L25: Renal System III Flashcards
aldosterone
a steroid hormone released from the adrenal cortex that regulates both Na+ reabsorption and K+ secretion
aldosterone pathway step 1
aldosterone binds to cytosolic receptors in renal tubule cells of the distal tubule and collecting duct
aldosterone pathway step 2
hormone-receptor complex initiates transcription in the nucleus
aldosterone pathway step 3
the synthesis of new channels and Na+/K+ pumps
aldosterone pathway step 4
aldosterone-induced proteins modify existing channels
aldosterone pathway result
increased Na+ reabsorption and K+ secretion
aldosterone increases Na+ reabsorption and K+ secretion __
simultaneously
the most important factor in the control of aldosterone release
renin-angiotensin-aldosterone (RAAS)
__ secrete renin
granular cells in the juxtaglomerular apparatus
renin
proteolytic enzyme
__ within the walls of the distal tubule detect changes in the Na+ and Cl- concentrations in the flow of the tubular fluid
macula densa
when sodium concentration in the tubular fluid decreases,
renin secretion increases
juxtaglomerular apparatus is formed where
the distal tubule travels close to the afferent and efferent arterioles
___ inputs to the granular cells to trigger Renin release
three distinct
first input to trigger renin release
a decrease in blood pressure, more specifically, in afferent arteriole pressure, because granular cells are directly sensitive to the degree of stretch of the afferent arterioles
second input to trigger renin release
a decrease in blood pressure causes GFR decrease, leading to Na+ and Cl- decrease in the distal tubules; this triggers macula densa cells secrete a chemical signal stimulating renin release
third input to trigger renin release
a decrease in blood pressure, baroreceptor reflex, sympathetic activity
renin release from the granular cells into the bloodstream
starts a series of reactions that lead to Aldosterone release
1: renin act on the protein ___, that is always secretes in the plasma by __
angiotensinogen, the liver
2: renin cleaves off some __ from ___ converting it to ___
amino acids, angiotensinogen, angiotensin I
3: angiotensin I is converted to __ by __ enzyme, which is bound to ___
angiotensin II, angiotensin-converting-enzyme (ACE), inner surfaces of capillaries
angiontensin II important functions
stimulation of aldosterone release from the adrenal cortex; the increase of mean arterial pressure by acting as a vasoconstrictor; acting in the hypothalamus to stimulate vasopressin release and thirst
angiotensin II increases MAP by four mechanisms
vasoconstriction of systemic arterioles (TPR up, MAP up);
stimulation of hypothalamic neurons for thirst and fluid intake (volume up, MAP up);
stimulation of ADH secretion to minimize fluid loss and maintain plasma volume (volume up, MAP up);
stimulation of aldosterone secretion by adrenal cortex (water reabsorption up)
atrium natriuretic peptide (ANP) is secreted by cells
in the atria of the heart
ANP are released in response to
distension of the atrial wall, which occurs when plasma volume has increased
ANP increases
sodium excretion by increasing GFR and by decreasing Na+ reabsorption
ANP affect on kidney arterioles
dilation of afferent arterioles, constriction of efferent arterioles
what does dilation of afferent and constriction of efferent lead to?
increase in glomerular capillary pressure, GFR increase, the filtered sodium load increase
increase in GFR causes
increased Na+ excretion
AND decreases sodium reabsorption
by decreasing the number of open sodium channels in the apical membranes of renal tubular cells
ANP ___ secretion of ___
decreases, renin and aldosterone
