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CNS Anatomy > Sheet 2 > Flashcards

Sheet 2 Flashcards

1
Q

Where is the spinal cord located?

A

Within the vertebral canal

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2
Q

Where does the spinal cord start and end?

A

It starts from the foramen magnum (occipital bone) and decends to end at the intervertebral disc L1/L2.

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3
Q

The spinal cord is slightly flattened ___.

A

Anteriorly and posteriorly

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4
Q

What is the length of the average adult’s spinal cord?

A

42-45cm.

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5
Q

Is the spinal cord uniform in diameter? Why or why not?

A

No, because we have two enlargements that give rise to plexuses to supply the upper and lower limbs.

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6
Q

What are the two enlargements in the spinal cord?

A

1) Cervical enlargement: Supplies the upper limbs (Brachial plexus (C5-C8 & T1))
2) Lumbar enlargement: Supplies the lower limbs (Lumbosacral plexus)

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7
Q

Are the spinal nerves motor, sensory, or mixed?

A

Mixed.

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8
Q

The number of segments =

A

The number of nerves

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9
Q

The number of segments does NOT =

A

The number of vertebrae

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10
Q

Why does the segment not correspond to the location of its vertebrae?

A

Because the growth of bone bypasses the growth of the spinal cord, so the spinal cord will occupy 2/3 of the canal

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11
Q

What does the lower 1/3 of the vertebral canal contain?

A

Lower spinal nerves called Cauda equina (horsetail appearance).

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12
Q

Why does the Cauda equina have longer roots?

A

Because the origin of spinal nerve extends inferiorly from conus medullaris.

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13
Q

How many vertebral bones is the average person born with?

A

33

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14
Q

How many vertebral bones does the average adult have? Why?

A

24, because the bottom vertebrae fuse together during normal growth and development.

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15
Q

What is the conus medullaris?

A

The tapered inferior end (conical structure) of the spinal cord.

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16
Q

What are the meninges?

A

The connective tissues that cover the spinal cord

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17
Q

What are the three meninges of the spinal cord?

A

1) Dura mater
2) Arachnoid mater
3) Pia mater

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18
Q

What is the outermost meninge layer of the spinal cord? What does it line?

A

The dura mater; the bony canal (closest to the bone)

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19
Q

The dura mater is continuous with:

A

The epineurium of the spinal nerves

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20
Q

What kind of connective tissue is the dura mater?

A

Dense irregular

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21
Q

Where does the dura mater begin and end?

A

It begins at the level of the foramen magnum and extends to end at the level of S2.

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22
Q

What is the closed end of the dura mater caudally called? What does it do?

A

Filum Terminale Externum; it is a connective tissue that anchors the dura mater to the coccyx bone.

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23
Q

What is the Arachnoid Mater attached to?

A

The inner aspect of the Dura Mater (there is no true space between them)

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24
Q

What is the Arachnoid Mater made of?

A

Thin web-like arrangement of delicate collagen and some elastic fibers.

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25
Q

Where does the Arachnoid Mater end?

A

The level of S2.

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26
Q

Which meningeal is found in the inner most layer?

A

Pia Mater

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27
Q

What does the pia mater do?

A

It is a thin transparent connective tissue layer that adheres to the surface of the spinal cord and brain.

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28
Q

Where does the Pia Mater end?

A

At the level of L1-L2 (since it is firmly attached to the spinal cord = end together)

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29
Q

What is the Filum Terminale Internum? What does it do?

A

The connective tissue at the caudal end of the Pia Mater; Anchors spinal cord to coccyx bone.

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30
Q

Filum Terminale Externa is to Dura Mater as the Filum Terminale Interna is to ____.

A

Pia mater

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31
Q

Filum Terminale Externum ____(directly/indirectly) and Internum ____(directly/indirectly) anchor the spinal cord to the coccyx.

A

Directly; indirectly

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32
Q

What do both Filum Terminale do?

A

Provide stability and protection within the vertebral canal.

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33
Q

What are the extensions from the Pia Mater called?

A

Denticulate ligaments

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34
Q

What does the denticulate ligament do?

A

Attaches the spinal cord to the arachnoid Mater and inner aspect of the Dura Mater + provides stability.

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35
Q

What are the 3 spaces of the spinal cord?

A

1) Epidural (Extradural/Outside the dura)
2) Subarachnoid
3) Subdural

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36
Q

What is the epidural space?

A

Space between the dura mater and the wall of the vertebral canal.

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37
Q

Which spinal cord space is filled with fat?

A

The epidural space

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38
Q

In which space is anesthesia used for labor pain injected?

A

The epidural space

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39
Q

What is the subdural space?

A

The space between the dura mater and the arachnoid mater. (Not a true space)

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40
Q

Which space is NOT a true space?

A

The subdural space

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41
Q

What does the subdural space contain?

A

Serous fluid

42
Q

What is the subarachnoid space?

A

The space between the pia mater and the arachnoid mater.

43
Q

Which is the most important spinal space and why?

A

The subarachnoid, because major blood vessels supplying the CNS pass through this space and because it has physiological functions related to temperature, protection…etc.

44
Q

Which space is filled with cerebrospinal fluid (CSF)?

A

The subarachnoid space.

45
Q

Where does the CSF circulate?

A

1) Brain ventricles
2) Central canal of the spinal cord
3) Subarachnoid space

46
Q

From the __ ventricle, the CSF passes into the subarachnoid space through 4 openings:

A

1) The central canal of the spinal cord
2&3) Two lateral apertures (Foramina of Luschka)
4) One median aperture (Foramen of Magendie)

47
Q

How do we take a sample of CSF?

A

Using a lumbar puncture (Spinal tap)

48
Q

What is the CSF diagnostic for?

A

It is diagnostic for infections, bleeding, and changes in CSF pressure.

49
Q

Where is lumbar puncture generally safe? Why?

A

Anywhere between L2-S2, because there is no spinal cord there.

50
Q

Where is the lumbar puncture more specifically done? Why?

A

Between L3-L4 at the level of the anatomical plane (Supracristal line), because the space is wider and there is no spinal cord.

51
Q

What is a segment?

A

The place where the spinal neve emerges from.

52
Q

Where exactly will the spinal nerve emerge from?

A

BELOW the corresponding vertebra through the intervertebral foramen, (T7 emerges from under the T7 vertebra) EXCEPT for cervical nerves which emerge ABOVE the corresponding vertebra (C8 emerges between C7 and T1 vertebra).

53
Q

The segments of the spinal cord are not in line with ____, and the difference increases as you go ___ (up/down).

A

The corresponding vertebrae; down.

54
Q

The nerve roots ___ (increase/decrease) with length as they go ___(up/down).

A

increase; down.

55
Q

Why does the spinal cord only fill 2/3 of the canal?

A

During early development, it fills the entire canal. However, as we grow older, the bony growth overrides the spinal cord growth, causing a space between them.

56
Q

What is a herniated disc?

A

A protrusion (leakage) of the gelatinous nucleus pulposus through the anulus fibrosus of an intervertebral disc.

57
Q

What is a herniated disc usually the result of?

A

Heavy weight pressuring these discs.

58
Q

Where is the annulus fibrosus thinnest and weakest?

A

Posterolaterally

59
Q

In which direction would the herniated disc leak?

A

Posterolaterally

60
Q

95% of herniated discs are between:

A

L4/L5 or L5/S1

61
Q

When do the symptoms of herniated discs start?

A

When the herniated disc compresses the spinal nerve.

62
Q

What is a dermatome?

A

Area of skin that is mainly supplied by one spinal nerve

63
Q

What is a myotome?

A

Group of muscles that one spinal nerve innervates.

64
Q

Give an example of a myotome.

A

The biceps; innervated by C6 (Musculocutaneous nerve)

65
Q

When a nerve is compressed by a herniated disc, we’ll see ___(abnormal sensation/weakness) in the myotome, and ____(abnormal sensation/weakness) in the dermatome supplied by this nerve.

A

weakness; abnormal sensation

66
Q

Why are both the myotome and dermatome affect by herniated discs?

A

Because every spinal nerve has a sensory and motor part.

67
Q

Which reflex is affected by the L3-L4 herniated disc?

A

Knee jerk

68
Q

Which reflex is affected by the L4-L5 herniated disc?

A

Hamstring jerk

69
Q

Which reflex is affected by the L5-S1 herniated disc?

A

Ankle jerk (Achilles tendon)

70
Q

What are the areas of the body that experience sensory changes from the L3-L4 herniated disc?

A

Anteromedial leg (Saphenous)

71
Q

What are the areas of the body that experience sensory changes from the L4-L5 herniated disc?

A

1) Big toe

2) Anteromedial leg (CPN-Common Peroneal Nerve)

72
Q

What are the areas of the body that experience sensory changes from the L5-S1 herniated disc?

A

Lateral border of foot (Sural)

73
Q

What is the root of an L3-L4 herniated disc?

A

L4

74
Q

What is the root of an L4-L5 herniated disc?

A

L5

75
Q

What is the root of an L5-S1 herniated disc?

A

S1

76
Q

Which is the most common herniated disc?

A

L5-S1

77
Q

What is the percentage of L5-S1 herniated disc cases?

A

45-50%

78
Q

What is the percentage of L4-L5 herniated disc cases?

A

40-45%

79
Q

What is the percentage of L3-L4 herniated disc cases?

A

3-10%

80
Q

What movements are weakened due to the L3-L4 herniated disc? (Motor weakness)

A

Knee extension (Quadriceps femoris)

81
Q

What muscle movements are weakened due to the L4-L5 herniated disc? (Motor weakness)

A

Big toe dorsiflexion (EHL-External Hallucis Longus) and (TA-Tibialis Anterior)

82
Q

What movements are weakened due to the L5-S1 herniated disc? (Motor weakness)

A

Foot plantar flexion (Gastrocnemius)

83
Q

What is reflex affected?

A

A test used to indicated the location of the injury.

84
Q

How do you test L5?

A

By asking the patient to stand on his heels (Dorsiflexion)

85
Q

How do you test S1?

A

By asking the patient to stand on his tiptoes (Plantar flexion)

86
Q

What is the major symptom of a herniated disc?

A

Lower back pain radiating to the gluteal region, the back of the thigh, and the back of the leg.

87
Q

Spinal nerves give a _____ that brings sensation from the ___, which is sensitive to ___.

A

meningeal branch (recurrent); dura mater; stretch.

88
Q

Why does a herniated disc compressing the spinal nerve and its meningeal branch cause diffused pain or numbness?

A

Due to overlapping dermatomes.

89
Q

What is the Straight Leg Raise Test (SLR)?

A

Pulling of the sciatic nerve (L4-S3) and pressure on the nerve root by flexing the hip joint while extending the knee.

90
Q

Which test is commonly used to check for a herniated disc?

A

Straight Leg Raise Test (SLR)

91
Q

What can confirm the diagnosis of a herniated disc?

A

An MRI

92
Q

The spinal cord is divided into:

A

1) Gray matter

2) White matter

93
Q

The spinal white matter is divided into:

A

1) Lateral column/funicului
2) Posterior column/funicului
3) Anterior column/funicului

94
Q

What does the spinal white matter consist of?

A

Neuronal dendrites and axons

95
Q

The spinal white matter has:

A

1) Anterior median fissure: A wide groove on the anterior aspect (deeper than the sulcus)
2) Posterior median sulcus: A narrow groove on the posterior aspect.

96
Q

What does the spinal gray matter consist of?

A

Neuronal cell bodies, dendrites, axons.

97
Q

The spinal gray matter has:

A

1) Posterior (Dorsal) horn: Collection of neuronal cell bodies of the sensory system
2) Anterior (Ventral) horn: Collection of motor neuronal cell bodies of skeletal muscles
3) Lateral (Autonomic) horn: Collection of preganglionic motor cell bodies (to involuntary muscles).

98
Q

In which segments does the Lateral horn not exist?

A

1) Thoracic segments
2) L1-L2
3) Sacral segments

99
Q

What does the center of the gray horn contain?

A

A central canal which contains the CSF

100
Q

What is the central canal of the gray horn linked to?

A

The 4th ventricle in the brain

101
Q

The white matter in the CNS is called:

A

Tracts

102
Q

The spinal tracts are divided according to:

A

The direction of the signal:

1) Ascending (sensory)
2) Descending (motor)

CNS Anatomy (19 decks)

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