Anterolateral System N21 Flashcards Preview

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Flashcards in Anterolateral System N21 Deck (28)
1

Anterolateral System is made up of what tracts?

Spinothalamic Tract (STT), Spinoreticulothalamic tract (SRTT), Spinotectal tract (SpTT)

2

Spinothalamic tract function

epicritic, sharp, fast, primary pain, slow, burning second pain

3

Direct spinothalamic tract

direct conscious appreciation of pain

4

Peripheral receptors associated with STT tract

Nociceptors (A-delta, III fibers, lightly myelinated) thermal receptors, thermal nociceptors (A-delta and C fibers for slow, burning second pain)

5

Primary neuron in STT

pseudounipolar, DRG --> Lissauer's tract (lateral entry zone) --> substantia gelatinosa

6

Secondary neuron in STT

cell body in substantia gelatinosa --> decussate at the anterior white commissure 1-2 segments rostral --> ventrolateral STT --> VPL of the thalamus

7

Decussation of STT

Anterior white commissure 1-2 segments rostral to entry

8

Somatotopy of STT

Inferior segments are located laterally in the STT and cervical segments medially

9

Third order neuron of STT

Located in the VPL of the thalamus -->posterior limb of internal capsule --> primary somatosensory cortex (3,1,2)

10

Spinoreticulothalamic Tract (SRTT) function

Protopathic, slow, dull aching pain and crude touch

11

Indirect spinothalamic tract

SRTT for affective and arousal impact of pain

12

Peripheral receptors for SRTT

Nociceptors (slow, burning pain), Thermal receptors, tactile receptors (crude touch)

13

All receptors of SRTT are associated with what type of fibers?

C fibers with slow conduction velocity

14

Primary neuron in SRTT

Periphery --> DRG --> Lissauer's Tract (medial entry zone)

15

Second neuron in SRTT

Substantia Gelatinosa (II or V) --> decussate at anterior white commissure (1-2 above)--> joins STT through spinal cord--> leaves ALS in brainstem to synapse on reticular formation

16

Third neuron in SRTT

Reticular formation --> intralaminar nuclei of the thalamus

17

Fourth neuron in SRTT

Intralaminar nuclei of thalamus --> widespread area of cerebral cortex (not just SI)

18

Spinotectal Tract (SpTT) Function

Slow, burning pain, temperature, crude touch, UNCONSCIOUS FEEDBACK (reflexes and inhibition of STT and SRTT)

19

Receptors associated with the SpTT

Nociceptors, thermal receptors, tactile receptors

20

Fibers associated with the SpTT receptors

ALL unmyelinated C-fibers (slow)

21

1 neuron in SpTT

periphery --> Lissauer's Tract --> substantia gelatinosa

22

2 neuron in SpTT

Substantia Gelatinosa --> anterior white commissure (1-2 segments above) --> ALS --> exits ALS at MIDBRAIN --> Periaqueductal gray (PAG) and Superior Colliculus

23

3 neuron in SpTT

Periaqueductal gray and superior colliculus --> S.C. contributes to the tectospinal descending tract for cervical reflexes from noxious stimuli and PAG descend to alter STT and SRTT incoming sensory information

24

Fate of PAG neurons of SRTT

descend to synapse on the primary neurons of STT and SRTT to inhibit pain transmission

25

mechanism of inhibition of pain by PAG on STT and SRTT

synapse and release ENKEPHALINS which inhibit release of Substance P from

26

Fate of Superior Colliculus neurons of SRTT

descends as the tectospinal tract and goves reflexes to the cervical region (head, neck, eye) towards noxious stimuli

27

When would STT and SRTT be suppressed by descending pathways

Times of emotional stress

28

Descending pathways that modify activity of ascending pathways include

corticospinal, reticulospinal, raphespinal