Junction

Chapter 6 was concerned with the ionic basis of the action potential, the electrical signal that carries messages long distances along nerve fibers. Using the patellar reflex as an example, we discussed the mechanism that allows the message that the muscle was stretched to travel along the membrane of the sensory neuron from the sensory endings in the muscle to the termination ofthe sensory fiber in the spinal cord. After the message is passed to the motor neuron within the spinal cord, action potentials also carry the electrical signal back down the nerve to the muscle, to activate the reflexive contraction of the muscle. This chapter will be concerned with the mechanism by which action potential activity in the motor neuron can be passed along to the cells of the muscle, causing the muscle cells to contract. In Chapter 9, we will consider how action potentials in the sensory neuron influence the activity of the motor neuron in the spinal cord.

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