Page 1 of 1: PACEMAKER POTENTIAL

rajponn · Credits: 4434 My Scrapbook

pacemaker potential is due to (JIPMER 2003)
a fast Na+ channel
b decrease in K+ permiability
c slow ca2+ channels
d rapid repolarisation..

plz give answer with explanation...

skjeev · Credits: 8370 My Scrapbook

Spontaneous depolarization (Phase 4) is due to a fall in gK+ as potassium channels close and to a small increase in gCa++. A slow inward Na+ current also contributes to Phase 4, and is thought to be responsible for what is termed the pacemaker or "funny" current (If). Once this spontaneous depolarization reaches threshold (about -40 mV), a new action potential is triggered.

i guess it shoud b Na...but doubt about fast/slow!!?

ujwals · Credits: 4860 My Scrapbook

ans a

ganong

Pacemaker Potentials

Rhythmically discharging cells have a membrane potential that, after each impulse, declines to the firing level. Thus, this prepotential or pacemaker potential triggers the next impulse. At the peak of each impulse, IK begins and brings about repolarization. IK then declines, and as K+ efflux decreases, the membrane begins to depolarize, forming the first part of the prepotential. Ca2+ channels then open. These are of two types in the heart, the T (for transient) channels and the L (for long-lasting) channels. The calcium current (ICa) due to opening of T channels completes the prepotential, and ICa due to opening of L channels produces the impulse. Other ion channels are also involved, and there is evidence that local Ca2+ release from the sarcoplasmic reticulation (Ca2+ sparks) occurs during the prepotential.

But note that T-channels are FAST channel

&
hari says that pace maker potential is due to Na and/or Ca

guyton says influx of +vely chargedNa causes rising membrane potential

srini23dr · Credits: 357 My Scrapbook

INITIAL DEPOLARIZATION IS DUE TO RAPID OPENING OF Na+ channels n sustained platue is due opening of slow Ca+ channels.... later repolarization is due to opens of K+ channels...

srini23dr · Credits: 357 My Scrapbook

its mainly due to Na+ channels...

punjabi_guy11 · Credits: 1148 My Scrapbook

answer is b

as the k chaneel close under ffect of the ca channel so please read ganong its very imp question

so answer above given are mostly wrong

other name of pacemaker potential is prepotential

		Sign In New User? Sign Up Sign in to access your control panel and messenger!
				TechZone \| SpiderNevi \| HowTo? \| Scrapbook!