PhD MD MBBS Faculty of Medicine Al Maarefa Colleges of Science & Technology Faculty of Medicine Al Maarefa Colleges of Science & Technology Lecture –

PhD MD MBBS

Faculty of Medicine

Al Maarefa Colleges of Science & Technology

Lecture – 6: Motor System - 2

Nervous SystemPhysiology

ByDr. SHAHAB

SHAIKH

••••••••••••••••••••••••••••••••••

PhD MD MBBS

Faculty of Medicine


EXTRA PYRAMIDAL SYSTEMDEFINATION • Tracts other than Corticospinal tracts are known

as EXTRA PYRAMIDAL TRACTS.

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COMPONENTS OF EXTRAPYRAMIDAL SYSTEM

• BASAL GANGLIA• BRAINSTEM Giving rise to following

tracts:o Rubrospinal tracto Vestibulospinal tracto Reticulospinal tracto Tectospinal tract

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RUBROSPINAL TRACT• Origin – Red nucleus in mid brain• Input - Red nucleus gets input from

both cerebellum and cerebral cortical motor areas

• Output - Via Rubrospinal tract is directed to contralateral spinal motor neurons ( crosses to opposite side at the level of nucleus and axons are located in lateral spinal white matter anterior to Corticospinal tract.

• Functions - Involved in movements of distal limbs (hand & feet) also regulates tone and posture.

• It is excitatory to flexors and inhibitory to extensor muscles.

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VESTIBULOSPINAL TRACT• Location - Vestibular nuclei

located in Pons & Medulla• Input - receive input from

Vestibular apparatus in the inner ear and Cerebellum

• Output – Mainly From Lateral vestibular nuclei to spinal cord in Vestibulospinal tract. It remains ipsilateral.

• Function - Excitatory to ipsilateral extensor. Inhibitory to flexor muscles

• Regulates muscle tone for maintaining balance in response to head movement 5

RETICULOSPINAL TRACT• Location - Reticular formation in

the central grey matter of brain stem

• Input - Afferent input to reticular formation comes from spinal cord, vestibular nuclei, cerebellum, Sensory motor cortex, globus pallidus & Lat. Hypothalamus

• Output - Descending tract arise from nuclei in pons and medulla

1]Pons – Pontine Reticulospinal tract runs ipsilaterally;

Function - Excitatory to Axial extensor muscles

2]Medulla – Medullary reticulospinal tract runs ipsilaterally (some cross also)Function - Inhibitory to axial extensor Muscle

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TECTOSPINAL TRACT

• Origin – originates in superior colliculus in midbrain

• Input – from visual stimuli• Output - Conveys nerve

impulses from superior colliculus (midbrain) to contralateral skeletal muscles that move the head and eyes in response to visual stimuli

• Function – Involved in control of neck muscle in response to visual stimuli

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EXTRA PYRAMIDAL TRACT

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These tracts terminate on interneurons usually. Occasionally they terminate directly on anterior horn motor neurons

SUMMARY OF DESCENDING TRACTS

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FUNCTIONS OF EXTRA PYRAMIDAL SYSTEM

• REGULATION OF BODY POSTURE, INVOLVING INVOLUNTARY MOVEMENTS OF LARGE MUSCLE GROUPS OF TRUNK AND LIMBS

• REGULATION OF VOLUNTARY MOVEMENT• REGULATION OF TONE

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APPLIED

• Of the Extra pyramidal tracts some are excitatory and other have inhibitory influence on muscle tone but overall there is strong inhibitory effect over Gamma Motor Neuron in anterior horn cell.

• Therefore in UMN lesions, this inhibitory effect is lost resulting in Hypertonia.

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Difference between Pyramidal and Extrapyramidal tractsPYRAMIDAL TRACTS

1. -Lateral corticospinal-Ant. or ventral corticospinal- Corticobulbar

2. Cell bodies that contribute to pyramidal tracts are located in precentral gyrus ( Primary, Premotor and supplimentary motor cortex) and somatosensory area.

3. Pyramidal tract descend directly without synaptic interruption from cerebral motor cortex to spinal cord ( on interneuron and ant. Horn cells)

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EXTRA PYRAMIDAL TRACTS

1. -Rubrospinal

-Vestibulospinal

-Reticulospinal

-Tectospinal

2. They originate in Midbrain and brainstem nuclei and have influence of cerbral cortex, basal ganglia and cerebellum which can stimulate or inhibit these nuclei

3. No direct control of motor cortex or basal ganglia on spinal cord but via nuclei in midbrain and brainstem

Difference between Pyramidal and Extrapyramidal TractPYRAMIDAL TRACTS

4. 80 % of Corticospinal tracts (lateral) cross in medulla

20 % of corticospinal tract (ventral) cross in spinal cord

Because of crossing cerebral cortex controls opposite side of the body

5. Function:

- Lat. Corticospinal tract – fine movement of fingers eg. Writing, needle work

- Ventral corticospinal tract – Axial or Postural Movement

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EXTRA PYRAMIDAL TRACTS

Major extra pyramidal tracts, some cross and others are uncrossed

Function:

Control of body posture involving involuntary movements of axial and Proximal limb muscle

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Motor System It is two neuron system1- Upper motor neuron – From motor cortex to anterior horn cell of spinal cord

2- Lower motor neuron – Starts from anterior horn cell and ends on muscle e.g. all peripheral nerves

MOTOR NEURON LESIONS

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UMN lesion causes:

o Increased tone (Spasticity)o Increased reflexeso Clonus: Repetitive contraction and relaxation

of muscle in oscillating fashion every second or so

o Babinski sign: o Note: below one year of age Babinski reflex is

normally present

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LMN lesion causes:oDecreased tone (Hypotonia / Flaccidity).oDecreased power of the muscles.oDecreased reflexes.oWasting of muscles.

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DIFFERENCE BETWEEN UPPER & LOWER MOTOR NEURON LESION

UMN LESION• Paralysis affect

movement rather than muscles

• Muscle wasting is only from disuse, therefore slight. Occasionally marked in chronic severe lesions.

• Spasticity of clasp-knife’ type. Muscles hypertonic.

LMN LESION• Individual muscle or

group of muscles are affected.

• Wasting pronounced.

• Flaccidity. Muscles hypotonic.

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UMN LESIONTendon reflexes increased.

Clonus often present.Superficial reflexes diminished

or modified. Abdominal reflex absent. Babinski’s sign +ve,

--Increased jaw jerk.

LMN LESIONTendon reflexes diminished or

absent.

Superficial reflexes often unaltered.

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COMMON TERMINOLOGIES IN CLINICAL NEUROLOGY

• HEMIPLEGIA – – Paralysis (loss of power) of half side of the body

• HEMIPARESIS – – Partial loss of power of half side of the body

• PARAPLEGIA – – Paralysis in both legs

• PARAPARESIS – – Partial loss of power in both legs

• QUADRIPEGIA – – Paralysis in all four limbs

• MONOPLEGIA – – Paralysis in one limb

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PhD MD MBBS

Faculty of Medicine


Sensory & Motor System Lesions

Nervous SystemPhysiology

ByDr. SHAHAB

SHAIKH

••••••••••••••••••••••••••••••••••

PhD MD MBBS

Faculty of Medicine


What is the impairment caused by Lesion of the right dorsal column at L1?

Click for answer

Damage to the right dorsal column at L1 causes the absence of light touch, vibration, and position sensation in the right leg. Only fasciculus gracilis exists below T6.

Click for explanation

R L

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Right Dorsal Column Lesion

Dorsal column lesionIpsilateral loss of light touch, vibration, and position sensegeneralized below the lesion level

Below T6 only the fasciculus gracilis is present.

R LDRG

L1

Common causes include MS, penetrating injuries, and compression from tumors.

Click to animate

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Click for answer

Damage to the right lateral spinothalamic tract at L1 causes the absence of pain and temperature sensation in the left leg.


what impairment Lesion of the right lateral Spinothalamic tract at L1 produces? R L

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R LDRG

Lateral spinothalamic tract lesionContralateral loss of pain and temperature sense

Right Lateral Spinothalamic Tract Lesion

L1

Common causes include MS, penetrating injuries, and compression from tumors.

Click to animate

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what impairment Lesion of the right lateral Corticospinal tract at L1 produces?

Click for answer

Damage to the right lateral corticospinal tract at L1 causes upper motor neurons signs (weakness or paralysis, hyperreflexia, and hypertonia) in the right leg.


R L

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R L

UMN

Lateral corticospinal tract lesionIpsilateral upper motor neurons signsgeneralized below the lesion level

UMN signsWeakness (Spastic paralysis)Hyperreflexia (+ Babinski, clonus)Hypertonia

Right Lateral Corticospinal Tract Lesion

L1

Common causes include penetrating injuries, lateral compression from tumors, and MS.

Click to animate

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Click for answer

Damage to the right dorsal columns at L1 causes the absence of light touch, vibration, and position sense in the right leg. Damage to the lateral corticospinal tract causes upper motor neuron signs in the right leg (Monoplegia), and damage to the lateral spinothalamic tract causes the absence of pain and temperature sensation in the left leg.


Complete transection of the right half the spinal cord (Hemicord or Brown-Sequard syndrome) at L1 produces what impairments?

R L

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R L

Hemicord Lesion (Brown-Sequard Syndrome)

Dorsal column lesionIpsilateral loss of light touch, vibration, and position sense

Lateral corticospinal tract lesionIpsilateral upper motor neurons signs


Hemicord lesion

Build the lesion

L1

Common causes include penetrating injuries, lateral compression from tumors, and MS.

Click to animate

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Hemicord Lesion (Brown-Sequard Syndrome)

Dorsal column lesionIpsilateral loss of light touch, vibration, and position sense

Lateral corticospinal tract lesionIpsilateral upper motor neurons signs


UMN

Hemicord lesion

R L DRGDRG

L1

Click to animate

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References

• Human physiology by Lauralee Sherwood, 8th edition

• Text Book Of Physiology by Guyton & Hall, 11th edition

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THANK YOU

Documents

PhD MD MBBS Faculty of Medicine Al Maarefa Colleges of Science & Technology Faculty of Medicine Al Maarefa Colleges of Science & Technology Lecture –