5 - Motor system 1 Flashcards

1
Q

In which part of the grey matter of the spinal cord, do UMN’s synapse with LMNs?

A

Ventral horn

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2
Q

Give some reasons why you may be unable to elicit a knee jerk reflex in a patient:

A
  • Faulty technique
  • Patient unconscious
  • Damage @ spinal level
  • Sensory neuropathy
  • UMN cell death ie stroke
  • UMN damage
  • LMN damage
  • Neuromuscular junction disease ie myasthenia gravis
  • Muscle damage ie late muscular dystrophy
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3
Q

If you are unable to elicit a knee jerk in a patient and you suspect its because they are overly conscious, what technique can you try?
How do you perform it?

A

Jendrassik manœuvre

- Ask patient to clench jaw and lock hands together and pull hard as you tap their quadriceps tendon

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4
Q

How does the Jendrassik manoeuvre increase the reflex response?

A
  • Removes some of the normal descending inhibition on the LMN
  • May prevent some unconscious inhibition
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5
Q

Why do people with UMN lesions have hyperreflexia?

A

UMN’s carry descending inhibition, regulating the LMN’s which elicit the reflex.
UMN lesion = less descending inhibition, which increases the excitability of the LMN, increasing the reflex response

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6
Q

Why do people with UMN lesions have hypertonia?

A

UMN’s carry descending inhibition, regulating the LMN’s which elicit the reflex.
UMN lesion = less descending inhibition, which increases the excitability of the LMN, increasing the reflex response

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7
Q

Where is the cell body of a LMN located?

A

Ventral horn of the spinal cord (CNS)

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8
Q

Where is the cell body of an UMN located?

A

Cerebral cortex or brainstem

NOT basal ganglia or cerebellum

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9
Q

What is meant by the positive signs of an UMN lesion? Give some examples?

A

Excessive normal resting state signs:

  • Hypertonia
  • Hyperreflexia
  • Positive Babinski sign
  • Clonus
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10
Q

What is meant by the positive signs of a LMN lesion? Give some examples?

A

Excessive normal resting state signs:

- Fasciculations

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11
Q

What is meant by the negative signs of a LMN lesion? Give some examples?

A

Loss of normal resting state signs:

  • Hyporeflexia
  • Hypotonia
  • Weakness
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12
Q

Which motor neurones can be affected in motor neurone disease?

A

Upper +/- lower

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13
Q

Why does LMN damage lead to wasting of the target muscle?

A

LMN’s provide growth factors to maintain muscle fibres

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14
Q

What is spasticity?

A

Spasticity is increased, involuntary, velocity-dependent muscle tone that causes resistance to movement.
^velocity of passive movement = ^resistance

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15
Q

Why do people with UMN lesions have clonus?

A

UMN’s carry descending inhibition, regulating the LMN’s which elicit the stretch reflex.
UMN lesion = less descending inhibition, which increases the excitability of the LMN, increasing the stretch reflex

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16
Q

Why do people with LMN lesions have fasciculation’s?

A

Damaged LMNs spontaneously fire APs causing involuntary muscle contractions/twitch

17
Q

Why do people with LMN lesions have hypotonia?

A

Tone is produced by low level contraction of muscles, if LMN to muscle is damaged, muscle cannot contract.

18
Q

Why do people with LMN lesions have areflexia/hyporeflexia?

A

Efferent portion of reflex arc damaged = reflex will be absent/reduced

19
Q

What are the causes of hypotonia?

A
  • LMN lesion
  • Muscle degeneration ie muscular dystrophy
  • Lesion of sensory afferent in skeletal muscle
  • Cerebral/spinal shock
  • Cerebellar lesions
20
Q

What are some example causes of LMN lesions?

A
  • Traumatic injury
  • Peripheral neuropathy
  • Motor neurone disease
21
Q

Damage to which motor neurone causes early wasting of muscles?

A

LMN - loss of growth factors to muscle

22
Q

Damage to which motor neurone causes late wasting of muscles?

A

UMN - late-disuse atrophy

23
Q

Damage to which motor neurone can cause fasciculations?

A

LMN - damaged motor neurone fires spontaneous APs = muscle twitch

24
Q

What is meant by ‘clasp-knife’ reflex? What type of UMN lesions is it seen in?

A

In a hypertonic muscle: following a sudden increase in resistance there is a swift decrease in tone of a muscle, allowing the muscle to easily be stretched.
- due to Golgi tendon reflex

25
Q

What is the Babinski reflex seen in UMN lesions?

A

Positive = dorsiflexion of big toe

26
Q

Why is a positive Babinski reflex normal in infants < 2yrs?

A

Corticospinal tracts have not properly developed

27
Q

What are the 2 structures which make up the lentiform nucleus?

A
  • Putamen

- Globus pallidus

28
Q

The posterior limb of the internal capsule is located between which 2 structures?

A

Thalamus (medially)
Lentiform nucleus (laterally)
- made up of putamen and globes pallidus

29
Q

Is the net effect of UMN on LMN excitatory or inhibitory?

A

Inhibitory

30
Q

Describe the type of gait often associated with an UMN lesion:

A

Hemiparetic