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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 human brain is primarily composed of neurons, glial cells, neural stem cells, and blood vessels. Types of neuron include interneurons, pyramidal cells including Betz cells, motor neurons (upper and lower motor neurons), and cerebellar Purkinje cells. Betz cells are the largest cells (by size of cell body) in the nervous system. [40]
The first list shows number of neurons in their entire nervous system. The second list shows the number of neurons in the structure that has been found to be representative of animal intelligence. [1] The human brain contains 86 billion neurons, with 16 billion neurons in the cerebral cortex. [2] [1]
The PNS includes motor neurons, mediating voluntary movement; the autonomic nervous system, comprising the sympathetic nervous system and the parasympathetic nervous system and regulating involuntary functions; and the enteric nervous system, a semi-independent part of the nervous system whose function is to control the gastrointestinal system.
Unlike the topographic maps of the senses, the neurons of the motor cortex are efferent neurons that exit the brain instead of bringing information to the brain through afferent connections. The motor system is responsible for initiating voluntary or planned movements ( reflexes are mediated at the spinal cord level, so movements associated ...
The pyramidal motor system, also called the pyramidal tract or the corticospinal tract, start in the motor center of the cerebral cortex. [4] There are upper and lower motor neurons in the corticospinal tract. The motor impulses originate in the giant pyramidal cells or Betz cells of the motor area; i.e., precentral gyrus of cerebral cortex ...
Sensory neurons respond to stimuli such as touch, sound, or light that affect the cells of the sensory organs, and they send signals to the spinal cord or brain. Motor neurons receive signals from the brain and spinal cord to control everything from muscle contractions [3] to glandular output.
These include sensory neurons that transmute physical stimuli such as light and sound into neural signals, and motor neurons that transmute neural signals into activation of muscles or glands; however in many species the great majority of neurons participate in the formation of centralized structures (the brain and ganglia) and they receive all ...