4 Control of Cardiac Output Flashcards
Define afterload.
Load heart must eject against
Define preload.
Amount ventricles stretched in diastole
Define Total Peripheral Resistance.
Resistance to blood flow from all systemic vasculature
What happens to the pressure in the capillaries on the venous side if the arterioles constrict?
Pressure falls (on venous side)
What happens to the pressure in the capillaries on the arterial side if the arterioles constrict?
Pressure rises (on arterial side)
Fill in the missing gaps (orange) with either increases or decreases.
Write out 2 equations which can be used to calculate stroke volume.
(Hint: use CO, SV, EDV, ESV)
What is the typical stroke volume for a 70kg man (at rest)?
70ml
(About 67% normal EDV)
What causes the ventricles to stop filling?
Pressure change
Intraventricular pressure is greater than/equal to venous pressure
What relationship does the ventricular compliance curve show?
Relationship between:
- How much ventricles fill
- Left ventricular pressure
What is the Frank-Starling law of the heart?
More heart fills, harder it contracts
How does the heart contract harder if it is filled more?
Increased Ca2+ sensitivity as muscles stretched
What is contractility?
Force of contraction for given fibre length
Draw the another line on this graph to show how the curve would change if there was an:
- Increase in contractility
- Decrease in contractility
Within the body, what causes contractility to increase or decrease?
What is Aortic impedence?
Pressure heart has to pump against
(sum of factors resisting venticular ejection)
(Same as pressure in aorta)
Which part of the peripheral nervous system controls contractility and HR? (somatic or autonomic)
Autonomic Nervous System
What happens in terms of PNS activity and SNS activity if the body’s blood pressure drops.
PNS activity decreases…
…SNS activity increases…
…increase HR and Contractility
What causes postural hypotension? (include references to venous and arterial pressure)
Pooling of Blood
Venous pressure drops, CO drops, Arterial pressure drops
How is cardiac output increased during exercise?
Why is it useful to measure Jugular Venous Pulse?
Direct column of blood connected to right atrium
Central line can be inserted into internal jugular –> allows wave form to be seen
What might cause the JVP to increase?
- Right side of heart doesn’t pump blood out properly
- Vol overload w./ IV infusion
- Something impairs heart filling eg stab wound (distended neck veins)
