The heart functions as a double pump to circulate blood through the body via the systemic and pulmonary circulations. It maintains blood pressure and pumps oxygenated blood and vital substances to different body parts. The heart's conduction system coordinates the contraction of cardiac muscle cells. It begins with the sinoatrial node generating spontaneous impulses at 72 beats/min which propagate through atrial pathways to both atria. The atrioventricular node then slows conduction to the bundle of His and Purkinje system to coordinate atrial and ventricular contractions and maintain an orderly heartbeat.

3. Physiological functions of the
heart
 The heart functions as a pump and acts
as a double pump in the cardiovascular
system to provide a continuous circulation
of blood throughout the body.
 The circulation includes the systemic
circulation and the pulmonary circulation.
 Maintaining blood pressure.
 Pumping oxygenated blood to the other
body parts.
 Pumping hormones and other vital
substances to different parts of the body

4. Atria ventricular node.
 It is the part of the wall of right atrium
close to the atrioventricular septum and
near to the tricuspid valve. It generates
impulses approximately at the rate of 60
times/min.

6. Bundle of Hits.
 It is a thick band of muscle fibers it runs
starting from A.V node. It runs along
with intra ventricular septum. It divides
into the right and left bundle branch. It

7. Sino atrial node.
It is a part of the wall of right atrium close to the
opening of superior venacava. It generate
impulses approximately at the rate of 72 times
/min. SA node is called the pacemaker
because it depolarizes at a faster rate than
any other group of cells in the heart, and
imposes that faster rate on the heart as a
whole.

8. Main functions of the heart
 Receiving deoxygenated blood and
carrying metabolic waste products from
the body and pumping into the lungs for
oxygenation.

9. Conduction Speeds in Cardiac
tissue.
 Tissue
SA node - 0.05
Atrial pathways – 0.1
AV node – 0.05
Bundle of His – 0.1
Purkinje system- 0.4
Ventricular muscle – 0.1

10. Conduction Speeds in Cardiac
tissue.
 Tissue

12. Cardiac excitation
 Cardiac excitation normally begins in the
sinoartial node, located in the right atrial
wall just inferior and lateral to the opening
of the superior vena cava.
 The spontaneous depolarization is a
pacemaker potential .
 When the pacemaker potential reaches
threshold, it triggers an action potential.
Each SA node propagates both atria via
gap junctions in their intercaletated discs of
atrial muscle fibers and contact both atria
at the same time.

13. Electrical Activity of the
heart
 The heart beat originates in a
specialized cardiac conduction system.
 The heart beat normally in an orderly
sequence: Contraction of the atria
(atrial systole) is followed by contraction
of the ventricles (ventricular systole) ,
and during diastole all four chambers
are relaxed.

14. CONDUCTION SYSTEM of the
heart
 Action potentials (electrical impulses) in the
heart originate in speacialized cardiac
muscle cells, called autrohythmic cells.
 These cells are self excitable able to
generate an action potential without
external stimulated by nerve cells.
 The autorhythmic cells serve as a
pacemaker to initiate the cardiac
cycle(pumping cycle of the heart) and
provide a conduction system to coordinate
the contraction of muscle cells throughout
the heart.