CONDUCTIVE SYSTEM OF HEART
The components of the conductive system are :
1.
S.A. node
2.
A.V node
3.
Internodal bundles
4.
Bundle of His (right and left branch bundles)
5.
Purkinjee fibres.
- The SA node is situated in the right atrium near the opening of superior venacava.
- The impulses originate from the AV node (situated on interatrial septum).
- A.V node receives impulses from SA node and conducts it to the ventricle through the bundle of His., it starts from AV node and ramifies in the interventricular septum.
- The bundles of His gives Right & left branches, and passes to the right ventricle and to the left ventricles. They merge into purkinjee fibres.
Functions of conducting system:
1.
Prevent overlapping of the atrial events with
ventricular events(systolic)
2.
Participates in syncytial nature of myocardium.
3.
Initiates impulses rhythmically and
automatically.
4.
Conducts the impulse at a rapid rate.
The properties of the cardiac muscle are
1.
Excitability and irritability .
2.
Conductivity.
3.
Contractility .
4.
Rhythmicity and automaticity
5.
Refractory period
6.
Indefatigability.
7.
Tonicity and
8.
All or none phenomenon
Nutrition of the cardiac muscle:
1.
ATP : (Adenosine
triphosphate) energy for the heart is obtained by glycolysis and most of
the energy by oxidation of glucose , lactate pyruvate, ketone bodies and
aminoacids.
2.
Oxygen : oxygen
regulates oxidative processes for cardiac energy.
3.
Sodium ion : it
initiates and maintains the heart beat.
4.
Calcium ion : it
initiates and maintains the heart beat.
5.
Potassium ion : it
inhibits the contraction and prolongs the relaxation i.e., diastole
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