LQ B388- Membrane Potential | Questions & Answers

Running head: QUESTIONS AND ANSWERS
Action Potential Q&A
Name of the Student
Name of the University
Author Note

QUESTIONS AND ANSWERS
Table of Contents
Answer 1....................................................................................................................................2
Membrane polarization..........................................................................................................2
Answer 2....................................................................................................................................4
Transmission of impulses across the synapse........................................................................4
Answer 3....................................................................................................................................6
Sequence of events of Spinal Reflex......................................................................................6
References..................................................................................................................................7

QUESTIONS AND ANSWERS
Answer 1
Membrane polarization
Resting potential (-65mV)
The movement of the K+ ions through the non-gated K+-ion channels, outside the cell
is driven by the concentration gradient of the potassium ions in the cytosol. This efflux
generates the resting membrane potential. The subsequent entry of the Na2+ ions into the cell
from the exterior side of the plasma membrane is thermodynamically favored and is also
influenced by the sodium concentration gradient inside the cell or the inside-negative
membrane potential. Most of the Sodim ion channels located in the plasma membrane are
closed during the resting cells membrane potential and hence, little inward movement of Na+
ions occur during this period.
Membrane depolarization
The release of the neuro transmitter causes opening of the Na 2+ ion channels,
resulting in the influx of the Na2+ ions into the cytosol. This overwhelms the entry of K+
ions through the resting passive K+ ion channels. The outcome is, inward movement of the
cations, generating extra positive charge on the cytosolic surface and corresponding negative
charges (Cl- ions are “left behind” outside the cells after the influx of the Na 2+ ions) on the
extracellular surface of the plasma membrane. Thus, the inside becomes positive and the
plasma membrane depolarizes.
Depolarization membrane (+40mv)
The membrane potential, at the peak of depolarization, is the action potential and is close to
the Na 2+ ions equilibrium potential, given by the Nernst equation.