Anatomy & Physiology Ch. 1 : Introduction to Anatomy & Physiology.
Anatomy and Physiology of Motor disorder
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Transcript of Anatomy and Physiology of Motor disorder
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Movement disorders Anatomy and physiology of
motor system
Shittu LAJ
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Motor systems
• Motor systems are complex and include sophisticated control systems the purpose of which is to serve locomotion, posture and work.
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Several feedback systems monitor muscle activity
The length of muscles and the strength of contractions are monitored by:
– Input from proprioceptive receptors in muscles, joints and tendons
– Local feedback from motor nerves (Renshaw inhibition)
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Posture
Monitored by:
• proprioceptors,
• vestibular system
• vision
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Causes of movement disorders
• More or less anatomically specific neural degeneration
• Injuries (trauma, strokes, surgery, etc)
• Chemicals (alcohol, drugs)
• Inflammations and infections (viral)
• Tumors
• Genetic
• Neural plasticity
• Genetic
• Idiopathic
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Motor disorders
• Lack of function
• Inadequate function
• Hyperactivity
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Disorders of motor systems
• Hypokinesia
• Hyperkinesia
– Spasticity
• Ataxia
• Gait and balance disturbances
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Two different descending motor pathways:
• Lateral system– Fine movements
• Medial system– Posture etc.
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Cortex(MI)
Internal capsule
BrainstemNucleus ruber
Midline
Propriospinalinterneuron
Pyramids
Spinal cord
a motoneuron
Distal limb muscles
Lateral system
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Medial system
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Motor pathways
The motoneurons (alpha motoneurons) are the final common pathways
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The alpha-motoneurons (common final pathway) receive many inputsSome are facilitating and some are inhibitory
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Motor pathways
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Somatotopic organization of the motor cortex
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Colony
Colony
Two motoneurons receiving input from cortical cells
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Motor areasSensory areas
Terminations of the corticospinal tract projections of sensory pathways
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Corticospinaltracts
Propriospinalinterneuron
Supraspinalinput
Ia interneuronSegmental
input
Renshaw cellMuscle
a motoneuron
a motoneuron
Midline
Renshaw inhibition
Fibers of the corticospinal tract terminate onmotoneurons or interneurons
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Extensive processing of motor command occurs in the spinal
cord (and brainstem)
• Spinal reflexes play an important role in all motor functions
• Some functions such as walking is programmed in the spinal cord
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From supraspinalsources
InterneuronPresynaptic(Axo-axonic)
synapse
Muscle
Muscle spindelafferent
la fibers
DRG
a motoneuron
Monosynaptic stretch reflex
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Stimulus
Stimulus
Stimulus strength (V)
Antidromicmotor
Motor
Orthodromicmotor (reflex)
EMG
A
B
C
10ms
M-wave H-reflex
400
2
4
6
8
80 120
M
H
Hoffman reflex
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Reflexes are modulated from supraspinal sources
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Supraspinalinput
la interneuron
Inhibition ona motoneuron
Agonistmuscle
Antagonistmuscle
Musclespindel
Stretch reflex arc
DRG
a motoneuron
Reciprocal spinal reflex
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From semicircular canals
From uticulus
Lateralvestibularnucleus
Medialvestibularnucleus
Medialvestibular
spinal tract
Lateralvestibular
spinal tract
Spinal cord
a motoneurons
motoneurons
Descending vestibularpathways
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Medial systemPosture and automatic functions
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Reticulospinal tract
la interneuron
Muscle
Tendon
Golgi tendonafferent
DRG
a Motoneuron(inhibitory input)
Tendon reflex
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Reticulospinal pathway
la interneuron
Extensormuscle
Flexsormuscle
Flexor reflexafferents
a Motoneurona Motoneuron
Inhibitoryinterneuron
Excitatoryinterneuron
Flexor reflex
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Interneuron
Input A
B
A
a motoneuron
Input B
Intracellularpotential ina motoneuron
Input A
B
A
a motoneuron
Input B
Intracellularpotential ina motoneuron
Convergence of excitatory inputs
Convergence of inhibitory and excitatory inputs
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Muscle
lb inhibitory
Forelimbafferents
la excitatory
Decending motor tracts
a motoneuron
Input to propriospinal neurons of the forelimb of the cat
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From Rosler Fig 2B
Magnetic stimulation of motor cortex in an awake individual
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MuscleMuscle
la afferents
Fromantagonist
musclespindle
From agonist muscle spindle
Renshaw
FRA
Corticospinal tractand interneurons
Contralat. Vest.Spinal, FRA etc.
Ipsi. vestibular tractPropriospinal input
Antagonist a motoneuron
Agonista motoneuron
Input to an Ia inhibitory interneuron
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Muscle
laNorepinephrineserotonin tract
Dorsal reticularspinal tract
lb
Decending motor tracts
Joint receptors
Skin receptors
a motoneuron
Input to an Ib (inhibitory) interneuron
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BASAL GANGLIA
Extrapyramidal system
Pyramidal system
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Cortex
To spinal cord
Thalamus
Basalganglia
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Cerebellum
Corticospinaltract
Brain stemmotor pathways
Interneurons
Motor cortex
Basalganglia
Thalamus
a motor neuron
muscle
Two descending motor tracts
The alpha-motoneuron is the final common pathway
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Fig 5.27B
Anatomical localizationmotor pathways
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Motor cortex
Caudatenucleus
Putamen
Claustrum
Globuspallidus Subthalamic
nucleus
Substantianigra
Thalamus
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Basal ganglia
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Parkinson’s disease
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Huntington’s disease
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SMA/PMC/CM
GPi/SNr
Putamen
Indirect Direct
GPe
STN
BrainstemSpinal Cord
VLoVApc/mc
CM
Direct and indirect pathways
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SMA MI
Putamen
Globus pallidus
STNThalamusVlo-CM
Basal ganglia connect to supplementary motor areas and primary motor cortex
SMA: Supplementary motor area
STN: Subthalamic nucleus
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Cortex
Thalamus
Dentatenucleus
Pontinenuclei
Cerebellarcortex
Involvement of the cerebellum
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Cerebral cortex(MI and SI)
Thalamus
Cerebellarnucleus
Pontinenuclei
Rednucleus
Cerebellarcortex
Fromspinal cord
Rubrospinaltract
Involvement of the cerebellum and pontine nuclei
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Overview of motor pathways
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ANATOMICAL LOCATIONS OF THE BASAL GANGLIA
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Middle cerebral artery
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BASAL GANGLIA
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ANATOMICAL LOCATION OF THE CAUDATE NUCLEUS
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Somatotopic organization of the motor cortex
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Cortical motor areas
The central sulcus divides motor and sensory areas
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Overview of motor pathways
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Cerebellum
Corticospinaltract
Brain stemmotor pathways
Interneurons
Motor cortex
Basalganglia
Thalamus
a motor neuron
muscle
Two descending motor tracts
The alpha-motoneuron is the final common pathway
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Motor cortex
Spinal cord
Basalganglia
BrainstemCerebellum
Thalamus
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80
90
100
110
120
2 3 4 5 6 7 8 9 10
Conditioning-test interval (ms)
Effect from spasticity
Soleus H-reflex: Effect on Ib inhibition on reflex response
Hemiplegic side
Normal side
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Inhibitory supraspinal input to motoneuron pool
Segmental input
Muscle
la(from muscle spindles)
lb(from Golgi tendon organs)
Supraspinal input
a motoneuron
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Spinal cord
T11-L4
S3-S 4
Viceralafferents
Uterus
Efferent
Nociceptors
Viceralafferents
DRGDRG
Viceralafferents
Painfibers
Viceralreceptors
Bladder
Visceral afferent innervation in the lower body and motor (efferent) innervation.