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PTH9111 > Lecture 12 -ascending tracts > Flashcards

Lecture 12 -ascending tracts Flashcards

1
Q

label the parts

A

a. dorsal horn
b. dorsal root ganglion
c. grey matter
d. white matter

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2
Q

Name the three ascending pathways

A
  1. dorsal column medial lemniscus pathway
  2. spinothalamic
  3. spinocerebellar
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3
Q

define ascending pathways

A

carry sensory information from peripheries to cerebral and/or cerebellar cortex

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4
Q

what are the 3 neurons present in ascending pathways and describe where they travel.

A
  1. first order/primary afferent: go from the periphery to the spinal cord
  2. second order - goes from spinal cord/brainstem to thalamus
  3. third order - travels from the thalamus to the primary sensory cortex
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5
Q

what is decussates mean and which neuron is responsible for this?

A

it means crosses the midline and is performed by the second order neuron.

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6
Q

what are the types of sensory receptors and what do they respond to?

A
  1. mechanoreceptor - tactile, vibration, proprioception
  2. nociceptors - pain (pin prick or tissue damage)
  3. thermoreceptors - cold/warm
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7
Q

what does this image represent?

A

the peripheral nerve distribution

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8
Q

name the 3 areas in the spinal cord where we can expect to see variation in white and gray matter regions:

A
  • cervical enlargements (brachial plexus)
    -lateral horns (thoracic region)
    -lumbar enlargements
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9
Q

organization of the tracts to corresponding body parts in the spinal cord is known as _______.

A

somatotopy

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10
Q

what corresponds to 1a&b and 3a&b?

A

1 dorsal column-medial lemniscus
a) cuneate fasciculus (C&T)
b) fasciculus gracilis (L&S)
3 anterolateral spinothalamic tracts
a) lateral spinothalamic tract
b) anterior spinothalamic tract

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11
Q

peripheral nerves travel in bundle to spinal cord and form one or more
_____ _____ ______.

A

spinal nerve roots

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12
Q

what is a dermatome?

A

the area of skin innervated by a spinal nerve

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13
Q

why is the peripheral nerve distribution and spinal nerve distribution clinically significant?

A

based on symptoms (numbness/tingling) in what regions, can help to determine if lesion occurred in the periphery or at the level of the spinal nerve

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14
Q

what are two important things that can help to facilitate clinical reasoning of lesion location?

A
  • peripheral nerve distribution
  • somatotopy
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15
Q

what 4 sensations ascend via DCML?

A

vibration, light touch, conscious proprioception, discrimminative touch

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16
Q

how would you assess each sensation ascending the DCML?

A
  1. vibration = tuning fork
  2. light touch = Qtip or cotton ball
  3. proprioception = mechanical movement of joints, patient eyes opened then closed
  4. discriminative touch = 2 point discrimination tool
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17
Q

where does the DCML 1st order neuron travel?

A

mechanoreceptors to the medulla (doesn’t terminate in the spinal cord)

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18
Q

where does the DCML 2nd order neuron travel? what is it called at this stage?

A

cross in the medulla and travel to thalamus. as the medial lemniscus

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19
Q

where does the DCML 3rd order neuron travel? what does it travel as?

A

from the ventral posterolateral (VPL) nucleus in the thalamus to the primary somatosensory cortex as the thalamocortical fibers

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20
Q

do DCML tracts for cervical region travel medial or lateral to tracts of the lumbar region?

A

lateral goes: cervical-thoracic-lumbar-sacruum.

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21
Q

what 4 sensations ascend via the spinothalamic tracts

A

pain, temperature, crude/non-discriminative touch, pressure

22
Q

how would you assess each sensation ascending the spinothalamic?

A
  1. pain - broken Qtip, dull side vs sharp side
  2. crude/non-discriminative touch - have them close their eyes, can they feel where you are touching
  3. temperature - test tubes of hot versus cold liquids
  4. pressure - by using a pressure algometer
23
Q

what type of sensory receptors are present in the spinothalamic tract?

A

nociceptors and thermoreceptors

24
Q

what is significant about the 1st order neurons in the spinothalamic tract?

A

they bifurcate at the spinal cord and one branch synapses on the dorsal horn at the same level and the other branch ascends or descends 1-2 levels in the spinal cord via the lissauer’s fasciculus

25
Q

Ascending pathways are also called

A

Somatosensory pathways

26
Q

The primary afferent covers specific areas of the body that….

A

are similar person to person

27
Q

Somas of second order afferents (spinothalamic tract) are found in the…

A

dorsal horn (gray matter)

28
Q

Axons of second order afferents travel in bundles called

A

tracts (white matter)

29
Q

Label what the missing parts represent

A
30
Q

Whats a name for this image

A

Homunculus

31
Q

If a lesions was found at the top cerebrum, what might we see

A

Sensory changes to lower extremities

32
Q

If the person presented sensory changes to the ulnar border of the hand and 4-5th fingers what might we suspect

A

A lesion to the ulnar nerve

33
Q

If a person presented with sensory changes to the ulnar border of the hand and forearm, and 4th-5th fingers, what might we suspect

A

Lesion to C8 nerve root

34
Q

where does the second order neuron cross over In the spinothalamic tract?

A

at the spinal level along the anterior white commissure

35
Q

Where are the somas for the primary, 2nd and 3rd order afferents located for DCML

A

1st = DRG
2nd = medulla
3rd = VPL of thalamus

36
Q

Where does the DCML pathway decussate

A

Medulla

37
Q

Why is bifurification of the spinothalamic tract 1st order neuron important

A

To preserve sensation if there is damage to the tract

38
Q

Describe the path of the first order neuron of the spinothalamic tract

A

nociceptors, thermoreceptors enter spinal cord and bifurcates

39
Q

Describe the path of the second order neuron in the spinothalamic tract

A

From dorsal horn it decussates at the spinal cord at the anterior white commissure and travels to the medulla where the anterior and lateral tracts merge to form the spinal lemniscus and then innervate the VPL of the thalamus

40
Q

What sensory info does the lateral tract of the spinothalmic second order neuron transmit

A

pain and temperature

41
Q

what are the 2 tracts of the spinothalamic 2nd order neuron as it travels to the medulla and what are they responsible for?

A

anterior tract; crude touch, pressure
lateral tract: pain, temperature

42
Q

What sensory info does the anterior tract of the spinothalamic second order neuron transmit

A

crude touch and pressure

43
Q

Describe the pathway of the 3rd order neuron of the spinothalamic tract

A

Travels from VPL to primary somatosensory cortex and elsewhere (eg. reticular formation, frontal cortex, etc.)

44
Q

when the ST 2nd order tracts merge in the medulla they form the:

A

spinal lemniscus

45
Q

what is the pathway of the ST 3rd order neuron?

A

ventral nuclues in thalamus (VPL) to the primary somatosensory cortex and elsewhere (front cortex, reticular formation, etc.)

46
Q

Where are the somas for 1st, 2nd and 3rd order afferents of spinothalamic tract

A

1st = DRG
2nd = Dorsal horn of spinal cord
3rd = VPL in thalamus

47
Q

where does the pathway of the spinothalamic tract decussate?

A

spinal cord at the white commissure

48
Q

Where does the pathway decussate in the spinothalamic tract

A

Spinal cord in the white commissure

49
Q

do tracts for cervical region travel medial or lateral to tracts from lumbar region in the spinothalamic tract?

A

medial

50
Q

what are the most common NT’s in the nociceptive processing system?

A

glutamate and substance P

51
Q

a delta fibers are responsible for transmitting signals of:

A

fast, well-localized pain

PTH9111 (15 decks)

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