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632: Neuroanatomy-Neuroscience > Spinal Region > Flashcards

Spinal Region Flashcards

1
Q

What does the spinal region include?

A
  • spinal cord
  • dorsal and ventral roots
  • spinal nerves
  • meninges
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2
Q

What are rootlets?

A

small groups of axons sending information to the periphery

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3
Q

The ventral root is the coalescence of what?

A

ventral rootlets

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4
Q

What does the dorsal root contain?

A

sensory axons bringing information into the spinal cord

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5
Q

Connections of nerve rootlets to the exterior of the cord indicate what?

A

segments

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6
Q

What do spinal nerves carry?

A

all motor and sensory axons of a single spinal segment

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7
Q

In the cervical region, spinals nerves are found ____ the corresponding vertebrae, except for which one?

A

above

except for the 8th spinal nerve (C8 is in between C6-C7)

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8
Q

In the thoracic and lumbar regions, spinals nerves are found ____ the corresponding vertebrae.

A

below

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9
Q

Describe the arrangement of white and gray matter in the spinal cord

A

White matter surrounds gray matter and contains axons that link the cord with the brain.

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10
Q

What does the dorsal horn of the spinal cord process?

A

sensory information

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11
Q

What does the lateral horn of the spinal cord process?

A

autonomic information

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12
Q

The lateral horn is present at what spinal levels?

A

T1-L2

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13
Q

What does the ventral horn of the spinal cord process?

A

motor information

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14
Q

What is the majority of gray matter composed of?

A

spinal interneurons

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15
Q

Gray matter is classified into 10 histologic regions, called what?

A

Rexed’s laminae (I-X)

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16
Q

Functionally, what do Laminae I and II process?

A

pain information

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17
Q

What are meninges?

A

layers of connective tissue that surround the spinal cord

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18
Q

What are the 3 meninges from internal to external?

A
  • Pia mater
  • Arachnoid
  • Dura mater
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19
Q

Do physiologic motions significantly change the vertebral canal space in people with normal vertebral canals?

A

No

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20
Q

What does extending and/or lateral bending of the neck do to cervical levels?

A

increases the intervertebral foramen pressure

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21
Q

What is the function of the spinal cord?

A
  • To convey information between the neurons innervating peripheral structures and the brain
  • To process and modify information within the cord through synapses
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22
Q

What are interneurons categorized by?

A

function

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23
Q

By integrating volleys of peripheral, ascending, and descending inputs, spinal circuitry provides what 3 things?

A
  • Modulation of sensory information
  • Coordination of movement patterns
  • Autonomic regulation
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24
Q

What do interneuronal circuits do?

A

integrate activity from all sources and adjust the output of lower motor neurons

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25
Q

What do interneurons coordinate?

A

activity in all the muscles when a limb moves

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26
Q

What determines whether a single alpha motor neuron will fire?

A

Summation of activity at 20,000 to 50,000 synapses

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27
Q

What are Stepping Pattern Generators?

A

adaptable neural networks that produce rhythmic output

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28
Q

How do SPGs contribute to stepping?

A

by activating lower motor neurons, eliciting alternating flexion and extension at the hips and knees

29
Q

When are SPGs normally activated?

A

when the person voluntarily sends signals from the brain to the stepping pattern generators (SPGs) in the spinal cord to initiate walking

30
Q

Describe the basis behind Stepping Pattern Generator function

A

1) Firing the UMN initiates cycles of activity in the SPG.
2) SPG neuron 1 activates extensor motor neurons that signal extensor muscles to contract.
3) Collaterals from neuron 1 synapse with an inhibitory interneuron (neuron 2), which inhibits neuron 3.
4) When this interneuron fatigues, neuron 3 can begin firing, which activates flexor motor neurons that signal flexor muscles to contract.
5) Collaterals from neuron 3 synapse with an inhibitory interneuron (neuron 4), which inhibits neuron 1.
6) When this interneuron fatigues, neuron 1 resumes firing.

31
Q

Can patients with a complete SCI elicit stepping-like movements?

A

Yes, by electrically stimulating the posterior spinal roots

32
Q

When walking, electrical stimulation to a single point on the foot produces different responses, depending on what?

A

the phase of the gait cycle

33
Q

If the electrical stimulus occurs at the onset of swing phase, which muscle activity increases?

A

tibialis anterior

34
Q

If the electrical stimulus occurs at the end of swing phase, which muscle activity increases and which decreases?

A

tibialis anterior activity decreases and antagonist muscle activity increases

35
Q

All spinal reflexes involve interneurons except for which one?

A

The monosynaptic phasic stretch reflex

36
Q

Which reflex demonstrates the capacity of interneuronal circuits to generate complex movements?

A

Withdrawal reflex

37
Q

What can elicit a withdrawal reflex?

A

Afferent information from skin, muscles, and/or joints

38
Q

The specificity of the movement pattern associated with the withdrawal reflex is referred to as what?

A

a local sign, which indicates that the response depends on the site of the stimulation

39
Q

What reflex is activated if a person is standing when a lower limb is abruptly withdrawn, another interneuronal circuit quickly adjusts the muscle activity in the stance limb to prevent the person from falling?

A

Crossed extension reflex

40
Q

What do interneurons in inhibitory circuits contribute to?

A

spinal cord motor coordination

41
Q

What 2 things do inhibitory interneurons provide?

A
  • Reciprocal inhibition

- Recurrent inhibition

42
Q

What does reciprocal inhibition do?

A

Decreases activity in antagonist when an agonist is active, allowing the agonist to act unopposed. This prevents unwanted activity of the antagonists.

43
Q

_____ inhibition separates muscles into agonists and antagonists.

A

Reciprocal

44
Q

Recurrent inhibition _____ agonists and synergists, and _____ antagonists.

A

inhibits

disinhibits/facilitates

45
Q

What type of interneuron cells produce recurrent inhibition?

A

Renshaw cells

46
Q

What stimulates Renshaw cells?

A

a recurrent collateral branch from the alpha motor neuron

47
Q

What do Renshaw cells inhibit and facilitate?

A

They inhibit agonists and synergists and facilitate agonists

48
Q

How do Renshaw cells isolate desired motor activity from gross activation?

A

By focusing motor activity

49
Q

What does a loss of descending influence on Renshaw cell activity cause?

A

difficulty in achieving fine-motor control

50
Q

A lesion in the spinal region may interfere with what 3 things?

A
  • Segmental function
  • Vertical tract function
  • Both segmental and vertical tract function
51
Q

What do segmental lesions interfere with?

A

neural function only at the level of the lesion

52
Q

What do segmental signs of dysfunction include?

A

abnormal or lost sensation in a dermatomal distribution and/or LMN signs in a myotomal distribution

53
Q

What do lesions interrupting vertical tracts result in?

A

a loss of function below the level of the lesion

54
Q

Ascending tract lesions result in what?

A

problems with the regulation of blood pressure, sweating, and bladder and bowel control.

55
Q

Descending tract lesions result in what?

A
  • paralysis
  • spasticity
  • muscle hypertonia
  • Babinski’s sign present
56
Q

All signs of damage to vertical tracts occur ____ the level of the lesion.

A

below

57
Q

What 3 things do peripheral nerve lesions cause?

A
  • Altered or lost sensation in a peripheral nerve distribution
  • Decrease or loss of muscle power in a peripheral nerve distribution
  • No vertical tract signs
58
Q

What 3 things do segmental spinal region lesions cause?

A
  • Altered or lost sensation in a dermatome
  • Decreased or lost muscle power in a myotome
  • Decreased or lost phasic stretch reflex
59
Q

What 3 things do vertical spinal region lesions cause?

A
  • Altered or lost sensation below the level of the lesion
  • Altered or lost descending control of BP, pelvic viscera, and thermoregulation
  • UMN signs
60
Q

What are the 4 characteristics of an UMN lesion?

A
  • Decrease or loss of muscle power
  • Spasticity
  • Muscle hypertonia
  • Positive Babinski’s sign and clonus
61
Q

What is a syndrome?

A

a collection of signs and symptoms that do not indicate a specific cause

62
Q

What are examples of syndromes resulting from tumors or trauma in the spinal region?

A
  • Anterior cord syndrome
  • Central cord syndrome
  • Brown-Séquard syndrome
  • Cauda equina syndrome
  • Tethered cord syndrome
63
Q

What does anterior cord syndrome interfere with?

A

pain and temperature sensation and motor control

64
Q

What does central cord syndrome result in? (small lesion)

A

loss of pain and temperature at the level of the lesion

65
Q

What does central cord syndrome result in? (large lesion)

A

Impairment of upper limb motor function

66
Q

What does Brown-Séquard syndrome result in?

A
  • Ipsilateral loss of voluntary motor control, conscious proprioception, and discriminative touch below the level of the lesion
  • Contralateral loss of pain and temperature sensation below the level of the lesion
67
Q

What does Cauda equina syndrome cause?

A

sensory impairment and flaccid paresis or paralysis of lower limb muscles, bladder, and bowels

68
Q

What does Tethered cord syndrome cause?

A
  • low back and lower limb pain
  • difficulty walking
  • excessive lordosis
  • scoliosis
  • problems with bowel and/or bladder control
  • foot deformities

632: Neuroanatomy-Neuroscience (26 decks)

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