Nervously humoral regulation of the heart
Nervously humoral regulation of the heart plays a subordinate role, as changes in metabolism caused by the nervous system. Shifts of various substances in the blood, in turn, influence the regulation of reflex cardiovascular system.
At the heart is affected by changes in potassium and calcium in the blood. The increase in the potassium content has a negative chronotropic negative inotropic negative dromotropic adversely and negatively bathmotropic tonotropnoe influence. Increased calcium acts contrary.
For normal operation of the heart must be known relation of both ions, which act similar to wandering (potassium) and sympathetic (calcium) nerves.
It is supposed that the depolarization of membranes of the muscle fibers of the heart are rapidly becoming the potassium and hydrogen ions, which contributes to reduction. Consequently, the reaction of the blood is important for the contraction of muscle fibers of the heart.
During stimulation of the vagus nerve in the blood to acetylcholine, and with stimulation of the sympathetic nerves – a substance similar in composition with epinephrine (O. Levy, 1912, 1921) – noradrenaline. The main mediator of the sympathetic nerves of the heart of mammals – noradrenaline (Euler, 1956). Adrenaline near about 4 times smaller. Heart more than any other organ accumulates adrenaline injected into the body (40 times more skeletal muscle).
Acetylcholine is rapidly destroyed. Therefore, it acts only locally, where it stands out, that is. E. In the endings of the vagus nerve to the heart. Small doses of acetylcholine stimulate the automatism of the heart and large – inhibit the frequency and force of heart contractions. Norepinephrine also destroyed in the blood, but it is more stable than acetylcholine.
During stimulation of the common trunk of the vagus and cardiac sympathetic nerves are formed both substances, but first manifested the action of acetylcholine, norepinephrine and then.
The introduction into the body of epinephrine and norepinephrine increases the release of acetylcholine and, on the contrary, the introduction of acetylcholine increases the formation of adrenaline and noradrenaline. Norepinephrine increases systolic and diastolic blood pressure, and adrenaline – only systolic.
Receipt of adrenaline from the adrenal glands increases during anger, fear, rage, pain and other emotions. Adrenaline has the same effect as the excitement of the sympathetic nervous system, so its entry into the blood causes a corresponding change of the heart (positive chrono, ino, Drome, BATM tonotropnoe and action).
This has the same effect on the heart and thyroid hormone – thyroxine. Choline affects the heart similar to the vagus nerve.
In the lumen of blood vessels, in addition to the concentration of hydrogen ions is affected by many substances produced in the body, which are divided into vasoconstrictor and vasodilator.
Narrowing mainly of arterioles and capillaries is adrenaline. Animals vasoconstriction is 0.00002 mg epinephrine per 1 kg of body weight. Adrenalin constricts arteries, arterioles and capillaries of the skin, all the organs of the digestive system, lungs and kidneys. Coronary arteries and blood vessels of the brain expands adrenaline, and the vessels of striated muscle narrows it only in very small concentrations, and more – is expanding. Adrenaline action based on stimulation of the sympathetic nerve endings to blood vessel walls.
Vasoconstrictor action has also posterior pituitary hormone vasopressin, which narrows the capillaries preferably in all organs except for the kidney and serotonin produced in the intestinal mucosa, in some areas of the brain and the decay of the platelets.
In the kidney in normal conditions, and especially in reducing their blood supply is formed rhenium, which acts on gipertenzinogen and turns it into gipertenzin that causes narrowing of blood vessels and raising blood pressure.
Local vasodilation caused by the accumulation of acid metabolic products, particularly carbon dioxide, lactic acid and adenylic.
A major role in the expansion of blood vessels also play acetylcholine and histamine. Acetylcholine and its derivatives irritate the end of the parasympathetic nerves and cause local expansion of small arteries. Histamine – a product of protein decomposition – is formed in the wall of the stomach and intestines, muscles and other organs. Histamine admission to the blood causes dilation of capillaries. Under normal physiological conditions, histamine in small doses improves the blood supply to the organs. In muscles during histamine dilates the capillaries along with carbon dioxide, lactic acid and adenylic and other substances that are formed during cutting. Histamine also causes dilation of the capillaries of the skin by irradiation sunlight (ultraviolet part of the spectrum), the action of hydrogen sulfide on the skin, heat, rubbing at her.
Increasing the amount of histamine released into the blood, leading to an overall expansion of capillaries and a sharp drop in blood pressure – circulatory shock.
(1 votes, average: 5.00 out of 5)