Internal carotid plexus Internal carotid plexus The internal carotid plexus (internal carotid plexus) is situated on the lateral side of the internal carotid artery, and in the plexus there occasionally exists a small gangliform swelling, the "carotid ganglion", on the under surface of the artery. Postganglionic sympathetic fibres ascend from the superior cervical ganglion, along the walls of the internal carotid artery, to enter the internal carotid plexus. These fibres then distribute to deep structures, which include the Superior Tarsal Muscle and pupillary dilator muscles. Some of the fibres from the internal carotid plexus converge to form the deep petrosal nerve. The internal
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