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Neuroscience > Somatosensory Tracts > Flashcards

Somatosensory Tracts Flashcards

1
Q

what types of sensory information is associated with skin sensation?

A
  1. touch
    1. superficial pressure
    2. vibration
  2. pain
  3. proprioception
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2
Q

what type of sensory information is associated with musculskeletal sensation?

A
  1. proprioception
  2. pain
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3
Q

proprioception can be further broken down to include what?

A
  1. muscle stretch (tension)
  2. tendon stretch (tension)
  3. deep vibration
  4. joint position (angle)
    1. during movement
    2. while static
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4
Q

what are the different functional receptor types? (based off of stimuli)

A
  1. mechanoreceptors = stretch
  2. thermoreceptors = temperature
  3. chemoreceptors = any chemical stimuli
  4. nociceptors = pain
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5
Q

what are the different receptor types based off of response time?

A
  1. tonic = respond the entire time a stimulus is present
  2. phasic = adapt to a constant stimulus and stop responding while the stimulus is present
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6
Q

what type of receptor is slow adapting? Rapid adapting?

A

slow = tonic

rapid = phasic

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7
Q

what are the different types of sensory neurons?

A
  1. viscerosensory
  2. somatosensory
  3. special sensory
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8
Q

what are viscerosensory neurons?

A

general visceral afferent (GVA)

carry unconscious signals

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9
Q

what are somatosensory neurons?

A

general sensory afferent (GSA)

carry conscious singals

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10
Q

what are special sensory neurons?

A

special sensory afferent (SSA)

carry sensory info from special senses

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11
Q

what structural type of neuron are all viscerosensory and somatosensory neurons?

A

pseudo-unipolar

made up of:

peripheral (distal) axon/process → soma → central (proximal) axon/process

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12
Q

where are the soma of most sensory neurons located?

A

dorsal root ganglia

OR

cranial nerve sensory ganglia

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13
Q

most sensory information will travel in what fiber types?

A

II or Aβ: medium dia., myelinated

III or Aδ: small dia., myelinated

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14
Q

skin sensation is _______sensory

A

somatosensory

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15
Q

what is a receptive field?

A

an area of skin that is innervated by a single sensory neuron

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16
Q

what is the difference between a receptive field and a dermatome?

A

dermatome = single nerve

receptor field = single neuron

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17
Q

the sensation of touch can be broken down into what 2 categories?

A

Fine and Course touch

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18
Q

what type (specific names) of receptors are sensitive to fine touch?

A
  1. Merkel’s
  2. Meissner’s
  3. Pacinian
  4. hair follicle receptor
  5. Ruffini
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19
Q

what type (specific names) of receptors are sensitive to course touch?

A
  1. free nerve endings
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20
Q

pain is sensed by what type of receptor and carried by what type of neuron?

A

nociceptive receptors (a type of free nerve ending)

Aδ and C neurons carry pain signals

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21
Q

temperature is sensed by what type of receptor and carried by what type of neuron?

A

thermoreceptor

Aδ neurons carry cooling sensation and C neurons carry heat sensation

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22
Q

proprioception is primarily sensed by ________

A

musculoskeletal receptors

BUT

skin receptors make secondary contributions from stretch (Ruffini) and pressure changes

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23
Q

proprioception is awareness of joint position and movement that are a result from what receptors?

A
  1. muscle spindles
  2. joint receptors
  3. cutaneous mechanoreceptors
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24
Q

where are muscle spindles?

A

inside of a muscle, parallel to muscle fibers

structure is referred to as an intrafusal fiber

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25
Q

what are the components of a muscle spindle?

A
  1. nuclear chain muscle fiber
  2. nuclear bag muscle fiber
  3. afferent sensor/receptor
  4. gamma motor neuron
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26
Q

what are the 2 types of afferent sensor/receptor within a muscle spindle?

A
  1. annulospiral receptor/group Ia sensory neuron
  2. flower spray/group II sensory neuron
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27
Q

what do annulospiral receptors detect?

A

dynamic length/stretch (speed of contraction)

associated with both bag and chain intrafusal fibers

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28
Q

what do flower spray sensory neurons detect?

A

static length/stretch (static angle of the joint/degree of stretch)

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29
Q

what is the role of the gamma motor neuron within a muscle spindle?

A

when whole muscle contracts via alpha motor neurons the muscle spindle fibers (intrafusal fibers) may also contract via gamma motor neurons to keep the spindle stretched/tense so it will remain sensitive even when the whole muscle is shortening during contraction

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30
Q

what and where are Golgi tendon organs?

A

a proprioceptive receptor

found in dense CT of tendons

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31
Q

what is the role of Golgi tendon organs?

A

sensitive to changes in tension of the tendon

part of a reflex that inhibits muscle contraction to reduce stretch on muscle/tendon

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32
Q

list the different types of joint receptors

A
  1. Paciniform
  2. Ruffini
  3. free nerve endings
  4. ligament receptors
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33
Q

what do joint receptor sense?

A

mechanical deformation of joint capsule and ligaments

(they are mechanoreceptors that are sensitive to stretch)

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34
Q

what is the difference between a tract and a pathway?

A
  1. tract = a bundle of axons in CNS with a common origin and destination
  2. pathway = peripheral nerve + tract that together carry info to a final destination
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35
Q

T/F: pathways are isolated from one another and protected from interference?

A

FALSE

pathways can communicate and interact via collateral branches and interneurons

36
Q

what are the 3 different classifications of pathways?

A
  1. conscious
  2. divergent
  3. unconscious
37
Q

what is a conscious pathway?

A

a pathway that ends in the cerebral cortex

38
Q

what is a divergent pathway?

A

a pathway that branches and ends in many CNS locations for both conscious and unconscious perception

39
Q

what is an unconscious pathway?

A

a pathway that ends at brain locations below the cerebral cortex

(brainstem, limbic, cerebellum, diencephalon)

40
Q

Information carried in different pathways can be described as/by ________, _________ and __________

A
  1. fidelity
  2. discriminative
  3. somatotopic
41
Q

what is fidelity?

A

describes the location that the signal originates from

high = pinpoint location of origin

low = signals have a general origin

42
Q

discriminative allows ____________

A

precise identification of stimuli

43
Q

generally conscious pathways have what 3 characteristics?

A
  1. they are 3 projection neuron pathways
  2. carry touch, proprioception, pain and temperature info
  3. tracts are somatotopically organized (high fidelity)
44
Q

List the conscious pathways

A
  1. Dorsal column/medial lemnsicus tracts
  2. Trigeminal nerve
  3. Spinothalamic tract
45
Q

what info is carried in the dorsal column/medial lemnsicus tract?

A
  1. discriminative touch
    • localization of stimulus
    • 2-point discrimination
  2. conscious proprioception
    • relative position and movement of body parts
46
Q

what is sterognosis?

A

identification of an object by touch and proprioception

cortex accomplishes this by processing discriminative touch and proprioceptive info together

47
Q

where/what is the primary/first-order neuron in the dorsal column/medial lemnsicus tract?

A

pseudo-unipolar neuron

carries signals from periphery to the medulla of the brain stem

48
Q

describe the pathway of the distal axon to the soma of the first-order neuron in the dorsal column/medial lemnsicus tract

A
  1. discriminative touch and proprioceptor receptors
  2. peripheral nerve
  3. spinal nerve rami (dorsal or ventral)
  4. spinal nerve
  5. dorsal root
  6. DRG (this is the soma)
49
Q

describe the pathway for the proximal axon to the synapse of the second-order neuron in the dorsal column/medial lemnsicus tract

A
  1. DRG
  2. dorsal root
  3. dorsal column of spinal cord
    1. fasciculus cuneatus/gracilis
  4. synapses in medulla w/second-order neuron
    1. nucleus cuneates/gracilis
50
Q

where/what is the 2 order neuron in the dorsal column/medial lemniscus tract?

A

soma = nucleus cuneatus/gracilis

axons = cross midline and ascend to VPL of thalamus

51
Q

where does the 3rd order neuron of the dorsal column/medial lemniscus tract originate and terminate?

A

soma of VPL of thalamus

thru internal capsule

to post central gyrus of parietal lobe

52
Q

what type of sensory info is carried by the Trigeminal nerve?

A
  1. discriminative touch
  2. conscious proprioception

from face to contralateral cortex

53
Q

describe the origin, soma and destination of the 1st order neuron in the trigeminal nerve pathway

A
  1. distal axon = receptors located in V1, V2, or V3 branch of the trigeminal nerve
  2. soma = trigeminal/semilunar ganglion outside of pons
  3. proximal axon = synapses with 1 of 2 nuclei in the pns
    • main sensory = sensory info from face
    • mesencephalic = proprioception of jaw
54
Q

describe the origin and destination of the 2nd order neuron in the Trigeminal nerve

A
  1. origin
    • soma of main sensory nucleus
    • soma of mesencephalic nucleus
  2. axon = cross to contralateral side and ascend in trigeminal lemnsicus (part of medial lemnsicus)
  3. terminal synapse = VPM of thalamus
55
Q

describe the origin and destination of the 3rd order neuron in the trigeminal nerve pathway

A

origin = VPM nucleus of thalamus

destination = post central gyrus via internal capsule

56
Q

what type of sensory info is carried by the spinothalamic tract?

A
  1. discriminative pain
  2. temperature
  3. course touch
    • non discriminative pleasant touch
    • skin to skin contact
57
Q

describe the origin and destination of the 1st order neuron carrying temperature sensation in the spinothalamic tract

A
  1. distal axon = receptors are free nerve endings
  2. soma = DRG
  3. proximal axon = synapses in dorsal horn
    1. Rexed’s laminae I and II = substantia gelatinosa
58
Q

describe the origin and destination of the 2nd order neuron carrying temperature sensation in the spinothalamic tract

A
  1. soma = dorsal horn
  2. axon = crosses at spinal cord and ascends in the contralateral anteriolateral column
  3. this becomes the spinothalamic tract
  4. synapse = VPL nucleus of thalamus
59
Q

describe the origin and destination of a tertiary neuron carrying temperature sensation in the spinothalamic tract

A
  1. origin = VPL nucleus of thalamus
  2. destination = post central gyrus
60
Q

how are the neurons carrying localized, fast pain sensation in the spinothalamic tract different from those carrying temperature sensation?

A

Fast Pain

  1. receptors = nociceptors
  2. tertiary neurons headed to primary and secondary (associative) somatosensory cortex
61
Q

T/F: fast pain from the face is carried within the trigeminal tract and has the same course as other sensations from the face?

A

FALSE

it is unique and will first descend to the medulla before ascending to the VPM

62
Q

describe the origin and destination of primary neurons carrying fast pain sensation from the face (trigeminal)

A
  1. distal axon = nociceptive receptors
  2. soma = trigeminal/semiulnar ganglion
  3. proximal axon = descending tract of trigeminal nerve
  4. synapse = spinal nucleus of CN 5 in medulla
63
Q

describe the origin and destination of the 2nd order neuron carrying fast pain sensation from the face

A
  1. origin = spinal nucleus of trigeminal nerve in medulla
  2. axon = crosses to contralateral side at the medulla and ascends in trigeminal lemnsicus
  3. synapses = VPM nucleus of Thalamus
64
Q

describe the origin and destination of a tertiary neuron carrying fast pain from the face

A
  1. origin = VPM nucleus of thalamus
  2. destination = postcentral gyrus and associative cortex
65
Q

Divergent pathways carry both __________ and ___________ signals

A

conscious

unconscious

66
Q

the medial pain system is a divergent pathway that is generally responsible for carrying info used for what?

A
  1. pain modulation
  2. motivational
  3. withdrawal
  4. arousal
  5. autonomic reponse to pain

*low fidelity and not localizable

67
Q

describe the origin and destination of a first order neuron in the medial pain system

A
  1. distal axon = nociceptor receptors
  2. soma = DRG
  3. proximal axon = branches to multiple spinal cord segments and synapses w/dorsal horn (lamina I, II, and V) using substance P as a NT
68
Q

describe the origin and destination of a 2nd order neuron in the medial pain pystem

A
  1. origin = soma of dorsal horn
  2. axon = crosses to contralateral side in spinal cord then ascends in 1 of 3 divergent neurons
69
Q

what are the 3 different divergent neurons that are 2nd order neurons in the medial pain system?

A
  1. spinomesencephalic
  2. spinoreticular
  3. spinolimbic
70
Q

the spinomesencephalic tract is headed to what structures in the mesencephalon and for what purpose?

A
  1. superior colliculus
    • turns head to position eyes on pain source
    • activate descending neurons that modulate pain
  2. periaqueductal gray
    • descending pain modulation
71
Q

where is the spinoreticular tract headed?

what is it’s role?

A

reticular formation (raphe nuclei, locus ceruleus)

modulates pain sensation to thalamus

72
Q

what is another name for the spinolimbic tract?

A

paleospinothalamic tract

73
Q

where is the spinolimbic tract headed and what is it carrying?

A
  1. to anterior cingulated cortex = links pain sensation to emotional response
  2. to posterior insula = pain sensation
74
Q

generally, unconscious pathways do what?

A

carry proprioceptive and feedback info about activity in motor tracts (via interneuron links) to cerebellum to adjust and refine conscious movement

75
Q

what tracts are included in the unconscious pathways?

A
  1. posterior spinocerebellar
  2. cuneocerebellar
  3. anterior spinocerebellar
  4. rostrospinocerebellar
76
Q

which unconsious pathways are high fidelty?

A

posterior spinocerebellar

cuneocerebellar

77
Q

which unconscious pathways remain ipsilateraly?

A

posterior spinocerebellar

cuneocerebellar

rostrospinocerebellar

78
Q

what is the posterior spinocerebellar tract?

A

2 neuron pathway carrying high fidelity, somatotopic info

from lower body to cerebellar cortex

on ipsilateral side

79
Q

describe the origin and destination of a first order neuron in the posterior spinocerebellar tract

A
  1. distal axon = afferent signals from proprioceptors in legs and lower body
  2. soma = DRG
  3. proximal axon = ascends dorsal column
  4. synpases with = dorsal horn >> nucleus dorsalis in T1 to L2 region
80
Q

describe the origin and destination of a 2nd order neuron in the spinocerebellar tract

A
  1. soma = nucleus dorsalis (dorsal horn)
  2. axon = ascends ipsilaterally as spinocerebellar tract to the medulla
  3. gets to cerbellum via inferior cerebellar peduncle
  4. synapses with cerebellar cortex ipsilaterally
81
Q

what is the cuneocerebellar pathway?

A

2 neuron pathway carrying high fidelity, somatotopic info

from upper body to ipsilateral cerebellar cortex

82
Q

describe the origin and destination of a first order neuron in the cuneocerebellar tract

A
  1. distal axon = afferent signals from proprioceptors in arms and upper body
  2. soma = DRG
  3. proximal axon = enters spinal cord and ascends in posterior column
  4. synapses = lateral (accessory) cuneate nucleus in medulla
83
Q

describe the origin and destination of a second order neuron in the cuneocerebellar tract

A
  1. soma = lateral (accessory) cuneate nucleus of medulla
  2. axon = ascends in cunecerebellar tract until it enters the cerebellum via the inferior cerebellar peduncel
  3. synapses with ipsilateral cerebellar cortex
84
Q

what is the anterior spinocerebellar tract?

A

1 neuron pathway that provides cerebellum with feedback from spinal cord ventral horn

monitors motor activity of lower body

85
Q

describe the origin and destination of the neuronal pathway of the anterior spinocerbellar tract

A
  1. soma = interneurons of spinal cord in the thoracolumbar lateral and ventral horns
  2. axon crosses to contralateral side
  3. ascends in anterior spinocerebellar tract
  4. enteres cerebellum via superior cerebellar peduncle
  5. collaterals branch to synapse with both cerebellar hemispheres
86
Q

what is the rostrospinalcerebellar tract?

A

1 neuron pathway that provides the cerebellum with feedback from spinal cord interneurons and motor activity of the upper body

87
Q

describe the origin and destination of the neuronal pathway in the rostrospinocerebellar tract

A
  1. soma = interneurons of cervical spinal cord ventral horns
  2. axons asend ipsilaterally in the rostrospinocerebellar tract
  3. enter the cerbellum via the S/I cerebellar peduncles
  4. synapses w/ipsilateral cerebellar hemisphere

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