The Cardiac Cycle Flashcards
cardiac excitation-contraction coupling process
1) AP enters form adjacent cell
2) voltage gated Ca channels open and Ca enters the cell
3) Ca induces Ca release from SR by opening the RyR receptor channel
4) local release causes Ca spark
5) Summed Ca sparks create Ca signal
6) Ca ions bind to troponin –> muscle contraction
7) relaxation occurs when Ca is released from troponin
8) Ca is pumped back into SR fro storage
9) Ca is exchanged with Na by NCX antiporter
10) Na gradient is maintained by Na-K ATPase
again.. valves are important. why?
the prevent back flow of the blood and are critical to the phases of the cardiac cycle
- semilunar prevent backflow into the ventricles
- mitral and bicuspid valves precent backflow into the atria
what is the cardiac cycle? what defines it (measurably)?
- the coordination of the electrical and mechanical events that occur within one heartbeat
- one period that goes form the beginning of one heart beat to the next (P-P or R-R)
what are the 2 main phases in the cardiac cycle?
- systole: the time at which the heart muscle is contracting (shorter)
- diastole: the time during which the muscle is relaxed
Important baseline to know:
- normal heart rate?
- avg length of cardiac cycle?
- which parts of the heart are synchronized?
- 70-75 bpm
- ~0.8sec cycle
- atria are synchronized with each other and the ventricles are synchronized with each other
Wigger’s diagram:
- what does it tell you?
- demonstrates the phases of the cardiac cycle
the events will tell you: - atrial pressure
- ventricular pressure
- aortic pressure
- ventricular volumes
- ECG
- Phonogram (heart sounds)
what are the phases of the cardiac cycle?
A: atrial systole
B: isovolumetric ventricular contraction
C: rapid ventricular ejection
D: slower ventricular ejection
E: isovolumetric ventricular relaxation
F: rapid ventricular filling
G: slower ventricular filling
what mechanical events occur during ventricular systole?
B: isovolumetric ventricular contraction
C: rapid ventricular ejection
D: slower ventricular ejection
what mechanical events occur during ventricular diastole?
E: isovolumetric ventricular relaxation
F: rapid ventricular filling
G: slower ventricular filling
compare the cardiac cycle between the left and right sides of the heart:
- resistance?
- pressure?
- strength?
- volume?
- left = higher pressure
- left = more resistance
- left = more muscle tissue so stronger muscle
- same volume
atrial pressure curve
- what are the peaks?
- what do they represent?
- a wave = atrial contraction –> atrial pressure increases and blood moves into the ventricles (contributes 15-20% of ventricular filling - important for periods of cardiac stress or disease)
- c wave: occurs during isovolumetric contraction (rapid increase in ventricular pressure causes AV valve to bulge –> causes a slight increase in pressure in the atria)
- v wave: occurs with atrial filling (AV valves are closed and the atria are filling with blood)
ventricular pressure curve
- what are the peaks?
- what do they represent?
- demonstrates the changes in ventricular pressure during systole and diastole
- remember blood flows from high pressure to low pressure
- AV valves close –> ventricles contract isometrically –> pressure rises quickly –> semilunar valves open when LVP > AoP –> ejection of blood
- during isometric ventricular relaxation (5) = rapid ejection
- during ventricular filling (6 and 7) = rapid fill then slower fill
Aortic pressure curve
- what are the peaks?
- what do they represent?
- lowest point = measured diastolic blood pressure
- semilunar valve opens when LVP > AoP
- during ejection = LVP ≈ AoP
- peak during ejection = measured systolic blood pressure
- after ejection, AoP decreases
- end of cycle indicated by the dicrotic notch = closure of aortic valves
why do we measure blood pressure via the upper arm?
we measure the “aortic pressure” by measuring the brachial artery pressure since they are closely related and about the same
ventricular volume curve
- blood is pushed into the ventricles
- during isometric ventricular contraction, the blood in LV is at the end diastolic volume (EDV)
- during rapid ejection, 2/3 of the LV is emptied
- during slower ejection, ventricles begin to relax and some more blood releases slowly – note: never fully empty. usually 40-50mL remain in ventricles at rest = end-stystolic volume
- rapid filling occurs and about 2/3 of blood fills ventricles
- remaining blood enters at slower rate
heart sounds
- what are normal?
- what are abnormal?
- there are 4 heart sounds that can occur
- the first (S1) and second (S2) are the normal sounds
- S3 and S4 are result from abnormal heart beat
Summary of Phases and events of the cardiac cycle in a chart
*** must know
what is the pressure volume loop?
what does it depict?
- depicts the changes in the ventricular pressure and volume that are in one cardiac cycle
cardiac cycle calculation and definitions
important cardiovascular parameters
what are valvular disorders? what can they result in
- problems with the valves
- result in variations in the normal blood flow patterns and heart murmurs
mitral valve stenosis results in?
- increased volume in LA
- increased LA pressure
- LA hypertrophy and dilation of atrial chamber
- reduction in LV filling (lower EDV and SV)
- atrial enlargement may cause abnormal electrical activation of the atrial chamber and atrial fibrillation
- can also lead to elevated pressure in pulmonary system –> pulmonary hypertension, pulmonary edema, right heart failure
mitral valve regurgitation results in?
- a regurgitant jet of blood flowing into LA during systole (volume overload)
- increase LA volume –> increased LA pressure at end of systole –> taller v wave
- atrial pressure peaks at time of second heart sound
- the sudden rise in LA pressure produces increased pulmonary pressures (increased pulmonary venous and pulmonary capillary pressures) –> pulmonary edema
- if chronic –> LV hypertrophy and dilation may occur bc of higher EDV
aortic stenosis and the cardiac cycle
- can be caused by?
- results in?
- congenital abnormality when the aortic valve has 2 leaflets instead of 3
& acquired abnormality –> in elderly patients, the valve becomes calcified - large pressure gradient LVP»AoP (higher afterload)
- elevated ESV and reduction in SV
- LV hypertrophy, myocardial dysfunction, arrhythmias, Left heart failure
