Long Term Control of Blood Pressure Flashcards
what three hormone system are involved in long term control of blood pressure?
> renin-angiotensin-aldosterone system
antidiuretic factor
atrial natriuretic peptide
what are the functions of the kidneys?
> excretion of waste products > maintenance of ion balance > regulation of pH > regulation of osmolarity > regulation of plasma volume
how does the kidney regulate plasma volume?
the kidney controls the sodium transport system determining how big the osmotic gradient is. it also controls the permeability of the collecting duct to water determining how much water follows the osmotic gradient or not.
this controls how much water is lost and retained in the urine.
what happens if the collecting duct is made very permeable to water?
lots of water will be reabsorbed resulting in little urine, conserving plasma volume
how does the kidney reduce the plasma volume?
it makes the collecting duct very impermeable to water resulting in little reabsorption of urine
where is renin produced?
from the juxtaglomerular (granule cells) of the kidney
what triggers renin production?
> activation of the sympathetic nerves to the juxtaglomerular apparatus
decreased distension of afferent arterioles
decreased delivery of sodium and chlorine through the tubule (macula densa)
what are the three triggers of renin production signs of?
low mean arterial pressure
what does renin do?
it converts inactive angiotensinogen to angiotensin 1.
what happens to angiotensin 1?
it gets converted to angiotensin 2 by an angiotensin converting enzyme
what is the regulating step in the renin-angiotensin-aldosterone system?
how much renin is produced
what does angiotensin2 do?
> stimulates release of aldosterone from the adrenal glands
increases release of ADH from the pituitary
causes vasoconstriction
what does aldosterone do?
increases sodium reabsorption in the loop of Henle reducing diuresis and increasing plasma volume
what does the increase in release of ADH from the pituitary gland do?
it increases water permeability of the collecting duct therefore reducing diuresis and increasing plasma volume. it also increase a sense of thirst.
what is the effect of angiotensin 2 as a vasoconstrictor?
this increases the total peripheral pressure
can the renin-angiotensin-aldosterone system be described as a negative feedback system?
yes: multiple mechanisms detect any decrease in mean arterial pressure which stimulates the release of renin. this evokes multiple mechanisms which increase mean arterial pressure
why is ADH produced?
it is synthesised in the hypothalamus and released form the posterior pituitary
what triggers ADH release?
> decrease in blood volume
increase in osmolarity of interstitial fluid
circulating angiotensin 2
these are signs of low MAP
where is atrial natriuretic peptide produced?
the myocardial cells of the atria and the ventricles and brain
what triggers atrial natriuretic peptide release?
increased distension of the atrium as a sign of increased mean arterial pressure
what does atrial natriuretic peptide do?
it increases the excretion of sodium and inhibits the release of renin. it acts on the medullary cardiovascular centre to reduce mean arterial pressure
how is the atrial natriuretic peptide system a negative feedback system?
it detects increase in MAP and stimulates release of ANP which evokes multiple mechanisms which reduce MAP.
