Spinal cord & reflexes Flashcards Preview

Neurology > Spinal cord & reflexes > Flashcards

Flashcards in Spinal cord & reflexes Deck (67)
1

What fibres are present in the dorsal root?

Sensory afferent fibres

2

What fibres are present in the ventral root?

Motor efferent fibres

3

Where is the grey matter in the spinal cord?

Central

4

Where is the white matter in the spinal cord?

Peripheral

5

In which horn are motor fibres found?

Ventral horn

6

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

3 - posterior, lateral & anterior

7

What are the 3 important tracts in the SC?

Dorsal column
Corticospinal
Spinothalamic

8

What type of sensation does the spinothalamic fibres carry?

Pain & temperature

9

Where do fibres in the corticospinal tract originate?

Primary motor cortex

10

Where do lateral corticospinal fibres cross over?

Medulla (pyramids)

11

How many neurons are present in descending motor pathways?

2 - upper & lower motor neurons

12

Where is the site of the lower motor neurone?

Ventral horn

13

How many neurons are present in sensory ascending pathways?

3 - afferent sensory, medulla, thalamus

14

What type of sensation does the dorsal column carry?

Touch, vibration, pressure & proprioception

15

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

Medulla

16

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

Medial lemniscus

17

Where do neurons radiate from the thalamus in ascending pathways?

Post central gyrus

18

In the spinothalamic tract, where neurons cross over?

At the spinal level it enters

19

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

Dorsal horn

20

What is a reflex?

An involuntary response to sensory stimuli

21

Where are reflexes mediated?

Spinal cord

22

Name a monosynaptic reflex

Stretch reflex

23

Name a polysynaptic refelx

Flexor reflex

24

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

Contraction of the agonist (quad)
Inhibition of the flexor

25

What initiates reflexes?

Painful stimuli

26

What does the flexor reflex initiate?

Flexor activity (withdrawal)
Extensor inhibition

Crossed extensor reflex - contraction of extensor on contralateral limb

27

Which neurons (UMN/LMN) mediate reflexes?

LMN

28

In an UMN lesion, what happens to reflexes?

Exaggerated

29

What happens to tone in UMN lesions?

Spasticity (hypertonicity)

30

What happens in LMN lesions?

Flaccidity (hypotoncity)

31

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

Right sided paralysis, hyper-reflexia & increased tone

32

What happens in UMN lesion on left side below decussation?

Left sided paralysis, increased reflexes & tone

33

What happens to left sides LMN lesion?

Left sided paralysis, no reflexes & flaccidity

34

Is motor neurone disease, UMN or LMN?

LMN disease at the ventral horn

35

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

Ipsilateral sensory loss

36

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

Contralateral sensory loss

37

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

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

38

What is the simplest spinal reflex?

Stretch reflex

39

What is the best example of the stretch reflex?

Patellar tendon (knee-jerk reflex)

40

In the stretch reflex, what afferent fibres are activated?

1a neurons

41

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

Alpha motor receptors

42

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

Muscle swindle

43

Ho many connections do the spindle sensory afferents make?

3

44

What do alpha motor neurones activate?

Agonist muscle (stretch muscle)

45

What type of reflex is the reflex arc?

Monosynaptic

46

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

Activate inhibitory interneurons (relax antagonist muscle)

47

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

Reciprocal inhibition

48

Name another type of connection which occurs in stretch reflex

Spindle afferent ascend in dorsal column to higher brain centres

49

The inverse stretch reflex is also called..

Clasp-knife reflex or Golgi-tendo organ reflex

50

What does the GTO monitor?

Muscle tension

51

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

1b afferent fibres

52

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

Relaxes

53

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

Contracts

54

What types of reflex is the inverse stretch reflex?

Polysynaptic

55

What is the role of the GTO reflex?

Prevents muscle from contracting so hard the tendon is torn

(Protective)

56

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

Pain receptors

57

What is the role of the withdrawal reflex?

Protective in order to remove body from painful stimuli

58

What afferent fibres are responsible for the withdrawal reflex?

Small diameter Ao nociceptors

59

What do afferents in the flexor reflex activate?

Excitatory interneurons to flexor muscles

Inhibitory interneurons to extensor muscles

60

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

Alpha motorneurons

61

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

Crossed extensor reflex

62

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

Excitatory interneurons will cross & activate contralateral extensors

Inhibitory interneurons will cross & inhibit contralateral flexors

63

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

Spinothalamic (contralateral)

64

Which is slower, stretch reflex or withdrawal? Why?

Withdrawal reflex
Because nociceptive fibres are narrower therefore conduct slower

65

How can the GTO reflex be overridden?

From voluntary inputs from CNS

66

Can the stretch reflex be overrridden?

Yes, by descending inhibitory pathways

67

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

Reinforcement
Clench teeth or Pull arms apart