Nervous system - spinal tracts

Question 1

Ascending fiber systems (sensory pathways

Answer 1

• Dorsal columns/medial lemniscal (DCML)
• spinothalamic
• spinocerebellar
• spinoreticular tracts

Question 2

Descending fiber systems (motor pathways)

Answer 2

• corticospinal tracts
• vestibulospinal tracts
• rubrospinal tracts
• reticulospinal system
• tectospinal tract

Question 3

Dorsal columns/medical lemniscal (DCML)

Answer 3

ascending. sensory pathway
- fasciculus cuneatus (laterally located for UE) and fasciculus gracilis (medically located for LE)

• proprioception, vibration, and tactile discrimination
• neurons ascend to medulla where fibers cross to form medial lemniscus; ascend to thalamus and then to somatosensory cortex

Question 4

Spinothalamic tract

Answer 4

ascending. sensory pathway
- pain and temperature (lateral spinothalamic tract), and crude touch (anterior spinothalamic tract)
- ascend one or two ipsilateral spinal cord segments, synapse and cross in spinal cord to opposite side and ascend in ventrolateral spinothalamic system

Question 5

spinoreticular tracts

Answer 5

ascending. sensory pathway
- deep and chronic pain
- to reticular formation of brainstem via diffuse, polysynaptic pathways.

Question 6

corticospinal tracts

Answer 6

descending. Motor pathways

**important for voluntary motor control

• arise from primary motor cortex, descend in brainstem, cross in medulla (pyramidal decussation), via lateral corticospinal tract to ventral gray matter (anterior horn cells)
• 10% of fibers do NOT cross and travel in anterior corticospinal tract to cervical and upper thoracic segments.

Question 7

Vestibulospinal tract

Answer 7

descending. Motor

**important for control of muscle tone, antigravity muscles, and postural reflexes

• arise from vestibular nucleus and descend to spinal cord in lateral (uncrossed) and medical (crossed and uncrossed) vestibulospinal tracts

Question 8

rubrospinal tracts

Answer 8

descending. motor

** assist in motor function

-arise in contralateral red nucleus and descend in lateral white columns to spinal gray

Question 9

reticulospinal system

Answer 9

descending. motor

• • dorsal gray = sensation, especially pain.
• • ventral gray = gamma motor neurons and spinal reflexes

-arises in the reticular formation of the brainstem and descends (crossed and uncrossed) in ventral and lateral columns, terminates both on dorsal gray and ventral gray

Question 10

Tectospinal tract

Answer 10

descending. motor

**assists in head-turning responses to visual stimuli

-arises from superior colliculus (midbrain) and descends to ventral gray.