Carotid body A decrease in oxygen partial pressure, an increase in carbon dioxide partial pressure, and a decrease in arterial pH can all cause depolarization of the cell membrane, and they affect this by blocking potassium currents. This reduction in the membrane potential opens voltage-gated calcium channels, which causes a rise in intracellular calcium concentration. This causes exocytosis of vesicles containing a variety of neurotransmitters, including acetylcholine, noradrenaline, dopamine, adenosine, ATP, substance P, and met-enkephalin. These act on receptors on the afferent nerve fibres which lie in apposition to the glomus cell to cause an action potential. The feedback from the carotid
Carotid sinus unstable, predispose to ischemic strokes and transient ischemic attacks, carotid endarterectomies are frequently done for prophylaxis. The carotid sinus can be oversensitive to manual stimulation, a condition known as carotid sinus hypersensitivity, carotid sinus syndrome or carotid sinus syncope, in which manual stimulation causes large changes in heart rate and/or blood pressure. This classically presents as a patient who has "fainted" (actually a presyncope) on several occasions while shaving, or in some other way coming into contact with their carotid sinus. Carotid sinus syndrome is a temporary loss of consciousness that sometimes accompanies convulsive seizures because of the intensity of