Body Fluids and Circulation
Cardiac cycle, cardiac output, ECG; double circulation; regulation of cardiac activity
CARDIAC CYCLE (1 Heat beat 1 systole & diastole)
- Cardiac cycle comprises of following steps :-
a) Atrial systole
(i) SA Node stimulation; triculpid and bicuspid valve open
(b)Beginning of ventricular systole
- AV node stimulation ; tricuspid and bicuspid valves closes to produce the first heart sound called "LUBB". (·15 sec) - Low pitch.
(c) completion of ventricular systole
(i) semi lunar valves open ;
(d) Beginning of ventricular diastole
(i) semi lunar valve closes to produce the second heart sound called "TUBB" (·1sec) - High pitch.
(e) Completion of ventricular diastole
(i) Again tricuspid and bicuspid valves open as the pressure in ventricles fall.
CARDIAC OUTPUT (Heart Output)
- Cardiac output is the amount of blood pumped by heart in one minute.
[C.O] = heart beat rate × stroke volume
= 72 beats/minute × 70 ml/beat
= 5040 ml / minute = 5.5 L/min.
- It is measured in the form of graph that is been produced by the excitation of cardiac muscles which was firstly recorded by Waller
- Father of ECG is EINTHOVEN.
- P → Atrial depolarization / contraction due to SA node activator.
QRS complex → ventricular depolarization due to AV node activation.
T → Ventricular repolarisation end of T wave → end of systole.
Double Circulation :-
- Both systemic circulation (greater circulation/peripheral circulation) and pulmonary circulation comprise double circulation.
- In systemic circulation oxygenated blood flows from left ventricle to all parts of body and deoxygenated blood flows from various parts to right atrium.
- Flow of blood from heart to lungs and vice versa constitute pulmonary circulation.
REGULATION OF CARDIAC ACTIVITY
- Neural regulation
Cardiac centre (medulla oblengata)
- Heart Rate decreases when the impulses receivers from aorta or carotid sinus.
- Heart rate increases when the impulses received from vena cava
- Hormonal regulation (influences SA Node)
Watch this video for the topic from 30:19 to 54:27
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