Exam 3 somatosensory pathways part 1- Michaels

Question 1

What sensations does dorsal column-medial lemniscus pathway deal with?

Answer 1

Fine touch, vibration, proprioception

Question 2

What sensations does the spinothalamic tract deal with?

Answer 2

Pain and temperature (monitory changes in temperature)

Question 3

where does sensory information go to in the cortex

Answer 3

S1 of the somatosensory cortex (post central gyrus)

Question 4

When does the Dorsal column-medial lemniscus pathway decussate?

Answer 4

2nd order neuron crosses over after the dorsal column nuclei (caudal medulla) up to the thalamus

Question 5

When does the spinothalamic pathway decussate?

Answer 5

the 2nd order neuron crosses midline at the same level or along lissauer’s tract

Question 6

what type of neurons are involved in the pain pathway?

Answer 6

A-delta and C fibers (which are much slower)

Question 7

Where does the corticospinal pathway decussate?

Answer 7

upper motor neuron decussates within the pyramids of the medulla

Question 8

what happens when lower motor neurons are injured?

Answer 8

muscle atrophies

Question 9

What happens when upper motor neuron is injured?

Answer 9

hyperreflexia

Question 10

As a general rule, do axons of primary sensory neurons cross the midline?

Answer 10

nope

Question 11

Where are the cell bodies of sensory neurons located in the dorsal root ganglia

Answer 11

Medial part of DRG

Question 12

What part of spinal cord section does spinal nerves ascend toward brain?

Answer 12

Dorsal column (gracile and cuneate fasciculi)

Question 13

Where are local branches of primary afferent sensory neurons terminating in the spinal cord?

Answer 13

Terminate in dorsal horn in Lamina V with interneurons that contribute to reflexes

Question 14

T/F: primary afferent neurons cross the dorsal column and ascend to the brain contralaterally?

Answer 14

False, don’t decussate until medulla

Question 15

What is convergence?

Answer 15

Neurons that supply a large area in terms of sensory feed back to a single secondary nerve

Question 16

Where are the cervical nerves located in the ventral posteriolateral nucleus in the thalamus? Sacral?

Answer 16

Cervical is more medial than sacral.

Question 17

Where do sensory neurons from the thalamus pass to?

Answer 17

Pass laterally through internal capsule and project to the postcentral gyrus of ipsilateral cortex (S1)

Question 18

What sensations does the spinothalamic tract deal with?

Answer 18

Pain and temperature

Question 19

What kinds of receptors provide input to the STT neurons?

Answer 19

nociceptors, thermoreceptors and mechanoreceptors

Question 20

T/F: damage to the STT results in deficits in pain and temp sensation but not touch

Answer 20

true

Question 21

At what level does the STT cross?

Answer 21

second order neuron cell bodies in the substantia gelatinosa of the dorsal horn can cross at the same level to the STT via the white commissure and ascent in the ventrolateral funiculus, or move up 1 or 2 segments via lissauer’s tract and then cross at that level

Question 22

Does a lesion at a specific level cut out all pain and temperature below that level?

Answer 22

No, 1 or 2 segments below it can move around the lesion via lissauer’s tract and still report pain receptor activity

Question 23

When is it certain that an axon of the STT has crossed?

Answer 23

within two spinal segments up the spinal cord

Question 24

What is syringomyelia?

Answer 24

a hole or cyst develops in the center of the cord and expands out rostral/caudally up to several inches, usually caused by CSF block, and blocks crossing STT fibers

Question 25

What results from a syringomyelia?

Answer 25

bilateral loss of pain and temperature sensation

Question 26

Where does the primary nociceptor neuron synapse with the secondary neuron NOT using the lissauer’s tract?

Answer 26

Within the substantia gelatinosa

Question 27

Where does the STT tract drop information off to awaken an individual in pain?

Answer 27

Reticular formation (leads to depolarization of cortical neurons and desynchronization of EEG)

Question 28

Besides thalamus, where does the reticular formation send information?

Answer 28

Central lateral nucleus synapsing to third order nuclei that sends information to limbic system of cortex, leading to the “suffering” of pain

Question 29

What do lesions of the VPL result in?

Answer 29

difficulty localizing pain

Question 30

Where is reticular formation located?

Answer 30

brainstem

Question 31

What is Brown séquard syndrome?

Answer 31

half of spinal cord is lesioned leading to hemiplegia