volume and osmolarity of ECF is compromised
volume considerations have primary if extra-cellular volume is compromised
so that ADH will increase because of baroreceptors, even though this is assoc with hypoosmolarity
when does volume become primary [ADH] driver
usually osmolarity is main determinant of [ADH] but if sufficient volume change to compromise brain perfusion then volume becomes primary drive
ANP
atrial natruiretic peptide
promotes Na+ excretion
