Download MBBS Physiology Presentations 32 Cardiac Cycle Lecture Notes

Download MBBS (Bachelor of Medicine, Bachelor of Surgery) 1st Year, 2nd Year, 3rd Year and Final year Physiology 32 Cardiac Cycle PPT-Powerpoint Presentations and lecture notes


Cardiac Cycle

Cardiac Cycle

? Cardiac cycle is the mechanical sequence of

events as blood enters the atria and leaves the

ventricles

? The events includes

1. Changes in the pressures in different chambers of the heart
2. Changes in the volume in different chambers of the heart
3. Changes in the aortic, pulmonary arteries
4. Heart sounds
5. ECG changes


Cardiac Cycle

0.5 sec

0.1 sec

0.7 sec

0.3 sec

Phases of Cardiac Cycle

Ventricular Systole
? Isovolumetric contraction
? Rapid ejection
? Slow ejection
Phases of Cardiac Cycle

Ventricular Systole
? Isovolumetric contraction
? Rapid ejection
? Slow ejection

Ventricular Diastole
? Isovolumetric relaxation
? Rapid filling
? Slow filling (Diastasis)
? Filling d/t Atrial Systole

Phases of Cardiac Cycle

Ventricular Systole
? Isovolumetric contraction
? Rapid ejection
? Slow ejection

Ventricular Diastole
? Isovolumetric relaxation
? Rapid filling
? Slow filling (Diastasis)

Start

? Filling d/t Atrial Systole


Cardiac Cycle

Phases

Cardiac Cycle

Phases


Cardiac Cycle

Phases

Cardiac Cycle

Phases


Cardiac Cycle

Phases

Phases of Cardiac Cycle

Ventricular Systole
? Isovolumetric contraction
? Rapid ejection
? Slow ejection

Ventricular Diastole
? Isovolumetric relaxation
? Rapid filling
? Slow filling (Diastasis)
? Filling d/t Atrial Systole
Ventricular Systole

? Isovolumetric contraction phase

? Rising ventricular pressure results in closing of AV valves (1st

heart sound ? "lubb")

? Ventricles are contracting but no blood is leaving
? Ventricular pressure not great enough to open semilunar valves
? Ventricular ejection phase opens semilunar valves

? Ventricular ejection phase

? Semilunar valves opens
? Rapid Ejection (70% blood)
? Slow ejection (30% blood)

Ventricular Diastole

? Isovolumetric relaxation

? volume does not change as ventricles relax, pressure

drops and AV valves open

? Ventricular fil ing

? Rapid ventricular filling:as blood flows from full atria
? diastasis: as blood flows from atria in smaller volume
? atrial systole pushes final 20-25 ml blood
Phases of Cardiac Cycle

Ventricular Systole

Duration (approximate)

? Isovolumetric contraction

0.05 sec

? Rapid ejection

0.10 sec

? Slow ejection

0.15 sec

Ventricular Diastole
? Isovolumetric relaxation

0.10 sec

? Rapid filling

0.10 sec

? Slow filling (Diastasis)

0.20 sec

? Filling d/t Atrial Systole

0.10 sec

Normal Volume of Blood in Ventricles

? Atrial systole pushes final 20-25 ml blood (20%)
? After atrial contraction, 110-120 ml in each ventricle

(end-diastolic volume)

? Contraction ejects ~70 ml (stroke volume output)
? Thus, 40-50 ml remain in each ventricle (End

systolic volume)

? The fraction ejected is then ~60% (ejection fraction)


A Simple Model of Stroke Volume


Ventricular Pressures

? Blood pressure in aorta is 120 ? 80 mm Hg
? Blood pressure in pulmonary trunk is 25 ? 8 mm Hg
? Ventricular pressure usually not increases during diastole
? Right Atrial pressure changes reflected in Jugular vein


Jugular venous pulse waves

Jugular venous pulse waves

? a-wave is due to atrial systole which causes increase in

the intra-atrial pressure

? C-wave occurs during the isometric contraction of the

ventricles due to bulging of the tricuspid valve

? V-wave is due to accumulation of blood during late part

of the ventricular systole or protodiastolic phase and

isometric relaxation of the ventricles


Jugular venous pulse waves

? X-wave is due to downward displacement of the A-V

valve (tricuspid valve) and the AV ring during maximum

ejection phase of ventricular contraction

? Y-wave is due to opening of the AV valve (tricuspid

valve) during maximal ventricular filling phase

Jugular venous pulse waves

? "a-c" interval measures the time of conduction of the cardiac impulse

from the right atrium to the ventricles

? The a-c interval corresponds to the P-R interval of the ECG

? The "a-c" interval is prolonged in cases of delayed conductivity in the

AV bundle which is an early sign of heart block

? In partial heart block, the number of "a" waves is greater than the

number of the "c" or "v" waves.

? In atrial fibril ation, the "a" wave is absent.


Putting it all together!

Putting it all together!
Thank You

This post was last modified on 08 April 2022