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Neurology > Lecture 11 Functional Hierarchy of the Motor System > Flashcards

Lecture 11 Functional Hierarchy of the Motor System Flashcards

1
Q

a-motorneurones can be referred to as what? and why>

A

Final common path

Contraction of muscle occurs through this whether voluntary contraction or involuntary contraction

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2
Q

What motor neuron is involved in LMN

A

Alpha motor neuron

Gamma motor neuron

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3
Q

What pathway is involved in UMN

A

Corticospinal tract

Ipsilateral/contralateral

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4
Q

What regulates trunk and limb muscle reflexes

A

Descending inputs from vestibulospinal and reticulospinal tracts

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5
Q

What 4 systems control movement

A
  1. Descending control pathways
  2. Basal ganglia
  3. Cerebellum
  4. Local spinal cord/bran stem circuits
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6
Q

What is the function of the basal ganglia

A

Gating proper initiation of movement

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7
Q

What is the function of the cerebellum

A

Sensory motor coordination of ongoing movement

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8
Q

What does the descending system consist of

A

Motor cortex and Brainstem centres

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9
Q

What is the function of the motor cortex

A

Planning, initiating and directing voluntary movements

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10
Q

What is the function of the brainstem centres

A

Basic movements and postural control

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11
Q

Where are proximal shoulder muscles mapped in the motor neurones

A

Medially

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12
Q

Where are distal finger muscles mapped in the motor neurone

A

Laterally

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13
Q

How does sensory input enter the spinal cord

A

In the form of proprioceptors, touch, pain

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14
Q

How does sensory input enter the brain stem

A

Vestibular system informs about balance

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15
Q

How does sensory inout enter at a cortical level

A

We make movements in response to visual, olfactory, auditory, emotional and intellectual cues

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16
Q

Where is the stretch reflex found

A

In all muscles

17
Q

What information does the stretch reflex use

A

Information from muscle spindles which monitor length

18
Q

Describe the stretch reflex

A

Sharp tap to inelastic tendon
Force is transmitted to the muscle fibres (more elastic and therefore stretch)
Stretch activates the sensory nerves in the muscle spindle which increases the number of AP in afferent nerve–> dorsal horn leading to a monosynaptic reflex

19
Q

During a stretch reflex why does the antagonist muscle relax in response to the agonist muscle contracting

A

Spindle afferents connect with and activate inhibitory interneurons which decrease activation of a-motorneurones to antagonist muscles (reciprocal inhibition)

20
Q

Why is the stretch reflex considered a negative feedback loop

A

Muscle stretch

Reflex causes muscle contraction and shorten to previous length

21
Q

What is responsible for the Golgi tendon organ reflex

A

Muscles contract and shorten which pulls strongly on the tendon and 1b sensory nerves from the GTP increase firing AP

22
Q

What is the result of the increase AP for 1b sensory nerves

A
  1. Activation of inhibitory interneurones to the agonist muscle and a decrease in contraction strength- relaxes rapidly
  2. Activation of excitatory interneurones to antagonist muscles- contracts
23
Q

What is the purpose of the GTO reflex

A

Prevents muscles contracting so hard that the tendon insertion is then away from the bone

24
Q

What is the clasp-knife reflex

A

Greatly increasing tension in tendon leads to collapse of resistance to protect muscles from damage

25
Q

Flexor or withdrawal reflexes uses information from where

A

Nociceptors in skin, muscles and joints and polysynaptic and protective

26
Q

When you withdraw a limb what also happens ti ensure you don’t fall over

A

Contralateral limb extends

27
Q

Describe the flexor reflex on the contralateral limb

A
  1. Several excitatory interneurones which cross the spinal cord excite the contralateral extensors
  2. At the same time, via several interneurones, there is inhibition of the contralateral flexors this helps to maintain an upright posture by extending the limb to bear the body weight.
  3. Sensory information ascends to the brain in the contralateral spinothalamic tract.
28
Q

Why flexor and crossed extensor reflex slower than stretch reflex

A

Nociceptive fibres have a smaller diameter

There are several interneurons in the pathway

29
Q

How can the inhibition of a-motorneurones be overridden

A

By descending voluntary excitation go a motorneurones and maintain contraction

30
Q

What are features of a LMN lesion

A 
Absent or reduced reflex (hyporeflexia, areflexia)
Flaccid paralysis
Muscle atrophy
Muscle weakness
Plantar reflex- flexor
Fasciculations
31
Q

Whats an example of a LMN lesion

A

Brachial plexus damage

32
Q

What are the features of an UMN lesion

A 
Spastic paralysis
Muscle weakness
Hyperflexia
Increased muscle tone (Hypertonia)
Babinski sign positive
Clonus
Clasp knife effect
33
Q

Whats an example of an UMN lesion

A

Stroke

Neurology (44 decks)

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