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Neurobiology II > Somatosensation (Exam 1) > Flashcards

Somatosensation (Exam 1) Flashcards

1
Q

what is superficial sensation?

A
  • Exteroreceptors: received information from the environment through the skin and subcutaneous tissue
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2
Q

What is deep sensation?

A

Proprioceptors: receive stimuli from muscles, tendons, ligaments, joints & fascia

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3
Q

What is cortical sensation?

A
  • Combination of superficial and deep sensory mechanisms
  • Require information from exteroreceptors and proprioceptors as well as intact function of the cortical sensory association areas
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4
Q

What sensations make up our primary somatosensory?

A
  • Superficial Sensation
  • Deep Sensation
  • Includes touch, pain, temperature, vibration & proprioception
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5
Q

What is included in cortical sensation?

A
  • Grapesthesia, stereognosis & tactile extinction
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6
Q

What is grapesthesia?

A

Ability to sense letter, number or symbol drawn into hand or body without seeing it

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7
Q

What is stereognosis?

A

Perception of the sense of the object

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8
Q

What is tactile extinction?

A
  • Seen in neglect of one side
  • One side over powers the other one, when you are touching both sides the individual can only feel one side
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9
Q

If sensory loss due to injury of a peripheral nerve occurs what will be seen?

A
  • Follow distribution for that specific nerve
  • Impact all sensory modalities
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10
Q

What is a dermatome?

A

Area of skin innervated by a dorsal nerve root

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11
Q

How will a lesion to a single nerve root present as?

A

Diminished not absent sensation

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12
Q

What type of fibers result in greater cortical representation?

A

Higher density which are more distal

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13
Q

What are mechanoreceptors?

A

Respond to mechanical deformation of the receptor by touch, pressure, stretch or vibration
- Deep receptors: proprioception, tendon tension

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14
Q

What are thermoreceptors?

A

Respond to heat or cold

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15
Q

What are nociceptors?

A

Sensitive to stimuli that damage or threaten to damage tissue

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16
Q

What do Ia, Ib axons target?

A
  • Muscle spindle
  • Golgi Tendon Organ
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17
Q

What do II axon target?

A
  • Muscle spindle
    -Merkel’s receptor, Meissner’s Corpuscle
  • Pacinian Corpuscle, Ruffini ending, hair receptor
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18
Q

What do III & IV axon target?

A

Free (bare) nerve endings

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19
Q

What are the sensory receptors for proprioception?

A

Muscle spindle
Golgi Organ Tendon

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20
Q

What are the sensory receptors for pressure, vibration, & fine touch?

A
  • Merkel’s receptor
  • Meissner’s Corpuscle
  • Pacinian Corpuscle
  • Ruffini ending
  • hair receptor
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21
Q

What are the sensory receptor for pain, temperature and touch?

A

Free (bare) nerve endings

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22
Q

What axon type conveys the modality of pain, temperature (COOL) and itch?

A

III

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23
Q

What axon type conveys the modality of pain, temperature (WARM) and itch?

A

IV

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24
Q

What is the order of axon diameter from largest to small?

A
  • Ia
  • Ib
  • II or A beta
  • III or A delta
  • IV or C
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25
Q

What is the general anatomic arrangement for a first order neuron?

A

Action potential in sensory receptors are triggered
- From sensory receptors (skin & musculoskeletal) to spinal cord

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26
Q

What is the general anatomic arrangement for a second order neuron?

A

Spinal cord to thalamus

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27
Q

What is the general anatomic arrangement for a third order neuron?

A

From thalamus to cerebral cortex

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28
Q

Where are somatosensory first order neurons located?

A

Dorsal root ganglion

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29
Q

What is afferent neuron has distal axon conducts signal from receptor to cell body and proximal axon conducts signal from cell body to spinal cord?

A

Pseudounipolar

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30
Q

What does the dorsal column- medial lemniscal pathway convey?

A

-Proprioception, Vibration & fine discriminative touch
- Conscious

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31
Q

What does the anterolateral pathway convey?

A
  • Pain, temp sense & crude touch
  • Conscious
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32
Q

What does spinocerebellar pathways convey?

A
  • Information from proprioceptors & interneurons to cerebellum
  • Unconscious
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33
Q

Conscious Somatosensory Pathway first order neuron includes?

A
  • Sensory neuron
  • Cell body in dorsal root ganglion
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34
Q

Conscious Somatosensory Pathway what occurs during the second order neuron?

A
  • Synapse with 1st order neuron in spinal cord or brainstem
  • Crosses
  • Carries info to thalamus
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35
Q

Conscious Somatosensory Pathway: What occurs during 3rd order neuron?

A

Carries information from thalamus to cortex

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36
Q

Describe the axons involved in Dorsal column- medial lemniscal pathway?

A
  • Large diameter, myelinated axons
  • Ia, Ib, II
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37
Q

Dorsal Column - Medial Lemniscal Pathway: 1st order neuron
Where is the cell body located?
Where do the axons enter spinal cord?

A
  • Dorsal root ganglion
  • Via the dorsal root
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38
Q

Dorsal Column - Medial Lemniscal Pathway: 1st order neuron
When axons enter the spinal cord where do go from there?

A
  • Enter ipsilateral dorsal column and ascend to medulla via either Fasciculus gracilis or cuneatus
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39
Q

When is fasciculus gracilis used?

A

Sensory information comes from LE & trunk

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40
Q

When is fasciculus cuneatus used?

A

Upper trunk (T6), arms & neck

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41
Q

Dorsal Column - Medial Lemniscal Pathway: 2nd order neuron
- Where does the synapse occur between 1st & 2nd order neuron?

A

Caudal medulla in either Nucleus gracilis or cuneatus

42
Q

Dorsal Column - Medial Lemniscal Pathway
- Axons of 2nd order neurons decussate as?

A

Internal arcuate fibers in the medulla

43
Q

Dorsal Column - Medial Lemniscal Pathway: 2nd order neuron
- After the decussation where do axons ascend and as what?

A
  • Ascend through brainstem as medial lemniscus on contralateral side to thalamus
44
Q

Dorsal Column - Medial Lemniscal Pathway:
- Where does synapse between 2nd & 3rd order neuron occur?

A
  • Located in the the ventral posterior lateral (VPL) nucleus of the thalamus
45
Q

Dorsal Column - Medial Lemniscal Pathway: 3rd order neuron
- After the synapse what happens next?

A
  • Projects in thalamic somatosensory radiations through the posterior limb of the internal capsule
46
Q

Where does the Dorsal Column- Medial Leminscal pathway terminate?

A

Primary somatosensory cortex (areas 3, 1 and 2) in post central gyrus

47
Q

What is the somatic organization of the spinal cord?

A
  • LE medial
  • UE lateral
48
Q

What is the somatic organization of the medulla?

A
  • LE ventral
  • UE dorsal
49
Q

What is the somatic organization of the pons/midbrain?

A
  • LE lateral
  • UE medial
50
Q

What is the somatic organization of the somatosensory cortex?

A
  • LE medial
  • UE lateral
51
Q

What is the trigeminal lemniscus?

A
  • Analogous pathway conveys touch sensation for the face
52
Q

Where does the trigeminal lemniscus pathway synapse?

A

Ventral posterior medial (VPM) nucleus of the thalamus

53
Q

What does anterolateral pathways convey?

A

Pain, temp sense & crude touch

54
Q

Describe the axons in anterolateral pathways?

A

Small diameter A delta and unmyelinated C axons
- A axons associated with first pain
- C axons associated with second Ian

55
Q

Anterolateral Pathways: 1st order neuron
Where is the cell body?
Where do axons enter spinal cord?

A
  • Dorsal root ganglion
  • Enters spinal cord via dorsal root
56
Q

Anterolateral Pathways: 1st order neuron
Where do the axons ascend once they enter the spinal cord?

A
  • 2 spinal segments in Lissauer’s tract then crosses
57
Q

Anterolateral Pathway: 1st order neuron
- Where does the 1st synapse occur?

A

Dorsal Horn (Gray matter of spinal cord)

58
Q

Anterolateral Pathways: 2nd order neuron
- Where do 2nd order neurons decussate?

A

In anterior (ventral) Commissure of the spinal cord

59
Q

Anterolateral Pathways: 2nd order neuron
- Where do the axons go after decussation?

A

Ascend in anterolateral white matter of the spinal cord on the contralateral side

60
Q

What is the somatotopic organization of the second order neuron in the anterolateral pathways?

A
  • UE medial
  • LE lateral
61
Q

What are the three tracts 2nd order neuron tracts of the anterolateral pathway?

A
  • Spinothalamic
  • Spinoreticular
  • Spinomesencephalic
62
Q

What does the spinothalamic tract convey?

A

Discriminative aspects of pain & temp (location & intensity)

63
Q

What does the spinoreticular tract convey?

A

Emotional & arousal aspects of pain

64
Q

What does the spinomesencephalic tract do?

A

Central pain modulation

65
Q

Spinothalamic Tract: 3rd order neuron
- Where does the synapse occur?

A
  • Located in ventral posterior lateral (VPL) nucleus of the thalamus
66
Q

Spinothalamic Tract: 3rd order neuron
- After the synapse where does the axon travel?

A

Along with dorsal column - medial pathways neurons but information is carried by separate neurons

67
Q

Spinothalamic Tract: 3rd order neuron
- Where do the axons project?

A

Projects in thalamic somatosensory radiations through the posterior limb of the internal capsule

68
Q

Where does the spinothalamic tract terminate?

A

Primary somatosensory cortex on post central gyrus

69
Q

What is the somatotropin organization of the spinothalamic tract?

A
  • Spinal Cord/Brainstem –> LE lateral & UE medial
  • Somatosensory Cortex –> LE medial & UE lateral
70
Q

Where does the second order neuron of the spinoreticular tract terminate?

A

Medullary-pontine reticular formation

71
Q

What is the spinoreticular tract involved in?

A
  • Behavioral arousal
  • Information relayed diffusely to entire cortex
72
Q

Where does the spinomesencephalic tract project and what does it participate in?

A
  • Projects to periaqueductal gray matter and superior colliculi of the midbrain
  • Participated in central pain modulation
73
Q

What is referred pain?

A

Visceral (internal) pain conveyed centrally via dorsal horn neurons that may also convey cutaneous pain
- So pain from an internal organ can be perceived as cutaneous pain

74
Q

What is the gate control theory?

A
  • Non painful inputs from Type II fibers
  • Descending signals from the brain
75
Q

Where is the nerve gate located?

A

Substantia gelatinous of the dorsal horn of the spinal cord

76
Q

What does the nerve gate control?

A

Passage of pain signals to the brain through interneurons that inhibit second order neurons from sending the pain signal to the brain

77
Q

Gate Control Theory:
- What does non painful input close the gate to?

A

Painful inputs, reducing pain

78
Q

What 2 areas in the brainstem become activated when the brain perceive pain?

A
  • Periaqueductal gray (PAG) in midbrain
  • Raphe nucleus in rostral ventral medulla (RVM)
79
Q

What does the PAG in the midbrain receive input from?

A

Hypothalamus
Amygdala
Cortex
Spinomesencephalic tract

80
Q

PAG and Raphe nucleus activate what?

A
  • Descending tracts that function to inhibit pain
81
Q

How does activation of descending tracts function to inhibit pain?

A
  • Descending tracts release serotonin to activate inhibitory interneurons
  • Then inhibits 2nd order neuron from sending pain
  • Some descending tracts act directly on C fiber axon terminal
  • Other descending tracts act directly on 2nd order neuron
82
Q

Spinocerebellar Fibers travel in what 4 tracts?

A

Dorsal spinocerebellar tract
Cuneocerebellar tracts
Ventral spinocerebellar tract
Rostral spinocerebellar tracts

83
Q

Where does input to the spinocerebebellum come from?

A

Directly from spinal cord (somatosensory and interneurons) and visual, auditory & vestibular system

84
Q

Where does the output from the spinocerebellum go to?

A

Lateral & medial motor tracts

85
Q

What is the function of the spinocerebellum?

A

Movement of distal & proximal muscle function

86
Q

Describe how feedback information provided to the cerebellum within pathways with 2 neurons?

A

Afferent information about limb movement; send information to cerebellum from peripheral receptors

87
Q

Describe how feedback tracts provide internal feedback from cerebellum?

A

-Send information to cerebellum about activity in spinal interneurons and descending motor pathway
- Pathways have a single neuron

88
Q

What does the dorsal spinocerebellar tract receive sensory from?

A

Proprioception, touch and pressure from LE

89
Q

Where do the first order neurons axons travel to in the Dorsal Spinocerebellar tract?

A

Travel up to L2-C8 in dorsal columns/fasciculus gracilis

90
Q

Where does the first order neuron of the Dorsal Spinocerebellar tract synapse?

A

Nucleus Dorsalis of Clarke

91
Q

Where do 2nd order neuron axons of the Dorsal Spinocerebellar tract ascend after synapsing on the Nucleus Dorsalis of Clarke?

A

Ascend ipsilaterally in dorsal spinocerebellar tract

92
Q

Dorsal Spinocerebellar Tract: 2nd order neuron
- Where do the axons project to?

A

Cerebellar cortex via ipsilateral inferior cerebellar peduncle

93
Q

What does the dorsal spinocerebellar tract convey?

A

-Unconscious proprioception
- Serves to give info to cerebellum

94
Q

Where is the input received from for the Cuneocerebellar tract?

A

Proprioception, touch, & pressure from UE & neck

95
Q

Where does the 1st order neuron of the cuneocerebellar tract ascend?

A

Along with dorsal column fibers in ipsilateral fasciculus cuneatus

96
Q

Where does the 1st order neuron of the cuneocerebellar tract synapse?

A

External/Lateral cuneate nucleus in the caudal medulla

97
Q

In the second order neuron were of axons travel from the lateral cuneate nucleus?

A

Travel ipsilaterally in cuneocerebellar tract and enter ipsilateral inferior cerebellar peduncle & terminate in cerebellar cortex

98
Q

Where does the Ventral Spinocerebellar tract arise from?

A

Cells in central gray of spinal cord

99
Q

Where does the ventral spinocerebellar tract cross over at?

A

In ventral commissure of the spinal cord

100
Q

Where does the ventral spinocerebellar tract ascend?

A

In contralateral ventral spinocerebellar tract to midbrain join superior cerebellar peduncle and cross over to cerebellum hemispheres ipsilateral to where it began

101
Q

What does the Rostral Spinocerebellar tract enter?

A

Both superior & inferior cerebellar peduncles
- Fibers are either ipsilateral or “double crossed”

102
Q

Cerebellum coordinates motor function for the (BLANK) side of body?

A

Ipsilateral

Neurobiology II (14 decks)

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