Their is none
It is the traveling of the electrical signal down the length of a neuron.
depends, could be over a meter long, could be less than a millimetre, it all depends upon if you have a sensory/motoric neuron or a switching-neuron
Axon
The length of a human nerve cell ranges from a fraction of a inch to several feet while it's diameter is 0.001mm to 1 mm.
The Inter-neuron (also known as the local circuit neuron, relay neuron or the association neuron) is the neuron which connects the afferent and the efferent neurons in the neural pathways.
The entire signal travels in the neuron by a graded potential which is created in the dendrites and the body (soma) of the neuron, then it reaches a spot of the neuron which is called the axon-hillock where the signal now for the first time has encountered "voltage-gated channels" and now can create an Action potential that can propagate through the terminus of the neuron which is the length of the axon.
The cells that makes up the nervous system is the Inter-neuron (circuit neuron), sensory neuron and motor neuron.
A neuron is called a inter-neuron because that specific neuron takes impulse from one neuron to a next neuron. For example your sensory neuron sends a impulse that you had felt a hot object. It goes through the spine to a inter-neuron to a motor neuron (this processes is called a reflex). Then the motor neuron tells your muscles in your hand to move
a relay neuron is the neuron that picks up the message from the sensory neuron and delivers it to the motor neuron in the spinal cord or the brain
A relay neuron is the neuron that picks up the message from the sensory neuron and delivers it to the motor neuron in the spinal cord then to the brain.
one type of neuron is the motor neuron