129; Neurological Basis of Movement Flashcards

1
Q

What is the Peripheral Nervous System?

A

All of the nerves outside of the brain and the spinal cord; Includes all Cranial Nerves except CN I and CN II

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2
Q

What is an Afferent Neuron?

A

Neuron conducting signals INTO the CNS

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3
Q

What is an Efferent Neuron?

A

Neuron conducting signals FROM the CNS

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4
Q

What is a Ganglion?

A

Collections of neurons (or nuclei of) usually collected outside of the brain

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5
Q

What are the 5 components of the reflex circuit?

A
  1. Sensory Receptor
  2. Afferent path to CNS
  3. Synapse with the CNS
  4. Efferent path from CNS
  5. Effector (muscle)
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6
Q

Describe the Myotatic reflex following a patellar tap

A

Patellar tap stretches the quadriceps muscle

  1. Muscle spindles are stretched
  2. Afferent neurone stimulated (1a afferent)
  3. Synapse with grey matter in spinal cord
  • Direct synapse to excitatory à neuron
  • Contraction of Quadriceps muscle (Homonymous muscle)

and

  • Synapse with Inhibitory interneuron
  • Inhibition of à motor neuron to the heterogymous muscle
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7
Q

What makes the reflex transient?

A

Recurrent inhibition

Renshaw cell is an inhibitory neuron

  • It is excited by the à motor neuron
  • Releases glycine back into à motor neuron
  • Inhibits firing of à motor neuron

= Negative feedback

Glycine has the inhibitory effect here; the Tetanus toxin inhibits glycine release, which causes prolonged contraction of muscle.

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8
Q

Describe the inverse Myotatic reflex

A

It provides inhibitory feedback;

Golgi Tendon Organ has a higher threshold than Spindle

  • It is activated by prolonged muscle tretch or contraction
  • 1b afferent activation

Activation causes inhibition of homonymous muscle

Prevents damage to tendon

(eg, Drop heavy things)

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9
Q

What is the role of ŷ motor neurons?

A

Maintains tension on the muscle fiber, even following contraction of the muscle that may cause the spindle to become flacid

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10
Q

How do ŷ motor neurons maintain the tension over the spindle?

A

They stretch each end of the spindle causing contraction;

Set a reference range around which further muscle regulation is established.

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11
Q

Briefly describe à and ŷ motor neurones

A

à- cause muscle contraction

ŷ- cause spindle contraction

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12
Q

Where do motor neurones originate?

A

Pyramidal cells of the motor cortex

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13
Q

Describe the course of Motor Neurones through the Corticospinal tract

A
  • Motor neurons originate in the pyramidal cells of the motor cortex
  • They descend through the internal capsule
  • Cross at ‘decussation of pyramids’ in the medulla

It is the largest descending ract

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14
Q

What are the major Cortical Motor Regions

A
  1. Primary Somatosensory Cortex- Parietal
  2. Pre-motor Area- Frontal
  3. Supplementalr Motor Area- Frontal
  4. Posterior Parietal Cortex- Parietal
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15
Q

What are the Main functions of the Primary somatosensory cortex?

A
  • Recieve ascending sensory input from Thalamus
  • (sensory homunculus)
  • Sends descending fibers to sensory regions to filter irrelevant signals
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16
Q

What are the main functions of the Pre-motor area?

A
  • Located in Frontal lobe
  • Involved in planning of intended movements
  • Particularly movements requiring visual guidance
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17
Q

What are the main functions of the Supplementary motor area?

A
  • Coordination of voluntary movements
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18
Q

What are the main functions of the Posterior Parietal Cortex?

A
  • Integration of other sensory information
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19
Q

What is Apraxia?

A

The inability to produce a specific motor event, even though sensory and motor pathways remain intact.

20
Q

What is Apraxia and indication of?

A
  • Damage to PMC, SMA or PPC
21
Q

What is the difference between Ideomotor and Ideational Apraxia?

A

Ideomotor Apraxia

Cannot execute a specific movement upon request; alothough may understand concept, and able to do movement spontaneously

Ideational Apraxia

Unable to conceptualise the movement required

22
Q

From where does tha Corticospinal tract arise?

A

Arises from the Cortex

23
Q

What does the Reticulospinal tract modulate?

A

Spinal extensor reflexes

24
Q

What does the Vestinulospinal tract modulate?

A

Posture & Balance

25
Q

What does the Tectospinal modulate?

A

It directs head movements in response to stimuli.

26
Q

What does the Rubrospinal tract modulate?

A

Flexor motor neurones.

27
Q

What do the Ascending tracts convey to the brain?

A

Afferent neurons carrying sensory information

28
Q

What information does the Spinothalamic tract convey?

A
  • Pain
  • Temperature
  • Touch
  • Pressure

They project this information to the thalamus

Thalamocortical projections convey info then to the cortex

29
Q

What information do the Dorsal column neurons convey?

A
  • Proprioception
  • Soft touch
  • Fine discriminatory touch

Conveyed to ventral, posterior, lateral nucleus of the thalamus

Thalamocortical projections then link to the cortex.

30
Q

What information does the Spinocerebellar tract convey?

A
  • Proprioception

Prijections travel directly to the cortex; do not synapse in thalamus first.

31
Q

What is the difference between the type of movements the **cortex **and brainstem regulate?

A

Motor cortex

Planning, initiating and directing voluntary movements

** Brainstem Centres **

Basic movements and postural control

32
Q

What is the relationship between UMN and LMN in Motor regulation?

33
Q

What is a Lower Motor Neurone?

A
  • They innervate skeletal muscle; release Ach
  • There are 2 types; à and ŷ
  • They arise in the brainstem and spinal cord
34
Q

What is an Upper Motor Neurone?

A
  • These innervate the LMNs
  • Do not project directly to muscle
  • They arise in the brain
  • They are Glutamatergic neurons
35
Q

List the signs and symptoms of LMN lesions

A
  • Hyporeflexia
  • Fasciculations
  • Muscle atrophy
  • Denervation

These signs are not present in UMN lesions

36
Q

What are the causes of LMN lesions?

A

Trauma

Virus (ee. Polio)

37
Q

What are the signs and symptoms of UMN damage?

A
  • Paralysis or weakness of movement of affected muscles
  • Hyper-reflexia
  • Increased muscle tone; hyper-tonicity
  • Spasticity
  • Positive Babinski reflex

Immediately following damage may get hypo-tonia, loss of myotatic reflexes, and flaccid paralysis.

May also impede autonomic function if damage to descending autonomic fibres.

38
Q

What is the consequence of UMN lesion at the Crevical level?

A

Quadriplegia

39
Q

What is the consequence of UMN damage below the Cervical spine?

A

Paraplegia

40
Q

What is decussation?

A

Crossing of nerve fibres

41
Q

Where do most Corticospinal fibres decussate?

A

At the junction of the medulla and the spinal cord; Decussation of the pyramids

  • Thise that do not decussate at this junction continue to the **anterior corticospinal tract, **to innervate the cervical and superior thoracic regions
42
Q

What information does the spinothalamic tract convey?

A

Affrent fibres that convey info on:

  • Temperature
  • Pain
  • Pressure
  • Touch
43
Q

Describe the route of the **spinothalamic **tract fibres.

A
  • Fibres enter and synapse in the Dorsal horn
  • Move forward and decussate in ventral white comissure
    • Pain and Temp axons decussate within one segment
    • Pressure and touch may decussate after several segments
  • Ascend in contralateral side, in lateral white matter
  • Synapse in the thalamus
44
Q

Describe the route of fibres within the dorsal column.

A

Soft touch and Proprioception info is transmitted here

  • Enter the dorsal horn
    • ​Fibres from lower body ascend to gracile nucleus in Medulla
    • Fibres from upper body ascend to cuneate nucleus
  • Upper and lower body fibres synapse and decussate at the Medulla before ascending to the cortex
45
Q

To summarise, what side of the spinal cord do the Spinothalamic thact and Dorsal column?

A

Spinothalamic

Contralateral

Dorsal Tract

Ipsilateral

46
Q

What is Brown-Sequard Syndrome?

A

The signs associated with hemisection of the spinal cord.

47
Q

What area of the spinal cord do th Motor, Spinothalamic and Dorsal Column neurones travel?

A

Motor pathway

Ventral horn

Spinothalamic

Lateral white matter (synapse in dorsal horn)

Dorsal Column

Gracile and Cuneate tracts in dorsal cord