Question

Why are neurotransmitters released?

Answer 1

following are the reasons !!

Explanation:

1. The action potential (electric current (>-65mv) that is propogated within and between individual neurons) is propogated into the presynaptic (before the synapse) neuron.

2. Voltage-gated calcium (Ca++) channels in the axon terminal (part of the neuron) open, and Ca++ ions enter the terminal.

3. Ca++ causes synaptic vesicles (filled with neurotransmitter) to fuse with the presynaptic terminal and burst, releasing the transmitter molecules into the synaptic cleft (the area between the presynaptic neuron and the postsynaptic neuron)

4. Some transmitter molecules bind to special receptor molecules in the postsynaptic membrane, leading-directly or indirectly-to the opening of ion channels in the postsynaptic membrane. The resulting flow of ions creates a local excitatory postsynaptic potential (EPSP) or inhibitory postsynaptic potential (IPSP) in the postsynaptic neuron.

5. The IPSP's and EPSP's in the postsynaptic cell spread toward an area known as the axon hillock. If the depolarization there is sufficient enough to reach threshold (-65mv), this neuron will fire an action potential.

6. Back in the synapse, unused neurotransmitter is inactivated by enzymes, reuptake, or may be used as an autocrine signal (a signal by a neuron that has a direct effect upon itself) resulting in decrease in neurotransmitter release.