Cardiac muscle tissue forms the thick myocardium of the heart wall. It contains cardiac muscle cells that are joined together by intercalated discs to form branching networks called cardiac fibers. The contractions of cardiac muscle cells are stimulated by electrical signals that cause calcium ions to enter the cells, triggering contraction via the sliding filament mechanism. This allows for the synchronized contraction of the entire heart to pump blood throughout the circulatory system.

2. Cardiac muscle tissue forms the thick myocardium of
the heart wall.
It contains cardiac muscle cells and the connective
tissues that surround these cells.
The contractions of cardiac muscle cells pump blood
through the heart and into and through the blood
vessels of the circulatory system.
Cardiac muscle tissue, like skeletal muscle tissue, is
striated, and it contracts by the sliding filament
mechanism.

3. cardiac muscle cell is a short, branching cell with one or
two large, centrally located nuclei.
Each cell averages about 25 μm in diameter and 120 μm in
length.
Adjacent cardiac muscle cells are joined together at their
ends to form cellular networks.
These branching networks of cardiac muscle cells are
called cardiac fibers.
The complex junctions that join cardiac muscle cells are
called intercalated discs.

5. Intercalated discs have two distinct regions:
Transverse regions contain desmosome-like junctions
called fascia adherens that function to bind adjacent
cells together and transmit the contractile force to
adjacent cells.
Longitudinal regions contain gap junctions that allow
ions to pass between cells, transmitting the contractile
signal to adjacent cells.
The free movement of ions between cells allows the
direct transmission of an electrical impulse through the
entire network of cardiac muscle cells.

7. This impulse in turn stimulates all the muscle cells in a heart
chamber (atria or ventricles) to contract at the same time.
In the intercellular spaces around each
cardiac fiber is aloose fibrous
connective tissue, the endomysium,
which aidsto bind adjacent cardiac fibers together and
contains the vessels and nerves that serve the muscle cells.
Groups of cardiac fibers form the cardiac muscle bundles in
the myocardium .
The connective tissues surrounding the cardiac fibers merge
with the fibrous skeleton of the heart and thus function to
anchor the muscle cells and transmit the contractile forces
produced by the muscle cells, similar
to the tendinous origins and insertions of skeletal muscles.

8. The molecular mechanism for contraction in cardiac muscle is
similar to that in skeletal muscle.
Cardiac muscle cells are triggered to contract by ionic calcium
(Ca2+) entering the sarcoplasm.
In response to an action potential, a small amount of Ca2+
from the extracellular tissue fluid enters the cardiac muscle
cell through the sarcolemma.
This rise in intracellular calcium signals the sarcoplasmic
reticulum to release its stored Ca2+

9. As with skeletal muscle, the amount of force that cardiac
muscle cells can generate depends on their length.
Significantly, these cells normally remain slightly shorter
than their optimal length. Therefore, when they are stretched
by a greater volume of blood returning to the heart, their
contraction force increases, and they can pump the additional
blood.
Unlike cells of skeletal muscle tissue, not all cells of cardiac
muscle tissue are innervated. In fact, an isolated cardiac
muscle cell will contract rhythmically without any
innervation at all.
This inherent rhythmicity of cardiac muscle cells is
the basis of the rhythmic heartbeat, as explained next.

10. Your heart's electrical system includes three important
part:
1. S-A node (sinoatrial node) — known as the heart's
natural pacemaker, the S-A node has special cells that
create the electricity that makes your heart beat.
2. A-V node (atrioventricular node) — the A-V node is
the bridge between the atria and ventricles.
Electrical signals pass from the atria down
to the ventricles through the A-V node.

11. 3. His-Purkinje system — the His-Purkinje system
carries the electrical signals throughout the ventricles to
make them contract. The parts of the His-Purkinje
system include:
o His Bundle (the start of the system)
o Right bundle branch
o Left bundle branch
o Purkinje fibers (the end of the system)

12. The S-A node normally produces 60-100 electrical signals
per minute — this is your heart rate, or pulse. With each
pulse, signals from the S-A node follow a natural
electrical pathway through your heart walls.
The movement of the electrical
signals causes your heart's chambers
to contract and relax.
In a healthy heart, the chambers
contract and relax in
a coordinated way, or in rhythm.
When your heart beats
in rhythm at a normal rate,
it is called sinus rhythm.

13. Step 1: Pacemaker Impulse Generation
The sinoatrial (SA) node contracts generating nerve impulses
that travel throughout the heart wall.
This causes both atria to contract.
Step 2: AV Node Impulse Conduction
The atrioventricular (AV) node lies on
the right side of the partition that divides
the atria, near the bottom of the right atrium.
When the impulses from the SA node reach the AV node they
are delayed for about a tenth of a second. This delay allows
the atria to contract and empty their contents first.

14. Step 3: AV Bundle Impulse Conduction
The impulses are then sent down the atrioventricular bundle.
This bundle of fibers branches off into two bundles and the
impulses are carried down the center of the heart to the left
and right ventricles.
Step 4: Purkinje Fibers Impulse Conduction
At the base of the heart the atrioventricular bundles start to
divide further into Purkinje fibers. When the impulses reach
these fibers they trigger the muscle fibers in the ventricles to
contract

16. Thank you for your attention