| S.No. | Class of vertebrates | Characteristics | more...
A graphic record of electrical events occuring during a cardiac cycle is called Electrocardiogram. The instrument used for recording the heart’s electrical variations is called Electrocardiograph in which the potential differences of heart muscles are recorded by a galvanometer. In ECG, there are 2 types of waves :
(1) Depolarisation waves : They represent the generation of the potential difference. These waves appear only when both electrodes of galvanometer are in different fields. When both the electrodes are in same field, there is no deflection and wave drops down to base line.
(2) Repolarisation waves : They appear when depolarisation is over and the muscle fibre is returning to its original polarity. When both electrodes are in same polarity (means 100% repolarisation and 100% depolarisation), there is no deflection.
A normal ECG has 5 deflection waves \[P,Q,R,S\] and T. Out of them \[P,R\] and T waves are above the base more...
During the completion of one heart beat is called as cardiac cycle. Following events are repeated in a cyclic manner during each heart beat.
(1) Auricular systole : The atria contract due to wave of contraction stimulated by S.A. node contraction of auricles drives most of their blood into respective ventricles as the A.V. valves are open. There is no backflow of blood into the large veins as the contraction begins at the upper end and passes towards ventricles and moreover, the valves present at the opening of these veins close. Also, blood is already present in large veins which offers resistance to the blood that may return from the atria. At the end of a atrial systole, there starts the relaxation of auricles (auricular diastole) and contraction of ventricles (ventricular systole) simultaneously. Atrial systole takes 0.1 second while atrial diastole is of about 0.7 seconds.
(2) Ventricular systole : more...
The study of blood vessels is called Angiology. The blood vessels are of following types :
(1) Arteries : Thick walled, carrying oxygenated blood (deoxygenated in pulmonary artery) from heart to various parts of body. These blood vessels are grouped as Aorta which branches to form arteries which further divides into thinner branches called arterioles inside the organ. Average diameter of arteriole is \[120\,\,\mu m\] the arterioles further divide into smaller vessels called meta-arterioles \[(70\,\,\mu m)\] which divide into capillaries. At the beginning of capillary, the arterioles posses circular muscles called precapillary sphincter which regulates flow of blood into the capillaries which is called vasomotion. Smooth muscles of arteries innervated by sympathetic fibers, their stimulation control vasoconstriction and vasodilation. Smooth muscles of arteries and arterioles also limit bleeding from wounds by producing vascular spasm during cut. Arteries two types.
(i) Conducting or elastic arteries
(ii) Distributing or muscular arteries.
Elastic more...
Blood circulation was discovered by William harvey. In case of vertebrates, blood circulation is of closed type, which can be grouped into two categories :
(1) Single circulation (2) Double circulation
Differences between single and double circulation
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