Lecture 2 - Cardiac Cycle Flashcards by Jidapa Tolley

What are the two phases of the cardiac cycle and what do they mean?

Systole - Contraction
Diastole - Relaxation

How well did you know this?

Not at all

Perfectly

What are the different stages of the cardiac cycle?

Diastole 1 – Isovolumic Relaxation
Diastole 2 – Ventricular Filling
Systole 1 – Isovolumic Contraction
Systole 2 – Ventricular Ejection

How well did you know this?

Not at all

Perfectly

What happens during Diastole 1 – Isovolumic Relaxation?

All valves shut
No change in ventricular volume
Minimal ventricular volume (end-systolic volume)
Relaxation of ventricles
Atrium fills with blood
Atria pressure increases until >ventricular pressure

How well did you know this?

Not at all

Perfectly

What happens during diastole 2 - ventricular filling?

When atrial pressure> ventricular pressure AV opens passively
Ventricular filling
90% filling passive
Last 10% from atrial contraction

How well did you know this?

Not at all

Perfectly

What happens during systole 1 - isovolumic contraction?

Ventricles filled
Ventricular depolarisation
Ventricle contracts
Ventricular pressure rises
AV valve closes so all valves shut

How well did you know this?

Not at all

Perfectly

What happens during systole 2 - Ventricular Ejection?

ventricular pressure> aortic pressure
aortic valve opens
blood into aorta

How well did you know this?

Not at all

Perfectly

What is the cardiac cycle?

The cardiac cycle is a series of mechanical events which associates temporally with electrical and valvular events.

How well did you know this?

Not at all

Perfectly

What happens to ventricular volume during isovolumic relaxation?

Constant

How well did you know this?

Not at all

Perfectly

What happens to ventricular volume during ventricular filling?

Rapid during early stages and slow during late stages (besides top up after atrial contraction). At this stage we have maximum ventricular volume (end of diastole volume – EDV).

How well did you know this?

Not at all

Perfectly

What happens to ventricular volume during isometric contraction?

Constant

How well did you know this?

Not at all

Perfectly

What happens to ventricular volume during ventricular ejection?

Decrease in volume, rapid in early stages, slower in later. At end of stage we have lowest ventricular blood volume (end-systole volume - ESV)

How well did you know this?

Not at all

Perfectly

What happens to ventricular pressure during diastole?

Minimum at beginning but slight rise during ventricular filling and after atrial contraction.

How well did you know this?

Not at all

Perfectly

What happens to ventricular pressure during systole?

Rapid rising during isometric contraction. Continues rising to maximum during ejection phase. Falls late systole to prepare for diastole.

How well did you know this?

Not at all

Perfectly

What happens to arterial pressure during diastole?

Continues to fall until minimum
Minimum at end of diastole/during isovolumetric contraction
(Diastolic blood pressure)

How well did you know this?

Not at all

Perfectly

What happens to arterial pressure during systole?

Rises to max
LVP > AP valves open
Rises to a maximum
(Systolic blood pressure)
LVP < AP valve closes

How well did you know this?

Not at all

Perfectly

Why do we have the aortic notch/dicrotic notch/incisura?

Aortic valve closing

How well did you know this?

Not at all

Perfectly

What happens when we miss 1-2 heart beats?

No problem

How well did you know this?

Not at all

Perfectly

What happens when we miss 5-10 heart beats?

unconscious

How well did you know this?

Not at all

Perfectly

What happens when we miss 5 mins of heart beats?

Clinical help - damaged heart

How well did you know this?

Not at all

Perfectly

What happens when we miss >10mins of heart beats?

Death

How well did you know this?

Not at all

Perfectly

Describe Diastole 1:
- Timing
- Valves
- Event

Diastole 1 0.05s
- All valves shut
Isovolumetric Relaxation

Describe Diastole 2:
- Timing
- Valves
- Event

Diastole 2 0.6s
- AV valves open
- Ventricular Filling, Atrial “top-up”

Describe Systole 1:
- Timing
- Valves
- Event

Systole 1 0.05s
- All valves shut
- Isovolumetric Contraction

Describe Systole 2:
- Timing
- Valves
- Event

Systole 2 0.3s
- SL valves open
- Ventricular Ejection

What is the function of the heart valves?

Preventing the back flow of blood

What are our two types of heart valves?

We have two types of valves which are AV (atrioventricular) and semilunar.

How many valves do we have in the heart?

Where are the AV valves located?

The AV valves exist between the atria and ventricles

When do the AV valves open?

When pressure in the atria exceeds that of the ventricle.

When do the AV valves close?

When the pressure of the ventricles are filled and pressure increases, the AV valve closes.

What is the first heart sound?

Closure of AV valves (M1-T1) Low, long sound (lub)

Where are the semilunar valves?

The semilunar valves exist between ventricle and either the aorta or pulmonary artery (depending on what side of the heart)

When do the semilunar valves open?

The semilunar valves open when pressure in the ventricle exceeds the aorta or pulmonary artery.

When do the semilunar valves close?

When ventricular decreases below aortic (or pulmonary artery) pressure, the semilunar valves shut

What are the left ventricular volumes (at rest)?

End-diastolic volume (EDV) 130 ml End-systolic volume (ESV) 60 ml Stroke volume (SV): EDV-ESV 70 ml Ejection fraction is: 55 - 60%

What is the difference in pressure between the left and right sides of the heart?

RV and pulmonary artery (PA) pressure are lower than LV pressure and aortic pressure

What is the difference in resistance between the left (systemic) and right (pulmonary) sides of the heart?

Pulmonary resistance is lower than total peripheral resistance (systemic circulation)

What system does the left side of the heart send blood to?

Systemic circuit

What system does the right side of the heart send blood to?

Pulmonary circuit

What is the RV and PA pressures (at rest)?

Diastole Systole RV pressure 0/1 25 mmHg PA pressure 8 25 mmHg

What is the second heart sound?

Closure of semilunar valves (A2-P2) Short, high pitch (dub)

What is the third heart sound?

Passive ventricular filling, early diastole Heard in the young

What is the fourth heart sound?

Ventricular filling following atrial contraction Reduced ventricular compliance

What are the effects of heart rate on cardiac cycle?

When we increase heart rate, the durations of diastole and systole decrease. However, although both events decrease, diastole shortens the most. The higher the heart rate, the faster the filling and ejection of blood but SV stay constant.

What event occurs during the P Wave in ECG?

P Wave: Atrial depolarisation precedes atrial contraction

What event occurs during the QRS complex in ECG?

QRS Complex: Ventricular depolarisation precedes ventricular contraction

What event occurs during the T Wave in ECG?

T Wave: Ventricular repolarisation/Ventricular relaxation

What is avg HR and cardiac at rest?

60bpm, cardiac cycle 1s

What are the timings of diastole and systole at rest?

Diastole: 0.66 s 2/3 cardiac cycle Systole: 0.34 s 1/3 cardiac cycle

What are the timings of diastole and systole at max HR?

Diastole: 0.13 s 1/3 cardiac cycle Systole: 0.20 s 2/3 cardiac cycle

What happens with the duration of systole and diastole when heart rate increases? A. Systole and diastole shorten equally B. Systole stays constant, and only diastole shortens C. Only systole shortens, and diastole stays constant D. Both shorten, with diastole more than systole

D. Both shorten, with diastole more than systole