Question

What substance allows the Action Potential to move so quickly?

Answer 1

Action potential are generated due to movement of sodium ions into the neuronal cell. When a signal reaches the neuronal cells, there is opening of voltage gated sodium channels across the cell membrane. As a result, there is movement of sodium ions into the cell, making the cell more positive. This results in depolarization. When the depolarization reaches a threshold value, the action potential is generated.

The action potential reaches the axon terminal/end plate of the neuron. The space that exists between one neuron and its effectors is known as synapse or synaptic cleft. Synapses are connection between end plates of one neuron and the dendrites/axon/cell body of another neuron or an effector cell such as muscle cell. A single neuron may be interconnected with several neurons. Once the action potential reaches the end plate, it stimulates the opening of calcium channels. This will lead to movement of vesicles carrying neurotransmitter to the presynaptic neuronal endplate. The vesicles fuse with the presynaptic membrane, releasing the neurotransmitters by exocytosis.

The neurotransmitter is the substance that will bind to specific receptors on the postsynaptic neuron, after diffusing through the synaptic cleft. Neurotransmitters propagate the action potential to the next neuron. The binding of neurotransmitter to the receptor will trigger the movement of ions in and out of the postsynaptic neuron due to opening of ligand gated ion channels. There is generation of action potentials in the postsynaptic neurons, if depolarization occurs. This will trigger a response in the postsynaptic cells. The neurotransmitter fragments after use, which then move back to the presynaptic neuron and can be recycled.

Neurotransmitters can be excitatory or inhibitory, which can propagate or inhibit action potential respectively. Serotonin is an