Internal carotid artery is known as the carotid sinus or the carotid bulb. The ascending portion of the cervical segment occurs distal to the bulb, when the vessel walls are again parallel. The internal carotid runs vertically upward in the carotid sheath and enters the skull through the carotid canal. During this part of its course, it lies in front of the transverse processes of the upper three cervical vertebrae. It is relatively superficial at its start, where it is contained in the carotid triangle of the neck, and lies behind and medial to the external carotid, overlapped by the sternocleidomastoid muscle, and
Carotid body been put forward as a hypoxia sensor. In normoxia, haem-oxygenase generates carbon monoxide (CO), CO activates the large conductance calcium-activated potassium channel, BK. Falls in CO that occur as a consequence of hypoxia would lead to closure of this potassium channel and this would lead to membrane depolarisation and consequence activation of the carotid body. A role for the "energy sensor" AMP-activated protein kinase (AMPK) has also been proposed in hypoxia sensing. This enzyme is activated during times of net energy usage and metabolic stress, including hypoxia. AMPK has a number of targets and it appears that, in the carotid