Bezold-Jarisch reflex
Encyclopedia
The Bezold–Jarisch reflex involves a variety of cardiovascular and neurological processes which cause hypopnea (overly shallow breathing or an abnormally low respiratory rate) and bradycardia
(abnormally low resting heart rate).
This phenomenon is accentuated if the individual is dehydrated.
The resultant arterial hypotension is sensed in the carotid sinus
baroreceptors, and efferent
fibers from these receptors trigger autonomic signals that increase cardiac rate and contractility.
However, pressure receptors in the wall and trabeculae of the underfilled left ventricle
may then sense stimuli, indicating high-pressure C-fiber afferent nerves from these receptors.
They may respond by sending signals that trigger paradoxical bradycardia
and decreased contractility, resulting in additional and relatively sudden arterial hypotension
.
It usually occurs in nitrate therapy and use of serotonin agonists.
Bradycardia
Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
(abnormally low resting heart rate).
Physiology
Prolonged upright posture results in some degree of pooling of blood in the lower extremities that can lead to diminished intracardiac volume.This phenomenon is accentuated if the individual is dehydrated.
The resultant arterial hypotension is sensed in the carotid sinus
Carotid sinus
In human anatomy, the carotid sinus is a localized dilation of the internal carotid artery at its origin, the common carotid artery.-Functions:...
baroreceptors, and efferent
Efferent
Efferent is an anatomical term with the following meanings:*Conveying away from a center, for example the efferent arterioles conveying blood away from the Bowman's capsule in the kidney. Opposite to afferent....
fibers from these receptors trigger autonomic signals that increase cardiac rate and contractility.
However, pressure receptors in the wall and trabeculae of the underfilled left ventricle
Left ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...
may then sense stimuli, indicating high-pressure C-fiber afferent nerves from these receptors.
They may respond by sending signals that trigger paradoxical bradycardia
Bradycardia
Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
and decreased contractility, resulting in additional and relatively sudden arterial hypotension
Hypotension
In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
.
It usually occurs in nitrate therapy and use of serotonin agonists.