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Anatomy > ascending sensory system > Flashcards

ascending sensory system Flashcards

1
Q

what are the 5 ascending systems

A

medial lemniscus pathway (posterior column), spinothalamic tract (anterolateral pathway), posterior spinocerebellar tract, cuneocerebellar tract, anterior spinocerebellar tract

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2
Q

three types of fibers in the ascending and descending pathways

A

long ascending fibers: going to thalamus, cerebellum or various brainstem nuclei

long descending fibers: going from cerebellar cortex or various brainstem nuclei to spinal cord gray matter

short propriospinal fibers: interconnecting different spinal cord lees. helps coordinate flexor reflexes

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3
Q

where are ascending tracts found

A

all three funiculi: anterior funiculi, lateral funiculi, and posterior funiculi

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4
Q

Descending tracts are primarily located in?

A

the anterior funiculi and the lateral funiculi

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5
Q

propriospinal fibers are found in

A

they surround the spinal cord gray matter

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6
Q

Somatosensory Receptors detect?

A

mechanical, chemical or thermal changes

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7
Q

Somatosensory receptor neurons?

A

all pseudiunipolar. Cell bodies are int the dorsal root ganglion or cranial nerve ganglion.

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8
Q

Where are somatosensory central processes and peripheral processes

A

Central: a central CNS process in the spinal cord or brainstem
Peripheral process: endings in the skin muscle or joint

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9
Q

merkel endings

A

discriminative touch

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10
Q

free nerve endings

A

pain, temperature, itch , touch

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11
Q

meissners corpuscle

A

discriminative touch (2 point discrimination)

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12
Q

cuneate tubercle

A

camp on back of the brainstem that contains the cuneate nucleus. components of the dorsal column medial lemniscus

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13
Q

Gracile tubercle

A

bump on back of brainstem that contains the gracile nuclei. 2nd order neurons that participates in the posterior column medial lemniscus pathway

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14
Q

in the medulla what is the orientation of the medial lemniscus

A

vertical

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15
Q

in the pons what is the orientation of the medial lemniscus

A

horizontal

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16
Q

medial lemniscus is responsible for what?

A

discriminative touch, 2 point discrimination, conscious proprioception and vibratory sense

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17
Q

what types of fibers are in the medial lemniscus

A

ascending, large, myelinated, primary afferent fives. mechanoreceptors

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18
Q

where does the posterior column medial lemniscus pathway synapse

A

synapses in medulla and then decussates to form medial lemniscus

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19
Q

where does the medial lemniscus relay

A

the lateral thalamus (ventral posterolateral nucleus)

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20
Q

where does the medial lemniscus terminate

A

postcentral gyrus

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21
Q

spinal afferents have their cell bodies?

A

in the ipsilateral dorsal root ganglion

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22
Q

dorsal root ganglion rootlets enter the spinal cord and divide it into two divisions? what are the divisions?

A

medial- heavily myelinated, large, enter posterior column and ascend to brainstem

lateral- finely myelinated and unmyelinated, small

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23
Q

at what level do fibers stop adding to fasiculus gracilis?

A

T6 and fasiculus cuneatus starts to form

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24
Q

when fibers enter the medial lemniscus pathway they are added…?

A

laterally so a pattern of lamination develops (sacral levels most medial and cervical levels most lateral)

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25
Q

where do the posterior column media lemniscus pathway fibers synapse

A

when they reach the caudal medulla they synapse in the nuclei gracilis and cuneatus (posterior columns) and synapse in VPL

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26
Q

what do second order fibers in the posterior column medial lemniscus pathway do?

A

cross the midline with in the caudal medulla and form the medial lemniscus

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27
Q

what do third order fibers in the posterior column media lemnsicus pathway do?

A

originate in the thalamus )(venture posterolateral nucleus) and ascend through internal capsule to synapse in the primary somatosensory cortex in the post central gyrus

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28
Q

injury to medial lemniscus pathway leads to?

A

impaired proprioception and discriminative tactile functions, especially complex.

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29
Q

how can you test for injury in the medial lemniscus pathway

A

place a vibrating tuning for on body surface or have patient id a pattern drawn on their skin

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30
Q

ataxia

A

uncoordinated movements as brain is unable to direct motor activity without feedback from body cause by injury to posterior column and medial lemniscus pathway

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31
Q

where does the medial lemniscus pathway decussate

A

caudal medulla

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32
Q

sensory info reaches brain in ___pathways

A

multiple pathways. so damage to single pathway rarely leads to total loss of function

33
Q

does injury to the posterior column cause total loss of function forever

A

No. there will be a large deficit at first but recovery over time is possible

34
Q

the one sense that will stay impaired after injury to posterior column media lemniscus pathway

A

ability to discriminated complex shape of object (stereognosis) or the direction or speed of the stimulus moving across the skin

35
Q

spinothalamic tract is also called

A

anterolateral pathway

36
Q

spinothalamic tract is responsible for what?

A

pain and temperature. awareness is localizing pain

37
Q

the spinothalamic tract terminated in the…

A

ventral posterolatereal nucleus (VPL) of the thalamus

Other fibers in the pathway: end in the reticular formation of the limbic system

38
Q

where do the spinothalamic fibers enter the spinal cord

A

lateral division of dorsal root (lissauer’s tract)

39
Q

where do the second order neurons of the spinothalamic tract synapse

A

the substantial gelatinosa

40
Q

where does the spinothalamic tract decussate

A

two levels about which they entered: ascends as its crossing in the ANTERIOR COMMISSURE in the cord

41
Q

when the spinothalamic fibers decussate where do they go to

A

the anterolateral part of the spinal cord

42
Q

where are the 1st order neurons in the spinothalamic tract

A

dorsal root ganglions (lissauer’s tract)

43
Q

where are the 3 places the spinothalamic tract sends extensions to? and where are they located

A
  1. reticular formation: caudal medulla
  2. central gray matter near the cerebral aqueduct in the rostral midbrain
  3. postcentral gyrus in the brain
44
Q

Where are the spinothalamic tract 2nd order neurons

A

in the posterior horn.

45
Q

how do 2nd order neurons in the spinothalamic tract move

A

cross the midline with a ROSTRAL INClNATION and collect to form the pathways

46
Q

where do new fibers join the the spinothalamic tract

A

the anteromedial edge

47
Q

somatotopic organization of spinothalamic tract

A

caudal body parts: posterolateral portion

rostral body parts: anteromedial portion

48
Q

where do other spinothalamic fibers project

A

intralaminar nuclei and other thalamic nuclei

49
Q

the spinothalamic fibers projected to the brainstem reticular formation are important for?

A

changes in the level of attention of pain response

50
Q

spinomesencephalic fibers are important in?

A

pain control mechanisms

51
Q

spinohypothalamic fibers mediate what?

A

autonomic response to pain

52
Q

damage to spinothalamic tract causes?

A

loss of pain, temperature, itch, and tickle sensations

53
Q

why are there no changes to bowel and bladder pressure and sexual sensations when you damage the spinothalamic tract

A

because it ascends bilaterally so unilateral injury doesn’t leave a deficit

54
Q

cordotomy

A

destroy the spinothalamic tract. cut lateral funiculars from dentate ligament to venture rostral to highest dermotomal pain level. For patients with pain. the analgesia lasts several months

55
Q

cerebral cortical representation of the medial lemniscus pathway

A

primary somatosensory cortex in postcentral gyrus

56
Q

cerebral cortical representation of the anterolateral pathway

A

widespread (post central gyrus, insula, and others) reflects complex conscious awareness of pain

57
Q

spinocerebellar tracts

A

information from spinal cord used by the cerebellum to coordinate movement

58
Q

direct and indirect spinal cord information to cerebellum

A

direct: spinocerebellar tracts
indirect: brainstem relay nuclei

59
Q

posterior spinocerebellar tract is responsible for

A

proprioceptive tactile and pressure info to the legs

60
Q

where do they posterior spinocerebellar tract fibers synapse

A

Clarkes nucleus

61
Q

how do axons ascend in the posterior spinocerebellar tract

A

ipsilateral in the lateral funicular. forming the psct

62
Q

how do the posterior spinocerebellar tract fivers enter the cerebellum

A

via the inferior cerebellar peduncle

63
Q

how to the leg fivers in the PSCT travel

A

ipsilaterally and bilaterally

64
Q

the posterior spinocerebellar tract send info for the ____ while the _____ sends info for the arms

A

legs, cuneocerebellar tract

65
Q

where does the 1st order neurons of the cuneocerebellar tract synapse

A

at the level at which they enter. axons from lateral cuneate nucleus collect and form cuneocerebellar tract

66
Q

where do the second order neurons of the cuneocerebellar tract synapse=

A

enters the inferior cerebellar peduncle to synapse int he VERMIS

67
Q

do the cuneocerebellar tract fibers synapse in clarks’s nucleus?

A

No

68
Q

arm afferent fibers ascend rom ____ to the ____ in the medulla

A

fasciculus cuneatus to the lateral cuneate nucleus in the medulla

69
Q

What is the anterior spinocerebellar tract (ASCT) responsible for

A

sending more complex information to the cerebellum

70
Q

what two tracts carry proprioception information from the legs

A

anterior spinocerebellar tract and posterior spinocerebellar tract

71
Q

how is the anterior different than the posterior spinocerebellar tract

A

inputs more complet. more related to attempted movement and not simple sensory signals.

72
Q

which pathway crosses the midline twice

A

canterior spinocerebellar tract. ultimately fibers end ipsilateral to source

73
Q

origin of PSCT

A

clarks’s nucleus )t1-L2/3)

74
Q

origin of ASCT

A

spinal border ells (T12-L5)

75
Q

origin of CCT

A

lateral cuneate nucleus in medulla

76
Q

major inputs of the ASCT

A

mechanoreceptors, movement0related interneurons

77
Q

where are the two places the ASCT crosses the midline

A

in the cord and in the cerebellum

78
Q

what peduncle do the major spincerebellar tracts use to enter the cerebellum

A

PSCT and CCT: inferior

ASCT: superior

Anatomy (12 decks)

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