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OT 441: Neuroscience - Summer 2017 > Somatosensory System (7) EXAM 2 Material > Flashcards

Somatosensory System (7) EXAM 2 Material Flashcards

1
Q

Sensory information from the skin and musculoskeletal systems

A

Somatosensation

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2
Q

What type of sensory info do we get from the skin? (Called superficial, cutaneous or exteroceptive)

A

Pain, touch, temperature

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3
Q

What type of sensory info do we get from the musculoskeletal system?

A

Pain, Proprioception

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4
Q

Proprioception

A

Provides information regarding stretch of muscles, tension on tendons, position of joints and deep vibration.

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5
Q

What does the speed of processing information depend on?

A

Diameter of axons, degree of myelination and number of synapses in the pathway.

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6
Q

Functions of receptors in PNS::

A

Transduction of stimulus into an electrical signal (so brain can process the information)

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7
Q

Where are the somatosensory receptors?

A

At the distal end of peripheral neurons

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8
Q

What type of somatosensory receptor continues to fire during entire presentation of the stimulus?

A

Slow adapting / tonic

ex: Yoga - stretching

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9
Q

What type of somatosensory receptor adapts quickly to stimulus and stops responding?

A

Fast adapting / Phasic

ex: Wearing a watch, we don’t notice it unless attention is called to it

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10
Q

Receptor Density

A

Number of receptors within a given area of body surface

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11
Q

Area of skin innervated by a single afferent neuron is called what?

A

Receptive field

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12
Q

Large receptive fields of somatosensors:

A

Borders are difficult to define; often cover a large area (ex: Back, stomach)

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13
Q

Small receptive fields of somatosensors:

A

Borders are sharply defined; cover small area

ex: Pads of fingers

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14
Q

Do distal or proximal regions tend to have greater density of receptors. Also, smaller or larger receptive fields?

A

Distal regions have GREATER density of receptors than proximal regions and smaller receptive fields.

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15
Q

Mechanoreceptors

A

Touch

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16
Q

Which kind of receptor responds to mechanical deformation of receptor?

A

Mechanoreceptor

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17
Q

Which kind of receptor deals with body part position and movement?

A

Proprioceptors

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18
Q

Thermoreceptors

A

Temperature:

Responds to heat or cooling

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19
Q

Chemoreceptors

A

Chemicals:

Responds to substances released by cells

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20
Q

Nocioceptors

A

Pain:
Sensitive to stimuli that damage or can damage
(Subclass of other types of receptors)

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21
Q

What are the three prime components of somatosensory pathways?

A

Receptors, Sensory Pathways, Brain Centers

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22
Q

Which pathway distinguishes info about location and type of stimulation to cortex? (Temperature, texture, detail)

A

Conscious relay pathway

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23
Q

Divergent Pathway

A

Transmit info to many areas of the brainstem and cerebrum

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24
Q

Unconscious pathway

A

Brings unconscious proprioceptive and other movement-related information to cerebellum.
(Ex: Walking on something bumpy)

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25
Q

Which type of neurons are counted in the somatosensory pathway?

A

Only projection neurons are counted (the long ones)

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26
Q

Are interneurons counted in the somatosensory pathway?

A

No

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27
Q

What is the pathway usually named after?

A

Often the origin and termination of the tract that contains the second neuron in the system

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28
Q

Primary somatosensory cortex =

A

Post-central gyrus

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29
Q

What sensory info does the post-central gyrus discern?

A

Touch, size, texture and shape of objects

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30
Q

What type of representation does the post-central gyrus use?

A

Somatotopic: Homunculus (Body on brain)

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31
Q

Most lateral on the primary somatosensory cortex?

A

Face

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32
Q

Most Medial on primary somatosensory cortex?

A

LE

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33
Q

In middle area on primary somatosensory cortex?

A

UE

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34
Q

Primary afferent fiber classification:

A

Afferent

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35
Q

Classification of conduction velocity of afferent fibers?

A

A, B, C (A is fastest, C is slowest)

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36
Q

Classification of diameter of afferent fibers?

A

I - IV (I is fastest, IV is slowest)

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37
Q

T or F, first order neurons are pseudounipolar?

A

True, they DONT receive info from other neurons

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38
Q

Sensory root that enters into the SC in the dorsal horn

A

Dorsal root

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39
Q

What type of matter is the dorsal horn?

A

Gray matter

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40
Q

What type of matter is the dorsal column?

A

White matter

41
Q

The area of skin innervated by axons from cell bodies in a single dorsal root?

A

Dermatomes:

These are overlapping (allows room for injury)

42
Q

Function of Dorsal Column-Medial Lemniscal Tract (DCML)

A
  1. Discriminative Touch - ability to discriminate b/w two closely spaced points touching the skin.
  2. Vibration
  3. Conscious Proprioception - awareness of movements and relative position of body parts.
43
Q

Receptor types in DCML

A

Mechanoreceptors and Proprioceptors, NO nocioceptors

44
Q

Where does the 1st order neuron (DCML) convey info from and to?

A

Conveys info from receptor on skin to the medulla

45
Q

Where are the cell bodies of the 1st order neuron (DCML)

A

Dorsal Root Ganglia

46
Q

Is the diameter of the 1st order neuron (DCML) large or small??

A

Large

47
Q

1st order neuron of DCML: Ipsilateral or contralateral projection into dorsal column?

A

Ipsilateral projection into dorsal column

48
Q

Fasciculus Cuneatus

A

Axons from upper limbs - more lateral

49
Q

Fasciculus Gracilis

A

Axons from lower limbs - more medial

50
Q

Where does the 1st order neuron of DCML synapse?

A

Nucleus cuneatus or nucleus gracilis

51
Q

Where does the 2nd order neuron of DCML convey info from and to?

A

Conveys info from Medulla to Thalamus

52
Q

Where are the cell bodies of the 2nd order neuron of DCML?

A

Nucleus gracilis or cuneatus

53
Q

Where does the decussation of the DCML occur? Is it 1st, 2nd or 3rd order neuron that does this?

A

At the level of the medulla

2nd order

54
Q

What does the 2nd order neuron (DCML) ascend as?

A

The medial lemniscus

55
Q

Where does the 2nd order neuron (DCML) project to/decussate to?

A

VPL (Ventral Posterolateral Nucleus) of the thalamus

56
Q

Where does the 3rd order neuron (DCML) convey info from and to?

A

Conveys info from VPN of Thalamus to the cortex

57
Q

Where are the cell bodies of the 3rd order neuron (DCML) located?

A

VPL of thalamus

58
Q

Where does the 3rd order neuron (DCML) project to/decussate to?

A

Projects through internal capsule to primary somatosensory cortex

59
Q

DCML mnemonic

A

De Cussates (in the) Medu Lla

60
Q

Anterolateral System: Spinothalamic Tract (STT) Functions

A
  1. Discriminate (fast) pain
  2. Discriminate temperature
  3. Coarse touch (skin to skin touch)
61
Q

Types of receptors in STT tract?

A

Nocioceptors (Mechanoreceptors, Thermoreceptors)

62
Q

Where does the 1st order neuron of the STT convey info to/from?

A

Conveys info from skin receptor to dorsal horn

63
Q

Where are the cell bodies of the 1st order neuron (STT)?

A

Dorsal root ganglion

64
Q

What does the Tract of Lisseauer do? what Tract is it in?

A

It conveys info up or down 1-2 levels (protective)

It’s in the Spinothalamic Tract (STT)

65
Q

Where does the 1st order neuron of the STT synapse?

A

Ipsilateral dorsal horn

66
Q

Where does the 2nd order neuron of the STT convey info to and from?

A

Conveys info from dorsal horn to thalamus

67
Q

Where are the cell bodies of the 2nd order neuron (STT) located?

A

Ipsilateral dorsal horn

68
Q

When does the STT tract decussate?

A

During the 2nd order neuron

69
Q

Where does the 2nd order neuron (STT) decussate to?

A

The anterolateral white matter of the SC

70
Q

Where does the 2nd order neuron (STT) ascend and where does it ascend to?

A

Ascends in the anterolateral white matter tract area.

Ascends to VPL of Thalamus

71
Q

Where does the 3rd order neuron (STT) convey info from and to?

A

Conveys info from Thalamus to Cortex

72
Q

Where are the cell bodies of the 3rd order neuron (STT) located?

A

In the VPL of the Thalamus

73
Q

Where does the 3rd order neuron (STT) project through?

A

Projects through Internal capsule to primary somatosensory cortex

74
Q

What information does the Trigeminal Thalamic Tract sense?

A

Fast pain, discriminative touch, temperature information from the face

75
Q

Divergent Anterolateral Tracts: How is the info from these pathways NOT organized?

A

The information from these pathways are not somatotopically organized

76
Q

Divergent Anterolateral Tracts:

A
  1. Spinomesencephalic Tract
  2. Spinoreticular Tract
  3. Spinolimbic Tract
77
Q

Activity in divergent anterolateral tracts results in what?

A

Looking at cause of pain, arousal, withdrawal, autonomic and affective responses to pain (non discriminative)

78
Q

Which divergent anterolateral tract is involved in turning the head and eyes toward the noxious input?

A

Spinomesencephalic Tract

79
Q

Which divergent anterolateral tract is involved in pain stimuli commanding attention and interfering with sleep?

A

Spinoreticular Tract

80
Q

Which divergent anterolateral tract is involved in emotions, personality, movement, etc?

A

Spinolimbic Tract

81
Q

What are the unconscious relay tract to cerebellum called?

A

Spinocerebellar Tracts

82
Q

What information do the spinocerebellar tracts transmit?

A

Information from proprioceptors transmitted to cerebellum

83
Q

What are the spinocerebellar tracts critical for?

A

Unconscious adjustments to movement and posture.

84
Q

Neuropathy Compression (Class I)

A

Large, myelinated fibers affected first

Tingling or prickling occurs as the blood supply increases once compression relieved.

85
Q

Neuropathy Complete Severance (Class II)

A

Lack of sensation in the distribution of nerve

Pain may occur

86
Q

Ataxia

A

Incoordination that is not due to weakness

87
Q

Sensory Ataxia

A

Lesion in peripheral sensory nerve, dorsal root or column of spinal cord, or medial lemnisci

88
Q

Sensory Ataxia problems

A

Balance, incoordination, impaired conscious proprioception and vibration

89
Q

Complete SCI (spinal cord lesion)

A

Loss of sensation one or two levels BELOW the level of the lesion (and all the way down)

90
Q

Brown-Sequard Syndrome

A

Incomplete SC lesion - “hemisection” (damage to left OR right half) of the SC.

91
Q

Results of Brown-Sequard Syndrome: Contralateral

A

Interruption of pain and temperature sensation CONTRALATERAL to the lesion (and below)

92
Q

Results of Brown-Sequard Syndrome: Ipsilateral

A
  1. Lack of discriminative touch and conscious proprioception IPSILATERAL to lesion (and below)
  2. IPSILATERAL paralysis
93
Q

Brain Stem Lesions

A

Only in the upper midbrain is all loss contralateral (because all sensation tracts have crossed).

94
Q

Thalamic Lesions

A

Everything has deccesated so there is a decreased or loss of sensation on CONTRALATERAL body or face

95
Q

Somatosensory cortex or internal capsule lesions

A

CONTRALATERAL decrease or loss of discriminative sensations

96
Q

Tactile Defensiveness

A

Aversive response to seemingly non-noxious tactile stimuli

97
Q

How does tactile defensiveness manifest itself in observable behaviors?

A

Overreaction to touch –> tantrums, avoiding touch of both people and objects.

98
Q

What is tactile defensiveness hypothesized to be due to lack of?

A

Lack of inhibition

OT 441: Neuroscience - Summer 2017 (11 decks)

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