In the peripheral nervous system, the cell bodies of sensory neurons are concentrated in ganglia, the cell bodies of sensory neurons are on sensory nerves, and the cell bodies of motor neurons are in the anterior horn of spinal cord gray matter. 1 sensory nerve endings, such as skin, are receptors, which can receive stimuli and produce excitement. The excitement that can be conducted is a nerve impulse; The nerve center is located in a gray matter in the center of the spinal cord (where the cell bodies of neurons are concentrated), which can receive nerve impulses and produce new nerve impulses; Second, the part where nerve fibers are concentrated is called white matter, which is located around the spinal cord and has conduction function; 4 is efferent nerve, which can transmit nerve impulses from nerve center to effector; Effectors can receive nerve impulses and respond. If your fingers accidentally touch something hot, retract your hand immediately. At this time, the pathway of nerve impulse transmission is 1 receptor on the hand →2 afferent nerves →3 nerve centers →4 efferent nerves →5 effectors (biceps brachii contraction and triceps brachii relaxation) retract the hand.

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