Motor Systems Flashcards
1
Q
Somatic motor pathways
A
- control of body movement (skeletal muscles)
- direct or pyramidal pathway - primary motor cortex
- initiate and control precise movements
- indirect/extrapyramidal pathways
- basal nuclei help establish muscle tone and integrate semi-voluntary automatic movements
- cerebellum helps make movements smooth and helps maintain posture and balance
2
Q
Direct motor pathway
A
- originates in primary cortex (precentral gyrus)
- upper motor neurons project to spinal cord (corticospinal tract) or brain stem (corticobulbar tract)
- in the diencephalon, descending axons gather together to form internal capsule
- in the midbrain the axons form the cerebral peduncles
- in the medulla oblongata they form pyramidal tracts
- 90% cross to opposite side of medulla at the pyramidal decussation
- crossed fibres for the lateral corticospinal tract, uncrossed fibres from the anterior tract
- in the spinal cord the axons from the lateral corticospinal tract enter the ventral horn and synapse on motor neurons
- axons in the anterior corticospinal tract cross to opposite side of spinal cord and synapse on ventral horn motor neurons
- axons from the ventral horn motor neurons project in the ventral root to skeletal muscles
3
Q
Motor areas of cerebral cortex
A
- voluntary motor initiation
- primary motor area: precentral gyrus
- controls voluntary contractions of skeletal muscles on other side of body
- primary motor area: precentral gyrus
4
Q
Primary motor cortex
A
- precentral gyrus initiates voluntary movement
- cells are called upper motor neurons
- muscles represented unequally (according to the number of motor units)
- more cortical area is needed if number of motor units in a muscle is high
- vocal cords, tongue, lips, fingers
5
Q
Indirect pathways
A
- complex polysynaptic circuits
- basal nuclei
- cerebellum
6
Q
Basal nuclei
A
- helps to program automatic movement sequences
- walking/arm swinging
- set muscle tone by inhibiting other motor circuits
- damage is characterized by tremors or twitches
- putamen
- globus pallidus
- caudate nucleus
7
Q
Basal Nuclei pathway
A
- cerebral cortex projections to the basal nuclei
- basal Nuclei has reciprocal projections to midbrain (substantia nigra, dopamine neurons)
- basal nuclei projects to the thalamus
- thalamus projects to the cerebral cortex
- direct corticospinal pathway projects to brain stem and spinal motor neurons
- damage to basal nuclei: Parkinson’s disease
8
Q
Cerebellar pathways
A
- aspects of function
- motor learning
- coordinated and skilled movements
- posture and equilibrium
- inferior cerebellar peduncle carries proprioceptive sensory inputs from the spinal cord and vestibular apparatus (inner ear)
- middle cerebellar peduncle carries motor commands from the cerebral cortex via the pontine nuclei
- superior cerebellar peduncle carries motor commands from cerebellum to brain stem, thalamus, basal ganglia and cerebral cortex
9
Q
Final common pathway
A
- lower motor neurons receive signals from both direct and indirect upper motor neurons
- sum total of all inhibitory and excitatory signals determines the final response of the lower motor neuron and the skeletal muscle
10
Q
Autonomic NS
A
- regulates activity of smooth muscle, cardiac muscle and glands
- involuntary control
- involves CNS motor neuron (preganglionic neuron) and PNS motor neuron (postganglionic neuron)
11
Q
Autonomic VS somatic
A
-ANS pathway is a 2 neuron pathway while somatic NS only contains one neuron
12
Q
Divisions of ANS
A
- 2 major divisions
- parasympathetic
- sympathetic
- dual innervation
- one speeds up organ
- one slows down organ
13
Q
Sources of dual innervation
A
- sympathetic (thoracolumbar) division
- preganglionic cell bodies in thoracic and first 2 lumbar segments of spinal cord
- parasympathetic (craniosacral) division
- preganglionic cell bodies in nuclei of 4 cranial nerves and the sacral spinal cord
14
Q
Anatomy of sympathetic NS
A
- preganglionic cell bodies found in lateral horn of thoracic and lumbar spinal cord
- postganglionic cell bodies located in the sympathetic trunk (paravertebral) or prevertebral ganglia
15
Q
Anatomy of parasympathetic NS
A
- preganglionic cell bodies found in
- 4 cranial nerve nuclei in brainstem
- S2 - S4 spinal cord
- postganglionic cell bodies very near or in the wall of target organ in terminal ganglia