Brainstem

Question 1

Ascending (Sensory) Tracts:
Where are the following located?
First order cell bodies
Second order cell bodies
Third order cell bodies

Answer 1

First - DRG
Second - spinal cord or brainstem
Third - thalamus

Question 2

Dorsal Column (Medial Lemniscus) System:
What sensations does the dorsal column carry?
What are the divisions of the dorsal columns?
What are their locations within the spinal cord?
What are the origins of the divisions?

Answer 2

Discriminative touch, pressure, vibration, proprioception, two-point discrimination
Gracilis (medial) - T7 and below (lower limb)
Cuneatus (lateral) - T6 and above (upper limb)

Question 3

Dorsal Column (Medial Lemniscus) System:
Where are the first order cell bodies?
What is the path of their tracts?

Answer 3

DRG

Follow fasciculus gracilis or cuneatus up to brainstem

Question 4

Dorsal Column (Medial Lemniscus) System:
Where are the second order cell bodies located?
What is the path of their tracts?

Answer 4

Caudal medulla of brainstem - nucleus gracilis or cuneatus

Cross neural axis on internal arcuate fibers (decussating axons) and ascend via medial lemniscus to thalamus

Question 5

Dorsal Column (Medial Lemniscus) System:
Where are the third order cell bodies located?
What is the path of their tracts?

Answer 5

VPL of thalamus

Fibers ascend to somatosensory cortex

Question 6

Dorsal Column (Medial Lemniscus) System:
What is the general somatotopy of the dorsal column?

Answer 6

Cranial sensations are more lateral
Caudal sensations are more medial
Gracile tract (medial) - sacral, lumbar, lower thoracic
Cuneate tract (lateral) - upper thoracic, cervical

Question 7

Spinothalamic (Anterolateral) System:
What are the two divisions of the spinothalamic system?
What sensations does each division carry?

Answer 7

Anterior tract - light touch

Lateral tract - fast, acute, sharp pain; painful pressure; temperature

Question 8

Spinothalamic (Anterolateral) System:
Where are first order cell bodies located?
What is the path of their tracts?

Answer 8

DRG

Lissauer’s tracts - can ascend a few levels ipsilaterally

Question 9

Spinothalamic (Anterolateral) System:
Where are second order cell bodies located?
What are the important laminae and what are their names?
What is the path of their tracts?

Answer 9

Dorsal horn of spinal cord
Rexed’s Laminae: marginal layer (I), substantia gelatinosa (II), nucleus proprius (V)
Cross neural axis in anterior white commissure and ascend via spinothalamic tract

Question 10

Spinothalamic (Anterolateral) System:
Where are third order cell bodies located?
What is the path of their tracts?

Answer 10

VPL of thalamus

Fibers ascend to somatosensory cortex

Question 11

Spinothalamic (Anterolateral) System:

What is the general somatotropy of the spinothalamic system?

Answer 11

Rostral regions are more medial
Caudal regions are more lateral
Neck, arm, trunk, leg

Question 12

Descending Somatic (Voluntary) Tracts:
What is the general structure of these pathways?
Where do they originate and travel?
What do they control?
What are first order neurons called and where are their axons located?
What are second order neurons called and where are their axons located?

Answer 12

Two-neuron chain
Brodmann area 4 of cortex to peripheral nerve
Voluntary muscle
Upper motor neurons (UMN) - tracts in CNS
Lower motor neurons (LMN) - nerves in PNS

Question 13

Lateral Corticospinal (Pyramidal) System:
Where do axons terminate?
What information to they provide? To which side?

Answer 13

Along all spinal cord levels

Voluntary muscle movement to contralateral limb musculature

Question 14

Lateral Corticospinal (Pyramidal) System:
Where are first order cell bodies located?
What is the path of their tracts?
Where do 85% of these fibers cross the neural axis?

Answer 14

Primary motor cortex (Brodmann area 4)
Internal capsule, cerebral peduncle, pons, pyramids
Decussation of pyramids (without synapse)

Question 15

Lateral Corticospinal (Pyramidal) System:
Where are second order cell bodies located?
What is their pathway?

Answer 15

Ventral horn of spinal cord

Output to voluntary skeletal muscle

Question 16

Anterior Corticospinal Pathway:
Where do axons terminate?
What do axons control?
Do they cross at the decussation of pryamids?

Answer 16

Mainly cervical and upper thoracic spinal cord
Bilateral control of axial and girdle muscles
No

Question 17

Anterior Corticospinal Pathway:
Where are first order cell bodies located?
What is their pathway?

Answer 17

Motor cortex

Internal capsule through cerebral peduncle and pons to cervical spinal cord levels

Question 18

Anterior Corticospinal Pathway:
Where are second order cell bodies located?
What is their pathway?

Answer 18

Ventral horn of spinal cord

Bilateral output to axial and girdle musculature