The sinoatrial node, located in the wall of the right atrium, is the heart's natural pacemaker. It generates electrical impulses that pass through the heart and cause it to contract. The sinoatrial node initiates action potentials that travel through the conduction system to the atrioventricular node and then to the ventricles. As the primary pacemaker, the sinoatrial node controls the heart rate by regulating the firing of action potentials. Dysfunction or ischemia of the sinoatrial node can lead to irregular heart rhythms.

1. Topics :Sainoatrial node
Name: Bidhan sarkar

2.  Sinoatrial node
• The sinoatrial node (SA node), also
known as sinus node, is a group
of cells located in the wall of the right
atrium of the heart.
• The SA node (SA stands for sinoatrial) is
one of the major elements in the cardiac
conduction system, the system that
controls the heart rate.

3.  Where it is located?
• The SA node is located in
The wall (myocardium) of the
right atrium, laterally to the
entrance of the superior vena cava
in a region called the sinus venarum.

4.  The structure of SA NODE
• The sinoatrial node is
a banana-shaped
structure that varies
in size, usually
between 10-30
millimeters (mm)
long, 5–7 mm wide,
and 1–2 mm deep.

5. • The SA node is the heart's
natural pacemaker.
• The electrical impulses are generated there.
• The SA node is also called the sinus node.
• The sinoatrial node was first discovered by a
young medical student, Martin Flack, in the
heart of a mole.

6.  How it works ?
• The main role of a sinoatrial node cell is to
initiate action potentials, so that it can pass
throughout the heart and cause contraction.
• An action potential is a change in voltage
(membrane potential) across
the membrane of the cell, produced by the
movement of charged atoms (ions)

7. •Normal cardiac
conduction is initiated
by the dominant
pacemaker of the
heart; the SA node

8. • The electrical signal generated by the SA
node moves from cell to cell down through
the heart until it reaches the atrioventricular
node (AV node).
• The atrioventricular node (AV node), a
cluster of cells situated in the center of the
heart between the atria and ventricles.

9. • The atrioventricular
node (AV node), a
cluster of cells
situated in the
center of the heart
between the atria
and ventricles.

10. • The AV node serves as a gate that slows
the electrical current before the signal is
permitted to pass down through to the
ventricles
• After passing the AV node, the electrical
current travels to the ventricles along
special fibers embedded in the walls of the
lower part of the heart.

11. • Other cells within the
heart (including the
purkinje fibers and
atrioventricular node
)can also initiate action
potentials; however, they
do so at a slower rate
and therefore, if the SA
node is working, it
usually beats the AVN to
it.

12. The heart rate
• The heart rate is the number of times the
heart beats in the space of a minute.
• Heart rate depends on the rate at which the
sinoatrial node produces action potentials.
• At rest, heart rate is
between 60 and 100 beats
per minute here

13. • The heart rate
during exercise
should be roughly
equal to 220
bpm minus the age
of the person.

14. • This quick response is important during
exercise when the heart has to increase its
beating speed to keep up with the body's
increased demand for oxygen.

17.  WHY SA NODE LEADS THE HEART?

18.  Clinical significance :
• Sinus node dysfunction describes an irregular heartbeat
caused by faulty electrical signals of the heart.
• When the heart's sinoatrial node is defective, the heart’s
rhythms become abnormal – typically too slow or
exhibiting pauses in its function or a combination, and
very rarely faster than normal.
 Sinus node dysfunction

19.  Ischaemia
• Blockage of the arterial blood supply to the SA
node can therefore cause ischaemia and cell
death in the SA node.
• This can disrupt the electrical pacemaker
function of the SA node, and can result in sick
sinus syndrome.