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Neurology > Spinal cord & reflexes > Flashcards

Spinal cord & reflexes Flashcards

1
Q

What fibres are present in the dorsal root?

A

Sensory afferent fibres

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2
Q

What fibres are present in the ventral root?

A

Motor efferent fibres

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3
Q

Where is the grey matter in the spinal cord?

A

Central

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4
Q

Where is the white matter in the spinal cord?

A

Peripheral

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5
Q

In which horn are motor fibres found?

A

Ventral horn

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6
Q

White mater is arranged in how many columns in the SC?

A

3 - posterior, lateral & anterior

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7
Q

What are the 3 important tracts in the SC?

A

Dorsal column
Corticospinal
Spinothalamic

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8
Q

What type of sensation does the spinothalamic fibres carry?

A

Pain & temperature

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9
Q

Where do fibres in the corticospinal tract originate?

A

Primary motor cortex

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10
Q

Where do lateral corticospinal fibres cross over?

A

Medulla (pyramids)

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11
Q

How many neurons are present in descending motor pathways?

A

2 - upper & lower motor neurons

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12
Q

Where is the site of the lower motor neurone?

A

Ventral horn

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13
Q

How many neurons are present in sensory ascending pathways?

A

3 - afferent sensory, medulla, thalamus

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14
Q

What type of sensation does the dorsal column carry?

A

Touch, vibration, pressure & proprioception

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15
Q

Where does the 2nd order neuron decussate in the ascending pathway?

A

Medulla

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16
Q

What is another name for the ascending sensory tracts in the brain?

A

Medial lemniscus

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17
Q

Where do neurons radiate from the thalamus in ascending pathways?

A

Post central gyrus

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18
Q

In the spinothalamic tract, where neurons cross over?

A

At the spinal level it enters

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19
Q

In the spinothalamic tract where does the 1st order neuronal synapse onto the 2nd order neuron?

A

Dorsal horn

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20
Q

What is a reflex?

A

An involuntary response to sensory stimuli

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21
Q

Where are reflexes mediated?

A

Spinal cord

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22
Q

Name a monosynaptic reflex

A

Stretch reflex

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23
Q

Name a polysynaptic refelx

A

Flexor reflex

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24
Q

In the stretch reflex, stretching of the tendon causes what?

A

Contraction of the agonist (quad)

Inhibition of the flexor

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25
Q

What initiates reflexes?

A

Painful stimuli

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26
Q

What does the flexor reflex initiate?

A 
Flexor activity (withdrawal)
Extensor inhibition

Crossed extensor reflex - contraction of extensor on contralateral limb

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27
Q

Which neurons (UMN/LMN) mediate reflexes?

A

LMN

28
Q

In an UMN lesion, what happens to reflexes?

A

Exaggerated

29
Q

What happens to tone in UMN lesions?

A

Spasticity (hypertonicity)

30
Q

What happens in LMN lesions?

A

Flaccidity (hypotoncity)

31
Q

What happens in UMN lesion, left-sided at the IC?

A

Right sided paralysis, hyper-reflexia & increased tone

32
Q

What happens in UMN lesion on left side below decussation?

A

Left sided paralysis, increased reflexes & tone

33
Q

What happens to left sides LMN lesion?

A

Left sided paralysis, no reflexes & flaccidity

34
Q

Is motor neurone disease, UMN or LMN?

A

LMN disease at the ventral horn

35
Q

In sensory pathways, a lesion below decussation will result in feeling lost on which side?

A

Ipsilateral sensory loss

36
Q

In sensory pathways, a lesion above decussation will result in feeling lost on which side?

A

Contralateral sensory loss

37
Q

A lesion affecting the spinothalamic tract will result in temperature/ pain being lost where?

A

Contralateral side (as crosses over at the level it enters)

38
Q

What is the simplest spinal reflex?

A

Stretch reflex

39
Q

What is the best example of the stretch reflex?

A

Patellar tendon (knee-jerk reflex)

40
Q

In the stretch reflex, what afferent fibres are activated?

A

1a neurons

41
Q

In the stretch reflex, what muscle fibres initiate the reflex?

A

Alpha motor receptors

42
Q

In the stretch reflex, where are sensory nerves found in the muscle?

A

Muscle swindle

43
Q

Ho many connections do the spindle sensory afferents make?

A

3

44
Q

What do alpha motor neurones activate?

A

Agonist muscle (stretch muscle)

45
Q

What type of reflex is the reflex arc?

A

Monosynaptic

46
Q

What other connections can the sensory afferents make at the spinal cord during stretch reflex?

A

Activate inhibitory interneurons (relax antagonist muscle)

47
Q

In the stretch reflex, the relaxation of an antagonist muscle is called?

A

Reciprocal inhibition

48
Q

Name another type of connection which occurs in stretch reflex

A

Spindle afferent ascend in dorsal column to higher brain centres

49
Q

The inverse stretch reflex is also called..

A

Clasp-knife reflex or Golgi-tendo organ reflex

50
Q

What does the GTO monitor?

A

Muscle tension

51
Q

In the inverse stretch reflex, what sensory fibres type carries info from GTO?

A

1b afferent fibres

52
Q

In inverse stretch reflex, what happens to the agonist muscle?

A

Relaxes

53
Q

In inverse stretch reflex, what happens to the antagonist muscle?

A

Contracts

54
Q

What types of reflex is the inverse stretch reflex?

A

Polysynaptic

55
Q

What is the role of the GTO reflex?

A

Prevents muscle from contracting so hard the tendon is torn

Protective

56
Q

The flexor or withdrawal reflex uses inputs from which sensory pathway?

A

Pain receptors

57
Q

What is the role of the withdrawal reflex?

A

Protective in order to remove body from painful stimuli

58
Q

What afferent fibres are responsible for the withdrawal reflex?

A

Small diameter Ao nociceptors

59
Q

What do afferents in the flexor reflex activate?

A

Excitatory interneurons to flexor muscles

Inhibitory interneurons to extensor muscles

60
Q

What is the efferent fibre type observed in the flexor reflex?

A

Alpha motorneurons

61
Q

In order to prevent falling over, what else happens in the withdrawal reflex?

A

Crossed extensor reflex

62
Q

What happens at the spinal cord in order to achieve crossed extensor reflex?

A

Excitatory interneurons will cross & activate contralateral extensors

Inhibitory interneurons will cross & inhibit contralateral flexors

63
Q

What tract do sensory fibres ascend in during the withdrawal reflex?

A

Spinothalamic (contralateral)

64
Q

Which is slower, stretch reflex or withdrawal? Why?

A

Withdrawal reflex

Because nociceptive fibres are narrower therefore conduct slower

65
Q

How can the GTO reflex be overridden?

A

From voluntary inputs from CNS

66
Q

Can the stretch reflex be overrridden?

A

Yes, by descending inhibitory pathways

67
Q

How can inhibitory descending pathways be overridden when testing stretch reflex?

A

Reinforcement

Clench teeth or Pull arms apart

Neurology (16 decks)

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