L2 Flashcards
is it physiologically possible for your heart to miss a beat? if so how missing how any beats leads to what issues
1-2 = no problem
5-10 = unconscious
5 min = clinical help is needed as you could have damage to the heart
10 min = no turning back
what is the cardiac cycle/what does it consist of
it is the complete set of contraction and relaxation of the heart
it consists of diastole (ventricles relaxing) and systole (contraction of the ventricles)
the full cycle includes mechanical events (pressure and flow changes), electrical events (ECG) and valvular events (heart sounds)
what is diastole
relaxation
contraction of the ventricles is known as
systole
what happens in the early stages of diastole (diastole 1)
isovolumetric relaxation
diastole is when contraction is finished and starts with all the valves shut therefore there is no blood flow and no blood entering the ventricle
blood is flowing into the artra therefore the pressure is rising. when the pressure in the atra is greater than than in the ventricles the AV valves open passively and ventricular filling begins
what is end systolic volume (ESV)
the minimal ventricular volume. this is when there is the least amount of blood in the heart
what happens in the later phase of diastole (diolstle 2 )
ventricular filling
The pressure gradient is diving the blood into the ventricles because the ventricle is still relaxing. The start of ventricular filling is very fast (about 90% of the total volume of blood).
late diastole is when the P wave happens as this is when the atria contracts. It only causes about 5mmHg therefore it is only responsible for 10% of blood ejected. this is called arterial top up
what is the end diastolic volume (EDV)
this is the amount of blood in a ventral at the end of diastole
at rest this is about 130mL
what happens at the start of systole (systole 1)
isovolumetric contraction
the ventricles depolarise causing the QRS complex to be seen in an ECG
the ventricles then contract the the pressure gradient reverces causing the AV valves to close
as all the valves are again closed the pressure in the ventricles increases because of the isovolumetric contraction
what happens in the later part of systole (systole 2 )
ventricular ejection
when the pressure in the ventricles exceeds that in the arteries the SL valves open causing arterial blood volume and pressure to increase
if you were looking at the left ventricles you would say that the left ventricular pressure (LVP) and the aortic pressure (AP) rise in parallel
this causes rapid ejection of blood from the heart
how much of the hearts blood volume is ejected in the first 1/3 of ventricular ejection
2/3rds of the total volume of blood ejected
what happens in the late part of ventricular ejection (still systole 2)
LVP and AP fall to a slow ejection rate as the heart has contracted as much as it can. the ventricle then repolarises which is shown as the T wave
the ventricular pressure falls below the arterial pressure causing the SL valves to close and the ecycle starts again
what is end systolic volume
the volume of blood left in the ventricle at the end of systole
at rest this is about 60mL
greater pressure in the atrum than the ventricle leads to the opening of the AV valve BECAUSE at rest, the majority of the ventricular filling happens before the atria contract
both statements are true but they are not causal
how long does each phase of the cardiac cycle last
diastole 1 = 0.05 sec
diastole 2 = 0.6 sec
systole 1 = 0.05 sce
systole 2 = 0.3 sec
all together the cardiac cycle is about 1 sce at rest
what is the name of the diagram which displays al of the information for the cardiac cycle
wiggers diagram
describe ventricular volume during diastole
V is constant during isovolumetric relaxation
early rapid ventricular filling followed by late slow ventricular filling
top up after atrial contraction
ventricle is at its max volume at EDV (130mL)
describe ventricular volume during systole
constant during isometric contraction
rapid fall during early ejection
slow fall during late ejection
volume is at its min at ESV (60mL)
describe ventricular pressure during diastole
pressure is at its min at the start of diastole but rises a little during ventricular filling and after atrial contraction (the A wave)
describe ventricular pressure during systole
pressure rises dramatically during isometric contraction and reaches its max pressure during the ejection phase
pressure falls during late systole
describe arterial pressure during diastole
pressure continues to fall during diastole to its min. it reaches its min arterial pressure at the end of diastole which is known as your diastolic blood pressure
describe arterial pressure during systole
the ventricular pressure is larger than the arterial pressure therefore the SL valves open and artery pressure rises to a maximum.
NOTE that the pressure in the ventricle drops faster than in the arterie as the heart is unable to contract any more
this is your systolic pressure
what can be seen when the semilunar valves snap shut
the incisura or dicrotic notch
at rest what is the average systolic and diastolic pressure
diastolic pressure = 80mmHg
systolic = 120mmHg
how could you calculate ejection fraction/what is the ejection fraction
(use average numbers for when at rest)
end diastolic volume = 130mL
end systolic volume = 60mL
therefore stroke volume is 70mL which is about 55-60% of the total volume. this is the ejection fraction
what can you tell from the ejection fraction
how healthy the heart is
above 50% is healthy and anything less suggests the heart is failing
this shows the strength of contraction
when is the pressure in the ventricle and the arteries the same
at the very start of systole
what are the differences between the left and the right side of the heart (in terms of resistance and pressure
pulmonary resistance (right side) is lower than the total peripheral resistance (left side)
the pressure in the right ventricle and the pulmonary artery is lower than the left ventricle and the aortic pressure
this is because the right only has to pump to the lungs whereas the left is around the whole body
what are the values for pressure in the right ventricle and pulmonary artery during diastole and systole
ventricle = 0/1 during diastole and 25mmHg during systole
pulmonary artery = 8 during diastole and 25mmHg during systole
describe the first heart sound (S1)
happens when the AV valves close (M1 -T1)
the sound is long and slow (lub)
describe the second heart sound (S2)
the closure of the semilunar valves (A2 - P2) which produces a short high pitch dub
describe the third heart sound (S3)
you hear this because of the passive ventricular filling during early diastole. you are only able to hear this in the young as their heart is able to relax very quickly
what is the 4th heart sound (S4)
this is the result of ventricular filling following atrial contraction. you hear this because of reduced ventricular compliance
you only hear the 4th heart sound in diseased hearts as the atria is trying to push more blood into the ventricles but the ventricles won’t stretch anymore
what makes up an ECG
PQRST
P wave = atrial depolarisation and contraction
QRS complex = ventricular depolarisation and contraction
T wave = ventricular repolarisation and relaxation
at rest how long is diastole and systole
D = 0.66s (2/3 of the cardiac cycle)
S = 0.33s (1/3 of the cardiac cycle)
when we exercise our heart rate increases. what effect does this have on the cardiac cycle
at max our heart rate can be 180bpm meaning that the cardiac cycle is about 0.33 sec rather than 1 sec
to achieve this we spend less time in diastole (about 0.13s (1/3)) and more time in systole (0.2s (2/3))
this is because the heart has a set time it needs for contraction but it is able to spend less time relaxing. this is important because we have to maintain SV otherwise there would be no point in speeding up our HR
