HEART’S PACE MAKER, THE SINOATRIAL NODE   

PRESENTED BY:MINHAZ AHMEDBBI11014INTEGRATED M.SC 3RD SEMESTER,MBBTTezpur University,Assam

THE SA NODE It is a tissue located in the right atrium of the

heart, near the entrance of the superior vena cava.

It is impulse-generating tissue responsible for sinus rhythm i.e. the normal beating of the heart

These cells are specialized cardiomyocytes ( The cells that comprise cardiac muscle, contains one, two, or (very rarely) three or four nuclei).

First described in 1907 by Arthur Keith and Martin Flack.

HOW IMPULSE ARE GENERATED

• RESTING POTENTIAL : Extra cellular fluid is positively charged with respect to the cell contents inside the plasma membrane. this difference in charge across the membrane is called RESTING POTENTIAL.

• DEPOLARIZATION: Na+ channels opens and Na+ ions move inward changing the polarity i.e. positive inward and negative outwards.

• REPOLARIZATION: Na+ channels closes as concentration increases, and K+ channels opens. More K+ ions are moved out than Na+ ions enters, hence the polarity again reverse back to, positive outside and negative inside.

This three processes results in generating impulses as action potential in the SA node that is been used for contraction of heart.

Resting , Depolarization, Repolarization

Source: med.edu.in

SA node(generates signal)

AV node Fascicular branch apexHis bundle

Purkinje fibres

fascicular branch

Purkinje fibers allow the heart's conduction system to create synchronized contractions of its ventricles, and are therefore essential for maintaining a consistent heart rhythm.

Pathway of impulse

Cardiac pacemaker

Primary (SA node): main generator of electrical impulse.

Secondary (AV junction & Bundle of His) If the SA node does not function, a group of cells further

down the heart will become the heart's pacemaker. AV node normally discharge at about 40-60 beats per

minute. Bundle of His along with the Purkinje fibres, can produce

a spontaneous action potential at a rate of 30-40 beats per minute

ARTIFICIAL PACEMAKER• pacemaker is a medical device that uses electrical impulses,

delivered by electrodes contacting the heart muscles, to regulate the beating of the heart.

• The primary purpose of a pacemaker is to maintain an adequate heart rate, either because the heart's native pacemaker is not fast enough, or there is a block in the heart's electrical conduction system.

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