Heart pumping The main function of the heart - pumping - is associated with the progressive contraction of the atria and ventricles. The corre

Heart functions (pumping, automaticity, excitability, conductivity, contractility)

Heart pumping

The main function of the heart — pumping — is associated with the progressive contraction of the atria and ventricles. The correct sequence of contractions of the atria and the ventricles is provided by other cardiac functions (properties).

Heart automaticity

The ability of the heart to contract rhythmically under the influence of pulses that occur in the heart muscle, is called the heart automaticity (from the Greek “independent action”). Certain areas of the heart muscle have a cluster of special cells or muscle nodes — heart pacemakers (fig. 60), that automatically, starting with the embryonic period of human life, produce electrical impulses. Under their influence the heart rhythmically contracts. The main pacemaker is a node located in the right atrium. Normally, it determines the heart rate. The autonomic nervous and endocrine systems affect the excitement frequency of the node.

Diagram 60. Heart pacemaker and conductive system: 1 — right atrium; 2 — right ventricle; 3 — left atrium; 4 — left ventricle; 5 — sinoatrial node; 6 — atrioventricular node; 7 — bundle of His; 8 — right bundle branch; 9 — left bundle branch; 10 — endings of branches; 11 — upper hollow vein; 12 — aorta
Diagram 61. Electrocardiogram

Heart excitability

Each cardiac muscle cell is excited when it receives the exciting pulse from the main pacemaker. It heart ability is called excitability. Without this function, contraction of the heart is impossible. Due to the structure features of the heart muscle, which has extremely lot of connections between cells, the excitement instantly cover a certain part of it, such as ventricles, and they contract all at once, rather than their individual muscle fibers. Taken from http://worldofschool.org

Heart conductivity

The ability to conduct excitation pulse from the pacemaker to the myocardium is called heart conductivity. Cardiac muscle in any of its parts can conduct an electrical impulse, which originated in the pacemaker. However, the heart has places where the excitation conducts at high speed, and instantly reaches the most distant areas of the myocardium. This is the conductive system of the heart (fig. 60). Due to its normal functioning, both of the atria and ventricles of the heart are covered at the same time with the excitation and thus contract simultaneously. The electrical impulses can be registered and graphically recorded on electrocardiograph. Electrocardiogram (ECG) (fig. 61) shows the moments of excitation of the atria and ventricles.

Heart contractility

The ability to contract, or contractility — is the basic function of the heart muscle. After exciting, it simultaneously contracts both atria and both ventricles and pumps blood.

Training improves the contractile function of the heart.

Categories:
Questions:
  • Define the location and functions of the heart in the cardiovascular system.

  • What are the main functions of the heart? Explain their meaning.

  • What methods of the heart diagnostics you know?