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NBB1 > Somatosensory Pathways > Flashcards

Somatosensory Pathways Flashcards

1
Q

What is meant by negative symptoms?

A

Loss of sensation

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2
Q

What is meant by positive symptoms?

A

Abnormal sensory phenomenon

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3
Q

Define analgesia.

A

Loss of pain

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4
Q

Define anesthesia.

A

Loss of touch

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5
Q

Define paresthesia.

A

Temporary mild pain (pins and needles, tingling, burning, prickling)

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6
Q

Define neuropathic pain/central pain syndrome.

A

Chronic intense pain (shooting, stabbing or electric shock like jolts”

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7
Q

What four areas contribute to encoding of elementary sensory attributes?

A

Modality
Intensity
Timing
Location

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8
Q

What is modality?

A

subsystem for processing different kinds of stimuli or the nature of sensory loss

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9
Q

What does the dorsal column-medial lemniscus system transmit?

A

Sensory: vibration, joint position, fine touch

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10
Q

What is the site of decussation of the DCMLS?

A

Internal arcuate fibers (lower medulla)

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11
Q

What does the spinothalamic tract transmit?

A

Sensory: pain, temperature, crude touch

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12
Q

Where does the spinthalamic tract decussate?

A

Anterior commissure (spinal cord)

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13
Q

Why do we have parallel pathways in the spinal cord?

A
  1. Redundancy/reliability

2. Increase speed to the cortex (multiple train line analogy)

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14
Q

What do DCMLS and STT have in common?

A
  1. receptors throughout body
  2. use sensory DRG as 1 neuron
  3. 3 neurons w/ 2 relay points
  4. cross over to contralateral side
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15
Q

How are DCMLS and STT different?

A

1 Types of receptors

2 Morphology of DRG

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16
Q

What is intensity?

A

Strength of stimulus

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17
Q

What is sensory threshold?

A

Lowest stimulus strength a subject can detect

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18
Q

How is sensory threshold determined?

A

Determined by lowest sensitivity of receptors

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19
Q

How does a slowly adapting receptor work?

A

Tonic: detect static qualities of stimulus

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20
Q

How does a rapidly adapting receptor work?

A

Phasic: detects dynamic qualities of stimulus

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21
Q

How does the two point discrimination test work?

A

Minimal interstimulus distance required to perceive two simultaneously applied stimuli as distinct

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22
Q

What 3 factors affect resolution of sensory attributes?

A

1 receptor diversity
2 receptive field
3 inhibitory mechanisms

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23
Q

What is the receptive field and how does it determine resolution?

A

The region in sensory space within a which a specific stimulus elicits the greatest action potential response

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24
Q

What is a dermatome?

A

Area of skin innervated by a single dorsal root

25
Q

What causes an overlaps of dermatomes?

A
  1. Axons makes up a dorsal root originate from several different peripheral nerves
  2. Individual peripheral nerves contribute axons to adjacent dorsal roots
26
Q

What is the order of cutaneous mechanoreceptors from surface of the skin inward?

A

Meissner
Merkel cell
Ruffini corpuscle
Pacinian corpuscle

27
Q

What is the function of Meissner corpuscle?

A

Detects surface, motion

28
Q

What is the function of a Merkel cell?

A

Detect edges, indentation

29
Q

What is the function of a a Ruffini corpuscle? How is it aligned?

A

detects skin stretch

With stretch lines

30
Q

What is the function of a Pacinian corpuscle?

A

vibration sense

31
Q

What is the morphology of a Pacinian corpuscle?

A

Deep and with onion like layers

32
Q

What is the pathway of the DCMLS?

A

Lumbar (lower body) – gracile tract
Cervical (upper body) – cuneate tract
Caudal medulla: relay point 1: dorsal column nuclei
Decussate to internal arcuate fibers
Rostral medulla, mid pons, midbrain
Ventral posterior lateral nucleus of thalamus: relay point 2
To primary somatic sensory cortex / postcentral gyrus

33
Q

What is the pathway of the trigeminal mechanosensory system?

A

Trigeminal ganglion
Principal nucleus of trigeminal complex (mid-pons): Relay point 1
Decussate across medial lemniscus
Ascends through midbrain
Ventral posterior medial nucleus of thalamus: relay point 2
Terminates: primary somatic sensory cortex

34
Q

What does the trigeminal mechanosensory system relay?

A

Touch and vibration information from face to cortex

35
Q

Why does the spincerebellar tract have large diameter sensory neurons?

A

1 receptor goes to multiple endpoints

36
Q

What is the spinocerebellar tract’s function?

A

Proprioception for the cerebellum

37
Q

How do lesions of the spinocerebellar tracts present?

A

Ipsilateral loss of muscle coordination

BUT: unlikely to be damaged in isolation.

38
Q

What are two ways that the dorsal columns or spinocerebellar tract can be damaged?

A
  1. Tabes Dorsalis (tertiary syphilis)

2. Subacute combined degeneration caused by B12/vit E deficiency

39
Q

What is the Romberg test?

A

tests stability and vision, particularly balance

40
Q

What is the somatotopic organization of DCMLS in the spinal cord?

A

(medial) leg –> arm –> neck –> occiput (lateral)

41
Q

What is the somatotopic organization of DCMLS in the medulla?

A

Upper limb: posterior

Lower limb: anterior

42
Q

What is the somatotopic organization of DCMLS in the midbrain?

A

Upper limb: medial

Lower limb: lateral

43
Q

How do the somatosensory and motor humunculus’ relate to each other?

A

They parallel each other

44
Q

Which receptors are located in the epidermis?

A

Free nerve endings
Meissner corpuscle
Merkel cell

45
Q

Which receptors are located in the dermis?

A

Ruffini corpuscle

46
Q

Which receptors are located in the dermis/subQ layer?

A

Pacinian corpuscle

47
Q

How many types of receptors can a thermoreceptive neuron have?

A

Only ONE!

48
Q

When do cold and warm receptors fire?

A

During changes of temperature and someone tonically at baseline

49
Q

What is the pathway of the spinothalamic system for discriminative aspects of pain and temperature in the body?

A

Lower body: Lissauer’s tract –> lumbar spinal cord
Upper body –> cervical spinal cord
Relay point 1 in dorsal horn
Decussates at segmental levels: takes 2 levels to traverse!
Anterolateral system: medulla (with anterolateral tract), pons, midbrain (with spinothalamic tract)
Relay point 2 at ventral posterior lateral nucleus of thalamus
Endpoint: Primary somatic sensory cortex

50
Q

What is the pathway for discriminative aspects of pain and temperature in the face?

A
  1. Mid pons: trigeminal ganglion enters
  2. Spinal trigeminal tract descends to caudal medulla and middle medulla
  3. Relay point 1: caudal medulla and middle medulla and DECUSSATES here
  4. Rises through middle medulla, mid-pons and midbrain
  5. Relay point 2: ventral posterior medial nucleus of the thalamus
  6. Terminates at Cerebrum
51
Q

What is the somatotopic orientation of the anterloateral system of the spinothalamic tract?

A

Ventral side

Neck: lateral —> leg medial

52
Q

What is the blood supply trend to the DCMLS and STT?

A

Caudal: anterior/posterior spinal artery
Cranial: PICA, AICA, vertebral

53
Q

What is Brown-Sequard syndrome?

A

Hemisection on the left side of the spinal cord at C5

Results in pain/temp from R side of body, touch/proprioception/vibration from L side of body

54
Q

Why does an individual experience a phantom limb? What is the result?

A

Reorganization of somatosensory cortex occurs in amputees so that neurons that used to be innervated by limb now respond to stimulation of other body parts

55
Q

What has shown to be the best treatment for phantom limb pain?

A

Mirror therapy

56
Q

What causes subacute combined degeneration?

A

Caused by B12/vit E deficiency:

57
Q

What are the symptoms of subacute combined degeneration?

A

demyelination causes:
ataxic gait
paresthesia
impaired position and vibration sense

58
Q

What causes Tabes Dorsalis?

A

tertiary syphilis infection: degeneration causes impaired sensation, proprioception and progressive sensory ataxia

59
Q

What are the symptoms of Tabes Dorsalis?

A

impaired sensation.
proprioception,
progressive sensory ataxia

NBB1 (16 decks)

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