Control Arterial pressure - long term Flashcards
Why can’t baroreceptors provide information about absolute blood pressure?
Relationship between pressure and baroreceptor action potential firing frequency is not fixed
What does resetting the baroreflex allow?
High cardiac output to be maintained without a fall in heart rate due to systolic pressure
What does hypertensive cause?
Sensitivity of baroreceptors is reduced
What is the major role of the baroreflex?
Buffer short-term fluctuations
How is blood pressure regulated in the long term?
Maintenance of a normal extracellular fluid volume
How is ECF volume regulated?
Renal excretion of salt and water
What happens if blood volume decreases?
MAP decreases
What do cardiovascular mechanoreceptors control?
Angiotensin II
Aldosterone
Vasopressin
Natriuretic peptides
What does the JGA comprise of?
Juxtaglomerular cells, mesangial cells and macula densa
What is the role of the macula densa cells?
Detect sodium levels
secrete vasoactive agents that affect afferent arterioles
What is the role of the juxtaglomerular cells?
Sense renal pressure changes - stretch receptors
Increases renin secretion
Depend on paracrine signalling from macula densa
What receptors act on the juxtaglomerular cells of afferent arterioles?
beta 1 adrenoreceptors
What factors stimulate renin release?
Low blood pressure
Increased sympathetic activity
What is the enzyme that converts angiotensin 1 to angiotensin 2?
ACE - angiotensin converting enzyme
What is the role of angiotensin II?
Increase blood pressure (MAP)
Stimulates sympathetic vasoconstriction
Increases thirst - increases secretion of vasopressin
When is renal sympathetic nerve activity (RSNA) increased?
Arterial baroreceptors detect a fall in arterial pressure
Veno-arterial mechanoreceptors detect a fall in central blood volume
What does increased RSNA cause?
Increases renin secretion
Salt and water retention by kidneys
What does increased RSNA stimulate?
Afferent arteriole constriction
Reduced GFR
Adrenaline release from adrenal medulla - renin release
What does renin release cause?
Noradrenaline release
Granular cells secretion
Vasoconstriction of afferent arterioles
Lower GFR
Macula densa cell secretion
What does aldosterone stimulate?
Increases Na+ reabsorption in collecting ducts and distal tubule
What does ADH stimulate?
Water retention by the kidneys
What is ADH secretion enhanced by?
Angiotensin II
Reduced central blood volume and arterial pressure
What are natriuretic peptides produced by?
Some atrial and ventricular myocytes in response to increased blood volume
What do natriuretic peptides stimulate?
Na+ excretion
Vasodilation
What are two types of natriuretic peptides?
Atrial natriuretic peptide (ANP)
Brain natriuretic peptide (BNP)
How do natriuretic peptides enhance renal salt and water excretion?
Afferent arteriole dilation
inhibition of Na+ reabsorption
inhibition of renin and aldosterone secretion
What happens in renal artery stenosis?
Blood supply decreased
Blood flow is decreased
less oxygen due to atherosclerosis
What does renal artery stenosis cause?
Renin secretion -> hypotension
