Pacemaker potential

Jump to navigation Jump to search

WikiDoc Resources for Pacemaker potential

Articles

Most recent articles on Pacemaker potential

Most cited articles on Pacemaker potential

Review articles on Pacemaker potential

Articles on Pacemaker potential in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Pacemaker potential

Images of Pacemaker potential

Photos of Pacemaker potential

Podcasts & MP3s on Pacemaker potential

Videos on Pacemaker potential

Evidence Based Medicine

Cochrane Collaboration on Pacemaker potential

Bandolier on Pacemaker potential

TRIP on Pacemaker potential

Clinical Trials

Ongoing Trials on Pacemaker potential at Clinical Trials.gov

Trial results on Pacemaker potential

Clinical Trials on Pacemaker potential at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Pacemaker potential

NICE Guidance on Pacemaker potential

NHS PRODIGY Guidance

FDA on Pacemaker potential

CDC on Pacemaker potential

Books

Books on Pacemaker potential

News

Pacemaker potential in the news

Be alerted to news on Pacemaker potential

News trends on Pacemaker potential

Commentary

Blogs on Pacemaker potential

Definitions

Definitions of Pacemaker potential

Patient Resources / Community

Patient resources on Pacemaker potential

Discussion groups on Pacemaker potential

Patient Handouts on Pacemaker potential

Directions to Hospitals Treating Pacemaker potential

Risk calculators and risk factors for Pacemaker potential

Healthcare Provider Resources

Symptoms of Pacemaker potential

Causes & Risk Factors for Pacemaker potential

Diagnostic studies for Pacemaker potential

Treatment of Pacemaker potential

Continuing Medical Education (CME)

CME Programs on Pacemaker potential

International

Pacemaker potential en Espanol

Pacemaker potential en Francais

Business

Pacemaker potential in the Marketplace

Patents on Pacemaker potential

Experimental / Informatics

List of terms related to Pacemaker potential

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]


In the heart, the pacemaker potential is the voltage created by impulses from an artificial electronic pacemaker or the SA node which drives the rhythmic firing of the heart.

The pacemaker potential brings the membrane potential to the threshold potential and initiates an action potential.

Distinctions among autonomic foci

In reality, the heart has several pacemakers known as autonomic foci, each which fires at its own intrinsic rate:

  • SA node: 80 - 100 bpm
  • Atrial foci: 60 - 80 bpm
  • Junctional foci: 40 - 60 bpm
  • Ventrical foci: 20 - 40 bpm

The potentials will normally travel in order SA node -> atrial foci -> junctional foci -> ventricular foci

Pacemaker potentials are fired not only by SA node, but the other foci. However, the other firing frequencies are slower than the one of the AV node (as seen above). Normally, all the foci will end up firing at the SA node rate, not their intrinsic rate. The other foci attempt to fire at their intrinsic rate, but they are activated by the SA node before they can fire. This rapid firing causes all the foci to fire faster than their intrinsic rates, a phenomenon known as overdrive-suppression. Thus, in the normal, healthy heart, only the SA node intrinsic rate is observable.

Pathology

However, in pathological conditions, the intrinsic rate becomes apparent. Consider a heart attack which damages the region of the heart between the SA node and the atrial foci.

SA node -> |block| atrial foci -> junctional foci -> ventricular foci

The other foci will not see the SA node firing; however, they will see the atrial foci. The heart will now beat at the intrinsic rate of the atrial foci.

Induction

The firing of the pacemaker cells is induced, as the firing of action potentials in any human action-potential rising cell (like nerve cells), electrically, by the reaching of the threshold potential of the cell membrane. It is reached by the constant increase of membrane potential (induced by the special "funny channel", which by its Na+-channel activity giving rise to a current, the "funny current"). Upon the reaching of the threshold potential, the action potential is fired, and then reset.


Template:WikiDoc Sources