|
In order to activate an
alphamotor neuron, we use neurotransmitters.
We have to use a neurotransmitter at a synapse (including the
neuromuscular junction) because there is no physical contact.
Two forms of neurotransmitters:
- Excitatory
- Inhibitory
In order for the cell of the
postsynaptic end to respond, some of the neurotransmitters must reach a
threshold concentration. The
concentration reaches is affected by both excitatory and
inhibitory signals.
Example:
Assume that 200 units is
threshold for the example cell.
There are 300 excitatory
neurotransmitter units released. This is in excess of 200 units,
so if only excitatory neurotransmitters were present then threshold
would be reached. However, there are 150 inhibitory
neurotransmitter units released as well. 300 –150 = 150 units.
Therefore, input into that cell is not enough to create threshold
and cell will not fire.
In summary, there are three ways
to get the postsynaptic cell to fire.
- Increase
excitatory input
- Decrease
inhibitory input
- Some
combination of both (the most common).
|
