<unk> s <unk> s) is a term introduced by William Gowers in 1886. They are found in the cerebral cortex and brainstem and carry information down to activate interneurons and lower<unk><unk> s, which in turn directly signal muscles to contract or relax.<unk> s in the cerebral cortex are the main source of voluntary movement. They are the larger pyramidal cells in the cerebral cortex. There is a type of giant pyramidal cell called Betz cells and are found just below the surface of the cerebral cortex within layer V of the primary<unk>  cortex. The cell bodies of Betz cell<unk> s are the largest in the brain, approaching nearly 0.1 mm in diameter. The primary<unk>  cortex, or precentral gyrus, is the most posterior gyrus of the frontal lobe and lies anterior to the central sulcus. The pyramidal cells of the precentral gyrus are also called<unk> s. The fibers of the<unk> s project out of the precentral gyrus ending in the brainstem, where they will decussate (intersect) within the lower medulla oblongata to form the lateral corticospinal tract on each side of the spinal cord. The fibers that do not decussate will pass through the medulla and continue on to form the anterior corticospinal tracts. The<unk>  descends in the spinal cord to the level of the appropriate spinal nerve root. At this point, the<unk>  synapses with the lower<unk><unk> , each of whose axons innervate a fiber of skeletal muscle. These<unk> s 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<unk><unk> s. The<unk> ransmitter glutamate transmits the nerve impulses from<unk>  to lower<unk><unk> s, where it is detected by glutamatergic receptors.
Upper motor neuron
Gamma motor neuron
Somatosensory system
Motor system
Sensory nerve
Primary sensory areas
Muscle spindle
Central pattern generator