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Cerebral blood vessels are able to change the flow of blood through them by altering their diameters in a process called cerebral autoregulation; they constrict when systemic blood pressure is raised and dilate when it is lowered. [15] Arterioles also constrict and dilate in response to different chemical concentrations.
The arteries are usually divided into different segments from 1–4 or 5 to denote how far the level of the branch with the lower numbers denoting vessels closer to the source artery. Even though the arteries branching off these vessels retain some aspect of constancy in terms of size and position, a great amount of variety in topography ...
The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. [2] It consists of the cerebral peduncles , tegmentum , and tectum . It is functionally associated with vision, hearing, motor control, sleep and wakefulness, arousal ( alertness ), and temperature regulation.
It also supplies blood to the anterior temporal lobes and the insular cortices. The left and right MCAs rise from trifurcations of the internal carotid arteries and thus are connected to the anterior cerebral arteries and the posterior communicating arteries, which connect to the posterior cerebral arteries.
Blood from the cerebellum and midbrain drains into the great cerebral vein. Blood from the medulla and pons of the brainstem have a variable pattern of drainage, either into the spinal veins or into adjacent cerebral veins.
The vasomotor center is a collection of integrating neurons in the medulla oblongata of the middle brain stem.The term "vasomotor center" is not truly accurate, since this function relies not on a single brain structure ("center") but rather represents a network of interacting neurons.
Brain ischemia has been linked to a variety of diseases or abnormalities. Individuals with sickle cell anemia, compressed blood vessels, ventricular tachycardia, plaque buildup in the arteries, blood clots, extremely low blood pressure as a result of heart attack, and congenital heart defects have a higher predisposition to brain ischemia in comparison to the average population.
The posterior perforated substance (PPS) is a layer of gray matter which is pierced by small apertures for the transmission of blood vessels.Its inferior part lies on the ventral aspect of the medial portions of the tegmenta and contains the interpeduncular nucleus; its superior part forms part of the floor of the third ventricle.