PhysioEx 6/Act 2: Examining the effect of vagus nerve stimulation

Results

Vagal escape involves sympathetic nerves

Sympathetic NS

fight or flight -stimulation increases heart rate and force of contraction of heart

Procedure

-Vagus nerve stimulation, multiple stimuli (50/sec) -Observe effects of stimulation on contractile activity (ventricular contractions)

Sinoatrial node (SA node)

Cluster of autorhythmic cardiac cells found in the right atrial wall in the human heart -has fastest rate of spontaneous depolarization, determines heart rate and therefore reffered to heart's "pacemaker"

Vagus nerve

Cranial Nerve X - Parasympathetic -Carries signal to the heart -Neurotransmitter is Acetylcholine

Vagal escape

The resumption of the heartbeat -When stimulation of vagus nerve is excessive, the heart will stop beating -The sympathetic NS takes control over the heart to increase the heart rate (Vagus nerve escapes control) -Can be a result of sympathetic reflexes or initiation of a rhythm by the Purkinje fibers

Parasympathetic NS

resting and digesting -stimulation decreases heart rate without directly changing force of contraction