Spinal cord & tracts

Question 1

Where in the spine is white matter largest? Where is grey matter largest?

Answer 1

White matter is biggest in the cervical spine.

Grey matter is biggest within the cervical and lumbar enlargements, corresponding to the arms and legs.

Question 2

What are funiculi?

Answer 2

Divisions of the white matter of the spinal cord composed of longitudinal bundles of axons

Question 3

What functional components are found within the posterior horn of the spine?

Answer 3

Sensory: GSA and GVA

*GSA is found most posterior column, GVA is anterior to that

Question 4

What functional components are found within the lateral horn of the spine?

Answer 4

GVE

Preganglionic sympathetics

Question 5

What functional components are found within the anterior horn of the spine?

Answer 5

Motor efferents: GSE

Question 6

Where is the substantia gelatinosa, and what is its function?

Answer 6

Nucleus within the posterior horn of the spine that modulates pain. Analogous to the spinal trigeminal nucleus.

Question 7

Where is the nucleus proprius and what is its function?

Answer 7

Nucleus within the posterior horn that receives many sensory inputs. Axons project from this nucleus to form the spinothalamic tract (STT)

Question 8

Where is the nucleus dorsalis and what is its function?

Answer 8

Found in the intermediate zone of the spinal cord. Receives muscle spindle information and projects to the cerebellum via the dorsalspinocerebellar tract (DSCT)

Question 9

Where is the intermediolateral nucleus and what is its function?

Answer 9

IML is found in the lateral horn, and contains cells that make up the preganglionic sympathetic efferents (GVE)

Question 10

Where are the medial and lateral motor nuclei and what are their functions?

Answer 10

Motor nuclei found in the anterior horn. Innervate skeletal muscle. Largest in the cervical and lumbar enlargements.

Question 11

Which nerve receptors are not encapsulated?

Answer 11

Free nerve endings (pain/temp)
Merkel’s disks (touch)
Hair follicles (touch)

Question 12

What receptors are fast adapting?

Answer 12

Hair follicles (touch)
Meissner's corpuscle (2 point discrimination)
Pacinian corpuscle (vibration)

Question 13

What is the difference between neuromuscular spindles and golgi tendon organs?

Answer 13

Spindles are found within muscles and sense muscle stretch/length. GTOs are found within tendons and sense muscle tension.

Question 14

What information is relayed by the dorsal column pathway?

Answer 14

2 point discrimination
Vibration sense
Proprioception

All GSA

Question 15

Describe the path of the dorsal column pathway

Answer 15

Peripheral sensory neurons have cell bodies in the dorsal root ganglion, enters spinal cord and ascends in the dorsal column (fasiculus cuneatus or gracilis).
Synapse in the ipsilateral nucleus cuneatus/gracilis of the lower medulla. Crosses in medulla and ascends to VPL of thalamus via the medial lemniscus. VPL neurons project to area 312.

Question 16

What physical exam test can detect posterior column damage?

Answer 16

Romberg sign: positive if patient requires vision to stand steadily with feet together

Question 17

What is the major spinal nucleus associated with the STT?

Answer 17

Nucleus proprius

Question 18

Describe the path of the STT

Answer 18

Primary neurons sense pain/temp, synapse in ipsilateral nucleus proprius. Secondary neuron crosses at that level and ascends in the contralateral anterolateral funiculus. Synapses in VPL of thalamus, which projects to area 312.

Question 19

What is sacral sparing?

Answer 19

Because of the somatotopic organization within the anterolateral funiculus, central lesions (like syringomyelia) will affect the upper body first, thus sparing the lower body.

Question 20

What is a Brown-Sequard lesion?

Answer 20

Spinal cord hemisection. Results in ipsilateral loss of proprioception below lesion and contralateral loss of pain/temp below lesion.

Question 21

What is the major spinal nucleus associated with the dorsal spinocerebellar tract?

Answer 21

Nucleus dorsalis (Clark’s nucleus) between C8-L2

Question 22

Describe the path of the dorsal spinocerebellar tract

Answer 22

Lower extremity neurons (C8-L2) from muscle spindles and golgi tendon organs synapse in nucleus dorsalis, ascend in ipsilateral lateral funiculus, pass through the inferior cerebellar peduncle and end in the ipsilateral cerebellum.

Question 23

Describe the path of the cuneocerebellar tract

Answer 23

Upper extremity neurons (C7-C1) from muscle spindles and golgi tendon organs synapse in the cuneate nucleus, passes through the inferior cerebellar peduncle and into the ipsilateral cerebellum.

Question 24

Describe the path of the ventral spinocerebellar tract

Answer 24

Samples interneuron activity in the intermediate spinal gray matter, crosses immediately and ascends in the contralateral anterolateral funiculus. After passing through the superior cerebellar peduncle, it crosses back over to end in the ipsilateral cerebellum.