A brief decription on Human heart and its cycles and blood floe

2. Diagram of
Heart
*Blood from superior and inferior venacava fills into
the RA i.e (deoxygenated blood)
*The blood then moves towards the RV via Tri-cuspid
valve.
*Due to the Iso-volumetric contraction the blood gets
pumped out to the pulmonary artery via Pulmonary
valve . The pulmonary valve prevents the backward
flow of blood into the RV.
*Then the blood flows to the lungs to get oxygenated
and purified , then it flows to the pulmonary vein
from lungs to LA.
*Blood gets fills into the left atrium , after the filling .
*The blood gets pumped out to the LV via Bi-cuspid
valve.
*Due to the Iso-volumetric contraction the blood gets
pumped out to the Aorta via Aortic valve.
*Then the blood gets circulated through out the whole
body.

4. o Heart is an intrinsic system . Where by the
cardiac muscles is automatically stimulated to
contact with out the need for a blood supply
from the brain.
o There are small group of specialised neuro-
muscular cell in the myocardium which
conduct impulses causing co-ordinated and
synchronised contraction of the heart muscle.

5.  SA NODE :-(Sino-atrial node)
o The small mass of specialised cells is in the wall of
right atrium near to the superior venacava .
o The SA Node is also called as pace-maker of the
heart,because it initiates more rapidly then the other group of
neuro-muscular cells.
 AV NODE :-(Atrio-ventricular node)
o This small mass of neuro-muscular tissue is situated in
the wall of the atrial septum, near the atrio ventricular valves.
o AV Node is stimulated by impulse that sweep over the atrial-
myocardium.
o It is capable of initiating impulse which cause contraction but
slower than SA node.

6. CONDUCTING SYSTEM
 ATRIO-VENTRICULAR BUNDLE:-
(Bundle of His)
o This is a mass of specialised fibres
that originate from the AV Node.
o The AV bundle crosses the fibrous
ring that separates atria and
ventricle,then at the upper end of the
ventricular septum and it divides into
right and left bundle branches.
o With in the ventricular myocardim the
branches breaks off in to fine fibre
known as purkinjee fibres.
o AV bundle branches and purkinjee
fibres convey electrical impules from
AV node to the apex of myocardium
where the wave of ventricular
contraction begins and compel the
blood in in to the pulmonary artery
and Aorta.

7. CARDIAC CYCLE
 Cardiac cycle is the
mechanical contraction and
relaxation of different heart
valves according to the
blood flow in heart.
 Then what is systole ? It’s
just can be called
contraction.
 Then what is diastole? It’s
nothing but Relaxation.
 One cardiac cycle= two
systole + one diastole
 Duration for one cardiac
cycle-0.8s

8. o So what just happens in 0.8s of time ?????????
Cardiac cycle works by three mechanism….
This can be divided into three phases:-
*ATRIAL SYSTOLE
*VENTRICULAR SYSTOLE
*JOINT DIASTOLE
 Human heart contains 4 valves…..
*TRI-CUSPID VALVE
*BI-CUSPID VALVE
*PULMONARY VALVE
*AORTIC VALVE
The whole cardiac mechanism is runed by the help
of these 4 valves.

9. o Atria contracts. Both Left and Right atrium
pushes the blood into ventricles via Atrio-
ventricular valves.
o While the atria pushes blood into the
ventricles the veins that pour blood into atria
are blocked .
o This all process happens in just 0.1s of time.

10. o Ventricular contraction starts and atria relaxes . So
atria comes into the diastole phase.
o Both the Atrio - ventricular valves gets closed.
o The closure of the valves produces a sound called
LUBB . This is the characteristic sound of heart
which can be heard by the help of Stethoscope.
o Here Iso - volumertic contraction starts .But there
is no change in the volume of blood.
o Due to that pressure the pulmonary valve and
aortic valve opens and the blood pumps out into
the great veins . So the ejection of blood occurs.
o This happens in 0.3s of time.

11. o We had seen that atria is already in diastole
phase , now after the blood is pumped from
ventricles to the great veins via Semilunar
valves.
o When the blood flow stops and the Semilunar
valve closes it produces the sound as DUBB.
o This is marked as the starting of ventricular
diastole.
o This joint diastole happens with in a time
period of 0.4s.
o Again the same process starts……..

13.  Atrial diastole :- Lasts 0.7s
 Ventricular diastole :- Lasts 0.5s
 Duration between LUBB and DUBB - 0.3s
 Duration between DUBB and LUBB - 0.5s