2. At the end of session student should be able to :
Define the Action Potential
Briefly discuss the Phases of Action Potential
Discuss the Refractory Periods
3. Sudden, Rapid, brief, large and
spontaneous change in
membrane potential from
negative value to positive value
and again return back to its
original position is called as
Action Potential
6. Is the membrane potential
before AP occurs
Membrane is said to be
polarized (At rest)
Its value is -70mv & in
large neurons it is-90mv
7. Membrane is permeable
to Na ions due to Na
influx
The polarized state of
membrane is lost
Potential rising in positive
direction
8.
9. The Na channels begin to
close &
K channels open more
than normally due to K
efflux
Reestablishes the normal
RMP
10. Sodium channels begin to close
Potassium channels open
More than normal
Potassium EFFLUX
RE-ESTABLISHES NORMAL
NEGATIVE RMP
11. After reaching RMP, the
potential further falls becomes
more negative
This is after polarization or
Positive after potential
This is due to slow opening and
closing of k channels
17. Action potential in skeletal muscles is
same as that of nerves
Only differs in some quantitative aspects
◦ RMP is -80 to -90 mv
◦ Duration of action potential is 1 to 5ms
◦ Velocity of conduction is 3 to 5m/s
18.
19.
20. Period during which a nerve fiber either does not
respond or responds if the strength of stimulus is
more than normal
22. It is a short period during which no action
potential develop no matter how strong the
stimulus is
A brief time when a neuron is unable to
conduct impulse (Signal)
23. It is a short period during which the nerve
fiber shows response, if the strength of
stimulus is more than normal
Stronger than normal stimulus is needed to
create action potential