What is Parasympathetic Nervous System

Control of motor function—our activities like walking, lifting an object, writing, etc.—is accomplished through integrated and coordinated action of motor neurons. Motor neurons can be classified into two broad categories: upper motor neurons and lower motor neurons. Upper motor neurons have cell bodies in the motor cortex of brain and carry the impulses from cortex to spinal cord segment. Cell bodies of lower motor neurons are located in the anterior horn of spinal cord. Axons of lower motor neuron end in neuromuscular junction, and excitation of muscle fibres leads contraction of muscle. Different types of receptors carry different sensations like touch, pain, position, and vibration through sensory nerve fibres. Fibers mediating fine touch and proprioception ascend in the dorsal columns to the medulla, where they synapse in the gracile and cuneate nuclei. This chapter explores the neurobiology of sensory motor systems and the internal environment.