The Spinal Cord and the Periphery

Question 1

Grey and white matter of the spinal cord

Answer 1

White outside

Grey inside

Question 2

How do axons of sensory fibres enter though into the spinal cord?

Answer 2

Through the dorsal route into the dorsal horn of grey matter

Question 3

Where do motor neurones have their cell bodies in the spinal cord?

Answer 3

In the ventral horn

Question 4

What is white matter made up from?

Answer 4

Tracts

Question 5

What are tracts?

Answer 5

Axons transmitting information between higher centres in the brain and peripheral nerves = pathways

Question 6

What type of information do ascending tracts take?

Answer 6

Sensory

Question 7

What type of information do descending tract take?

Answer 7

Motor

Question 8

What columns does white matter have?

Answer 8

Posterior
Lateral
Anterior

Question 9

Function of ascending spinal tracts

Answer 9

Carries sensory information to the brain (cerebral cortex and cerebellum)

Question 10

Features of ascending spinal tracts

Answer 10

3 neurones between the peripheral receptor and the cortex

Question 11

Order of features in ascending spinal tracts

Answer 11

1. receptor - first order neurone (dorsal root present off this)
2. Reaches grey matter of spinal cord or nucleus in medulla
3. 2nd order neurone - crosses over to contralateral side in spinal cord or medulla
4. Reaches Nucleus in contralateral thalamus
5. 3rd order neurone - to contralateral parietal cortex

Question 12

What does the posterior/dorsal column of ascending tracts carry?

Answer 12

Fine touch
Tactile localisation
Vibration sense
Proprioception

Question 13

Journey of posterior/dorsal column of ascending tracts

Answer 13

1. Gracile and cuneate nuclei in medulla -> 1st order neurone to
2. 2nd order neurone -> Crosses over to medial lemniscus in pons to the
3. VPL nucleus in thalamus
4. 3rd order neurone -> post central gyrus in parietal lobe

Question 14

What does the lateral spinothalamic tract carry on the right side?

Answer 14

Pain and temp from left side of body

Question 15

What does the lateral ascending tracts carry?

Answer 15

Pain

Temperature

Question 16

Journey of Lateral spinothalamic tract

Answer 16

2nd order neurone crosses over at the level of entry to reach lateral column in the spinal cord
VPL nucleus of thalamus
Post central gyrus of parietal lobe

Question 17

Where do motor/descending tracts of the spinal cord originate?

Answer 17

Within the cerebral cortex and brainstem

Question 18

Function of descending tracts

Answer 18

Control of movement
Muscle tone
Spinal autonomic fibres

Question 19

How many neurones do descending tracts have?

Answer 19

2

Question 20

Features of descending tracts

Answer 20

Motor
2 Neurones in the pathway
They decussate to the opposite side of the brainstem

Question 21

Function of the corticospinal/pyramidal tract

Answer 21

Control of voluntary skilled movements

Question 22

What kind of pathway is the corticospinal/pyramidal tract?

Answer 22

Descending

Question 23

What is the blood supply to the corticospinal/pyramidal tract?

Answer 23

MCA

Question 24

Where do corticobulbar fibres go?

Answer 24

Go to contralateral cranial nerve nuclei

Question 25

Where do corticospinal fibres go?

Answer 25

Mostly cross in decussation of pyramids (lateral corticospinal tract)

Question 26

How much of the fibres does the anterior corticospinal tract have?

Answer 26

10 - 15%

Question 27

What is the lower motor neurone responsible for?

Answer 27

Muscle tone and reflexes

Question 28

What is the autonomic nervous system?

Answer 28

Nerve cells within both CNS and PNS concerned with innervation and control of visceral organs, smooth muscle and secretory glands

Question 29

How many neurones does the basic autonomic efferent pathway have?

Answer 29

2

Question 30

What nerves does the sympathetic ANS have an effect on?

Answer 30

T1-12 | L1 + 2

Question 31

What nerves does the parasympathetic ANS have an effect on?

Answer 31

III, VII, IX, X | S2-4

Question 32

What is the outflow of sympathetic fibres taken by?

Answer 32

Thoracolumbar

Question 33

What is the outflow of parasympathetic fibres taken by?

Answer 33

Craniosacral

Question 34

What is motor neurone disease?

Answer 34

A group of diseases affecting the motor neurone in the ventral horn of the spinal cord (LMN). The neurone dies and as a result the muscle supplied by it atrophies

Question 35

Presentation of an UMN lesion

Answer 35

Exaggerated reflexes - hyperflexia | Exaggerated tone - spasticity (spastic paralysis)

Question 36

Presentation of a herniated disc on the left side of C3 (e.g. brown sequard syndrome)

Answer 36

Left sided paralysis Left sides loss of touch, vibration and sense Right sided loss of temp and pain Reflexes on left side exagerated

Question 37

What is a reflex?

Answer 37

An involuntary stereotyped pattern of response brought about by a sensory stimulus

Question 38

Where are many reflexes mediated?

Answer 38

At the level of the spinal cord (spinal reflexes)

Question 39

Types of reflexes anatomically

Answer 39

Monosynaptic | Polysynaptic

Question 40

Example of a monosynaptic reflex

Answer 40

Stretch reflexes

Question 41

Example of a polysynaptic reflex

Answer 41

Flexor reflex

Question 42

How does a stretch reflex work?

Answer 42

1. Tendon stretched 2. Intrafusal muscle fibres stimulated 3. Sensory neurone activated 4. Monosynaptic reflex arc 4b. Polysynaptic reflex arc to inhibitory interneurone 5. Muscle contraction 5b. Reciprocal innervation

Question 43

What is the stretch reflex important in?

Answer 43

Control of muscle tone and posture

Question 44

What is the function of the flexor reflex?

Answer 44

Helps to protect the body from painful stimuli

Question 45

How does the flexor reflex work?

Answer 45

1. pain stimulus 2. Sensory neurone activated 3. Polysynpatic reflex arc 4. Flexion and withdrawal from noxious stimulus 4b. Crossed extensor response to contralateral limb (only in weight bearing limbs)