Tracts.pptx

7/24/2019 Tracts.pptx

1/42

Ascending andDescending tracts ofthe central nervous

systemDr Chathuranga Ranasinghe


2/42

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


3/42

#euron


4/42

#euromuscular $unction


5/42

%pinal cord


6/42

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


7/42


8/42

uscle spindle


9/42


10/42


11/42

uscle spindle is sensiti"e to stretch+ change o length


12/42

olgi tendon Organ


13/42


14/42

Reciprocal inner"ation


15/42

Crossed extensor refex


16/42

-hat is .pper motor neuron/

-hat is lower motor neuron/


17/42

.pper motor neuron and lower

motor neuron


18/42

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


19/42

-hat are ascending anddescending tracts/


20/42

Descending tracts

34 Corticospinal tract (Pyramidaltract) Lateral

5nterior

64 2xtrapyramydaltracts


21/42

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


22/42

rain stem


23/42


24/42

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


25/42

!"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/


26/42

Ascending tracts

34 Lateral spinothalamictract0 !ainand temparature0

64 5nterior spinothalamic tract0 ouchand pressure

94 !osterior white columnswo point discrimination

!roprioception

:ibration


27/42

Lateral spinothalamictract

!ain and temperature

7ast a delta

%low c ;bers 5bo"e ;bers heat and cold


28/42

!athway06 m+s

urning, aching

%ubstance !


30/42

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


31/42

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


32/42

Discriminati"e touch, "ibration,proprioception(conscious)


33/42

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


34/42

Read other ascending tracts

%pinocerebellar tracts


35/42

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


36/42

Cerebellum

Clinical

-ide drun8en gait, ataxia

%canning o speech !ast pointing

&ntention tremor

Rebound phenomenon A canBt putbra8es

5diadocho8inesia


37/42

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


38/42

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


39/42

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


40/42

-rite the pathway

!rimary motor cortex


41/42

%eparate paper ? F G H 3=


42/42

94 -as the lecture interesting or not/

. (#ot interesting) (%ame as beore) (interesting

than beore)3 6 9 E > ? F G H

3=

Tracts.pptx

Documents

Transcript of Tracts.pptx