Arterial Supply ofthe Heart
Myocardial cells receive blood
supply from coronary arteries both
right and left.
The closure of aortic valve during
ventricular relaxation prevents the
backflow of the blood and fills the
coronary artery.
The arterial supply of the heart is
provided by the right and left
coronary arteries, which arise from
the ascending aorta immediately
above the aortic valve.
3.
Branches of CoronaryArteries
1. Right Coronary artery: Branches
Right marginal arteries.
Posterior descending artery
2. Left Coronary artery: Branches
Circumflex artery.
Left Marginal artery.
Left anterior descending artery
Diagonal branches
5.
Venous Drainage ofthe Heart
Most venous blood from
the coronary veins drain
into the coronary sinus,
which lies in the posterior
part of the atrio-ventricular
groove .
Some veins do not enter
the sinus rather it drain the
venous blood directly into
right atrium with inferior
vena cava.
6.
Nerve supply ofthe heart
The innervation of the heart refers to the network of
nerves (cardiac plexus) that are responsible for
the functioning of heart.
The heart is innervated
by sympathetic and parasympathetic fibres from the
autonomic branch of the peripheral nervous system.
It receives contributions from the right and left vagus
nerves and from the sympathetic trunk (T1-T4) which
are responsible for influencing heart rate, cardiac
output and contraction forces of the heart.
7.
Cont..
The cardiacplexus refers to a large network of
nerves located around the base of the heart, formed
by cardiac sympathetic nerves and the cardiac
branches of the vagus nerve.
8.
Cont..
Parasympathetic nerves areresponsible for:
Reducing the heart rate
Reducing the force of contraction of the heart
Vasoconstriction (narrowing) of the coronary arteries
Sympathetic nerves are responsible for:
Increasing heart rate
Increasing the force of contraction of the myocardium
9.
CARDIAC CONDUCTION SYSTEM
The cardiac conduction
system is a network of
specialized cardiac muscle cells
that initiate and transmit the
electrical impulses responsible
for the coordinated
contractions of each cardiac
cycle.
10.
Cont..
Two types ofcells control heartbeat:
1. Conducting cells carry the electric signals.
2. Muscle cells control heart’s contractions.
11.
Components of theCardiac
Conduction System
1. The sino-atrial (SA) node
2. The atrio-ventricular (AV) node
3. The bundle of His
4. The left and right bundle branches
5. The Purkinje fibres
13.
1. Sinoatrial Node
Sinoatrial node is sometimes called as heart’s
natural pacemaker. It sends the electrical
impulses that start the heartbeat.
The SA node is in the upper part of heart’s
right atrium. It is at the edge of atrium near
superior vena cava.
15.
2. Atrioventricular Node
The atrio-ventricular node delays the SA
node’s electrical signal. It delays the signal by a
consistent amount of time (a fraction of a
second) each time.
The AV node is located in an area known as
the triangle of Koch.This is near the central
area of the heart.
17.
3. Bundle ofHis
The Bundle of His is also called the atrioventricular
bundle. It is a branch of fibers (nerve cells) that
extends from AV node.
This fiber bundle receives the electrical signal from
the AV node and carries it to the Purkinje fibers
through right and left branch.
The bundle of His runs down the length of the
interventricular septum.
19.
4. Left andRight bundle branches
The bundle branches are two pathways that carry
electrical impulses to the muscular walls of the
ventricles.
The left bundle branch conducts impulses to the
left ventricle, and the right bundle branch
conducts impulses to the right ventricle.
These electrical impulses instruct the heart walls
when to contract and pump blood through the
heart.
20.
5. Purkinje Fibers
The Purkinje fibers are branches of specialized
nerve cells. They send electrical signals very
quickly to the right and left ventricles.
When the Purkinje fibers deliver electrical
signals to the ventricles, the ventricles
contract.
Conduction of Impulsein the Heart
Initiation of impulse: Impulse is generated in SA
node at a rate of 70-80/minute. Therefore SA
node is called as pacemaker of heart.
23.
Cont..
Spread of impulse:
The wave of impulse spreads to both atria through
muscle tissues simultaneously causing them to
contract.
From SA node impulse passes to ventricles through
AV node.
Upon reaching the atrioventricular (AV) node, the
signal is delayed by 0.13 seconds.
This delay causes ventricles to contract after atrial
contraction is over.
24.
Cont..
It isthen conducted into the bundle of his, down
the interventricular septum.
The bundle branches and the Purkinje
fibres spread the wave impulses at fastest rate
along the ventricles, causing them to contract.
Impulse generation and transmission is an
electrical event whereas contraction and
relaxation of heart muscle are mechanical event.
Mechanical events always follow electrical events.
