Types of Heart
Depending upon their mode of contraction, two kinds of hearts are:
|Neurogenic Heart||Myogenic Heart|
|The heart in which the contraction wave takes its origin from nerve cells or group of such cells situated near the heart are said to be neurogenic hearts.||The hearts in which the wave of contraction starts in the muscle fibers of heart (nodule tissue) are said to be myogenic hearts. |
|The impulse of contraction originates from nervous system.||The impulse of contraction originates itself in the heart.|
|The heart normally stops beating immediately after removal from the body.||The heart continues to beat for sometime even after removal from the body.|
|Examples are the hearts of some annelids and most arthropods.||Examples are the hearts of molluscs, vertebrates.|
The circulatory patterns are of two types – open or closed.
1. Open circulatory system
The open circulatory system is present in arthropods and mollusks in which blood pumped by the heart passes through large vessels into open spaces or body cavities called sinuses.
2. Closed circulatory system
Annelids and chordates have a closed circulatory system in which the blood pumped by the heart is always circulated through a closed network of blood vessels. This pattern is considered to be more advantageous as the flow of fluid can be more precisely regulated.
Types of Circulation
|Single circulation||Double circulation|
|Blood flows only once through the heart in a complete cycle.||Blood flows through the heart in a complete cycle.|
|Heart pumps de oxygenated blood only.||Heart pups de oxygenated blood to lungs and oxygenated blood to the body.|
|Blood get oxygenated by gills.||Blood get oxygenated by lungs.|
|Blood flow is slow and of low pressure.||Blood flow is fast and of high pressure.|
|It occurs in fish.||It occurs in amphibians, reptiles, birds and mammals.|