Descending Motor Tracts - PDF

Descending tracts Ekman Ch 9 Dr. Meeyoung Kim Neurosciences Physiotherapy Dept. University of Sharjah  (a) Ascending (sensory or afferent) (b) Descending (motor or efferent) diiitioimnpat.ua middlymedialPart lateral Part...

Descending tracts Ekman Ch 9 Dr. Meeyoung Kim Neurosciences Physiotherapy Dept. University of Sharjah  (a) Ascending (sensory or afferent) (b) Descending (motor or efferent) diiitioimnpat.ua middlymedialPart lateral Part 19ᵗʰ 89ᵗʰ ascending Paintemp lightley im tentromedial pathway  Dosal tract Open class quiz: fluid https://www.youtube.com/watch?v=B88BNYWVkWE ventromedial dorsolater How to divide descending tracts? innervate appside it aant.EE matiEIi 1. Pyramidal Vs 2. Dorsolateral ExtraPy Vs Ventromedial  ventromedial trait I aii.EE maieiti * vestromedial Pursolateral vintromedial *Function: control of movements in response of proprioceptive stimuli and facilitate muscle tone. Only in cervical region.  Pyramidal tracts – These tracts originate in the cerebral cortex, carryi ng motor fibres to the spinal cord and brain stem. They are responsibl e for the voluntary control of the musculature of the body and face. Extrapyramidal tracts – These tracts originate in the brain stem, carry tintang ing motor fibres to the spinal cord. They are responsible for the involu ntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion. The Direct (Pyramidal) System Impulses from pyramidal neurons in the precentral gyri pass through the pyramidal (corticospinal, corticobulbar) tracts Axons synapse with interneurons or ventral horn motor neurons The direct pathway regulates fast and fine (skilled) movements Conscious control  corticospinal trait Pyramidal tracts Cortinobulbar trait Lateral corticospinal tract Limb control mostly Ventral corticospinal tract Proximal muscle control; mostly upper body For cranial muscle control: Corticobulbar tract with medial and lateral components  3 4 56 7 9 10 11 12 Indirect (Extrapyramidal) System startfrom Includes the brain stem motor nuclei, and all motor pathways except pyramidal pathways Also called the multi-neuronal pathways subconscious motor commands These pathways are complex and multisynaptic, and regulate: Axial muscles that maintain balance and posture Muscles controlling coarse movements Head, neck, and eye movements that follow objects  Dorsolateral Rubrospinal tract: distal limb control; crude esp Shoulder (red nucleus) Ventromedial rest all here Tectospinal tract: eye-head coordination (superior colliculus) Reticulospinal tract: automatic postural adjustments and movements (hip; shoulder) (reticular formation) Vestibulospinal tract: balance (axial muscles); automatic postural adjustments (vestibular nuclei) Two different descending motor pathways: innervation Dorsolateral (contralateral) system Corticospinal (pyramidal tract) spinal (Cortico)rubrospinal Laval fat Terminate in one contralateral spinal segment Distal muscles Limb movement Ventromedial (Bilateral) system Tectospinal Vestibulospinal Reticulospinal Corticobulbar (pyramidal tract) Corticospinal (10-25% pyramidal tract) w articospinal tract Diffuse and bilateral innervation Proximal muscles um Posture and whole-body movement  Lateral pathways: limb control Medial pathways: trunk control Ventral horn motoneuron topographical organization: Proximal - distal rule  Ventromedial Dorsolateral Ventromedial Tectum Reticular formation Vestibular & IL Tectospinal Reticular tract Red nucleus Vestibular nuclei nuclei Vestibulospinal tracts I Reticulospinal Medial brain stem Rubro- spinal Mina tract tract tracts paths Pyramidal X Bilateral in_ Ventral corticospinal Lateral Cortico- spinal tract Bilateral Contralateral tract  it ipsilateral piitac.siiaside beatniks Motor or Descending Tracts of the Spinal Cord Name Location Function Lateral Corticospinal Lateral column Muscles of the limbs, hands, and feet Anterior Corticospinal Anterior column Muscles of the axial skeleton ventral system Corticobulbar Cerebral Skeletal muscles of the head and neck via cranial Peduncle nerves Rubrospinal Lateral column Skeletal muscles of the limbs, hands, and feet Tectospinal Anterior column Skeletal muscles of the head and eyes in response to expense visual stimuli Vestibulospinal 2 Anterior column Muscle for maintaining balance in response to head movements extensor reflexes F Lateral reticulospinal (MO) Anterior column O Medulla Facilitates flexor reflexes only Inhibits ont reflexes extensor standing onwobbly surface veryimp Medial reticulospinal (pons) Anterior column Facilitates extensor reflexes up withpsi Inhibits Flexor reflexes vestibulo trunk facilitate  corticospinal tract 1. Corticospinal Tract after internal capsule, midbrain, after midbrain it passes through cerebral siteIn peduncle - ant part of has 2 neurons medulla (post part has colliculus) goes down with crossover https://www.youtube.com/watch?v=NKLw5vLNFd0&list= after crossover, goes to PL0dtIx3ogTeAz2rl-qmDvEb_eeFvN_kP-&index=15 part of spinal cord, meets the low motor neuron Origin Pyramidal cells of motor cortex primary motor cortex (area 4), secondary motor cortex (area 6), parietal lobe (areas 3, 1, and 2) Pass through Corona radiata, posterior limb of Internal Capsule middle 3/5 of basis pedunculi of midbrain Site of crossover pyramids of medulla Pathway Corticospinal tracts Termination 98% on contralateral alpha and gamma motor neurons in grey matter or interneurons. a man any any any man  py cortex of medulla Corticospinal tract also known as pyramidal tracts. cerevisiae 0 Controls rapid, skilled, non-postural, voluntary movements, especially distal ends of limbs gives branches to cerebral cortex, basal nuclei, red nucleus, olivary nuclei, reticular formation. pyramid main  decuscation in midbrain 2. Rubrospinal tract 0 red nucleus Origin Red nucleus of midbrain Site of crossover Immediately in midbrain Pathway decussating at the level of red nucleus and pass down through pons & medulla Destination Motor neurons in grey matter Function Facilitates activity of flexor muscles and inhibits activity of extensor muscles in the upper limb for hand funition were shoulder hasto be flexed  works with corticospinal tract and does flexion Rubrospinal tract Reflexes flexor Red nucleus receive afferent impulses through connections with: inmidbrain 1. cerebral cortex 2. cerebellum imitate 3. Globus Pallidus Cortico-rubral connections from ipsilateral red nucleus indirect pathway by which the cerebral cortex and the cerebellum can influence the activity of motor neurons of the spinal cord. to meet  workfor balance posture 3. Reticulospinal tract ventromedial Origin Reticular formation, mainly from caudal pons and rostral medulla. Pontine and medullary nuclei. Site of Bilaterally from origin crossover Destination Motor neurons in grey matter (multiple levels) Function -Lateral (MO) -Facilitates flexor reflexes and Inhibits extensor reflexes Pink Filitate-Medial (Pons) - Facilitates extensor reflexes and Inhibits Flexor reflexes Medial tract -Influence motor functions as voluntary einen & reflex movement. -Regulate muscle tone o.fiiateraltrait lateral tractfrom Medulla HMedulla  Medial (pontine) Lateral (medullary) Reticulospinal tract Reticulospinal tract Cells of Pontine Reticular Formation Medullary Reticular Formation origin i Receive  Vestibular nuclei  The corticospinal tract input  Deep nuclei of the cerebellum.  The rubrospinal tract. from Functio -Increases Gamma efferent activity Inhibits Gamma efferent activity n -Excitatory, increases muscle tone inhibitory= decreases muscle tone -Exciting anti-gravity, extensor Inhibiting anti-gravity, extensor muscles. muscles. is again iii in iii it Is in  work for balance posture 4. Vestibulospinal tract Origin From vestibular nucleus (situated in the pons & medulla). - fibers originate in vestibular nuclei in pons (which receive inputs from inner ear, vestibular apparatus and cerebellum). Site of Lateral - No crossover. only ipsilateral crossover Medial – bilaterally immediately Destinatio Motor neurons in grey matter (multiple n levels) Function 1.Excitatory to ipsilateral spinal motor neurons that supply axial & postural muscles, acts on extensors (Lateral) 2. Controls postural& righting reflexes (Lateral) 3.Control eye movements (Medial)  Lateral vestibulospinal tract Origin: Lateral Vestibular Nucleus Path: Axons descend in the ipsilateral ventral white column of spinal cord Function: mediates excitatory influences upon extensor motor neurons to maintain posture Medial Vestibulospinal tract Medial Vestibular Nucleus As its axons descend bilaterally in the ventral white column of spinal cord , they form part of the Medial Longitudinal Fasciculus fibers in brain stem that link vestibular nuclei to nuclei supplying the extra-ocular muscles coordination of head and eye movements  vestibularspinal trait work cith Retinto spinaltract for balance Role of the vestibular nuclei to excite the anti-gravity muscles iii mi All the vestibular nuclei function in association with the pontine reticular nuclei to control the antigravity muscles. The vestibular nuclei transmit strong excitatory signals to the antigravity muscles by the lateral and medial vestibulospinal tract in the anterior column of the spinal cord Without this support the pontine reticular system would lose much of its excitation of the axial antigravity muscles. The specific role of the vestibular nuclei, is to selectively control the excitatory signals to the antigravity muscles to maintain equilibrium in response to signals from the vestibular apparatus  5. Tectospinal tract Colliculus Sup inf Origin from superior (VISUAL) & inferior colliculi (AUDITORY) of midbrain. Site of Dorsal tegmental decussation crossover Destination Motor neurons in cervical segments Function Mediate/facilitate turning of the head in response to visual or Auditory stimuli. (Ex. Hearing the sound from the Tv and you move your head to it) aiiiijfinfiiiii.ir FUNCTION OF EACH TRACT ( IMPORTANT ) Corticospinal: “Initiation of fine, discrete skilled voluntary movements” Rubrospinal: “accessory route for transmission of relatively discrete signals from the motor cortex to the spinal cord” = Facilitates activity of flexor muscles and inhibits activity of extensor muscles in the upper limb Vestibulospinal: “Controls Postural & righting reflexes” Reticulospinal: 1. “Influence motor functions as voluntary & reflex movement” 2. “Excitatory or inhibitory to muscle tone” Tectospinal: “Mediate/facilitate turning of the head in response to visual or Auditory stimuli” MNEMONIC “VIP MAKED YOU STAND” V= VESTIBULARSPINAL (VESTIBULAR NUCLEI) P= PONTINE RETICULARSPINAL SYSTEM STAND= Excite ANTIGRAVITY MUSCLE Lesions Upper motor neuron (UMN) lesions: hypertonia spasticity Lesions of corticospinal tracts (Pyramidal Tracts) babinski sign Lesions of Extrapyramidal Tracts Lower motor neuron (LMN) lesions hypotonia A  419Akefexia Lesions Hyperreflexia, Spasticity, Babinski Flaccid paralysis, Areflexia, sign, Clonus, hemipleigs gait Atrophy, Fasciculations https://www.youtube.com/watch?v=1zHhE9PhMXE&index=23&list=PL0dtIx3ogTeAz2rl-qmDvEb_eeFvN_kP- (8.30-13)  Corticospinal tract Which side would have paralysis? fam problem medki'ñ m CST at MO rostral (white CST at cortex, internal capsule colored area) affected, beforeeitherseverely involved= recent the decussation= medial infarct problem opp side medullary syndrome of Body Before crossover  of body hateproblem py lower Lesions of corticospinal tracts (Pyramidal Tracts) Babinski sign: present. superficial abdominal reflexes: absent. cremasteric reflex: absent. tieinto flexion tve Bigtoe go opting There is loss of performance of fine-skilled, voluntary into externs movements, especially at the distal end, of the limbs. hyperexten  Spastic paralysis, (lower limb extended, and the upper limb flexed) Lesions of Exaggerated deep muscle reflexes in some Extrapyramidal flexors Tracts lesions Clasp-knife reaction -the muscles, after resistance on stretching, suddenly give way. Lower motor neuron (LMN) lesions impd lesion of lower motorneuron By any lesion (ex. Poliomyelitis) destroying neurons in the anterior grey column or its axon in the anterior root or spinal nerve. Clinical signs: 1. Flaccid paralysis 2. Muscular Atrophy 3. Loss of muscular reflexes: Areflexia 4. Muscular fasciculation 5. Muscular contracture and degeneration.  Overview of motor pathways Di D2 iridation ret vestina trubro map BasalGanglia cerebellum don'thavedirectoutput I EE  Cortical motor areas Motor Basal ganglia Systems Cerebellum Descending cortical motor paths Descending brain stem paths Spinal cord: Intermediate zone Ventral horn Muscle  Destending trait Motor control pyrimidal vs Extrapy at us ventromedia iiiii.ie.ee Eti i man iiii F.EE train II IIII i mommson vaniQm i ftp.fntdesp viii shoulder it E.EEiitiaii yta iiipiiiii ninalcrsuaniaasa. i iit itpiimaiiiitiin a'side i i ebods movement Beate Eitispinal trait tenign a qq.gg viiiiiititeiitantstitoppe.ua careriurwinm coitiii.ie tract o.it i odat Iat automatic Postural adjustments vestibularan This iiiii component EEiEii i EEE.it 1 ii i ian all levels of brain stem erminate on cranial motornuller enteritis iii man e innervate E IT.tt epperm eatto Extrapyramidal tract viginatein the brainstem motor nuclei and 11motorpathway except pyramidal pathway t.it nandvesuate Eatenim i ntainmriiianidanmah iii t.li e iiiiniiimatanowmint  i vestibulospinal tract it ztajmftariatit originate vestibular nuclei in Pons medulla fibers originate from vestibular nullii in Pon Post limb internal capsule which recives input from intestine cerebral pedmiles of Midbrain apparatus mean tain Responsible pyrimidine for Rapid skilled Non iiiÉ i maraimer headandeye is Iii iiipetition Eii i i and extensor me EEE.IE EE EE i i no tuition facilitator IIIII EE IiE i i Estaminet msn.ee mantitia Rednu.si YIiciv t.ie i iiciie eIerentimputrestro m i i i iii.fiE man.ee E i i is hiiiii ii matter Eatin Rst lateral RST from MO IEEY.lttfet ysu Facilitates flexors and Inhibits extensors Blamma efferent Inhibiti exciting InGamma efferent T.EEeEEngayits EnibittEtieit