The heart as a pump Flashcards
The heart beats every…
1 second and if we know what happens in this one second, we know how the heart beats over a period of time
What does the heart need to do?
Develop high pressure
Arteries carry…
Blood Away from heart
Veins carry blood…
towards the heart
Why are there so many tubes
So that the blood is as close as it can be to the tissues
Part of the heart that does most of the work
Ventricles
What happens during relaxation?
The blood fills the atria and vens as the AV valves are open but others are closed to prevent high P blood from coming in
How are the valves controlled?
Not through muscle or nerves, but by Pressure
How does cardiac muscle contract?
Same concept as skeletal muscle
Why is everything activated in cardiac muscle unlike skeletal
We can vary our force in skel due to recruitment and its a voluntary process
How to ^ force of cardiac contraction if all fibres recruited?
Release more Ca2+
How do cardiac muscles relax
Decrease in cytosolic Ca2+ levels.
* Ca2+ pumped back into the SR.
* Cross-bridges release when ATP i.e active use of E to relax by changing the myosin head
binds to myosin.
* Reduction in force means the heart
can relax.
* All cardiac myocytes relax each beat.
Diastole
Relaxation + falling pressure
Systole
Contraction + rising P
Atrial systole before ven
How many parts to cardiac cycle
5
What happens at the start?
Ven in diastole while atrial systole occurs first
Atrial systole
Artrium contract, open AV valves, Passive vens
Lubb sound
When P in vens ^ and AV slams shut to prep for ven contraction
Isovolumetric ven contraction
All entrances closed but not enough P in vens to open up the semilun valves so V doesnt change even though vens constrict
Ven ejection
The P is large enough so semilun valves open
Dupp sound
Ca2+ goes away and when the P in vens is less than Aorta and pulm, the semilun shuts to prevent backflow
Isovol ven relaxation
Blood fills in atrium but AV valves shut
Passive filling
Ven P lower than atrium so AV valves open
Features of BP graph
*Pulsatile change in pressure
in the major arteries linked to
ejection of blood
* Periods of systole (rising
pressure) and diastole
(falling pressure)
* Diastole is typically longer
than systole
* Systemic arterial pressure is
much higher than pulmonary
arterial pressure as you need to eject over long distances over multiple branches and back
How long in systole and diasole
40% and 60%
Features (sys/diastolic p)
*Systolic pressure is the
highest point on the trace
* Diastolic pressure is the
lowest point on the trace
* Pulse pressure is the
difference between the
highest and lowest points
* Mean pressure is the average
across the full cycle but usually a bit lower than the “middle” as the cycle is 60% diastole (not a fair divide)
* Hypertension is high blood
pressure, while hypotension
is low blood pressure
What is systolic P
P in arteries when vens contract
