The carotids are two large arteries that run from your heart up the middle part of the neck to the brain, supplying the neck and head with oxygenated blood; one on the left and one the right side of the body. The Carotid Sinus (or carotid bulb) is a dilated area of the carotid artery, located just before the artery reaches the brain.
The Carotid Sinus is under the control of the autonomic nervous system (ANS) and consists of various nerve receptors for baroregulation (pressure regulation of the body), making it sensitive to pressure changes in the arterial blood at this level, caused both by internal (medical) and external (manual stimulation) triggers.
Its primary objective is maintaining blood pressure and regulating blood flow to the brain, but has the ability to cause severe and/or lethal effects to the body, due to its high sensitivity; symptoms include cardiac arrhythmia and cardiac arrest.
The mechanics behind this are simple: If the Carotid Sinus senses high blood pressure, it stimulates the corresponding brain canter to slow the heart down, at least until the blood pressure comes down.
This has the following effect (reflex): The disturbance in normal heart function (bradycardia), decreases blood flow to the brain, which causes hypoxia -diminished oxygen availability to the brain. In this state, brain functionality starts to decline! It’s worth mentioning that the brain, one of the body’s vital organs, starts deteriorating after 4-6 minutes without being supplied with oxygen, sometimes irreversibly; prolonging the deficiency any further may be fatal!
Symptoms include: dyspnea, rapid pulse, sweating, syncope, and mental disturbances such as delirium or euphoria
It is evident, why those of us interested in Scuba diving –an activity that takes place in a harsh environment, as it is- should be concerned with the pressure placed on this sensitive area of our neck. A diver’s gear includes tight hoods, wetsuit collars and more importantly dry-suit collars, all of which have to be chosen, modified or replaced, so that they fit perfectly and don’t cause any restrictions!