Question

Can you articulate, in your own words, the step-by-step processes involved in Action Potentials? Your post MUST include:

• voltages, thresholds, and specific ions
• an explanation of depolarization
• an explanation of the Action Potential and its effect on vesicles in the axon terminal
• a description of neurotransmitters, agonists, and antagonists
• what happens when a neurotransmitter binds to a receptor

Answer 1

Stages of Action potential

1. RESTING STAGE:
The membrane is in polarised state with potential in nerve about - - 85mV.
Sodium and potassium channels are closed. Na+ are more outside the cell; K+ are concentrated inside the cell. Potential difference: - 70mV.

2. Depolarization STAGE:
When local potential touches the threshold level it opens up sodium channel in the membrane causing abrupt rising of membrane potential towards positivity. It overshoot beyond the zero level and become positve.
This is because of entry of Positive Sodium ions into the cell

3.Stage of Repolarization:
Within fractions of second the sodium channel begins to close and potassium channels open up causing diffusion of positive potassium to outside the cell.
This results in decreasing of membrane potential towards negativity.

4. Resting Conditions Re-established
Na+ and K+ channels are closed. Sodium-potassium exchange pump moves Na+ out and K+ in. Resting potential difference: -85 mV

Role of Sodium voltage gated channels:
These channels are essential for Depolarization stage.
If these channels are blocked, the Depolarization will not occur and the nerve will be hyperpolarised.
If these channels are stimulated then it results in more rapid functioning of the nerve.

Role of potassium voltage gated channels :
These channels are essential for Repolarization of the nerve potential
If the get blocked the nerve will be in sustained state of Depolarization.
If these channels are stimulated. Action potential will cease more rapidly and there will occur a hyperpolarization state.

Neurotransmitters are the chemicals released by the neuron that binds to the receptors on the next neuron to either stimulate or inhibit them.

Agonists are the neurotransmitter that produces Excitatory potential when binds to the receptors.

Antagonists are the neurotransmitter that produces inhibitory potential when binds to the receptors.

When a neurotransmitter binds the receptors, it opens the ligand gated ion channels associated with the receptors resulting in either EPSP ( Excitatory postsynaptic potential) or IPSP ( Inhibitory Postsynaptic Potential)