Tracts.pptx
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Ascending andDescending tracts ofthe central nervous
systemDr Chathuranga Ranasinghe
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Learning outcomes
Describe stretch refex
Describe upper motor neuron and lower motor neuron
Describe the motor pathways(corticospinal, pyramidal
tracts) and arrangement
Outline the unctions o the extrapyramidal system
riefy describe pathways or !ain, touch ,"ibration riefy describe the physiology o pain
Outline the unctions o cerebellum , brain stem
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#euron
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#euromuscular $unction
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%pinal cord
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Refex arc
&n"oluntary response to stimulus
!arts o a refex arc
#euromuscular spindle
&n spinal cord refex arc plays a main role inmaintaining muscle tone ' basis o posture
uscle tone continuous partial contraction o
muscle ' depend on refex arc
his refex arcs in the spinal cord is e*ected by thedescending tracts rom higher centers
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uscle spindle
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uscle spindle is sensiti"e to stretch+ change o length
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olgi tendon Organ
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Reciprocal inner"ation
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Crossed extensor refex
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-hat is .pper motor neuron/
-hat is lower motor neuron/
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.pper motor neuron and lower
motor neuron
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Upper motor neuron and lowermotor neuron
Lesions
Corticospinal excitatory0 increase muscletone
Other tracts inhibit muscle tone
1ypotonia Refex arc disrupted
1ypertonia 2xtrapyramidal tracts disrupted
ut clinically isolated lesions are rare
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-hat are ascending anddescending tracts/
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Descending tracts
34 Corticospinal tract (Pyramidaltract) Lateral
5nterior
64 2xtrapyramydaltracts
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Descending tracts
First order neuron(upper motor)0 cerebral cortex0corona radiata0 post limb o internal capsule0
&n the pons
&n medulla0 anteriorly pyramids
&nerior medulla deccussation o pyramids
Lateral corticospinal tract
7ibers do not cross anterior corticospinal tract 'later cross0cer"ical and upper thoracic
5nterior gray column0 2ndorder neuron(interneuron) or directly
3rdorder neuron(lower motor) ' alpha or gammamotor neuron
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rain stem
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orticospinal tract
5lso called pyramidal tract
!erorm rapid s8illed mo"ements
ranches gi"en to other parts o cortex, nuclei
Recei"e inormation rom other descending
tracts(extrapyramidal tracts)
Continues tonic excitatory infuence on lower
motor neuron
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!"trapyramidal tracts
#eticulospinalinfuence "oluntery mo"ements and
refex acti"ity
$ectospinal ' refex posturalmo"ements in response
to "isual stimuli
%esti&ulospinal0 muscle acti"ity association with
balance (inner ear, cerebellum)
#u&rospinal
&nhibitory infuence in muscle tone(L#)
7unctions/
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Ascending tracts
34 Lateral spinothalamictract0 !ainand temparature0
64 5nterior spinothalamic tract0 ouchand pressure
94 !osterior white columnswo point discrimination
!roprioception
:ibration
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Lateral spinothalamictract
!ain and temperature
7ast a delta
%low c ;bers 5bo"e ;bers heat and cold
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!athway06 m+s
urning, aching
%ubstance !
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ating theory
!eripheral ner"e ;ber and dorsalhorn cell( gate)
Considerable plasticity
%timulate large ;bers touch
Collaterals rom those ;bers &nhibitpain ;bers at dorsal horn
-hen that stimuli ta8en o* painoccur again
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Anterior spinothalamic tract
%ame as lateral spinothalamic tract
a8e touch and pressure sensations
ross to other side withinseveral spinal segments
a8e spinal leminiscus with lateralspinothalamic tract
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Discriminati"e touch, "ibration,proprioception(conscious)
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Posterior white column
%acral, lumber ,lower ? thoracic0 fasciculusgracilis
.pper thorsic, cer"ical0 fasciculus cuneatus
5scend ipsilaterally
6ndorder gracilis cuneatus nucleas at medulla
'ensory deccusation
Ascend as medial leminiscus
9rd
order nueron at thalumus0 post limb o internalcapsule0 corona radiata0 sensory cortex
Cuneocerebellar tract 'propriocepti"e sense tocerebellum
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Read other ascending tracts
%pinocerebellar tracts
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Cerebellum
7unctions
Recei"e propriocepti"e,"isual, balanceinput rom body and a copy o motor
plan rom the motor cortex %moothness and coordination o motor
acti"ity by infuencing cortex and brain
stem 2@uilibrium and learning
Control o limb muscles
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Cerebellum
Clinical
-ide drun8en gait, ataxia
%canning o speech !ast pointing
&ntention tremor
Rebound phenomenon A canBt putbra8es
5diadocho8inesia
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rain stem
7unctions %er"es as a conduit or ascending and
descending tracts which connect spinal
cord and higher centers4 Contains important centers which control
Respiration
Cardio"ascular system
Consciousness
1as cranial ner"e nuclei iii to xii
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Learning outcomes
Describe stretch refex
Describe upper motor neuron and lower motor neuron
Describe the motor pathways(corticospinal, pyramidal
tracts) and arrangement
Outline the unctions o the extrapyramidal system
riefy describe pathways or !ain, touch ,"ibration
riefy describe the physiology o pain
Outline the unctions o cerebellum , brain stem
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uestions/
34 List 9important ascending tracts4nameunction o one tract
64 -hat is the unction o the corticospinal
tract94 5rrange the sectionso the central
ner"ous system rom cortexdownwards(write the letters 5,,C
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-rite the pathway
!rimary motor cortex
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%eparate paper ? F G H 3=
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94 -as the lecture interesting or not/
. (#ot interesting) (%ame as beore) (interesting
than beore)3 6 9 E > ? F G H
3=