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Neurology > Motor system > Flashcards

Motor system Flashcards

1
Q

List the 4 main parts of the motor system

A
  • upper motor neurons
  • lower motor neurons
  • extrapyramidal motor system
  • cerebellar system
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2
Q

What are upper motor neurons

A
  • belong to the pyramidal system
    It refers to the giant pyramidal (Betz) cells, found in the 5th cortical layer of the precentral gyrus, along with their descending fibres called the pyramidal tract; including the corticospinal tract (spinal cord) and corticobulbar tract (brainstem)
  • the upper motor neurons control the lower motor neurons
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3
Q

What are the lower motor neurons

A
  • acts as the final common pathway for impulses from the upper motor neurons, cerebellar system and extrapyramidal system
  • refers to the anterior horn cells of the spinal cord and the motor nuclei of the brainstem; as well as their axons forming peripheral nerves and cranial nerves
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4
Q

Describe the different motor pathways

A

Precentral gyrus (Betz cells) –>pyramidal tract (corticobulbar/spinal) –> internal capsule

  1. corticobulbar tract –> cross to other side at different brainstem level –> cranial motor nuclei –> cranial n
  2. corticospinal tract –> middle basis of cerebral peduncle –> basis of pons –> most fibres cross at pyramidal decussation –> lateral corticospinal tract –> motor neurons of anterior grey horn –> anterior root –> spinal n –> skeletal m
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5
Q

Based on clinical types, what are the 5 classifications of paralysis

A
  1. monoplegia: paralysis of one extremity only
  2. paraplegia: symmetric paralysis of 2 extremities
  3. quadriplegia: paralysis of all 4 extremities
  4. hemipleglia: paralysis of one side of the body, limited by the median line
  5. crossed paralysis: paralysis of one or more ipsilateral cranial nerves and contralateral hemiplegia
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6
Q

Based on the location of a lesion, what can paralysis be classified into

A
  • Neurogenic paralysis: lesion on motor neuron or peripheral nerve
  • Myogenic paralysis: caused by muscular diseases
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7
Q

Based on clinical characteristics, how can paralysis be classified

A
  1. UMN paralysis: spastic paralysis or central paralysis or hard paralysis
  2. LMN paralysis: flaccid, peripheral or soft paralysis
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8
Q

What is the difference between UMN and LMN paralysis?

A

First UMN paralysis, 2nd LMN paralysis

Distribution of paralysis: General (mono, hemi, para) Local, often involving some muscle group

Muscle tone: Hyper myotonia Hypo myotonia

Tendon reflex: Hyperactive Hyporeflexia

Pathologic reflex: Yes No

Muscular atrophy: No (or diffuse) Yes, early

Reaction of degeneration: No Yes

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9
Q

How would one diagnose paralysis of precentral gyrus

A

The precentral gyrus is a long stripe
- local destructive lesion usually damages part of it causing contralateral monoplegia with or without contralateral facial palsy
large lesion may cause contralateral hemiplegia
- irritative lesion often causes epilepsy of contralateral extremity

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10
Q

How would one diagnose paralysis of the internal capsule

A

The internal capsule is the most concentrated part of the pyramidal tract; lesions will cause:
- contralateral hemiplegia, central facial palsy and central hypoglossal palsy
- contralateral hemianaesthsia
- hemianopsia is sometimes present

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11
Q

How would one diagnose paralysis of the brainstem

A
  • indication of brainstem lesion in crossed paralysis (because involvement of ipsilateral motor nucleus of cranial neve and uncrossed pyramidal tract
    i.e., midbrain lesion: weber syndrome
    Pons lesion: Millard-Gubler syndrome
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12
Q

How would one diagnose paralysis of the spinal cord?

A
  1. Spinal hemisection syndrome
    - ipsilateral deep sensation disturbance
    - ipsilateral UMN paralysis belowe level of lesion
    - contralateral superficial sensation disturbance below level of lesion
  2. Spinal transection lesion
    - loss of all sensation below level of lesion
    - paraplegia or quadriplegia below level of lesion
    - disturbance of bladder and rectum function
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13
Q

What is the location diagnosis paralysis for the anterior horn cells

A
  • ipsilateral segmental lower motor neuron paralysis of the muscles that these cells supply, usually with fasciculation but no sensory disturbance
    (polymyelitis)
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14
Q

What is the location diagnosis paralysis for anterior root lesions

A
  • ipsilateral segmental lower motor neuron paralysis of muscles that the anterior root supplies, radicular pain may be presented if posterior root is involved as well
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15
Q

What is the location diagnosis paralysis for the peripheral nerve

A

The peripheral nerve is a mixed nerve, so lesion involving a peripheral nerve will cause motor and sensation disturbance of muscles and skin that the nerve supplies

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16
Q

Describe the anatomy of the extrapyramidal system

A
  • corpus striatum
  • neostriatum (caudate nucleus, putamen)
  • paleostriatum/globus pallidu (red nucleus, substantia nigra, subthalamic nucleus)

*lenticular nucleus = globus pallidua + putamen

17
Q

What is the extrapyramidal system mainly related to and what is the main structure relating to its function

A
  • main function is movement adjustment
  • corpus striatum is the main structure
18
Q

Why is the corpus striatum the main structure regarding movement adjustment?

A

The structures within the the corpus striatum have extensive connections to each other and to the cerebral cortex and many other subcortex structures (red nucleus, substantia nigra and brain stem reticular formations)

19
Q

What is the
1. anatomic basis
2. biochemical basis
of movement adjustment

A
  1. fibre connection circles
  2. neurotransmitters (Glu, GABA, DA)
20
Q

Generally speaking, lesions to the extrapyramidal system will result in______

A

changes in muscle tone (hypertonia, hypotonia) and involuntary movements

21
Q

What are two main clinical syndromes relating to the extrapyramidal system

A
  1. hypertonia hypokinesia syndrome: caused by lesion of globus pallidus and substantia nigra –> present with static tremor (parkinson’s disease)
  2. hypotonia hyperkinesia syndrome: lesion of caudate nucleus and putamen –> Gilles de la tourette syndrome
22
Q

Provide the general anatomy of the cerebellum

A
  • posterior fossa of the skull, behind the pons and medulla
  • separated from the overlying cerebrum by the cerebellar tentorium
  • connected to the midbrain, pons and medulla by way of its 3 pairs of cerebellar peduncles
  • cerebellum is composed of small unpaired medial port, the vermis and 2 large lateral masses (cerebellar hemispheres)
23
Q

List the 3 main functions of the cerebellum

A
  • keeping the balance of the body in space
  • adjusting the muscle tonus
  • coordinating movements of the extremities
24
Q

What is meant by “ataxia”

A

decompostion and inco-ordination of movements caused by a lesion in the cerebellum, cerebrum, deep sensation pathway or vestibular structures

25
Q

List the 4 types of ataxia

A
  • cerebellar ataxia
  • cerebral ataxia
  • sensory ataxia
  • vestibular ataxia
26
Q

Describe cerebellum ataxia
- how is it caused
- symptoms

A

**most important symptom of cerebellar disease is ataxia
caused by:
1. lesion of vermis:
*cause disturbance of equilibrium and truncal gait: gait is unsteady, wide-based, irregular and drunken
2. lesion of the cerebellar hemispheres
*causes ataxia of the ipsilateral extremities: finger-to-nose and heel-knee-shin test is inaccurate, dysmetria, adiadokokinesia, intention tremor, nystagmus, hypotonia, explosive and slurred speech, tendency to lean and fall to the side of the lesion

27
Q

Describe cerebral ataxia

A

there are fibre connections between the cerebellum and cerebrum (frontal, temporal, parietal lobe), so lesions of cerebrum may cause ataxia
*symptoms are relatively mild

28
Q

Describe sensory ataxia

A

Lesion of posterior column of spinal cord may cause disturbance of deep sensation and sensory ataxia
- difficulty standing steady (especially in the dark or when patient closes eyes - Romberg’s sign)
often seen in neurosyphilis and spinal combined degeneration

29
Q

Describe vestibular ataxia

A

Vestibulocochlear tract carries impulses from vestibular nuclei to the flocculonodular lobe (participate in keeping bodies balance in space and movement of eyes

Lesion on the vestibular system may cause vestibular ataxia
- vertigo
- vomitting
- nystagmus

Neurology (13 decks)

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