Space
Carotid sinus
An arterial stretch sensor for the baroreflex
High-yield
Carotid baroreceptor input travels mainly through Hering's nerve and CN IX to the solitary nucleus. Aortic-arch baroreceptor input follows CN X.
Overview
The carotid sinus is a widened arterial region near the carotid bifurcation, usually extending into the proximal internal carotid. Stretch-sensitive afferent endings monitor changes in wall tension. Increased input normally promotes cardiac slowing and reduced sympathetic vascular tone. The adjacent carotid body instead primarily detects changes in blood gases and acidity.
Reference facts
- Boundaries
- Usually distal common/proximal internal carotid wall near the upper thyroid-cartilage level. Both bifurcation height and the extent of the sinus vary.
- Contents
- An arterial lumen surrounded by a wall specialized for stretch sensing, with abundant sensory endings toward the outer wall. The carotid body is a nearby separate structure.
- Communications
- Sensory axons primarily enter the carotid sinus branch of IX and project to the solitary nucleus, where cardiovascular reflex circuits integrate them with other inputs.
Clinical correlation
An exaggerated reflex can cause marked slowing of the heart, a fall in blood pressure, or both. In carotid sinus syndrome this response produces symptoms such as syncope, sometimes associated with neck movement or pressure. A measured hypersensitive response alone does not establish symptomatic syndrome.
Frequently asked questions
What are the boundaries of the carotid sinus?
Usually distal common/proximal internal carotid wall near the upper thyroid-cartilage level. Both bifurcation height and the extent of the sinus vary.
What does the carotid sinus contain?
An arterial lumen surrounded by a wall specialized for stretch sensing, with abundant sensory endings toward the outer wall. The carotid body is a nearby separate structure.
What does the carotid sinus communicate with?
Sensory axons primarily enter the carotid sinus branch of IX and project to the solitary nucleus, where cardiovascular reflex circuits integrate them with other inputs.