16.1 Myogenic mechanisms of heart self-regulation
16.2 Intracardiac peripheral reflexes
16.3 Nervous regulation
16.4. Humoral extracardiac regulation
16.5 Effect of electrolytes
16.6 Integration of heart regulating mechanism
16.7 Myocardial blood supply
Profile materials Control questions Situational tasks
The regulation of cardiac activity is an adaptation of the minute cardiac output to the metabolic requirements of the body. In the myocardium, the initiator of contraction is the pacemaker action potential, while the nervous and endocrine influences are modulators of the rhythm and strength of its contraction.
Main types of regulatory effects on the heart
Chronotropic effects are positive and negative effects on the heart rhythm (?+" and ?-") manifested by a change in the heart rate.
Inotropic effect changes the strength of heart contractions (?+" and ?-").
Bathmotropic effect influences cardiac excitability (?+" and ?-").
Dromotropic effect influences cardiac conductivity (?+" and ?-").
Heterometric regulation is carried out as a result of a change in the length of myocardial fibers in response to changes in blood flow to the heart; homeometric regula-
tion is carried out at the same initial length of the myocardial fibers, e.g. with a stable blood supply to the heart chambers.
16.1. Myogenic mechanisms of heart self-regulation
Frank-Starling law of the heart (O. Frank, 1895; E. Starling, 1912). The strength of the heart?s systolic contraction is directly proportional to its diastolic expansion, with the result that under normal physiological conditions the heart pumps out of the right atrium all the blood returned to it without letting any back up in the veins (positive inotropic effect, heterometric regulation).