Ex 3 Hormone control of the heart Flashcards
What does RAS stand for?
Renin-Angiotensin System
What is RAS?
The result of renin cleaving angiotensinogen (large liver protein) to form Angiotensin I, then Angiotensin II
Where does angiotensinogen reside?
freely in the blood
Which is the most active peptide in the Renin-Angiotensin system cascade?
Angiotensin II
How is angiotensin form?
angiotensinogen is cleaved by Renin (from the kidney) to form angiotensin I
How is angiotensin II formed?
angiotensinogen I is cleaved by angiotensin converting enzyme (ACE) in the lung to form angiotensin II
How is the Renin-Angiotensin System regulated?
the rate limiting step is the release of renin
Where is ACE found (angiotensin converting enzyme) in the body?
in the endothelial cells
How are most effects of AngII are mediated through what?
AT1 receptor
What are the effects of Angiotensin II on vasculature?
acute peripheral vasoconstriction
What are the effects of Angiotensin II on the kidney?
decrease sodium and water excretion
What are the effects of Angiotensin II on the stimulation of vasopressin (ADH) release?
increase thirst (dipsogenic), water retention by kidney
What are the effects of Angiotensin II on aldosterone production?
increase sodium and water retention by kidney
What are the chronic effects of angiotensin II?
growth factor which leads to vascular and cardiac hypertrophy
Angiotensin II also activates central nervous system which contributues to what?
mediate sympathetic outflow
Where is renin released?
juxtaglomerular cells
This is a specialized structure formed by what?
distal convoluted tubule and glomerular afferent arteriole
What is the main function of the juxtaglomerular apparatus?
regulate blood pressure and filtration rate
What are the three types of cells in the juxtaglomerular apparatus?
macula densa
mesangial cells
granular cells
Which kidney cells contain granules of renin, and when contracted, release renin?
granular (juxtaglomerular cells)
What is the function of the macula densa?
sense salt concentration in the filtrate and repsond
What is the function of mesangial cells?
specialized cells in kidney that have contracting and phagocytic function
What trigger renin release from JG cells?
- increases sympathetic nerve activity (B1 receptor)
- decreased Ang-II at AT1 receptor
- Decreased NaCl to macula densa
- Decreased afferent arteriolar pressure
What are the short term effects of Angiotensin II, within minutes?
vasoconstriction thirst
What are the short term effects of Angiotensin II, within hourse?
retention of salt and water
What are the short term effects of Angiotensin II, within days?
sympathetic stimulation
What are the long term effects of angiotensin II, within months?
vascular and cardiac hypertrophy
Cardiac Hypertrophy results in what?
increase systolic pressure, increase volume load
What is the Law of Laplace?
T=PR, R is radius
What does the Law of Laplace mean?
the larger the vessel radius, the larger the wall tension required to withstand a given internal fluid pressure
What is increased wall tension is related to?
increased pressure,
increased radius
decreased wall thickness
What is the significance of cardiac hypertrophy?
increased pressure results in increased wall tension and a response in smooth muscle hypertrophy in arteries and arterioles
