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Neuroanatomy > DCML and ALS sensory pathways > Flashcards

DCML and ALS sensory pathways Flashcards

1
Q

what general sensations does the anterior lateral system (ALS) do?

A
  • crude (non discriminative) touch. cannot localize sensation
  • temperature
  • pain
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2
Q

what general sensations does the Dorsal column-Medial lemnisucs (DCML) do?

A

proprioception
vibration
Fine (discriminative) touch. Can localize sensation

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3
Q

T/F Receptor distribution is NOT uniform over the body surface; receptor density varies, as does receptive field size.

A

true, this results in distorted cortical maps representing different parts of the body

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4
Q

what is the primary sensory neuron type in the DCML pathway?

A

pseudo-unipolar neuron with a central and peripheral branch, with it’s cell body in the dorsal root ganglion

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5
Q

what are the skin mechanoreceptors that detect mechanical inputs?

A

fine touch, vibration, pressure, motion

DCML pathway

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6
Q

what do free nerve detect?

A

pain, temperature, itch

ALS pathway

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7
Q

what do proprioceptors detect?

A

muscle stretch, tension, and joint position

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8
Q

the speed of conduction depends upon axon diameter and degree of myelination, what are the two types of neurons in the DCML pathway?

A

Alpha(group I): largest diameter, fastest, proprioceptors in muscles
Beta(Group II): second largest diameter and speed, mechanoreceptors of skin

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9
Q

what is the receptive field?

A

the area detected by a single receptor neuron

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10
Q

what is a dermatome?

A

an area of skin that is mainly supplied by a single spinal nerve

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11
Q

where do mechanical and proprioceptive information go once the information is in the spinal cord?

A

dorsal (or posterior) columns

no synapse yet and still ipsilateral

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12
Q

what are the two tracts within the dorsal column and what part of the body do they contain?

A
  • gracile tract (more medial tract): 1st order sensory neurons of the lower half of the body below thoracic level 6
  • cuneate tract (more lateral): 1st order sensory neurons of the upper half of the body above thoracic level 6
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13
Q

where is the first synapse in the in the dorsal column nuclei?

A

caudal medulla

**still ipsilateral

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14
Q

after the synapse in the caudal medulla what happens?

A

the second order neurons then cross the midline (decussate) in the internal arcuate and ascend in the medial lemniscus.

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15
Q

where is the medial lemniscus?

A

just behind the pyramid of the medulla and medial to the inferior olive

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16
Q

is the information in the medial lemniscus ipsilateral or contralateral?

A

contralateral

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17
Q

where is the medial lemniscus in the pons?

A

just posterior to the pontocerebellar fibers and bobs big belly. its more in the middle part of the pons and is horizontal (medial lateral orientation)

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18
Q

in the inferior portion of the midbrain where is the the medial lemnisucs?

A

just behind the substantia nigra

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19
Q

in the rostral midbrain where is the medial lemniscus located?

A

just lateral to the red nucleus

20
Q

is somatotopy maintained throughout the pathway?

A
  • yes, it starts aligned ventral and dorsally with the arms(upper body) is dorsal and the legs are ventral.
  • as it moves up the brainstem the medial lemniscus rotates laterally until in the midbrain the legs are more dorsal and the arms and ventral
21
Q

where is the second synapse in the DCML pathway?

A

in the VPL of the thalamus

**this is contralateral to the original sensory input.

22
Q

where do axons from the thalamus (3rd order neurons) ascend to?

A

to post central gyrus of the cortex traveling in the internal capsule

23
Q

what does VPL mean?

A

ventral posteriolateral

24
Q

how is the primary somatosensory cortex organized?

A

somatotopicly

25
Q

can the cortical sensory map change?

A

yes, it is plastic.

if you lose a finger the region of the brain the neighboring finger can move into the now dead area

26
Q

what types of general sensation is associated with the ALS or spinothalamic system?

A

crude touch (non discriminative) touch
temperature
pain

27
Q

why is the anterolateral system related to feelings from our body?

A

associated with emotion, drives behavioral motivation, hunger, thirst, visceral sensations, TEMPERATURE, PAIN, ITCH, tickle

28
Q

although the ALS has pseudo-unipolar neurons with a central and peripheral branch, which is different about the peripheral end?

A

it is a free nerve ending

29
Q

what are the two neuron types of the ALS system?

A

delta (group III): 3rd smallest diameter and speed. Pain, temperature
C (group IV): smallest diameter and speed. Temperature pain and itch. not myelinated

30
Q

which cell type is responsible for the first pain ada sharp pain?

A

delta nociceptors

31
Q

which cell type is responsible for the second pain aka burning slower longer lasting pain?

A

polymodal C-nocicpetors

32
Q

where does the ALS pathway decussate?

A

in the spinal cord via anterior white commissure to the ALS white matter(spinothalamic tract)

33
Q

where do the first order neurons synapse in the ALS pathway?

A

dorsal horn of the spinal cord

ipsilateral

34
Q

what is the tract of lissauer?

A

some of the 1st order neurons of the ALS pathway will not synapse at the level they enter the spinal cord, but will travel up to another level and synapse there.

35
Q

where do second order neurons decussate?

A

in the anterior white commissure and ascend in the anteriolater system (ventral white commissure).

36
Q

at the spinal cord (cervical level) are the ALS and DCML pathways ipsilateral or contralateral?

A

ALS is contralateral

DCML is ipsilateral

37
Q

where is the anteriolateral (ventral white commissure) located?

A

just lateral the the ventral horn

38
Q

is there somatotopy in the ALS system?

A

yes

39
Q

where is the anteriolateral (ventral white commissure)?

A

just dorsal to the interior olive on the most lateral portion

40
Q

what is unique about the medulla?

A

both the ALS and DCML pathways have decussated

41
Q

in the pons what it the relationship in location of the ALS to the DCML

A

the anterolateral system is just dorsal and lateral to the medial lemniscus which is dorsal the the pontocerebellar tracts

42
Q

in the midbrain where is the ALS in relation to the DCML?

A

dorsal to the most lateral edge of the medial lemniscus

43
Q

where does the second order neuron synapse?

A

in the VPL (same as the DCML)

44
Q

the third order neuron in the thalamus then follows a similar path the to post central gyrus via the internal capsule. T/F

A

true

45
Q

does the ALS pathway follow somatotopic organization in the somatosensory cortex?

A

yes

Neuroanatomy (8 decks)

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