Lower motor neurons (LMNs) are the motor neurons connecting the brainstem and spinal cord to muscle fibers, bringing the nerve impulses from the upper motor neurons out to the muscles. In Vertebrates the term motor neuron (or motoneuron) classically applies to Neurons located in the Central nervous system (or CNS that project The brain stem (or brainstem) is the lower part of the Brain, adjoining and structurally continuous with the Spinal cord. 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 Skeletal muscle is a type of Striated muscle, which usually attaches to tendons In Neurophysiology, the action potential is a self-regenerating Wave of Electrochemical activity that allows Nerve cells to carry a signal Upper motor neurons are Motor neurons that originate in motor region of the Cerebral cortex or the Brain stem and carry motor information down Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the A lower motor neuron's axon travels through a foramen and terminates on an effector (muscle).
Classification
The axons of lower motor neurons are a type of motor fibers. An axon or nerve fiber is a long slender projectionof a nerve cell or Neuron, that conducts electrical impulses away from the neuron's Cell Lower motor neurons are classified based on the type of muscle fiber they innervate:
- Alpha motor neurons (α-MNs) innervate extrafusal muscle fibers, the most numerous type of muscle fiber and the one most involved in muscle contraction. Alpha motor neurons ( α-MNs) are large Lower motor neurons of the Brainstem and Spinal cord. Extrafusal muscle fibers are a class of Muscle fiber innervated by Alpha motor neurons They generate tension do mechanical work and allow for movement by contracting A muscles contraction (also known as a muscle twitch or simply twitch) occurs when a Muscle fibre generates tension through the action of Actin
- Gamma motor neurons (γ-MNs) innervate intrafusal muscle fibers, which are involved with muscle spindles and the sense of body position. Gamma motoneurons ( γ-motoneurons) also called gamma motor neurons, are a component of the Fusimotor system, the system by which the Central Intrafusal fibers are Muscle fibers that comprise the Muscle spindle and are innervated by the gamma motor neurons ( Gamma motoneuron) Muscle spindles are Sensory receptors within the belly of a Muscle, which primarily detect changes in the length of this muscle Proprioception (ˌproʊpriːəˈsɛpʃən PRO -pree-o-SEP-shun from Latin proprius, meaning "one's own" and perception is the Sense
Physiology
Glutamate released from the upper motor neurons triggers depolarization in the lower motor neurons in the ventral horn which in turn causes an action potential to propagate the length of the axon to the neuromuscular junction where acetylcholine is released to carry the signal across the synaptic cleft to the postsynaptic receptors of the muscle cell membrane, signaling the muscle to contract. 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 In biology depolarization is a decrease in the Absolute value of a cell's Membrane potential. An axon or nerve fiber is a long slender projectionof a nerve cell or Neuron, that conducts electrical impulses away from the neuron's Cell A neuromuscular junction ( NMJ) is the Synapse or junction of the Axon terminal of a Motoneuron with the motor end plate, the The Chemical compound acetylcholine (often abbreviated ACh) is a Neurotransmitter in both the Peripheral nervous system (PNS and Central Chemical synapses are specialized junctions through which Neurons signal to each other and to non-neuronal cells such as those in Muscles or Glands Skeletal muscle is a type of Striated muscle, which usually attaches to tendons
Consequences of lesions
Damage to lower motor neurons (lower motor neurone lesions) is indicated by abnormal EMG potentials, fasciculations, paralysis, weakening of muscles, and neurogenic atrophy of skeletal muscle. A lower motor neuron lesion is a lesion which affects nerve fibers travelling from the anterior horn of the Spinal cord to the relevant Muscle (s -- the Electromyography (EMG is a technique for evaluating and recording the activation signal of muscles A fasciculation (or "muscle Twitch " is a small local involuntary Muscle contraction (twitching visible under the skin arising from the spontaneous discharge Paralysed redirects here For other uses see xx Paralysed (disambiguation Paralysis is the complete loss of Muscle function Muscle weakness (or "lack of strength" is a direct term for the inability to exert force with one's Muscles to the degree that would be expected given the individual's Atrophy is the partial or complete Wasting away of a part of the Body.
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