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Three main systems coordinate together to perform proper different body
movements which are:

a) The skeletal (bony) system: as it provides a suitable site of connection of muscles
from one side and to support the moving limbs from the other side, accordingly the

joints play an important role in movment.
b) The nervous system: which gives the orders for muscles (in the from of nerve
impulse) to contract and relax.

c) The muscular system: which is responsible for movement.

Most of the body muscles are under the control of will and called voluntary muscles
(skeletal, striated muscles). Other muscles are not under the control of will and called
involuntary muscles.

According to the previously mentioned information we have to answer the following

questions:

a) How does the muscle contract?

b) What are the role of nerve impulse and the physiology of muscle response to nervous
stimulation?

c) How all these parts coordinate together?

How the nerve impulse pass to the skeletal muscle:

1. In skeletal muscles, the outer surface of the muscle fibre membrane is (+ve) positively
charged while the inner surface is (-ve) negatively charged, that form potential

difference due to the difference of the ions concentrations between outside and inside
the membrane.

2. The stimulus for muscle contraction is the motor impulses that coming from the

brain and spinal cord through the motor nerve which is connected firmly with muscle
fiber through synapse.

3. The synapse has synaptic vesicles contain neurochemical transmitters as acetylcholine.

4. When the motor impulses reach the synapse, the calcium pump in the cell membrane
push the calcium ions inside the cell causing rupture of the synaptic vesicles to release

the neurochemical transmitters as acetylcholine through the synaptic cleft between

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