FLG 332 Copyright Micaela de Jager
Unit 2 – Nervous System
LECTURE 1 – MOTOR SYSTEM
NERVOUS SYSTEM
MICAELA DE JAGER 18
,FLG 332 Copyright Micaela de Jager
SOMATIC MOTOR DIVISION
MOTOR CORTICAL HOMUNCULUS
MICAELA DE JAGER 19
,FLG 332 Copyright Micaela de Jager
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
MICAELA DE JAGER 20
, FLG 332 Copyright Micaela de Jager
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:
MICAELA DE JAGER 21
Unit 2 – Nervous System
LECTURE 1 – MOTOR SYSTEM
NERVOUS SYSTEM
MICAELA DE JAGER 18
,FLG 332 Copyright Micaela de Jager
SOMATIC MOTOR DIVISION
MOTOR CORTICAL HOMUNCULUS
MICAELA DE JAGER 19
,FLG 332 Copyright Micaela de Jager
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
MICAELA DE JAGER 20
, FLG 332 Copyright Micaela de Jager
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:
MICAELA DE JAGER 21
