Topic name: Regulation of cardiac activity
Plan:
1. Levels and mechanisms of regulation of cardiac
activity.
2. Influence of the vagus and sympathetic nerves on the
work of the heart.
3. Centrifugal nerves of the heart according to Pavlov.
4. Reflex regulation of cardiac activity.
5. Humoral regulation of cardiac activity.
6. Unity of neurohumoral regulation of cardiac activity.
The levels of the regulation of
cardiac activity
1. Intracellular and intercellular
interactions.
2. Intracardiac: heterothermic,
homeometric , hydrodynamic
mechanisms and intracardiac
peripheral reflexes
3. Extracardiac mechanisms of
regulation: nervous, reflex and
humoral.
1. Intracellular mechanisms of
regulation are carried out due to:
• changes in protein synthesis;
• changes in membrane permeability;
2. Intercellular mechanisms of regulation
are carried out due to nexuses, which
perform a number of functions:
•
•
•
•
transport;
support;
carrying out excitation;
creative connections.
Intracardiac mechanisms of
regulation
1. Peripheral reflexes.
2. Heterothermic mechanisms.
3. Homeometric mechanisms.
4. Hydrodynamic autoregulation.
Intracardiac peripheral reflex arc (which is not in the
CNS) involving intramural myocardial ganglia.
Preganglionic fibers
(n.n vagi)
Adrenergic efferent
neuron
Cholinergic efferent
neuron
Brake cell
(Renshaw type)
Afferent neurons
Myocardial cell
Myocardial stretch
receptors
Heterothermic mechanism of regulation of
cardiac activity
The strength of cardiac
contraction depends on the
initial length of the muscle
fiber during diastole (the
Frank – Starling law).
Homeometric mechanism of
regulation:
The strength of the cardiac contraction
can be changed without changing of the
length of the muscle fiber (Anrep’s
effect).
Hydrodynamic selfregulation (Shydlovsky A.P.):
coordinated activity of the right and left
heart.
Extracardiac regulation mechanism
Regulation is
carried out by
the sympathetic
and
parasympathetic
nervous system.
The influence of the vagus nerve on the heart was studied
by the Weber brothers in 1845, 5 effects were established:
-
negative inotropic;
negative chronotropic;
negative dromotropic ;
negative bathmotropic;
negative tonotropic
Cardiac arrest with vagal stimulation
The effect of the escape of the heart from
under the influence of the vagus nerve is
observed with prolonged irritation of the vagus
nerve..
Effect of sympathetic nerve on the heart
activity has been studied by Zion in 1867,
found the same effects, but the opposite to
the effects of n. vagus.
1. Positive inotropic effect;
2. Positive chronotropic effect;
3. Positive dromotropic effect;
4. Positive bathmotropic effect;
5. Positive tonotropic effect.
In 1887, Pavlov I.P. dissected separate branches of
the vagus and sympathetic nerves, irritated them, and
discovered a monotypic effect.
Irritation of the right vagus
nerve
Irritation of the
reinforcing nerve
Irritation of the left vagus
nerve
Irritation of the accelerating
nerve
Reflex regulation of cardiac
activity
It is carried out by changing the tone of the
centers of the vagus and sympathetic nerves.
The tone of centers maintain by impulses from:
1. exteroceptors,
2. proprioceptors,
3. interoceptors,
4. reflexogen zones (aortic arch, carotid sinus,
lung, Beyinbridge zone)
Heart work
Humoral regulation of cardiac activity
• It is carried out by
means of substances
circulating in the
blood (hormones,
neurotransmitters,
ions, BAS).
Acetylcholine
Adrenalin
The unity of the neuro-humoral regulation proved
Levi O. in 1921.
Chemical substances, circulating
in the blood, influence on the tone
of the center of the vagus nerve,
that has been proved by Heymans
in his experience.
Thus, the heart is a self-regulating
system. The mechanism of selfregulation is carried out at the cellular,
organ and whole organism level.