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Module 202 Theme 2 > Structure and function of the spinal cord > Flashcards

Structure and function of the spinal cord Flashcards

1
Q

Where does the spinal cord extend from and to?

A

Atlas - C1

L1

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2
Q

The spinal cord narrows at L1 to form what?

A

Conus medullaris

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3
Q

What attaches to the coccyx?

A

Terminal filum

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4
Q

What is found in the lumbar cistern?

A

Cauda equina (lumbar/sacral, dorsal/ventral roots)

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5
Q

What surrounds the spinal cord?

A

Sits within vertebral canal and surrounded by meninges and fat

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6
Q

What 4 regions are the spinal cord divided into?

A 
Cervical region (C1-8)
Thoracic region (T1-12)
Lumbar region (L1-5)
Sacral nerve (S1-5)
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7
Q

What is the cervical enlargement?

A

Innervation to upper limb

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8
Q

What is the lumbosacral enlargement?

A

Innervation to lower limb

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9
Q

How many spinal nerves are there?

A

31 pairs formed by dorsal and ventral roots

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10
Q

What do spinal nerves do?

A

Connect the periphery to the spinal cord

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11
Q

What fibres are ventral roots?

A

Efferent

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12
Q

What fibres are dorsal roots?

A

Afferent

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13
Q

Describe the inner core of the spinal cord

A

gray matter - neuronal cell bodies, H shaped, ventral,lateral and dorsal horn

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14
Q

Describe the outer anatomy of the spinal cord

A

Myelinated axons

White columns/tracts or funiculi

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15
Q

What happens to the gray matter at levels that supply the limbs?

A

Expands

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16
Q

Where are lateral horns found?

A

Only on thoracic vertebrae T1-12

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17
Q

Where are sensory inputs received?

A

Dorsal horn

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18
Q

Where are preganglionic sympathetic neurons found?

A

Lateral horn

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19
Q

Where are motor neurons found?

A

Ventral horns

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20
Q

Where are interneurons found?

A

In or between levels

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21
Q

What does the white matter contain?

A

Tracts

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22
Q

What are long ascending tracts?

A

Carry afferent impulses to centres within the brain

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23
Q

What are long descending tracts?

A

Long descending tracts carry efferent (motor) impulses from centres within brain.

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24
Q

What happens to the tracts to and from the cerebral hemispheres?

A

Tracts to/from cerebral hemispheres – crossed

(i.e. left cerebral hemisphere controls right side of body)

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25
Q

What is found in dorsal column?

A

Ascending tracts

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26
Q

What is found in lateral column?

A

Descending and ascending tracts

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27
Q

What is found in the ventral column?

A

Mainly descending tracts

28
Q

What two types of sensory information is carried in the ascending tracts?

A

Proprioceptive
- Information originating from inside the body (from muscles, joints, tendons)

Exteroceptive
- Information originating from outside the body (pain, temperature, touch)

29
Q

Describe the 3 neurons in circuit in ascending tract

A
  1. First order (primary sensory) neuron
    - Enters spinal cord via dorsal root
  2. Second order neuron
    - Ascends spinal cord or brainstem
  3. Third order neuron
    - Projects to the cerebral cortex
30
Q

What information does the dorsal column-medial lemniscus pathway carry?

A

Fine touch (From cutaneous mechanoreceptors)

Proprioception (From muscle spindles, golgi tendon organs, joints)

  • Provides brain with positional information
31
Q

Describe the first order neurons in the dorsal column medial lemniscus pathway

A

Enter spinal cord and ascend dorsal column on same side within the:

	- Fasciculus gracilis	(medial) 
	- Fasciculus cuneatus	(lateral)

Fibres ascend dorsal column uncrossed
Longest neurons in the body

32
Q

Where do the first order neurons synapse on second order neurons in the dorsal column-medial lemniscus pathway?

A

In the medulla

33
Q

Where does fasciculus gracilis terminate?

A

Nucleus gracilis (gracile)

34
Q

What does fasciculus gracilis give information about?

A

Information of lower limb

35
Q

Where does Fasciculus cuneatus terminate?

A

nucleus cuneatus (cuneate)

36
Q

What does fasciculus cuneatus give information about?

A

Information of upper limb

37
Q

Describe the second order neurons of the dorsal column-medial lemniscus pathway

A

Cross in medulla and ascend to thalamus

- Form medial lemniscus (ribbon)

38
Q

What do the third order neurons of the dorsal column medial lemniscus pathway do?

A

Project from thalamus to somatosensory cortex

39
Q

Describe what happens when there is a lesion on one side of the spinal cord in the dorsal column

A

E.g. in multiple sclerosis
- Loss of tactile discrimination + proprioception on same side

  • Symptoms include sensory ataxia - Loss of coordination and balance without visual cues
    (i. e. no positional information)
40
Q

What is a clinical test for a lesion on one side of spinal cord in the dorsal column

A

Romberg’s sign - severe swaying on standing with eyes closed and feet together

41
Q

What does the spinothalamic tract give information about?

A

Pain, temperature and crude touch (from nociceptors)

42
Q

Describe the first order neurons of the spinothalamic tract

A

Enter dorsal horn and form tract of Lissauer- collateral branches given off at tip of dorsal horn. Run up and down 1-2 segments.

43
Q

Where do the 1st and 2nd order neurons synapse in the spinothalamic tract?

A

Synapse in dorsal horn with second order neurons

44
Q

Describe the second order neurons of the spinothalamic tract

A

Cross in dorsal horn at each level

Ascend in anterolateral column to thalamus

45
Q

Where do the third order neurons of the spinothalamic tract project?

A

From thalamus to somatosensory cortex

46
Q

Describe a lesion on one side of spinal cord to the anterolateral column

A
  • Loss of pain, temperature and crude touch on opposite side
47
Q

What does an outside compression of the cord cause?

A

loss of lower limb pain first (fibres sit laterally)

48
Q

What does an inside grey matter tumour cause?

A

loss of upper limb pain first (fibres sit medially)

49
Q

What information do spinocerebellar tracts carry?

A

Unconscious muscle proprioception

	- For smooth motor coordination
50
Q

What is special about the spinocerebellar ascending tract#?

A

Two neurons only
Four tracts
Uncrossed - left cerebellum controls left side of the body

51
Q

What do anterior and posterior spinocerebellar tracts carry?

A

Proprioceptive information from trunk and lower limb

52
Q

Describe the first order neuron of the spinocerebellar tract

A

Synapse in dorsal horn

53
Q

Describe the second order neuron of the spinocerebellar tract

A

Ascend in lateral column to cerebellum - very fast axons

54
Q

What does a lesion on one side of the spinal cord in the spinocerebellar tract cause?

A

Uncoordinated lower limb muscular activity on same time although rarely damaged in isolation

55
Q

What are descending (motor) tracts?

A

Control of muscular activity

From the cortex

Many descending tracts

56
Q

What is the purpose of the corticospinal tract?

A

Great voluntary motor pathway

57
Q

Describe the upper motor (premotor) neuron of the corticospinal tract

A

From cerebral cortex to ventral horn

58
Q

Describe the lower motor neuron

A

From ventral horn to skeletal muscle

59
Q

Describe the pyramidal tract of the corticospinal tract

A 
Primary motor cortex
Posterior limb of internal capsule
Cerebral peduncle
Pons
Pyramids of medulla
Lateral/anterior corticospinal tract
60
Q

What are the pyramids of decussation?

A

80% cross - lateral corticospinal tract
20% on same side - anterior corticospinal tract
(cross in spinal cord - supply deep neck muscles)

61
Q

Describe the topographical organisation in the ventral horn

A

Medial = Trunk
Anterolateral = Proximal limb segments
Posterolateral = Distal limb segments

62
Q

What is motor neuron disease?

A

Disruption of the corticospinal tract

63
Q

Describe upper motor neuron disease

A

Degeneration of upper motor neurons

  • Spastic paralysis (increased muscle tone)
  • Overactive tendon reflexes
  • No significant muscle atrophy

Above pyramids: Opposite side
Below pyramids: Same side

E.g. Following a stroke

64
Q

Describe lower motor neuron disease

A 
Degeneration of lower motor neurons in ventral horn
- Flaccid paralysis (no muscle tone)
- No tendon reflexes
- Muscle atrophy
E.g. Spinal muscular atrophy
	- caused by defects in the SMN1 gene
65
Q

What is amyotrophic lateral sclerosis?

A

Selectively affects upper and lower motor neurons
- Progressive muscle weakness and atrophy but mind intact

  • Symptoms initially in limbs or bulbar signs (speech and swallowing difficulties)
  • Spasticity present when upper motor neurons affected
  • Short life span (~5 years – due to respiratory failure)
    • Affects 4-5 in 100,000
    • Genetic mutations identified (e.g. SOD1 gene)
66
Q

What are extrapyramidal tracts?

A

Do not pass through the pyramids
Descending tracts from basal ganglia, cerebellum and pons
E.g. Reticulospinal tract

67
Q

Describe the reticulospinal tract

A
  • From reticular formation (pons) to spinal cord

Regulates ventral horn motor activity/reflexes

Facilitates and inhibits lower motor neurons

Important for posture and locomotion

Module 202 Theme 2 (12 decks)

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