Search results
Results From The WOW.Com Content Network
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.
Vagusstoff (literally translated from German as "Vagus Substance") refers to the substance released by stimulation of the vagus nerve which causes a reduction in the heart rate. Discovered in 1921 by physiologist Otto Loewi , vagusstoff was the first confirmation of chemical synaptic transmission and the first neurotransmitter ever discovered.
As a general consideration, increased vagal tone (and thus vagal action) is associated with a diminished and more variable heart rate. [ 18 ] [ 19 ] The main mechanism by which the parasympathetic nervous system acts on vascular and cardiac control is the so-called respiratory sinus arrhythmia (RSA).
This is a potential cause of vomiting due to the inability of the proximal stomach smooth muscle to undergo receptive relaxation. The vagal afferents are activated during the gastric phase of digestion when the corpus and fundus of the stomach are distended secondary to the entry of a food bolus. The stimulation of the mechanical receptors ...
Methyldopa acts on the vasomotor center, leading to selective stimulation of α 2-adrenergic receptor. [8] Guanfacine also causes the same stimulation. [9] This reduces sympathetic tone to vascular smooth muscle. [9] This reduces heart rate and vascular resistance. [9] Digoxin increases vagal tone from the vasomotor centre, which decreases ...
The vagus nerve is also responsible for regulating inflammation in the body, via the inflammatory reflex. [7] Efferent vagus nerve fibers innervating the pharynx and back of the throat are responsible for the gag reflex. In addition, 5-HT 3 receptor-mediated afferent vagus stimulation in the gut due to gastroenteritis is a cause of vomiting. [8]
The vomiting center is not a discrete or specific place in the brain, but rather an area consisting of many nuclei, axons, and receptors that together cause the physical changes necessary to induce vomiting. [6] Also, emesis can occur by direct neural stimulation of the vomiting center. [11]
Vagus nerve stimulation (VNS) is a medical treatment that involves delivering electrical impulses to the vagus nerve. It is used as an add-on treatment for certain types of intractable epilepsy , cluster headaches, treatment-resistant depression and stroke rehabilitation.