Physiology

1. NAME:SONI KHAN
ROLL NO.56
B.U.M.S 1ST PROFF
SUBJECT:HUMAN PHYSIOLOGY
TOPIC:ACTION POTENTIAL

2. Acknowledgment
I would like to express my gratitude to Professor
Dr.Ghazala Mulla for providing support and
guidance. I got to learn a lot more from this project
which cleared many of my doubts and build the
concept of action potential.

3. WHAT IS ACTION POTENTIAL?
• The change in electrical potential associated
with the passage of an impulse along the
membrane of a muscle cell or a nerve cell.
• An action potential occurs when the
membrane potential of a specific axon
location rapidly rises and falls ,this
depolarisation then causes the adjacent
locations to similarly depolarise.

4. BIOPHYSICAL BASIS OF ACTION POTENTIAL
• Action potential result from the presence of special types of Voltage-gated
ion channel in the cell membrane.
• Inside cell membrane-more Potassium ion
• Outside cell membrane more sodium ion
• Polarised cell membrane : inside –negative charge
• Outside--positive charge

6. STAGES OF ACTION POTENTIAL
• There are six stages of action potential they
are:
1. RESTING STAGE
2. DEPOLARISATION STAGE
3. REPOLARISATION STAGE
4. SPIKE POTENTIAL

7. • Resting Stage-this is the resting membrane
potential before the action potential begins. The
membrane is said to be ‘Polarised’ during this
stage because of the very large potential that is
present
• Depolarisation stage-when the negativity of the
membrane potential rises rapidly in positive
direction due to influx of Sodium ions is called
depolarisation stage.

8. • Repolarisation stage –immediately after
depolarisation the negativity of the
membrane potential re establishes towards
the normal negative membrane due to efflux
of potassium ions
• Spike potential- initially the depolarisation
wave overshoots the zero line and then
sharply falls ,this sharp rise of the
depolarisation wave and the rapid fall of
repolarisation wave is called spike potential

10. ROLE OF MYELIN
• Myelin insulates an axon
• Action potential jumps from node to node called
Saltatory conduction
• Action potential travels much faster in mylinated
neuron than unmylinated neuron

11. BIBLIOGRAPHY
• Images-kenhub.com and Wikipedia
• Other-www.slideshare.net
• Book- NCERT Biology class 11th
• Essentials of Medical Physiology