ABSTRACT
The peripheral nervous system consists of a loop of nerves. Nerves emanating from the spinal cord to the muscle transmit signals to the muscle to contract or elongate. The nervous system also needs to know the state of the muscle, so there is another nerve going from the muscle to the spinal cord relaying information about the muscle. This loop of nerves produces the spinal reflex. If there is no other influence on the nerves, the spinal nerve loop and reflex tries to stop the muscle moving. Thus there is resistance to any movement at the joint, be it active, that is, produced by the person themselves, or passive, when the joint is moved by somebody else. This is the basis for spasticity, which is seen in cases such as cerebral palsy. The spinal reflex is very powerful and tries to maintain the status quo. Any movement within muscles is resisted and the muscle goes into spasm, or is spastic.
