General Overview on generation of Resting and Action Potential

1. RESTING MEMBRANE
POTENTIAL AND
ACTION POTENTIAL.

2. RESTING MEMBRANE POTENTIAL
• The resting potential of a cell is defined as the difference in electrical potential
across the membrane. It represents the electrical charge difference between the
inside and outside the membrane.
• In a typical resting potential, the inside of the cell is more negative and more
positive to the outside of the cell.
• It is of approximately -70mV.
• The resting membrane potential is generated due to ions and the concentration of
ions across membrane.

3. • In animal cells the resting potential is dictated pridominantely by the K+ ions
gradient. The predominant positive ion inside the cell is the k+ ions.
• The concentration of k+ ions is higher inside the cell and the concentration of Na+
is higher outside the cell.
• The membrane also contain K+ leaky channel
• The higher concentration of k+ ions is generated by NA+-k+ pump which actively
pumps K+ ions into the cell.
• The open leaky channels allow free movement of K+ ions.
• Its expel 3 Na+ ion outside and 2 Ka+ ions inside the cell.
• Transfer of +ve charge to the exterior leaves behind unbalanced negative charge
within the cell thereby creating resting potential.

5. ACTION POTENTIAL
• An action potential occurs when the membrane potential of a specific cell rise and
falls.
• Action potential occur in several types of animal cells called the excitable cells which
include neurons, muscle etc.
• The action potential include three stages:
Depolarization
Repolarization
Refractory Period

6. • Depolarization:
A voltage gated Na+ channels opens up a result of electrical stimulus, the Na+
ions is pumped inside the cell.
Due to the positive charge of Na+ when it enters the cell it changes the potential
of the cell from negative to positive.
• Repolarization:
During repolarization, the voltage gated K+ channels are opened by the positive
potential inside the cell. K+ ions moved towards the exit of the cell with the help of an
electrochemical gradient. Due to the k+ efflux the membrane potential shifts towards
more negative and thus repolarizes.
Typically repolarization (the restoration of a polarized condition) exceeds the resting
cell membrane potential resulting in the membrane potential more negative. This is
known as hyperpolarization.

7. • Refractory Period:
Absolute Refractory : The time frame between which two consecutive action
potential is not generated. Na+ channels closed after an action potential it then enter
the inactive state during which they cannot reopened, regardless of membrane
potential.
In the relative refractory the Na+ channel slowly came out of inactivation.