Neuroscience Week 3: Major Tracts of the Spinal Cord

Question 1

Posterolateral Spinal Tract

Answer 1

• 1st order neuron (1PCP) - Dorsal root ganglia
• posterior nerve root to posterior column and ascends spinal cord ipsilaterally
• synapses with ↓ not in the spinal cord
• 2nd order neuron (2PCP) - Gracile & cuneate nuclei (medulla)
• send decussating fibers across the medulla via internal arcuate fasciculus
• synapses in thalamus ↓
• 3rd order neuron (3PCP) - contralateral Thalamus (ventroposterior lateral nucleus)
• thalamus projects to Primary sensory cortex

Question 2

Posterolateral Spinal Tract Ipsilateral of Contralateral

Answer 2

Ascend spinal cord ipsilaterally and decussates via the internal arcuate fasciculus in the medulla to synapse contralaterally in the thalamus

Question 3

Anterolateral System (ALS) AKA

Answer 3

Spinothalamic Tract

Question 4

Anterolateral System (ALS)

Answer 4

• 1st order neuron (1ALS) - dorsal root ganglion
• projects from dorsal root ganglion into the dorsal horn of the spinal cord
• 2nd Order neuron (2ALS) - dorsal horn of spinal cord
• from the dorsal horn, the anterolateral fibers decussate across the ventral commissure and bundle in the anterolateral spinal cord where they ascend the spinal cord to synapse in the thalamus
• 3rd order neuron (3ALS) - contralateral ventroposterior lateral nucleus of the thalamus
• Thalamus projects to the primary sensory cortex

Question 5

Anterolateral System (ALS) ipsilateral or contralateral?

Answer 5

Contralateral at the ventral commissure of the spinal cord at the level of the dorsal ganglion and ascend the anterolateral system contralaterally

Question 6

Lateral Corticospinal Tract (CST)

Answer 6

• 1st order neuron (1CST) - Primary motor cortex
• projects from primary motor cortex through the ipsilateral brain stem and decussate within the medullary pyramids through the Cervico-medullary junction and descend contralaterally through the spinal cord in the lateral corticospinal tract to synapse with the spinal motor neuron in the ventral horn
• 2nd Order neuron (2CST) - spinal motor neuron
• Spinal motor neuron projects motor fibers via the anterior nerve root to form the motor division of the peripheral nerve

Question 7

Lateral Corticospinal Tract (CST) ipsilateral or contralateral

Answer 7

projects from primary motor cortex through the ipsilateral brain stem and decussate within the medullary pyramids through the Cervico-medullary junction and descend contralaterally through the spinal cord in the lateral corticospinal tract

Question 8

Which side do the posterior column fibers ascend the spinal cord (in reference to their side of origin)?

Answer 8

posterior column fibers ascend the spinal cord in the posterior column of the ipsilateral side and cross via internal arcuate fasciculus

Question 9

On which side do the anterolateral system (eg, spinothalamic tract) fibers ascend the spinal cord (in reference to their side of origin)?

Answer 9

the contralateral side in the anterolateral system

Question 10

On which side do the lateral corticospinal tract fibers descend the spinal cord (in reference to their side of origin)?

Answer 10

The lateral corticospinal tract fibers descend contralteral to their side of origin by crossing in the cervical medullary junction and descending in the lateral corticospinal tract

Question 11

In the posterior column pathway, where does the 1st order neuron lie?

Answer 11

Dorsal Root Ganglion

Question 12

In the posterior column pathway, where does the 2nd order neuron lie?

Answer 12

Cuneate and gracile nuclei

Question 13

In the posterior column pathway, where does the 3rd order neuron lie?

Answer 13

Ventroposterior lateral nucleus of thalamus

Question 14

In the anterolateral system pathway, where does the 2nd order neuron lie?

Answer 14

The dorsal horn of the spinal cord

Question 15

In the anterolateral system pathway, where does the 1st order neuron lie?

Answer 15

The dorsal root ganglion

Question 16

In the lateral corticospinal tract, where does the 2nd order neuron lie?

Question 17

Legs in lateral corticospinal tract, spinothalamic tract

Answer 17

Legs are lateral

Question 18

Dorsal columns arms and legs organization

Answer 18

hands at sides and legs inside

Question 19

Identify

Answer 19

Question 20

Identify

Answer 20

Question 21

Dorsal Column Function

Answer 21

• Pressure
• Vibration
• Fine touch
• Proprioception

Question 22

Dorsal Column 1st order neuron

Answer 22

Sensory nerve ending → bypass psuedounipolar cell body in dorsal root ganglion → enter spinal cord → ascend ipsilaterally in dorsal column

Question 23

Dorsal Column Synapse 1

Answer 23

Nucleus gracilis, nucleus cuneatus (ipsilateral medulla)

Question 24

Dorsal Column 2nd order neuron

Answer 24

Decussates in medulla → ascends contralaterally as the medial lemniscus