For one moment, if you think of nerves as long, thin wires, then by stretching the metaphor, a neuro muscular junction can be considered as the latest wireless technology. Its like a wifi router, which converts the wired signal into wireless ones so that your phone or laptop in which you are reading this article can understand that.
Now, if you read my previous article, you could understand that a nerve conduction is nothing but a disturbance, which moves along the entire length of the axon. But when the axon terminates, it ends in a synapse. So in simple terms, a synapse is where an axon ends.
On the other end of the synapse, if it is a nerve, it is called a neuronal synapse, if it is a muscle, it is called a Neuro Muscular Junction. Simple.
The tip of the axon has a lot of small packets, filled with chemicals, called the neurotransmitters. Now when the disturbance reaches the end of the axon, these packets open and a large amount of neurotransmitters are released into the synapse. These neurotransmitters are of various types, some are excitatory and some are inhibitory. So basically, the impulse is going wireless here. A large number of molecules are released into the interspace and many of them reach the other end.
Now the neurotransmitter released will reach the other end, which could be a nerve, or a muscle or a gland. If it is a nerve, this impulse travels as a disturbance in the other neuron. If it is an effector organ, like the muscle, it contracts.
However if the synapse still contains the neurotransmitter, it may repeatedly stimulate the other end, causing undesired effects, so they must be removed. This is done by specific enzymes, which can degrade a particular neurotransmitter.
If either the neurotransmitter is being degraded before reaching the other end, or if sufficient amount of neurotransmitter is not being released, the disturbance does not travel in the next neuron or the muscle does not contract. This is called the all or none law.
- Dr. Jana: http://docjana.com/cervical-vertebrae/ (CC BY 4.0).