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NSB Lectures > Structure and function of the spinal cord > Flashcards

Structure and function of the spinal cord Flashcards

1
Q

The spinal cord is continuous with which structure in the brain?

A

Medulla Oblongata.

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2
Q

The base of the brain is also known at the what?

A

Atlas.

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3
Q

At the level of L1, the spinal cord narrows to form which structure?

A

The conus medullaris.

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4
Q

The conus medullaris is formed at which vertebral level?

A

L1.

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5
Q

Spinal nerves extend past L1 and form a bundle of nerves. What is this bundle called?

A

Cauda equina.

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6
Q

What structure protects the spinal cord?

A

The vertebral canal within the vertebral column and the meninges.

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7
Q

How many meninges are protecting the spinal cord?

A

3.

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8
Q

Which meninge layer directly lines the spinal cord and is highly vascular?

A

Pia mater

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9
Q

The Pia mater thickens to form what ligament?

A

The denticulate ligament.

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10
Q

What is the role of the denticulate ligament?

A

Anchors the spinal cord to the middle of the central canal.

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11
Q

Which CSF filled space sits between the Pia mater and the Arachnoid mater?

A

Subarachnoid space.

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12
Q

What separates the vertebral column from the Dura mater?

A

Epidural space.

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13
Q

Which meninge layer is the outermost from the spinal cord?

A

Dura mater.

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14
Q

At the conus medullaris, a fibrous extension of the Pia mater forms. What is this called?

A

Filum terminale.

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15
Q

What is the role of the Filum Terminale?

A

Anchors and stabilises the distal spinal cord.

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16
Q

At what vertebral level is a lumbar puncture usually done for an adult and why?

A

Below L3 - To avoid the L1/L2 conus medullaris as anything above would likely hit the spinal cord.

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17
Q

At which vertebral level is a lumbar puncture usually done on a child?

A

Below L4.

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18
Q

How many pairs of spinal nerves are there?

A

31.

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19
Q

What the regions of the spinal cord?

A

Cervical nerves 1-8
Thoracic nerves 1-12
Lumbar nerves 1-5
Sacral nerves 1-5
Coccygeal 1

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20
Q

Spinal nerves usually exit the vertebral column below their corresponding vertebral level. How is this different in the cervical region?

A

There are 8 cervical nerves but 7 cervical vertebra.
C1 nerve exits above C1 vertebra, C2 exits before C1 vertebra.
C8 exits below C7 vertebra.

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21
Q

What are each of the spinal nerve pairs formed from?

A

Dorsal and ventral root

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22
Q

Which nerve root brings sensory information into the spinal cord?

A

Dorsal root.

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23
Q

Which nerve root takes information out of the spinal cord, into the muscles?

A

Ventral root.

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24
Q
A
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25
Q

Where and why does grey matter expand?

A

Expand at sites where more neuronal cell bodies are needed e.g. at the level that supply the limbs.
Cervical and thoracic region.

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26
Q

Grey matter is organised into how many different ‘horns’?

A

3

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27
Q

What are the three different horns in grey matter named?

A

Dorsal
Lateral
Ventral

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28
Q

What is the role of the neurons in the dorsal horn?

A

To receive incoming sensory input from the periphery.

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29
Q

What is the role of neurons in the ventral horn?

A

Motor neurons take information away from spinal cord, into periphery.
Also contains interneurons

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30
Q

Which type of neurons are located within the lateral horn?

A

Preganglionic sympathetic neurons.

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31
Q

Neurons within the grey matter are arranged into layers. What is the collective name for this group of layers?

A

Laminae.

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32
Q

What is exteroceptive information?

A

Information that originates from outside the body, coming in to the brain.
Touch, pain etc.

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33
Q

What is proprioceptive information?

A

Information within the body e.g. from muscles, coming into the brain.
Tells us where are joints are in space

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34
Q

Do tracts of white matter stay in one side of the body?

A

No, they cross the midline at some point during the tract.

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35
Q

Which type of tract sends sensory information to the brain?

A

Ascending tract (Afferent - dorsal)

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36
Q

Name three different ascending tracts.

A

Dorsal column
Spinothalamic
Spinocerebellar

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37
Q

Which ascending tract conveys proprioception and light touch?

A

Dorsal column.

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38
Q

Where is the cell body of the first order neuron located for the dorsal ascending pathway?

A

Outside the spinal cord in the dorsal root ganglion.

39
Q

What does the epidural space contain?

A

Lymphatics, nerve roots, blood vessels, adipose and connective tissue.

40
Q

Which ascending tract conveys unconscious proprioception?

A

Spinocerebellar.

41
Q

Pain and temperature are transmitted along which ascending tract?

A

Spinothalamic.

42
Q

Name two subtypes of dorsal column tracts.

A

Cuneate fascilicus (Lateral) - arms
Gracile fascilicus (medial) - legs

43
Q

Where does the cuneate fascilicus and gracile fascilicus receive sensory information from?

A

Cuneate fascilicus - Arms
Gracile fascilicus - Legs

44
Q

The dorsal column ascends to which area of the body to decussate?

A

Medulla oblongata.

45
Q

Where does the first order neuron synapse with the second order neuron in the dorsal column?

A

In either the nucleus cuneatus or nucleus gracilis in the medulla.

46
Q

In the dorsal tract, where about in the medulla does the 2nd order neuron cross the midline?

A

Medial lemniscus.

47
Q

Which tract allows entry into the spinal cord from the dorsal root?

A

Tract of Lissauer.

48
Q

In the dorsal column, after the 2nd order neuron crosses the midline in the medulla, where does it ascend to?

A

Thalamus to synapse with the 3rd order neuron and then to the somatosensory cortex.

49
Q

What clinical presentation would suggest a lesion in the dorsal column?

A

Unilateral loss of proprioception or light touch below the level of the lesion, on the same side as the lesion (as wouldn’t have crossed midline yet).

50
Q

What conditions can cause loss to the dorsal column?

A

MS
B12 deficiency

51
Q

What problems can nitrous oxide cause in the spinal cord?

A

NO depletes B12, leading to lesions or loss of dorsal column = uni/bilateral somatosensory loss.

52
Q

In the spinothalamic tract, where does the first order neuron enter and go into?

A

Through the dorsal root via the tract of lissauer, into the dorsal horn of the grey matter to synapse with the second order neuron.

53
Q

Where does the spinothalamic tract cross the midline?

A

At its level of entry.

54
Q

In the spinothalamic tract, once the 2nd order neuron crosses the midline at the nerves level of entry, where does it ascend to?

A

The thalamus to synapse with the 3rd order neuron and into the somatosensory cortex.

55
Q

In the spinothalamic tract, which structure do neurons have to pass through, to get to the somatosensory cortex?

A

Internal capsule.

56
Q

What clinical presentation would suggest a lesion in the spinothalamic tract?

A

Loss of pain, temperature, or crude touch on opposite side of lesion (as it crosses midline at point of entry), below the level of lesion.

57
Q

What is a syrinx?

A

Where the central canal expands with CSF, and starts affecting the spinal tracts.
Arms usually affected first as they are most medial, then affects legs when it’s bigger.
Can be bilateral as starts in the middle and expands out.

58
Q

Which ascending tract is most likely to be affected by a syrinx?

A

Spinothalamic as it crosses the midline at the level of the syrinx.

59
Q

A syrinx can cause dissociated sensory loss. What is this?

A

Where there is loss of one type of modality but another modality is maintained.

60
Q

What information does the spinocerebellar tract transmit?

A

Unconscious proprioception and smooth motor control.

61
Q

Describe the pathway of the spinocerebellar tract.

A

1st order neuron enters dorsal root, synapses with 2nd order neuron and is then projected to cerebellum very quickly.
There is no crossing of the midline.

62
Q

How many neurons are involved in the spinocerebellar tract and why?

A

Only 2 - 1st and 2nd order neuron - speeds up response time.

63
Q

Where does the first order neuron in the spinocerebellar tract originate from?

A

Muscle spindles, Golgi tendon organs (posterior tract) or interneurons (anterior tract).

64
Q

The posterior and anterior spinocerebellar tract are located on which border of the spinal cord?

A

Lateral border.

65
Q

Descending tracts are involved in the control of what?

A

Movement.

66
Q

What descending tract controls voluntary movement?

A

The corticospinal tract of the pyramidal tract.

67
Q

What descending tract controls involuntary movement?

A

Extrapyramidal tract.

68
Q

The corticospinal tract works as a two neuron circuit. What are these two neurons?

A

Upper motor neuron
Lower motor neuron

69
Q

Where does the upper motor neuron originate and extend to?

A

The cerebral cortex to the anterior ventral horn.

70
Q

Where does the lower motor neuron originate and extend to?

A

The anterior ventral horn to the peripheral muscle.

71
Q

Describe the path of the corticospinal tract.

A

Cell bodies start in motor cortex, axon travels down internal capsule into brainstem then medulla. 80% cross in pyramids of medulla into the lateral corticospinal tract. 20% don’t cross and continue down anterior corticospinal tract. Synapse with LMN + tell muscles what to do.

72
Q

Lower motor neurons link the CNS to what type of muscle?

A

Skeletal muscle.

73
Q

Which motor neurons supply voluntary muscle?

A

Alpha motor neurons.

74
Q

Which motor neurons supply muscle spindles?

A

Gamma motor neurons.

75
Q

Which parts of the ventral horn supplies the trunk, proximal limb and distal limb?

A

Trunk - medial part
Proximal limb - anterolateral part
Distal limb - posterolateral part

76
Q

If a lesion is located in the corticospinal tract above the medulla, which side would be affected?

A

The opposite side as the fibres cross in the medulla.

77
Q

Is a lesion is located in the corticospinal tract below the medulla, which side would be affected?

A

Same side.

78
Q

What signs would suggest an upper motor nerve disorder?

A

Spasticity (increased muscle tone), brisk reflexes, weakness.
No muscle wasting.

79
Q

What can cause upper motor nerve disorders?

A

Stroke
Cord injury
Cord compression

80
Q

What signs would suggest a lower motor nerve disorder?

A

Flaccid paralysis (no/reduced muscle tone)
No tendon reflexes
Muscle atrophy

81
Q

Which conditions can lead to lower motor neuron problems?

A

Spinal muscular atrophy where the anterior horn cell degenerates.
Guillain-Barre syndrome
Injury

82
Q

Does motor neuron disease affect the upper or lower motor neurons?

A

Both.
There can be a combination of UMN/LMN signs e.g. wasting in arms (LMN) but same arm may be stiff (UMN).

83
Q

Where does the extrapyramidal tract originate?

A

In the brainstem.

84
Q

How many tracts are there within the extrapyramidal tract?

A

4

85
Q

What are the different tracts of the extrapyramidal tract and where do they originate?

A

Rubrospinal - red nucleus of midbrain
Reticulospinal - medullary reticular formation
Vestibulospinal - vesticular nuclei
Tectospinal - superior colliculus

86
Q

Where does the rubrospinal tract run and what is its role?

A

Runs from the red nucleus in the brain stem to the ventral horn.
Role is to facilitate the action of upper limb flexors and extensors.

87
Q

Which tracts of the extrapyramidal tract are medial?

A

Tectospinal
Vestibulospinal

88
Q

Where does the tectospinal tract run and what is its role?

A

Runs from the superior colliculus to the ventral horn.
Role is to modulate postural movement in response to visual stimuli.

89
Q

What is the role of the vestibulospinal tract?

A

To stabilise you when your head is tilted.

90
Q

What is Brown Squared syndrome?

A

Where there is loss of one half of the spinal cord.

91
Q

Do extrapyramidal tracts pass through the pyramids in the medulla?

A

No

92
Q

How would brown sequard syndrome affect the ascending and descending tracts?

A

Spinothalamic tract (pain + temp) - opposite side of spinal cord loss affected as tract crosses cord at point of entry.
Dorsal column (proprioception) - same side of spinal cord loss affected as tract enters spinal cord and ascends on the same side up to medulla.
Corticospinal tract (voluntary movement - strength) - below lesion, same side weakness as tract crosses medulla then travels down same side.
LMN affected at site of lesion (loss of sensation at lesion site) as anterior horn cells in grey matter affected.

93
Q

Describe the afferent pathway of a stimulus being received by the dorsal column tract.

A

Proprioceptive/light touch stimulus received, cell body of 1st order in dorsal root ganglion, axon enters spinal cord via tract of lissauer, enters dorsal horn and exits via the dorsal tract (inc cuneate fascilius and gracile facilius) - travels up to medulla, synapses with 2nd order neuron, crosses midline (medial lemniscus) and travels to thalamus - synapses with 3rd order neuron and travels to somatosensory cortex.

94
Q

Describe the afferent pathway of a stimulus being received by the spinothalamic tract.

A

Pain / temp stimulus received by 1st order neuron, enters dorsal root via tract of lissauer, enters dorsal horn and synapses with 2nd order neuron (anterior white commissure) and then travels to the thalamus where it synapses with a 3rd order neurone and travels through the internal capsule to the somatosensory cortex.

NSB Lectures (48 decks)

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