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A motor neuron (or motoneuron or efferent neuron [1]) 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. [2]
The spinal cord functions primarily in the transmission of nerve signals from the motor cortex to the body, and from the afferent fibers of the sensory neurons to the sensory cortex. It is also a center for coordinating many reflexes and contains reflex arcs that can independently control reflexes. [ 1 ]
Each area is made up of many segments. Motor and sensory nerve fibers to and from every area of the body are found in the spinal nerve. A dermatome is innervated by each segment of the spinal cord. The spinal cord is organized into segments, each corresponding to specific regions of the body: 8 cervical (neck) 12 thoracic (chest) 5 lumbar ...
Motor pools in the spinal cord are clustered in distinct columns of motor neurons extending over multiple spinal cord segments; although, there is significant overlap. Motor pools that control proximal muscles are generally located medial to the ventral horn , while those that control distal muscles are located laterally.
These neurons connect the brain to the appropriate level in the spinal cord, from which point nerve signals continue to the muscles by means of the lower motor neurons. The neurotransmitter glutamate transmits the nerve impulses from upper to lower motor neurons, where it is detected by glutamate receptors.
The location of motor neurons in the anterior grey column of the spinal cord. The anterior grey column, (also known as the anterior horn of spinal cord and anterior cornu) is broad and of a rounded or quadrangular shape. Its posterior part is termed the base, and its anterior part the head, but these are not differentiated from each other by ...
Alpha motor neurons (α-MNs) innervating the head and neck are found in the brainstem; the remaining α-MNs innervate the rest of the body and are found in the spinal cord. There are more α-MNs in the spinal cord than in the brainstem, as the number of α-MNs is directly proportional to the amount of fine motor control in that muscle.
A spinal interneuron, found in the spinal cord, relays signals between (afferent) sensory neurons, and (efferent) motor neurons. Different classes of spinal interneurons are involved in the process of sensory-motor integration. [1] Most interneurons are found in the grey column, a region of grey matter in the spinal cord.