Descending Motor Pathways

The brain is the origin of the descending motor pathways or tracts. These are responsible for the origination or modification of motor activity. This action is performed by motor signals, which transmitted from the brain and target lower motor neurons. Motor control is a chief task of the central nervous system (CNS). It can be recognized as the initiation of signals to coordinate muscle contraction of the body and head, aiming to keep a posture or to make a movement (transition between two postures). A large amount of the CNS is included in the process of motor control. The term "motor neuron, also known as motoneurons" may refer to single or one type of neurons responsible for the movement. However, this is not the truth. Actually, the “motor neuron” describe two categories of neurons, the “upper and lower motor neurons”. They are significantly different in their origins, synapses, pathways, neurotransmitters and developed lesions due to their affection. Motor neurons are essential constituents of two different circuits “the upper and lower motor circuits”. These circuits control both voluntary and involuntary movements. This was achieved by the connection of higher centers with muscles and glands Descending tracts of the motor system are originating mainly from two parts, the cortex and the brainstem. Tracts originating from the cortex control the voluntary movements and adjust posture relating to voluntary movement. Furthermore, the descending pathways are subdivided into (pathways) describing their start and termination. These are (1) corticospinal and corticobulbar, (2) cortico-reticulo-spinal, (3) cortico-rubro-spinal (4) cortico-tecto-spinal, (5) vestibulo-spinal and (6) raphe–spinal and ceruleus–spinal tracts (aminergic pathways) Pyramidal tracts, originating in the cortex and carry motor fibres to the spinal cord and brain stem. It is subdivided into corticospinal and Corticobulbar tracts. The extrapyramidal tracts originate in the brainstem. Then carry motor projections to the spinal cord. These tracts are primarily concerned with the control of the involuntary and automatic innervations for all musculature (e.g., muscle tone, balance, posture and locomotion).