Ascending Pathways

Question 1

What are the ascending pathways in the nervous system?

Answer 1

DORSAL COLUMN – MEDIAL LEMNISCUS PATHWAY

VENTRAL TRIGEMINOTHALAMIC TRACT

ANTEROLATERAL PATHWAY

SPINOCEREBELLAR PATHWAY

Question 2

What sensations does the DCML interpret?

Answer 2

Discriminative Touch, Vibration, Conscious Proprioception

Question 3

Outline the pathway of the PCML

Answer 3

1st order neuron enters dorsal column and ascend ipsilaterally to medulla via fascicula gracillis (below T7) or fasciculus cuneatus (above T7)

synapse in cuneate/gracile nucleus in posterior medulla (CB = dorsal root ganglion)

2nd order neuron decussates across internal arcuate fibres to contralateral medial lemniscus

2nd order ascends in medulla/pons/midbrain and into VPL of thalamus and synapses (CB = gracile/cuneate nucleus)

3rd order neuron ascend via posterior limb of internal capsule and corona radiata into postcentral gyrus gyrus (CB = VPL)

Question 4

What sensations does the Ventral Trigeminothalamic Tract interpret?

Answer 4

Proprioceptors, Fine touch and Vibration from face

Question 5

Outline the pathway of the VTT

Answer 5

1st order sensory neurons via its three main branches: ophthalmic [V1], maxillary
[V2], and mandibular [V3] nerves

Cell body in trigeminal ganglion in pons synapse in the main sensory nucleus in the PONS

2nd order neurons decussate in pons and ascend in the VTT – ventral Trigeminothalamic tract (close to the medial lemniscus)

2nd order synapse in VPM

3rd order neurons travel through posterior limb of internal capsule->corona radiata->head region of primary somatosensory cortex (more lateral)

Question 6

What sensations does the Anterolateral pathway interpret?

Answer 6

Pain, Temperature, Crude Touch

Question 7

What are the 2 anterolateral pathways?

Answer 7

Lateral spinothalamic tract

Anterior spinothalamic tract

Question 8

What sensations does the Anterior spinothalamic tract convey?

Answer 8

Dull pain, Crude touch, Pressue

Question 9

What sensations does the Lateral Spinothalamic tract convey?

Answer 9

Temperature and sharp pain

Question 10

Outline the pathway of the Spinothalamic tract (Anterolateral System)

Answer 10

1st order neuron synapse in substantia
gelatinosa (CB = dorsal root ganglion)

2nd order neurons decussate in anterior white commissure and ascends in lateral spinothalamic tract

2nd order neuron ascend through midbrain in the spinal lemniscus pathway and into ventral posterolateral thalamic nuclei (VPL) and synapse (CB = substantia gelatinosa)

3rd order neuron ascend via posterior limb of internal capsule and corona radiata into postcentral gyrus

Question 11

What sensations does the Spinocerebellar Pathway convey?

Answer 11

Unconscious proprioception

Question 12

What are the 3 spinocerebellar pathways?

Answer 12

Anterior spinocerebellar

Cuneocerebellar Spinocerebellar Pathway

Posterior Spinocerebellar Pathway

Question 13

Outline the Posterior Spinocerebellar pathway

Answer 13

1st order neuron ascends through the fasciculus Gracilis until they reach L3

1st order neuron synapses in Clarke’s Nucleus

2nd order neuron ascends in posterior spinocerebellar tract

2nd order neuron enters cerebellum via inferior cerebellar peduncles

Question 14

What spinal levels does the Clarke’s nucleus extend from?

Answer 14

L3 to C8

Question 15

Outline the cuneocerebellar Pathway

Answer 15

1st order neuron ascends in fasciculus cuneatus

1st order neuron synapses in accessory cuneate nucleus

2nd order neuron ascend in cuneocerebellar tract, enters cerebellum via inferior cerebellar peduncle

Question 16

What spinal cord levels contribute to the cuneocerebellar tract?

Answer 16

C8 and above

Question 17

Outline the Anterior Spinocerebellar tract

Answer 17

1st order neuron in the lateral side of ventral horn and synapses

Decussates across the anterior white commissure

2nd order neuron decussates and ascends in ventral spinocerebellar tract

2nd order neuron enteres cerebellum by superior cerebellar peduncle and decussates to the ipsilateral side

Question 18

What happens when there is a lesion above the level of decussation in the Spinothalamic tract and VTT?

Answer 18

Contralateral loss of pain, temperature and crude touch

Question 19

What happens when there is a lesion in the spinal cord in the Spinothalamic tract and VTT?

Answer 19

contralateral loss of pain, temperature, crude touch on that side of body but from 2 SC levels down

(for example, C4 lesion will cause loss of sensation from C6 and below)

Question 20

What happens when there is a lesion above the decussation in the DCML?

Answer 20

Contralateral loss of proprioception, vibration and discriminative touch on body and face

Question 21

What happens when there is a lesion below the decussation in the DCML?

Answer 21

Ipsilateral loss of proprioception, vibration and discriminative touch of the trunk and limbs below level of lesion

Question 22

What is the function of the Anterior Spinocerebellar Tract?

Answer 22

Ipsilateral Stretch reflex