Tuesday, 4/19-Pain And Temperature Pathways (Stephens)

Question 1

What type of nerve fibers comprise the primary axons in the indirect spinothalamic pathway?

Answer 1

Unmyelinated, C type fibers with a very slow conduction rate

Question 2

When unmyelinated C type fibers (primary fibers) enter the SC (Indirect spinothalamic pathway), they bifurcate and ascend and descend a variable number of segments in the ___.

The C type fibers will terminate in the __ although some fibers may terminate in the substantia gelatinosa and ascend in the direct spinothalamic system.

Answer 2

Dorsolateral fasciculus of Lissaur

Nucleus proprius

Question 3

In the indirect spinothalamic pathway, secondary axons from the nucleus proprius course bilaterally in the anterior, lateral, and posterior regions of the ___.

Answer 3

Fasciculus proprius

Question 4

The fasciculus proprius is part of a diffuse neuronal net called the ___, which surrounds the grey matter of the SC and extends rostrally through the core of the brainstem to the thalamus

Answer 4

Reticular formation

Question 5

Slow or visceral pain is principally perceived at the __ level

Answer 5

Thalamic

Question 6

This pathway is for “fast” pain

Answer 6

Direct spinothalamic pathway

Question 7

This pathway is associated with “Slow” pain. It conveys a more crude and diffuse type of pain sensation. Most of its receptors are associated with the viscera and is often described as a burning sensation or as a deep, dull, aching, poorly-localized pain

Answer 7

Indirect spinothalamic pathway

Question 8

Fill in the blank for the following regarding the Direct Spinothalamic Pathway for “Fast” pain:

Where is the primary neuron located and how do the axons enter and distribute?

Where are the secondary neurons located and what are its distributions?

Where are tertiary neurons located and where do they project?

Answer 8

Primary neuron=spinal ganglion, enters the SC, bifurcates, and ascends and descends 2 SC segments

Secondary neurons=Substantia gelatinosa–> decussates through Anterior white commissure to form the LSTT and will join with VSTT and spinotectal tract in the medulla to form the Spinal Lemniscus (SL)

Tertiary neurons=VPL in the dorsal thalamus and project to the primary somesthetic cortex

Question 9

What is a consequence of a unilateral lesion of the LSTT?

Answer 9

Contralateral loss of pain and temperature sensation 2 sensory dermatomal segments BELOW level of lesion

Question 10

What is a consequence of a unilateral lesion of the SL?

Answer 10

Contralateral hemianalgesia and thermal hemianesthesia

Question 11

Describe what happens with a unilateral lesion of the spinoreticular fibers (Indirect spinothalamic pathway for Slow pain):

Answer 11

Do NOT result in significant sensory deficits. The pathway is too bilateral and diffuse to be affected by unilateral lesions.