Question

Define threshold. How do neurotransmitters bring target cells toward or away from threshold. What happens to the response of the target cell if threshold is not reached? What happens if threshold is reached? Once threshold is reached, can the target cell get turned “off”?

Answer 1

Definition:  Threshold potential is the critical level to which a membrane potential must be depolarized to initiate an action potential.

The neurotransmitter binds to the target cell causes opening of ion channels. Influx and efflux of the ions through these channels take membrane potential towards and away fro the threshold.

If the target cell are unable to reach the threshold then target cells won't be able to produce any response.

When the threshold is reached, it will cause opening of the voltage gated channels leading to depolarization of the cell and hence the target cell will give a response.

Once the threshold is reached, target cells undergo depolarization and get activated.