Heart as a pump Flashcards
How many times greater is the resistance in the rest of the body than the lungs?
6x
What are the atria sometimes referred to?
The priming pumps
priming pumps function
pumps blood over a short distance into the ventricles- ventricle will fill spontaneously due to elastic walls causing recoil
ensures the ventricles are filled
How do all the cells contract at once?
gap junctions between cells forming an electrical syncytium
Negative aspect of electrical syncytium
arrhythmias will also be propagated
What causes heart sounds?
Opening and closing of valves
Two layers of heart cells
subendocardial myocytes and subepicardial myocytes
Apex beat definition
When the heart rotates and moves forwad, causing the apex to tap against the 5th intercostal space during systole
What can the apex beat be used to diagnose?
cardiomegaly, due to the lateral or inferior displacement of the apex beat suggesting that the heart has become enlarged
isovolumetric phase definition
ventricular pressure sufficient to close inlet valve but not sufficient to open outlet valve
Cardiac cycle definition
the sequence of events that occurs in a single heartbeat. The cycle has two main phases of systole and diastole and is complete in around 1 second at rest
atrial systole- ventricular systole- ventricular diastole
Why do elderly people require atria more than young? + how much they contribute?
Elastic hearts are able to recoil to collect blood, do not need the atria to completely fill the ventricles
ventricles more stiff and fibrotic, thus cannot depend on recoil
10-20% in young
50% in old
How many isovolumetric phases are there in one cardiac cycle?
2
murmur definition
sound that emits when there is a fault with the valves
Two iconic heart sounds + what causes them
lub- AV valves shutting during ventricular systole
dub- semilunar valves shutting during atrial systole
What is the jugular venous pulse?
the indirectly observed pressure over the venous system via the visualisation of the internal jugular vein at the semi supine angle
why does the vein pulse?
very close to the right atrium and so the atrial pressure cycle creates a visible pulse
explain the shape of the pulse recordings
two main pressure waves per cycle named A and V and a smaller peak called C
two sharp falls called C and Y descents
A- increase in pressure caused by atrial systole, raising central venous pressure to maximum of 3-5mmHg, very little backflow
C- wave caused by the bulging of cusps of the tricuspid or mitral valve into the atrium as the valves close. Also caused by stoic expansion of the adjacent carotid artery. Jugular veins are some way away from the right atrium hence the time delay
X descent- sharp fall in pressure due to atrial relaxation and downwards movement of the annulus fibrosis as it contracts. The downward movement of the base stretches the atria and sucks blood into them, reaching peak velocity of venous inflow
V wave- atrial pressure rises due to filling, occurs during ventricular systole
Y descent- AV valves open as a result of build up of atrial pressure exceeding ventricles, rapid drainage leads to drop in pressure
important muscles in valve function
papillary muscles
papillary muscle structure + function
inward projections of the ventricular wall which contract and tense the chord tendineae during systole which prevents the valves from inverting into the atria as pressure builds up in the ventricle
ejection fraction definition + value at rest
the percentage of blood leaving the ventricles compared to total possible volume of blood that could be ejected
50%
how are heart sounds formed?
cardiac valves close, where the cusps balloon back as they check the momentum of there fluxing blood
the sudden tensing of the cusps sets up a brief vibration which is transmitted through the tissues to the chest wall and can be heard through a stethoscope
what is heard with healthy valves?
only the closure, not the opening
explain first heart sound
lubb
caused by the vibration from the near simultaneous closure of the tricuspid and mitral valves at the start of ventricular systole
