what is the job of a motor neuron
Motor neuron A motor neuron (or motoneuron) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands.[1] There are two types of motor neuron â€“ upper motor neurons and lower motor neurons. Axons from upper motor neurons synapse onto interneurons in the spinal cord and occasionally directly onto lower motor neurons.[2] The axons from the lower motor neurons are efferent nerve fibers that carry signals from the spinal cord to the effectors.[3] Types of lower motor neurons are alpha motor neurons, beta motor neurons, and gamma motor neurons.
Primary motor cortex At the primary motor cortex, motor representation is orderly arranged (in an inverted fashion) from the toe (at the top of the cerebral hemisphere) to mouth (at the bottom) along a fold in the cortex called the central sulcus. However, some body parts may be controlled by partially overlapping regions of cortex. Each cerebral hemisphere of the primary motor cortex only contains a motor representation of the opposite (contralateral) side of the body. The amount of primary motor cortex devoted to a body part is not proportional to the absolute size of the body surface, but, instead, to the relative density of cutaneous motor receptors on said body part. The density of cutaneous motor receptors on the body part is generally indicative of the necessary degree of precision of movement required at that body part. For this reason, the human hands and face have a much larger representation than the legs.