Lower Motor Neurons and Their Regulation

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Lower motor neurons

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Somatic neurons that emanate from the brainstem and spinal cord to innervate skeletal muscle. They are the final common pathway.

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Sources of lower motor neuron input

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1) Local circuit neurons (nearby interneurons) 2) Upper motor neurons (cell bodies in the upper part of the CNS) 3) Basal nuclei (provide input to upper motor neurons via the thalamus) 4) Cerebellum (provides input to upper motor neurons and monitors intended vs. actual movements)

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Diagram showing lower motor neuron regulation

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Diagram illustrating the regulation of lower motor neurons and their connections with various brain regions and pathways.

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Somatic reflexes

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Allow fast, involuntary contractions of skeletal muscle.

Front

Components of a somatic reflex arc

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1. Sensory receptor 2. Sensory neuron 3. Integrating center 4. Motor neuron 5. Effector

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Role of sensory receptor in somatic reflex arc

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Detects stimuli such as nociceptors, muscle spindles, and tendon organs.

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Function of sensory neuron in somatic reflex arc

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Conveys action potentials (AP) to the central nervous system (CNS).

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Integrating center in somatic reflex arc

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Gray matter of spinal cord or brain stem; can be monosynaptic or polysynaptic.

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Role of motor neuron in somatic reflex arc

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Carries action potentials (AP) from CNS to effector via somatic motor neuron.

Front

Effector in somatic reflex arc

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Target organ such as skeletal muscle, smooth muscle, cardiac muscle, or glands.