10. Neuromuscular junction

In the previous topics we have studied about the voluntary and involuntary actions. Both these actions are controlled by the brain with one being controlled through the process of thinking and other being controlled without any thinking respectively.

Here the question arises. How do the animal's muscles move? How the nerve impulses stimulating the muscle cell makes the muscle fibres move?

 

 

There are three steps involved in the movement of a muscle,

When the nervous system sends out a signal, muscle contraction occurs. A motor neuron transmits the signal, which is called as an action potential. The motor neuron meets a muscle cell at the neuromuscular junction. Muscular fibres are the cells that make up skeletal muscle tissue.

 

 

A chemical message is released by the motor neuron when the nervous system signal reaches the neuromuscular junction. A neurotransmitter called acetylcholine connects to receptors on the exterior of the muscle fibre to send a chemical message. A chemical reaction occurs within the muscle as a result of this connection.

 

If we see at cellular level, the nerve impulses stimulate the chemical reaction in the muscle cells, which results in the change in the shape of the cell. This change in shape results in the shortening of the cell and so the movement of the muscle occurs.

 

The reason for the shortening of the cell remains in the chemical structure of muscle cells. Muscle cells are made up of special type of proteins called contractile proteins, which change their arrangement in the cellular structure when stimulated by a electrical nerve impulse, results in the contraction of the muscle.

 

When the motor neuron stimulation stops, the electrical nerve impulse at the neuromuscular junction will stop. As a result, the chemical reaction that shortens the muscle cells will stop and proteins will rearrange themselves in the muscle fibres. This rearrangement results into relaxation of the muscle.