Complex sentence: The brain maintains proper CPP through a process called autoregulation: to lower pressure, blood vessels in the brain called arterioles dilate, or widen, creating more room for the blood, and to raise pressure they constrict, or narrow.
Split into simpler sentences: The brain maintains proper CPP through a process called autoregulation. To lower pressure, blood vessels in the brain called arterioles dilate, or widen, creating more room for the blood, and to raise pressure they constrict, or narrow.