The vascular system of the body is very important. After all, thanks to the arteries and veins, blood and oxygen are delivered. Without this feature, people would not be able to live. The vasomotor center is responsible for this function of the body. Like all regulatory mechanisms, it is located in the brain. Its damage is very dangerous and often incompatible with life. After all, thanks to the vasomotor center, blood is distributed to the organs. It also partially regulates cardiac activity. Despite the autonomy of the myocardium, control of the nervous system is still necessary.
The concept of the vasomotor center
The concept of "vasomotor center" is explained in this way: it is an anatomical formation located in the brain. However, this term should be considered more broadly. First of all, this is not one organ, but a collection of formations consisting of nervous tissue. Each part is responsible for certain functions. However, they all work together in order to ensure the activity of the cardiovascular system. These departments of the vasomotor centerare interconnected not only functionally, but also anatomically. That is, through nerve fibers. For the first time, the regulation of the vascular system became known at the end of the 19th century. When conducting experiments on animals, the scientist Ovsyannikov discovered that when the nervous tissue located below the tubercles of the quadrigemina is cut, changes in blood pressure occur. The physiologist made the following conclusion: a violation of this structure of the brain causes the expansion of some vessels, and the narrowing of others. After that, the regulatory function began to be actively studied.
Location of the vasomotor center
It is believed that the vasomotor center is located in the medulla oblongata. But if we take into account all the structures that affect the regulatory function of blood supply, then this judgment is not entirely correct. Since the nerve fibers of the vasomotor center originate from the spinal cord, and its last link is the cortical layer. The first are axons - processes of cells. The neurons themselves are located in the three upper lumbar and all thoracic segments of the spinal cord. Their exact localization is the lateral horns. Because of their location, they are called spinal vasoconstrictor centers. However, this name is incorrect, since the fibers are not able to act separately from other links. The vasomotor center of the medulla oblongata is located in the 4th ventricle. It is a collection of nerve cells. A more precise localization of the vasomotor center is the lower and middle part of the rhomboid fossa. Partneurons located in the reticular formation.
The next departments related to the regulatory links of the center are the hypothalamus and the midbrain. There are nerve fibers responsible for changes in vascular activity. The final link is the cerebral cortex. The pre-, motor and orbital departments are more involved.
Vasomotor center: organ physiology
If you imagine all the links of the vasomotor system from the bottom up, you should start with the neurons located in the spinal cord. Sympathetic preganglionic axons (fibers) depart from them. These links are not able to independently regulate the tone, but they transmit impulses from other nerve cells to the vessels. For the first time, the scientist Ovsyannikov learned about their significance, thereby making a great discovery in physiology. He discovered that when the brain and spinal cord separate, there is a drop in blood pressure. However, after some time, blood pressure rises again (below the initial level) and is independently maintained by preganglionic fibers. In the medulla oblongata there is a nerve center - vasomotor. It is he who is responsible for the regulation of the spinal region. Its physiology is as follows: the neurons located in this center are divided into 2 types. The former are responsible for the pressor function (vasoconstriction). The second group leads to relaxation of the endothelium. It is believed that neurons responsible for vasoconstriction predominate in number. Cells present in the midbrain can cause an increase in blood pressure. The neurons of the hypothalamic region, on the contrary, act as depressors, that is, they lead to the relaxation of blood vessels. Most of the nerve fibers pass through the center located in the medulla oblongata. In addition, part of the axons directly connect the spinal region and the hypothalamus. The anterior region of the cerebral cortex affects both the enhancement and inhibition of the activity of neurons located in the underlying links.
Division of the vasomotor center into departments
Given that the regulation is carried out by several links of the nervous system, the following departments of the vasomotor center can be distinguished:
- Spinal cord. The lateral horns of the thoracic and lumbar segments contain the preganglionic nuclei. Axons - fibers - depart from them.
- Directly the vasomotor center. This section contains neurons responsible for endothelial relaxation and vasoconstriction.
- Midbrain. The cells present in this section are capable of causing narrowing of the vascular wall.
- Hypothalamic region. The neurons responsible for the relaxation of the vascular tissue are connected both with the center itself and separately with the cells of the spinal cord.
- Cortex area. Despite the fact that the main part of the neurons is located in the anterior region, the influence of other parts of the brain is not excluded.
Despite the presence of 5 departments, physiologists divide vasomotor regulation into only 2 links. These include the fibers of the spinal cord and the bulbar region. It contains everythingother nerve cells that affect vascular tone. Both classifications are considered correct.
Vasomotor center: organ functions
As you know, the main purpose of the vasomotor center is the regulation of tone. Each of its departments performs its own function. However, the shutdown of at least one link leads to disruption of the vessels of the whole organism. The following functions are distinguished:
- Conducting impulses (signals) from the cortical regions and the medulla oblongata to the periphery. This refers to the influence of neurons on the vessels that supply blood to the organs. This function is carried out thanks to the spinal preganglionic fibers.
- Maintenance of vascular tone. With the normal operation of each department, blood pressure is maintained at the proper level.
- Relaxation and vasoconstriction. The center located in the medulla oblongata has a direct influence.
- Ensuring adequate blood flow and distributing it to every organ.
- Thermoregulation. This function is carried out by changing the lumen of the vessels. Their expansion is observed in a warm environment, and their contraction occurs at a low temperature.
Connection of the center with the heart
In addition to the fact that the vasomotor center is responsible for the contraction and expansion of endothelial tissue, it also affects the heart muscle. This involves cells located in the lateral part of the fossa of the 4th ventricle.
It is known that the innervation of the heart is due to sympathetic fibers. They carry impulses from the medulla oblongata. As a result, cardiac activity is activated. This is manifested by tachycardia. The neurons of the vasomotor center also participate in the weakening of the activity of the heart. They are located in the medial part. From there, the signals go to the dorsal nuclei of the vagus nerve. Despite the fact that one function of the heart muscle is automatism, its work is impossible without the participation of the brain.
Regulation of the vasomotor center
Cortical structures can influence the neurons of the vasomotor center located in the medulla oblongata. After all, they are the main mechanism for the regulation of all underlying departments. Cortical neurons can cause both a decrease and an increase in the activity of the vasomotor center. In addition, there is also a reflex regulation. It is carried out from the sinuses of the carotid arteries and from the aortic arch. This is due to mechanoreceptors. From their surface, impulses rise along the vagus and depressor nerves to the vasomotor center. At the same time, the activity of the depressor part of this department is enhanced. The result is a relaxation of blood vessels and a decrease in blood pressure. Activation of the nuclei of the vagus nerves also causes vasodilation.
Changes in the tone of the vasomotor center
Deregulation occurs under the influence of various factors. The result is a change in tone.vasomotor center. Under normal conditions, this is carried out due to reflex regulation. In pathologies, there is a violation of tone. Examples are various vascular diseases, atherosclerosis, and obesity. Also, a decrease or increase in tone can be regulated under the influence of drugs (antihypertensive drugs, vasopressors).
Influence of chemicals on the vascular center
The regular mechanisms of the vascular system can be directly affected by chemicals in the body. An example is carbon dioxide, which accumulates in the blood when there is a lack of oxygen (asphyxia). Under the influence of this substance, the vasomotor center is stimulated. In severe cases, a prolonged lack of oxygen can lead to paralysis.
