The Pial Arteries
As was shown above, it is the pial arteries (especially the small ones) which play an important role in regulating the adequate blood supply to the brain tissue in order to meet its metabolic requirements. These arteries dilate when the neural elements experience a deficient blood supply, especially if the existing blood supply is inadequate at a time when activity is considerably increased. Under these conditions, influences from the brain tissues on the arteries supplying them with blood (i.e., feedback) can take place either by direct action of vasodilator metabolites accumulating in the blood vessel walls, or by the intervention of vasomotor nervous impulses, not necessarily involving the participation of the vasomotor center of the medulla, which is known to be obligatorily concerned only in regulating the level of the systemic arterial pressure.
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