| Upper motor neuron | |
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| The motor tract. | |
| Dorlands/Elsevier | m_20/12542910 |
Upper motor neurons are motor neurons that originate in motor region of the cerebral cortex or the brain stem and carry motor information down to the final common pathway, that is, any motor neurons that are not directly responsible for stimulating the target muscle. Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group In Vertebrates the term motor neuron (or motoneuron) classically applies to Neurons located in the Central nervous system (or CNS that project Motor cortex is a term that describes regions of the Cerebral cortex involved in the planning control and execution of voluntary motor functions The cerebral cortex is a structure within the Brain that plays a key role in Memory, Attention, perceptual Awareness, Thought, The brain stem (or brainstem) is the lower part of the Brain, adjoining and structurally continuous with the Spinal cord. Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the The main effector neurons for voluntary movement lie within layer V of the primary motor cortex and are called Betz cells. The primary motor cortex (or M1) works in association with pre-motor areas to plan and execute movements Betz cells are Pyramidal cell Neurons located within the fifth layer of the Grey matter in the Primary motor cortex. The cell bodies of these neurons are some of the largest in the brain, approaching nearly 100μm in diameter. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information Geometry, a diameter of a Circle is any straight Line segment that passes through the center of the circle and whose Endpoints are on the
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 brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain The spinal cord is a long thin tubular bundle of Nerves that is an extension of the Central nervous system from the brain and is enclosed in and protected In Neurophysiology, the action potential is a self-regenerating Wave of Electrochemical activity that allows Nerve cells to carry a signal Lower motor neurons ( LMNs) are the Motor neurons connecting the Brainstem and Spinal cord to Muscle fibers, bringing the nerve The neurotransmitter glutamate transmits the nerve impulses from upper to lower motor neurons where it is detected by glutamatergic receptors. Glutamic acid (abbreviated as Glu or E) is one of the 20 Alpha Amino acids It is not among the human Essential amino acids Its Glutamic acid (abbreviated as Glu or E) is one of the 20 Alpha Amino acids It is not among the human Essential amino acids Its
Pathways
Upper motor neurons travel in several pathways through the CNS:
| Tract | Pathway | Function |
| corticospinal tract | from the motor cortex to lower motor neurons in the ventral horn of the spinal cord | The major function of this pathway is fine voluntary motor control of the limbs. The corticospinal or pyramidal tract is a massive collection of Axons that travel between the Cerebral cortex of the Brain and the Spinal Motor cortex is a term that describes regions of the Cerebral cortex involved in the planning control and execution of voluntary motor functions Lower motor neurons ( LMNs) are the Motor neurons connecting the Brainstem and Spinal cord to Muscle fibers, bringing the nerve The pathway also controls voluntary body posture adjustments. |
| corticobulbar tract | from the motor cortex to several nuclei in the pons and medulla | Involved in control of facial and jaw musculature, swallowing and tongue movements. The corticobulbar (or corticonuclear) tract is a White matter pathway connecting the Cerebral cortex to the Brainstem (the term "bulbar" Motor cortex is a term that describes regions of the Cerebral cortex involved in the planning control and execution of voluntary motor functions The pons (sometimes pons Varolii after Costanzo Varolio) is a structure located on the Brain stem. |
| tectospinal tract/colliculospinal tract | from the superior colliculus to lower motor neurons | Involved in involuntary adjustment of head position in response to visual information. In humans the tectospinal tract (also known as colliculospinal tract) is a nerve pathway which coordinates head and eye movements The superior colliculus ( Latin, higher hill) is a paired structure that is part of the Brain 's tectal area. |
| rubrospinal tract | from red nucleus to lower motor neurons | Involved in involuntary adjustment of arm position in response to balance information. The rubrospinal tract is a part of the Nervous system. It is a part of the Lateral indirect Extra-pyramidal tract. The red nucleus is a structure in the Rostral Midbrain involved in Motor coordination. |
| vestibulospinal tract | from vestibular nuclei, which processes stimuli from semicircular canals | It is responsible for adjusting posture to maintain balance. The vestibulospinal tract is one of the descending spinal tracts of the ventromedial pathway The semicircular canals are three half-circular interconnected tubes located inside each Ear that are the equivalent of three Gyroscopes located in three orthogonal |
| reticulospinal tract | from reticular formation | Regulates various involuntary motor activities and assists in balance. The reticulospinal tract (or anterior reticulospinal tract) is an Extrapyramidal motor tract which travels from the Reticular formation. The reticular formation is a part of the Brain that is involved in actions such as awaking/ sleeping cycle, and lying down |
Lesions
Upper motor neuron lesions are indicated by spasticity, muscle weakness, exaggerated reflexes, and an extensor plantar response known as the Babinski sign. An upper motor neuron lesion is a lesion of the neural pathway above the Anterior horn cell or Motor nuclei of the Cranial nerves. Spasticity or muscular hypertonicity is a disorder of the body Motor system, and especially the central nervous system (CNS in which certain Muscles continually A reflex action, also known as a reflex, is an involuntary and almost instant movement in response to stimulus. In Medicine and Neurology, the Babinski response to the plantar reflex is a Reflex, named after Joseph Babinski ( 1857 - 1932) (a French
External links
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