Internal carotid artery mainly of historical significance. The segments of the internal carotid artery are as follows: The internal carotid artery is a terminal branch of the common carotid artery; it arises around the level of the fourth cervical vertebra when the common carotid bifurcates into this artery and its more superficial counterpart, the external carotid artery. The cervical segment, or C1, or cervical part of the internal carotid, extends from the carotid bifurcation until it enters the carotid canal in the skull anterior to the jugular foramen. At its origin, the internal carotid artery is somewhat dilated. This part of the artery
Carotid body central chemoreceptors in the medulla oblongata that are primarily sensitive to changes in pH and P (a decrease in pH and an increase in P). The carotid body chemoreceptors are also sensitive to pH and P, but only secondarily. More specifically, the sensitivity of carotid body chemoreceptors to decreased P is greater when pH is decreased and P is increased. The output of the carotid bodies is low at an oxygen partial pressure above about 100mmHg (13,3 kPa) (at normal physiological pH), but below 60mmHg the activity of the type I (glomus) cells increases rapidly due to a decrease in