Bacterial meningitis causes a partial break down of the BBB, which leads to enhanced antibiotic entry into the brain. The antibiotic can then act to suppress the infection. Some situations, leukocyte movement across the BBB results in neurological disorders. The Circle of Willis is a ring of vessels that unites the anterior and posterior circulation at the base of the brain. The vertebral and basilar arteries supply the cerebellum , brain stem and spinal cord.
Blood also supplies glucose principal energy source of neurons.
Stores of Oxygen and glycogen in the brain enough for only about 2 mins. Cerebral veins drain into large vascular channels - sinuses. Venous blood returns to the heart via the jugular veins. Normally blood flow to brain remains fairly constant over a range of mean arterial pressure between 50 -160mmHg. Achieved by compensatory dilation or constriction of cerebral blood vessels in response to changes in systemic blood pressure.