What about cerebral circulation and its functional relationship, and what are the physiological char

1 Pinyin 2 English references.

3 Overview 4 Characteristics of cerebral circulation.

nǎo xún huán

cerebral circulation

Cerebral circulation is another extremely important local vascular system in the systemic circulation that supplies blood to brain tissue. The blood circles of the brain contain circles from the internal carotid and vertebral arteries. The vertebral arteries on the left and right sides merge into the basilar artery in the abdomen of the pont, which in turn communicates with the internal carotid arteries on both sides to form a cerebral artery ring, which then branches out for the cavity to dig up the parts of the brain.

Veins in the brain drain into the interdural venous sinuses, then into the internal jugular veins on both sides, and then back to the right atrium via the superior vena cava. The veins of the brain do not run with the arteries. The brain is rich in blood**, and the cerebral blood flow accounts for about 13 16 of the cardiac output.

The blood flow per 100 grams of brain tissue is 50-60 ml per minute.

The spike nucleus is located in the cranial cavity in the brain, so that the cerebral circulation has the following characteristics:

1) The volume of the cranial cavity is quite fixed, filled by the brain, blood vessels and cerebrospinal fluid, so the sum of the three is also quite fixed. If cerebral edema or cerebrospinal fluid volume increases, it causes an increase in intracranial pressure, which increases cerebral blood flow resistance and thus decreases cerebral blood flow when the intracranial pressure exceeds 30 mm Hg (1 mm Hg kPa). On the other hand, the cerebral blood vessels cannot be dilated significantly, and when the cerebral arteries are dilated, the veins of the brain will contract accordingly, so that the venous blood will flow out rapidly.

2) Because the cerebral blood vessels cannot be greatly dilated and contracted, the total cerebral blood flow mainly depends on the arterial blood pressure. When arterial blood pressure increases, cerebral blood flow increases; Otherwise, it will be reduced. Therefore, the relative constant arterial blood pressure is of great significance for maintaining normal blood in the brain.

3) The cerebral blood flow in normal people is relatively constant, with an average of about 750 ml minutes. The total cerebral blood flow in different functional states did not change much, only increasing or decreasing by 30 50. The blood flow in each part of the brain is related to its functional activity, and the blood flow in the more active brain area is higher than that in other brain areas.

The local regulation of the main receptor fluid factors of the cerebral blood vessels, such as hypoxia, carbon dioxide increase or pH decrease, etc., makes the cerebral blood vessels dilate and blood flow increases, among which the effect of carbon dioxide is the most obvious. Cerebrovascular innervation is innervated by sympathetic and parasympathetic nerves, but the effect is not obvious.

The brain is located in the cranial cavity. The cranial cavity is bony and its volume is fixed. The cavity is filled with the brain, cerebrovascular and cerebrospinal fluid, and the sum of the volumes of the three is also fixed.

Because brain tissue is incompressible, the degree of cerebral vasomotor is quite limited, and the change in blood flow is smaller than that of other organs.

The endothelial cells of the capillary wall of the cerebral circulation are in close contact with each other and overlap to a certain extent, and there are no small holes in the tube wall. In addition, there is no direct contact between the capillaries and the neurons, but the glial cells are afraid of separation. This structural feature acts as a barrier to the diffusion of substances between the blood and brain tissue, known as the blood-brain barrier.

The physiological characteristics of cerebral circulation, that is to say, there are many blood vessels in the brain for the brain to think, and these blood vessels are used to provide energy, so the physiological characteristics of cerebral circulation are that your brain needs energy to attack, that is, blood circulation to be able to work normally.

There are five physiological characteristics of cerebral circulation:

1. Cerebral blood** comes from internal neck A and vertebral A.

2. The head is high and Xingheng education is whole|Reason.

3. Cerebral blood flow decreases with age.

4. The blood flow of gray matter is greater than that of white matter.

5. The cerebral blood flow is relatively stable, and the change range is very small.

Cerebral circulation is the most important component of circulation in a particular area. For example, the oxygen consumption of the human brain is about 1 5 of the total body oxygen consumption, and the blood flow of the human brain accounts for about 13% to 15% of the total cardiac output. Adequate cerebral blood flow is the primary condition for normal brain activity.

Insufficient blood flow to the brain** can quickly seriously affect brain function. The cerebral cortex is very sensitive to cerebral circulatory ischemia and hypoxia in the blood, and the lack of oxygen in the cerebral circulation blood for half a minute or completely blocking the cerebral blood flow for 10 seconds will lead to coma, and the lack of oxygen for 3 minutes may cause irreparable damage to the brain nerve cells, and the lack of oxygen for 6 minutes can cause death. It can be seen that cerebral circulation is related to the life and death of animals.

The cerebral circulation supplies nutrients to the central nervous system and eliminates its harmful metabolites, thereby maintaining its normal function.

Cerebral circulation is regulated by a variety of factors, and even if the internal and external environment changes through the regulation mechanism, the cerebral blood flow can remain stable, which is of great significance for the normal function of the brain. For example, total cerebral blood flow does not increase due to stressful mental activity, nor does it decrease due to relaxation of mental activity or even sleep (and even increases some during sleep). Humoral factors, especially carbon dioxide pH, K+, and Ca2+ in cerebral blood flow, have obvious regulatory effects on cerebrovascular movement, while neuromodulation is weaker and occupies a secondary position.

Because cerebral circulation is within the cranial cavity, changes in intracranial pressure are bound to have an effect. In addition, the average arterial and venous pressure at the brain level, as well as the viscosity of the blood, have an impact on cerebral circulation. The arterioles in the brain, like the arterioles in other organs of the body, are directly affected by the oxygen and carbon dioxide levels of local tissues.

Carbon dioxide, oxygen and pH levels in the brain also have a certain effect on cerebral blood flow: the increase in the partial pressure of carbon dioxide causes a significant increase in cerebral blood flow; The increase in partial pressure of oxygen has the opposite effect. However, changes in the pH of cerebrospinal fluid and extracellular fluid in tissues have a major regulatory effect on cerebral blood flow.

Brain tissue has a high level of metabolism and more blood flow. In the quiet condition, the blood flow per 100 grams of brain is 50-60 ml min. The blood flow throughout the brain is about 750 ml min.

It can be seen that although the proportion of the brain accounts for only about 2% of body weight, blood flow accounts for about 15% of cardiac output. Brain tissue also consumes more oxygen. In quiet conditions, oxygen consumption per minute per 100 grams of brain; In other words, the oxygen consumption of the whole brain accounts for about 20% of the total body oxygen consumption.

I hope that friends will learn the correct breathing method, skillfully use simple breathing to regulate the blood circulation of the head, and restore the vigorous functions of the brain, eyes, mouth and nose.

The common carotid artery on each side bifurcates into the external carotid artery and the internal carotid artery, the latter has no branch in the neck, rises vertically to the base of the skull, penetrates the petrous part of the temporal bone through the carotid artery canal against the petrosal bone tip, enters the skull through the rupture hole, penetrates the dura mater through the cavernous sinus, and divides the ophthalmic artery, the posterior communicating artery, and the anterior choroidal artery, and divides into two terminal branches on both sides of the optic chiasm: the anterior cerebral artery and the middle cerebral artery. The internal carotid artery system ** blood flow in the anterior 3 5 parts of the cerebral hemispheres such as the frontal lobe, temporal lobe, parietal lobe and basal ganglia, so it is also called the anterior circulation.

a) The anterior choroidal artery is the internal carotid artery that divides into anterior cerebral artery, anterior middle artery, or a large perforating branch emanating from the proximal middle cerebral artery. It first gives off some small perforating branches** caudate nucleus, part of the internal capsule, and half of the brain's foot and lateral geniculate body.

b) The anterior cerebral artery is called the internal cerebral artery. After exiting from the internal carotid artery, it walks anteriorly medially in the frontal orbital face. There is an anterior communicating artery anastomosis on both sides of the anterior cerebral artery.

The perforating branches that emanate along the way are mainly **hypothalamus, anterior caudate and lenticular nucleus, and internal capsule forelimbs. Cortical ramus is the main ** cerebral hemisphere medial aspect of the cerebral hemisphere before the parieto-occipital fissure; Superior frontal gyrus on the dorsolateral aspect of the cerebral hemisphere, upper half of the middle frontal gyrus, superior 1 4 of the anterior and posterior gyrus, paralobules, etc.

3) The middle cerebral artery is actually the external cerebral artery, which is a direct continuation of the internal carotid artery, and enters the lateral fissure after branching, giving out many small perforating branches, ** putamen nucleus, caudate nucleus and anterior 3 5 of the posterior branch of the internal capsule (equivalent to the passage of the pyramidal tract), these branches are called the lateral lenticular artery, which is a good site for hypertension, cerebral hemorrhage and cerebral infarction. The main trunk of the middle cerebral artery divides into many cortical branches, which are distributed over most of the lateral aspect of the cerebral hemispheres.

The cerebrospinal fluid produced by the choroid plexus of the lateral ventricle flows through the interventricular foramen to the third ventricle, and together with the cerebrospinal fluid produced by the choroid plexus of the third ventricle, it flows into the fourth ventricle through the mesocerebral aqueduct, and then flows into the subarachnoid space through the median foramen and two lateral foramen of the fourth ventricle, and then the cerebrospinal fluid flows along this gap to the subarachnoid space on the back of the brain, and penetrates into the dural sinus (mainly the superior sagittal sinus) through the arachnoid granules, and then flows back into the blood.

That is: cerebrospinal fluid produced by the choroid plexus of the left and right ventricles through the interventricular foramen of the third ventricle; Together with the cerebrospinal fluid produced by the choroid plexus of the third ventricle via the midcerebral aqueduct of the fourth ventricle; It then flows into the cerebrospinal fluid produced by the choroid plexus of the fourth ventricle through the median foramen and lateral foramen of the fourth ventricle, the subarachnoid space, the arachnoid granules, the superior sagittal sinus, the sinus manifold, the left and right transverse sinuses, the left and right sigmoid sinuses, and the internal jugular vein.