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Neurobiology II > Somatosensation (Exam 1) > Flashcards

Somatosensation (Exam 1) Flashcards

(102 cards)

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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
What is the general anatomic arrangement for a first order neuron?
Action potential in sensory receptors are triggered - From sensory receptors (skin & musculoskeletal) to spinal cord
26
What is the general anatomic arrangement for a second order neuron?
Spinal cord to thalamus
27
What is the general anatomic arrangement for a third order neuron?
From thalamus to cerebral cortex
28
Where are somatosensory first order neurons located?
Dorsal root ganglion
29
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?
Pseudounipolar
30
What does the dorsal column- medial lemniscal pathway convey?
-Proprioception, Vibration & fine discriminative touch - Conscious
31
What does the anterolateral pathway convey?
- Pain, temp sense & crude touch - Conscious
32
What does spinocerebellar pathways convey?
- Information from proprioceptors & interneurons to cerebellum - Unconscious
33
Conscious Somatosensory Pathway first order neuron includes?
- Sensory neuron - Cell body in dorsal root ganglion
34
Conscious Somatosensory Pathway what occurs during the second order neuron?
- Synapse with 1st order neuron in spinal cord or brainstem - Crosses - Carries info to thalamus
35
Conscious Somatosensory Pathway: What occurs during 3rd order neuron?
Carries information from thalamus to cortex
36
Describe the axons involved in Dorsal column- medial lemniscal pathway?
- Large diameter, myelinated axons - Ia, Ib, II
37
Dorsal Column - Medial Lemniscal Pathway: 1st order neuron Where is the cell body located? Where do the axons enter spinal cord?
- Dorsal root ganglion - Via the dorsal root
38
Dorsal Column - Medial Lemniscal Pathway: 1st order neuron When axons enter the spinal cord where do go from there?
- Enter ipsilateral dorsal column and ascend to medulla via either Fasciculus gracilis or cuneatus
39
When is fasciculus gracilis used?
Sensory information comes from LE & trunk
40
When is fasciculus cuneatus used?
Upper trunk (T6), arms & neck
41
Dorsal Column - Medial Lemniscal Pathway: 2nd order neuron - Where does the synapse occur between 1st & 2nd order neuron?
Caudal medulla in either Nucleus gracilis or cuneatus
42
Dorsal Column - Medial Lemniscal Pathway - Axons of 2nd order neurons decussate as?
Internal arcuate fibers in the medulla
43
Dorsal Column - Medial Lemniscal Pathway: 2nd order neuron - After the decussation where do axons ascend and as what?
- Ascend through brainstem as medial lemniscus on contralateral side to thalamus
44
Dorsal Column - Medial Lemniscal Pathway: - Where does synapse between 2nd & 3rd order neuron occur?
- Located in the the ventral posterior lateral (VPL) nucleus of the thalamus
45
Dorsal Column - Medial Lemniscal Pathway: 3rd order neuron - After the synapse what happens next?
- Projects in thalamic somatosensory radiations through the posterior limb of the internal capsule
46
Where does the Dorsal Column- Medial Leminscal pathway terminate?
Primary somatosensory cortex (areas 3, 1 and 2) in post central gyrus
47
What is the somatic organization of the spinal cord?
- LE medial - UE lateral
48
What is the somatic organization of the medulla?
- LE ventral - UE dorsal
49
What is the somatic organization of the pons/midbrain?
- LE lateral - UE medial
50
What is the somatic organization of the somatosensory cortex?
- LE medial - UE lateral
51
What is the trigeminal lemniscus?
- Analogous pathway conveys touch sensation for the face
52
Where does the trigeminal lemniscus pathway synapse?
Ventral posterior medial (VPM) nucleus of the thalamus
53
What does anterolateral pathways convey?
Pain, temp sense & crude touch
54
Describe the axons in anterolateral pathways?
Small diameter A delta and unmyelinated C axons - A axons associated with first pain - C axons associated with second Ian
55
Anterolateral Pathways: 1st order neuron Where is the cell body? Where do axons enter spinal cord?
- Dorsal root ganglion - Enters spinal cord via dorsal root
56
Anterolateral Pathways: 1st order neuron Where do the axons ascend once they enter the spinal cord?
- 2 spinal segments in Lissauer's tract then crosses
57
Anterolateral Pathway: 1st order neuron - Where does the 1st synapse occur?
Dorsal Horn (Gray matter of spinal cord)
58
Anterolateral Pathways: 2nd order neuron - Where do 2nd order neurons decussate?
In anterior (ventral) Commissure of the spinal cord
59
Anterolateral Pathways: 2nd order neuron - Where do the axons go after decussation?
Ascend in anterolateral white matter of the spinal cord on the contralateral side
60
What is the somatotopic organization of the second order neuron in the anterolateral pathways?
- UE medial - LE lateral
61
What are the three tracts 2nd order neuron tracts of the anterolateral pathway?
- Spinothalamic - Spinoreticular - Spinomesencephalic
62
What does the spinothalamic tract convey?
Discriminative aspects of pain & temp (location & intensity)
63
What does the spinoreticular tract convey?
Emotional & arousal aspects of pain
64
What does the spinomesencephalic tract do?
Central pain modulation
65
Spinothalamic Tract: 3rd order neuron - Where does the synapse occur?
- Located in ventral posterior lateral (VPL) nucleus of the thalamus
66
Spinothalamic Tract: 3rd order neuron - After the synapse where does the axon travel?
Along with dorsal column - medial pathways neurons but information is carried by separate neurons
67
Spinothalamic Tract: 3rd order neuron - Where do the axons project?
Projects in thalamic somatosensory radiations through the posterior limb of the internal capsule
68
Where does the spinothalamic tract terminate?
Primary somatosensory cortex on post central gyrus
69
What is the somatotropin organization of the spinothalamic tract?
- Spinal Cord/Brainstem --> LE lateral & UE medial - Somatosensory Cortex --> LE medial & UE lateral
70
Where does the second order neuron of the spinoreticular tract terminate?
Medullary-pontine reticular formation
71
What is the spinoreticular tract involved in?
- Behavioral arousal - Information relayed diffusely to entire cortex
72
Where does the spinomesencephalic tract project and what does it participate in?
- Projects to periaqueductal gray matter and superior colliculi of the midbrain - Participated in central pain modulation
73
What is referred pain?
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
What is the gate control theory?
- Non painful inputs from Type II fibers - Descending signals from the brain
75
Where is the nerve gate located?
Substantia gelatinous of the dorsal horn of the spinal cord
76
What does the nerve gate control?
Passage of pain signals to the brain through interneurons that inhibit second order neurons from sending the pain signal to the brain
77
Gate Control Theory: - What does non painful input close the gate to?
Painful inputs, reducing pain
78
What 2 areas in the brainstem become activated when the brain perceive pain?
- Periaqueductal gray (PAG) in midbrain - Raphe nucleus in rostral ventral medulla (RVM)
79
What does the PAG in the midbrain receive input from?
Hypothalamus Amygdala Cortex Spinomesencephalic tract
80
PAG and Raphe nucleus activate what?
- Descending tracts that function to inhibit pain
81
How does activation of descending tracts function to inhibit pain?
- 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
Spinocerebellar Fibers travel in what 4 tracts?
Dorsal spinocerebellar tract Cuneocerebellar tracts Ventral spinocerebellar tract Rostral spinocerebellar tracts
83
Where does input to the spinocerebebellum come from?
Directly from spinal cord (somatosensory and interneurons) and visual, auditory & vestibular system
84
Where does the output from the spinocerebellum go to?
Lateral & medial motor tracts
85
What is the function of the spinocerebellum?
Movement of distal & proximal muscle function
86
Describe how feedback information provided to the cerebellum within pathways with 2 neurons?
Afferent information about limb movement; send information to cerebellum from peripheral receptors
87
Describe how feedback tracts provide internal feedback from cerebellum?
-Send information to cerebellum about activity in spinal interneurons and descending motor pathway - Pathways have a single neuron
88
What does the dorsal spinocerebellar tract receive sensory from?
Proprioception, touch and pressure from LE
89
Where do the first order neurons axons travel to in the Dorsal Spinocerebellar tract?
Travel up to L2-C8 in dorsal columns/fasciculus gracilis
90
Where does the first order neuron of the Dorsal Spinocerebellar tract synapse?
Nucleus Dorsalis of Clarke
91
Where do 2nd order neuron axons of the Dorsal Spinocerebellar tract ascend after synapsing on the Nucleus Dorsalis of Clarke?
Ascend ipsilaterally in dorsal spinocerebellar tract
92
Dorsal Spinocerebellar Tract: 2nd order neuron - Where do the axons project to?
Cerebellar cortex via ipsilateral inferior cerebellar peduncle
93
What does the dorsal spinocerebellar tract convey?
-Unconscious proprioception - Serves to give info to cerebellum
94
Where is the input received from for the Cuneocerebellar tract?
Proprioception, touch, & pressure from UE & neck
95
Where does the 1st order neuron of the cuneocerebellar tract ascend?
Along with dorsal column fibers in ipsilateral fasciculus cuneatus
96
Where does the 1st order neuron of the cuneocerebellar tract synapse?
External/Lateral cuneate nucleus in the caudal medulla
97
In the second order neuron were of axons travel from the lateral cuneate nucleus?
Travel ipsilaterally in cuneocerebellar tract and enter ipsilateral inferior cerebellar peduncle & terminate in cerebellar cortex
98
Where does the Ventral Spinocerebellar tract arise from?
Cells in central gray of spinal cord
99
Where does the ventral spinocerebellar tract cross over at?
In ventral commissure of the spinal cord
100
Where does the ventral spinocerebellar tract ascend?
In contralateral ventral spinocerebellar tract to midbrain join superior cerebellar peduncle and cross over to cerebellum hemispheres ipsilateral to where it began
101
What does the Rostral Spinocerebellar tract enter?
Both superior & inferior cerebellar peduncles - Fibers are either ipsilateral or "double crossed"
102
Cerebellum coordinates motor function for the (BLANK) side of body?
Ipsilateral

Neurobiology II (14 decks)

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