Nutrition of the cardiac muscle::
1. ATP: Energy for the heart is obtained in the form of adenosine tri-phosphate (ATP) little by glycolysis and mostly by oxidation of glucose lactate pyruvate fatty acids ketone bodies and amino acids In short heart muscle obtains its energy from oxidation processes in presence of oxygen
2. Oxygen: It is the most important gaseous nutrition of the heart that regulates oxidative processes for cardiac energy Lack of oxygen gives rise to partial anoxia which produces pain in the heart a painful cry of the hypoxic hungry heart for more oxygen (myocardial ischaemia)
3.Sodium Ion: It initiates and maintains the heart beat
4.Calcium Ion: It strengthens the systole and inhibits the diastole of the heart with excessive Ca+2 ion the heart stops in systole
5. Potassium Ion : It inhibits the contraction and prolongs the relaxation i.e diastole with excess of K+ ion the heart stops in diastole
Junctional Tissues of the heart:
The heart muscle is a Syncytin since all muscle -fibres are interlinked However atrial impulses cannot a conducted to the ventricles because of its valvular rings the specialised junctional conducting tissues over come this difficulty.
Junctional tissues of the heart are highly specialised tissues which generate and conduct the cardiac impulse all over the heart they are:
1.The sino-atrial node (SA node): 2. Atrio-ventricular node (AV node): 3. Atrio-ventricular bundle (AVB) or Bundle of his 4. Right and left branches of AVB and 5. Purkinjee fibres (PF)
The SA node is situated in the right atrium near the opening of superior vena cava The impulses originate from the A Vnode which is situated on inter -atrial septum near the coronary sinus it receives impulses from SA node and conducts it to the ventricle through the bundle of his when SA node fails to generate impulses as seen during the heart block a new nodal rhythm is generated from the AV node the bundle of his starts from AV node and ramifies in the interventricular septum The bundle of his gives two bundle branches the right bundle branch passes to the right ventricle and the left one to the left ventricle they merge into purkinjee fibres
In short these specialised fibres serve as quick conducting media for all the terminal points of the heart
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