Why does vagal stimulation cause bradycardia

Hypokalemia increases the rate of phase 4 depolarization and causes tachycardia by enhancing phase 3 repolarization, which causes greater activation of channels responsible for the inward pacemaker currents. Note, however, that the effects of changes in serum potassium are complex with multiple channels and ion pumps being affected by potassium concentration.

Cellular hypoxia usually due to ischemia depolarizes the membrane potential causing bradycardia. Without adequate oxygen, ATP dependent ion pumps in the cell membrane cannot operate. Because a hyperpolarized state at the end of phase 3 is necessary for pacemaker channels to become reactivated, pacemaker channels remain inactivated in depolarized cells. This suppresses pacemaker currents and decreases the slope of phase 4.

This is one reason why cellular hypoxia, which depolarizes the cell and alters phase 3 hyperpolarization, leads to a reduction in pacemaker rate i. Severe hypoxia completely stops pacemaker activity. Various drugs used as antiarrhythmics also affect SA nodal rhythm.

Drugs affecting autonomic control or autonomic receptors e. Publication types Review. Substances Vasopressins. Other studies include vagus nerve stimulation as a potential treatment for headaches, chronic pain, multiple sclerosis, and other diseases. In traditional vagus nerve stimulation, a device is implanted in the chest and a wire is connected to the left vagus nerve. The right vagus nerve contains fibers that supply nerves to the heart, so it is not used for vagus nerve stimulation typically.

However, an implantable device to stimulate the right vagus nerve as a treatment of heart failure is currently being studied. J Child Neurol 16 : — , false. J Exp Physiol 22 : 79 — 93 , false. Epilepsia 50 : — , false. Childs Nerv Syst 25 : — , false. Epilepsy Res 56 : 1 — 4 , false. Arch Pediatr Adolesc Med : — , false. Epilepsy Res 90 : 1 — 7 , false. J Neurosurg Pediatr 5 : — , false. Neurosurgery 47 : — , false. Pediatr Neurol 35 : — , false.

Neurology 59 : 6 Suppl 4 S15 — S20 , false. Epilepsy Res 82 : — , false. Neurology 52 : — , false. Epilepsia 31 : Suppl 2 S7 — S19 , false. Clark Articles by Rachel A.

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