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Physiology Of Heart

Physiology Of Heart

The whole heart pumping is composed of systolic and diastolic phases. these phases are collectively called the ” cardiac cycle of heart”. 

DIASTOLE OF ATRIA:

“A period of relaxation of atria is called atrial diastole.” 

In this phase left atrium receives blood from the pulmonary vein while the right atrium receives blood from both vena cava.

SYSTOLE OF ATRIA AND DIASTOLE OF VENTRICLES:

The period of contraction of the atria is called atrial systole. In this phase, both bicuspid and tricuspid valves open and blood enter into both ventricles

SYSTOLE OF VENTRICLES:

The period of contraction of ventricles is called ventricular systole. In this phase both bicuspid and tricuspid valves become close, and aortic and pulmonary artery opening becomes open. Due to ventricular contraction blood enters into the aorta and pulmonary artery and distributes it to the whole body and lungs respectively.

WHAT IS A PACEMAKER:

“THE SPECIALIZED AREA OF HEART RESPONSIBLE FOR DEVELOPMENT OF EXCITATION WAVE IS CALLED PACEMAKER.”

The cardiac conducting system comprises of following in a sequence

  • SA node (sinoatrial node)
  • AV node (Atrioventricular
  • Purkinje fibers 
  • Bundle of His

SA NODE AND WHAT IS ITS FUNCTION:

” THIS IS A CLUSTER OF SPECIALIZED CELLS IN THE WALL OF THE RIGHT ATRIUM CLOSE TO THE ENTRY OF OF SUPERIOR VENA CAVA “

The stimulus for the contraction of the heart originates in this region of the heart. It consists of cardiac muscle fibers possessing few myofibrils and a few nerve endings of the autonomic nervous system.

AV NODE AND ITS  FUNCTION:

THE TISSUE OF AV NODE ARE SIMILAR TO THE TISSUE OF THE SA NODE”

  • It is located at the lower part of the right atrium and stimulates by the wave of excitement send by AV NODE. 
  • This is the only electrical bridge between the atria and ventricles. Its excitation all parts of the ventricles through two bundles of specialized muscle fibers of the bundle of His in the ventricular septum and then into the wall of the ventricle through a network of fibers called Purkinje fibers.
  • There is a delay of about 0.15-second conduction s in from the SA NODE  to AV NODE permitting atrial systole to be completed before ventricular systole begins.

“EXERCISE SHOULD BE REGARDED AS TRIBUTE TO THE HEART “

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