Summary Nervous System Study Unit 2

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Unit 2 – Nervous System


LECTURE 1 – MOTOR SYSTEM

NERVOUS SYSTEM




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SOMATIC MOTOR DIVISION




MOTOR CORTICAL HOMUNCULUS




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MOTOR SYSTEM
≫ Single efferent neuron
≫ Leaves CNS via ventral horn towards target tissue
≫ Synapse of somatic motor neuron on muscle fibre = NEUROMUSCULAR JUNCTION
≫ Somatic efferent neuron vesicles release acetylcholine (Ach)
≫ Ach taken up by nicotinic Ach receptors
≫ Acetylcholine esterase inactivates Ach (by degrading it)
≫ The esterase is in high concentration at cholinergic nerve ending
≫ Inhibits contraction of skeletal muscles




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UPPER & LOWER MOTOR NEURONS


UMN  neurons in the higher centers of brain
 control LMN

3 types:
1. Motor neurons in cerebral cortex
2. Neurons in basal ganglia and brainstem nuclei
3. Neurons in cerebellum


LMN  anterior gray horn cells in the spinal cord and the
motor neurons of the cranial nuclei in brainstem
 innervates muscles directly




DIRECT PYRAMIDAL/CORTICOSPINAL PATHWAY

 Voluntary movement
 From cerebral cortex  descend to thalamus  brain stem  spinal cord

• Fibers that end in the brain stem (corticobulbar tracts)
- Innervates muscles of head (larynx, tongue, eye movement )




3 Descending tracts:
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