Spinal cord & reflexes

Question 1

What fibres are present in the dorsal root?

Answer 1

Sensory afferent fibres

Question 2

What fibres are present in the ventral root?

Answer 2

Motor efferent fibres

Question 3

Where is the grey matter in the spinal cord?

Answer 3

Central

Question 4

Where is the white matter in the spinal cord?

Answer 4

Peripheral

Question 5

In which horn are motor fibres found?

Answer 5

Ventral horn

Question 6

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

Answer 6

3 - posterior, lateral & anterior

Question 7

What are the 3 important tracts in the SC?

Answer 7

Dorsal column
Corticospinal
Spinothalamic

Question 8

What type of sensation does the spinothalamic fibres carry?

Answer 8

Pain & temperature

Question 9

Where do fibres in the corticospinal tract originate?

Answer 9

Primary motor cortex

Question 10

Where do lateral corticospinal fibres cross over?

Answer 10

Medulla (pyramids)

Question 11

How many neurons are present in descending motor pathways?

Answer 11

2 - upper & lower motor neurons

Question 12

Where is the site of the lower motor neurone?

Answer 12

Ventral horn

Question 13

How many neurons are present in sensory ascending pathways?

Answer 13

3 - afferent sensory, medulla, thalamus

Question 14

What type of sensation does the dorsal column carry?

Answer 14

Touch, vibration, pressure & proprioception

Question 15

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

Answer 15

Medulla

Question 16

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

Answer 16

Medial lemniscus

Question 17

Where do neurons radiate from the thalamus in ascending pathways?

Answer 17

Post central gyrus

Question 18

In the spinothalamic tract, where neurons cross over?

Answer 18

At the spinal level it enters

Question 19

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

Answer 19

Dorsal horn

Question 20

What is a reflex?

Answer 20

An involuntary response to sensory stimuli

Question 21

Where are reflexes mediated?

Answer 21

Spinal cord

Question 22

Name a monosynaptic reflex

Answer 22

Stretch reflex

Question 23

Name a polysynaptic refelx

Answer 23

Flexor reflex

Question 24

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

Answer 24

Contraction of the agonist (quad)

Inhibition of the flexor

Question 25

What initiates reflexes?

Answer 25

Painful stimuli

Question 26

What does the flexor reflex initiate?

Answer 26

``` Flexor activity (withdrawal) Extensor inhibition ``` Crossed extensor reflex - contraction of extensor on contralateral limb

Question 27

Which neurons (UMN/LMN) mediate reflexes?

Answer 27

LMN

Question 28

In an UMN lesion, what happens to reflexes?

Answer 28

Exaggerated

Question 29

What happens to tone in UMN lesions?

Answer 29

Spasticity (hypertonicity)

Question 30

What happens in LMN lesions?

Answer 30

Flaccidity (hypotoncity)

Question 31

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

Answer 31

Right sided paralysis, hyper-reflexia & increased tone

Question 32

What happens in UMN lesion on left side below decussation?

Answer 32

Left sided paralysis, increased reflexes & tone

Question 33

What happens to left sides LMN lesion?

Answer 33

Left sided paralysis, no reflexes & flaccidity

Question 34

Is motor neurone disease, UMN or LMN?

Answer 34

LMN disease at the ventral horn

Question 35

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

Answer 35

Ipsilateral sensory loss

Question 36

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

Answer 36

Contralateral sensory loss

Question 37

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

Answer 37

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

Question 38

What is the simplest spinal reflex?

Answer 38

Stretch reflex

Question 39

What is the best example of the stretch reflex?

Answer 39

Patellar tendon (knee-jerk reflex)

Question 40

In the stretch reflex, what afferent fibres are activated?

Answer 40

1a neurons

Question 41

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

Answer 41

Alpha motor receptors

Question 42

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

Answer 42

Muscle swindle

Question 43

Ho many connections do the spindle sensory afferents make?

Answer 43

3

Question 44

What do alpha motor neurones activate?

Answer 44

Agonist muscle (stretch muscle)

Question 45

What type of reflex is the reflex arc?

Answer 45

Monosynaptic

Question 46

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

Answer 46

Activate inhibitory interneurons (relax antagonist muscle)

Question 47

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

Answer 47

Reciprocal inhibition

Question 48

Name another type of connection which occurs in stretch reflex

Answer 48

Spindle afferent ascend in dorsal column to higher brain centres

Question 49

The inverse stretch reflex is also called..

Answer 49

Clasp-knife reflex or Golgi-tendo organ reflex

Question 50

What does the GTO monitor?

Answer 50

Muscle tension

Question 51

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

Answer 51

1b afferent fibres

Question 52

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

Answer 52

Relaxes

Question 53

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

Answer 53

Contracts

Question 54

What types of reflex is the inverse stretch reflex?

Answer 54

Polysynaptic

Question 55

What is the role of the GTO reflex?

Answer 55

Prevents muscle from contracting so hard the tendon is torn | Protective

Question 56

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

Answer 56

Pain receptors

Question 57

What is the role of the withdrawal reflex?

Answer 57

Protective in order to remove body from painful stimuli

Question 58

What afferent fibres are responsible for the withdrawal reflex?

Answer 58

Small diameter Ao nociceptors

Question 59

What do afferents in the flexor reflex activate?

Answer 59

Excitatory interneurons to flexor muscles Inhibitory interneurons to extensor muscles

Question 60

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

Answer 60

Alpha motorneurons

Question 61

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

Answer 61

Crossed extensor reflex

Question 62

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

Answer 62

Excitatory interneurons will cross & activate contralateral extensors Inhibitory interneurons will cross & inhibit contralateral flexors

Question 63

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

Answer 63

Spinothalamic (contralateral)

Question 64

Which is slower, stretch reflex or withdrawal? Why?

Answer 64

Withdrawal reflex | Because nociceptive fibres are narrower therefore conduct slower

Question 65

How can the GTO reflex be overridden?

Answer 65

From voluntary inputs from CNS

Question 66

Can the stretch reflex be overrridden?

Answer 66

Yes, by descending inhibitory pathways

Question 67

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

Answer 67

Reinforcement | Clench teeth or Pull arms apart