Homeometric regulation of the heart

Characteristics

 * the ability to change the force of contraction of the cardiac muscle even with a constant length of cardiomyocytes
 * does not depend on changes in sarcomere length
 * affects inotropy (contractility)
 * in contrast to heterometric control, more beats are required for the regulation to take effect
 * the goal is to change cardiact output

Sympathetic

 * Positively chronotropic, inotropic, dromotropic i batmotropic effect

Parasympathetic

 * Negatively chronotropic, inotropic, dromotropic i batmotropic effect

Potassium cations

 * At elevated extracellular concentrations, there is a slow depolarization of the resting membrane potential (values closer to zero) and a concomitant inactivation of some sodium channels (thus preventing the action potential),, net effect is:
 * the intensity of the action potential is reduced
 * heart dilated, flaccid
 * heart rate slows down
 * in severe hyperkalaemia –up to blockage of impulse transmission through the atrioventricular bundle

Calcium cations

 * opposite effect to potassium cations
 * increased concentration gradually leads to spastic contraction (calcium cations initiate contraction)
 * at reduced concentration - flaccidity

Bowditch (Treppe) effect

 * see Bowditch effect

Temperature

 * heat increases the permeability of the membrane to ions
 * frequency
 * Increased temperature significantly increases frequency
 * reduced temperature significantly decreases frequency
 * in near-death hypothermia (15-20 °C) frequency only a few beats per minute
 * frequency only a few beats per minute


 * force of contraction
 * temporarily strengthened when the temperature rises, then the metabolic system is exhausted and the contraction is weakened

Related articles

 * Frank-Starling mechanism (heterometric regulation of the heart)