BIOLOGY 3U03 Lecture Notes - Lecture 22: Angiotensin, Extracellular Fluid, Cardiac Output
14 Dec 2016
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Document Summary
Sodium intake & excretion are precisely matched under steady- If disturbances of kidney function are not too severe, sodium balance may be achieved mainly by intrarenal adjustments with minimal changes in extracellular fluid volume (or other systemic adjustments) When perturbations to kidneys are severe & intrarenal compensations are exhausted, systemic adjustments must be invoked (e. g. changes in bp, circulating hormones, & alterations of sympathetic nervous system activity) Sodium excretion is controlled by altering glomerular filtration or tubular sodium reabsorption rates. Small changes in either (in absence of compensation by other) would result in dramatic changes in urine volume (& sodium excretion in the case of the latter) Kidneys vasodilated --> increase in gfr --> nacl delivery to tubules increases --> two intrarenal compensations . Glomerulotubular balance: increased tubular reabsorption of nacl filtered. Macula densa feedback: increased nacl delivery to dt causes afferent arteriolar constriction (returning gfr to normal) Importance of pressure natriuresis & pressure diuresis in.
