Search results
Results from the WOW.Com Content Network
Episodes of vasovagal syncope are typically recurrent and usually occur when the predisposed person is exposed to a specific trigger. Before losing consciousness, the individual frequently experiences early signs or symptoms such as lightheadedness, nausea, the feeling of being extremely hot or cold (accompanied by sweating), ringing in the ears, an uncomfortable feeling in the heart, fuzzy ...
Vagovagal reflex refers to gastrointestinal tract reflex circuits where afferent and efferent fibers of the vagus nerve [1] coordinate responses to gut stimuli via the dorsal vagal complex in the brain. The vagovagal reflex controls contraction of the gastrointestinal muscle layers in response to distension of the tract by food.
A frequent type of syncope, termed vasovagal syncope is originated by intense cardioinhibition, mediated by a sudden vagal reflex, that causes transitory cardiac arrest by asystole and/or transient total atrioventricular block. [1] [2] It is known as “Vaso-vagal Syncope”, “Neurocardiogenic Syncope” or “Neurally-mediated Reflex Syncope ...
For premium support please call: 800-290-4726 more ways to reach us
In most cases, vagal tone is not measured directly. Instead the processes affected by the vagus nerve – specifically heart rate and heart rate variability – are measured and used as a surrogate for vagal tone. Increased vagal tone (and thus vagal action) is generally associated with a lower heart rate and increased heart rate variability.
A feedback response to the medulla is triggered via the afferent vagus nerve. The high (ineffective) sympathetic activity is thereby modulated by vagal (parasympathetic) outflow leading to excessive slowing of heart rate. The abnormality lies in this excessive vagal response causing loss of blood flow to the brain. [9]
A message is also sent via the vagus nerve to the main pacemaker of the heart to decrease the rate and volume of the heartbeat, typically by a third. [9] In some cases there is evidence that this may escalate into asystole, a form of cardiac arrest that is difficult to treat. [10]
The slowed heart rate results from a vagal response unopposed by a sympathetic nervous system (SNS) response. [2] Such cardiovascular instability is exacerbated by hypoxia, or treatment with endotracheal or endobronchial suction used to prevent pulmonary aspiration. [3]