ch 36 - second A Flashcards
equation for cardiac output
CO =HR x SV
Determined by myocardial contractility, cardiac afterload and preload
stroke volume
the amount of tension (stretch) applied to a muscle before contraction
Preload
the load a muscle must overcome in order to contract
arterial pressure that the left ventricle must overcome to eject blood
Afterload
if Afterload increased, _____ will decrease
SV (stroke volume)
If afterload falls, _____ will rise
SV
the force of ventricular contraction is proportional to muscle fiber length (up to a point)
Starling Law
most important factor that determines venous return
systemic filling pressure (force that returns blood to the heart)
what raises filling pressure?
constriction of veins
increase in blood volume
formula for arterial pressure
AP = PR x CO
PR is peripheral resistance
CO is cardiac output
Arterial pressure is regulated by what 3 systems
Autonomic NS
RAAS
Kidneys
The Autonomic Nervous System regulates Arterial pressure by adjusting
Cardiac output and Peripheral resistance
Baroreceptor reflex
Baroreceptors sense BP in the aortic arch and carotid sinus and relay info to the medulla
1-When Arterial pressure drops, vasoconstriction of all arterioles which increases Peripheral Resistance
2-Constriction of all veins, increases venous return
3-Accelerated HR
1-When Arterial pressure rises, dilation of arterials which decrease peripheral resistance
2-Dilation of all veins, decreases venous return
3-slows HR
RAAS supports arterial pressure by
1) constricting arterioles and veins
2) retention of water by the kidneys
In the RAAS system, Vasoconstriction is mediated by what hormone
Angiotensin II
In the RAAS system, water retention is mediated in part by what hormone
aldosterone through retention of sodium
what is the fastest way the RAAS works
Vasoconstriction (hours)
what is the slowest way that RAAS works
Water retention (days)
when AP remains low for a long time, the kidneys respond by
retaining water which in turn causes Arterial pressure to rise. (fluid retention increases blood volume )
Reduction in AP causes the kidneys to
retain water, because low AP reduces renal blood flow (RBF), which in turn reduces GFR
reduction in AP that can occur when we move from a supine or seated position to an upright position
orthostatic hypotension
when postural hypotension occurs, the baroreceptor reflex can restore AP by
1) constricting veins and arterioles
2) increasing HR
Drugs that reduce arterial pressure by relaxing veins can trigger what which causes what
the baroreceptor reflex and cause reflex tachycardia
Natriuretic peptides serve to protect
the cardiovascular system in the event of volume overload
