ICL 2.2: Introduction to the Spinal Cord & Internal Organization

Question 1

what are the components of the central vs. peripheral nervous systems?

Answer 1

CNS = brain and spinal cord

PNS = all neural tissue not brain nor spinal cord

this includes cranial nerves, spinal nerves, autonomic ganglia and plexuses

Question 2

where does the spinal cord end?

Answer 2

it extends caudally to the L1-2 intervertebral disc level

the end of the spinal cord is called the conus medullaris

below the L2 level, nerve roots exit the tapered end of the cord = cauda equina

Question 3

where do the afferent and efferent neurons enter/exit the spinal cord?

Answer 3

the afferent neurons enter on the dorsal side of the spinal cord in the posterior horn of the grey matter

the efferent neurons exit on the ventral side of the spinal cord in the anterior horn of the grey matter

Question 4

where are the cell bodies of afferent neurons located?

Answer 4

dorsal root ganglion

dorsal root ganglion is a cluster of neurons

Question 5

what are the arteries that supply the spinal cord?

Answer 5

2 posterior arteries that travel down the posterior intermediate septums

there is also an anterior vertebral artery that enters through the anterior media fissure

Question 6

what are rexed lamina?

Answer 6

the Rexed laminae comprise a system of ten layers of grey matter (I–X)

used to label portions of the grey columns of the spinal cord

Question 7

what is the substantial gelatinosa? which rexed laminae is it found in?

Answer 7

a section of the grey matter of the spinal cord found in rexed laminae II at the apex of the horn

composed of large neurons and extends throughout the length of the spinal cord

has to do with afferent neurons so it’s responsible for pain, temperature and touch

Question 8

what is the nucleus proprius?

Answer 8

a section of the grey matter of the spinal cord found in rexed laminae IV, anterior to the substantial gelatinosa

composed of large neurons and extends throughout the length of the spinal cord

has to do with afferent neurons so it’s responsible for sense of position and movement = proprioception

Question 9

what is the DCML pathway?

Answer 9

DCML = dorsal column-medial lemniscus pathway found in the white matter of the spinal cord

it conveys localized sensations from skin and joints:

1. fine touch
2. two-point touch discrimination
3. vibration
4. joint position (proprioception)

Question 10

what is the 1st, 2nd, and 3rd order of the DCML pathway?

Answer 10

FIRST ORDER
the proprioceptors or mechanoreceptors enter via dorsal root ganglion and ascend ipsilateral in gracile or cuneate fasciculus

gracile fasciculus carries information from the lower body while the cuneate fasciculus carries information from the upper part of the body

SECOND ORDER
the gracile or cuneate fasciculus synapse in the dorsal column nuclei and then the pathway crosses to the opposite side of the dorsal medulla via the internal arcuate fibers of the medulla oblongata

then it ascends via the medial lemniscus to the ventroposterolateral (VPL) nucleus of the thalamus

THIRD ORDER
the pathway then synapses in the VPL and ascends through the Internal Capsule to the post-central gyrus which contains the primary somatosensory cerebral cortex

Question 11

what is the spinothalamic system?

Answer 11

the spinothalamic system is composed of the lateral spinothalamic tract and the anterior spinothalamic tract

the lateral spinothalamic tract converts pain and temperature

the anterior spinothalamic tract conveys information about crude touch

overall, this pathway conveys localized sensations from skin, joints, viscera about:

1. pain
2. temperature (Hot/Cold)
3. crude touch

Question 12

what is the 1st, 2nd, and 3rd order of the spinothalamic system?

Answer 12

FIRST ORDER
nociceptors or thermoreceptors enter through the dorsal root ganglion and ends in the substantial gelatinosa

SECOND ORDER
the pathway synapses ipsilaterally in the substantial gelatinosa then crosses to the opposite anterior/lateral tract through lamina X in the middle of the grey matter

the pathway then ascends contralateral in the Lissauer’s tract through the medulla oblongata all the way up to the ventroposterolateral nucleus of the thalamus

THIRD ORDER
the pathway then synapses in the VPL and ascends through the internal capsule to the post-central gyrus which contains the primary somatosensory cerebral cortex

Question 13

what are the two ascending afferent pathways through the spinal cord?

Answer 13

1. dorsal column-medial lemniscal pathway

fine touch, vibration, proprioception

2. spinothalmic tract

pain, temperature, crude touch

Question 14

what is the corticospinal tract?

Answer 14

conveys:

1. motor impulses from cortex to the end organ (skeletal muscle)
2. voluntary movement for limbs and trunk

Question 15

what is the 1st, 2nd, and 3rd order of the corticopsinal tract?

Answer 15

FIRST ORDER
starts in primary motor cortex and descends through posterior internal capsule and through the cerebral peduncles (basis pedunculi)

it then continues down through the brain to the medulla where in the medulla it crosses over in the caudal medulla = axons descend contralaterally to synapse with lower motor neurons (LMN)

SECOND ORDER
the pathway synapses with α-motor neurons in Lamina VIII/IX and exits cord through the ventral root to spinal nerve (lower motor neurons)

Question 16

what is the somatotopy of the grey and white matter of the spinal cord? aka where are all the different pathways?

Answer 16

SLIDE 14 GO LOOK AT IT

Question 17

what is the succession of the parts of a nerve coming into the spinal cord?

Answer 17

anterior primary ramus or posterior primary ramus –> mixed spinal nerve –> dorsal root ganglion –> posterior root –> posterior rootlets –> posterior horns of the gray matter

Question 18

what is the succession of the parts of a nerve exiting the spinal cord?

Answer 18

anterior horn of the gray matter –> anterior rootlets –> anterior root –> mixed spinal nerve –> anterior primary ramus or posterior primary ramus

Question 19

in what position do the spinal nerves exit?

Answer 19

C1-C7 spinal nerve pairs exit spine SUPERIOR to same numbered vertebra

C8 spinal nerve pair exits spine inferior to C7 vertebra

T1-Co exit VC inferior to same numbered vertebra

Question 20

what is the location of the two spinal cord enlargements?

Answer 20

1. cervical enlargement
2. lumbosacral enlargement

they are due to the plexuses arising from those levels

Question 21

what is the cervical enlargement of the spinal cord?

Answer 21

innervates pectoral girdle & upper limb

anterior primary rami of the C5-T1 spinal cord segments contribute to brachial plexus

Question 22

what is the lumbosacral enlargement of the spinal cord?

Answer 22

innervates pelvic girdle & lower limb

anterior primary rami of the L1-S4 spinal cord segments contribute to lumbar plexus and sacral plexus

Question 23

what are the layers of the spinal cord meninges?

Answer 23

OUTSIDE
1. dura mater

2. arachnoid mater
3. pia mater
   INSIDE

Question 24

where is the CSF found?

Answer 24

in the arachnoid mater!!

the arachnoid mater is a layer of the spinal cord meninges

the arachnoid mater also contains spinal artier and veins and the rootlets and roots of nerves – so where there is a subdural hematoma it’s between the dura mater and the arachnoid mater

Question 25

what is the filum terminale interna?

Answer 25

it’s the continuation of the pia mater inferior to the conus medullaris aka the end of the spinal cord

it descends all the way to the end of the lumbar cistern (S2)

it then fuses with the dura mater to form the filum terminale externa and extends caudally all the way to the coccyx - anchoring the spinal cord

Question 26

what is the cauda equina?

Answer 26

the collection of nerve roots coming from the end of the spinal cord, within the lumbar cistern, traveling to the vertebral foramina inferior to the conus medullaris

it extends to the S2 tubercle which is the end of the meninges (even though the spinal cord ended at L2)

Question 27

what is the artery of Adamkiewicz?

Answer 27

the major arterial supply of the anterior spinal artery supplying arterial blood to the spinal cord from T8 to the conus medullaris

Question 28

what is the origin of the artery of Adamkiequiwz?

Answer 28

variable origin but most commonly ariseson the left (~80%), arises on the right (20%)

usually it’s at the level of of the 9th-12thintercostal artery (~70%)

it ascends on the mid-sagittal anterior surface of the spinal cord, usually less than two-and-a-half vertebral body lengths

Question 29

what is the vertebral venous plexus of Batson?

Answer 29

a network of valveless veins in the human body that connect the deep pelvic veins and thoracic veins to the internal vertebral venous plexuses

the internal vertebral venous plexus is within the vertebral canal and is embedded in fat

the external vertebral venous plexus is external to vertebral canal

Question 30

what disease is the vertebral venous plexus of Batson associated with?

Answer 30

prostate cancer that has spine mets!!!

this is because the vertebral venous plexus of Batson communicates with the prostatic venous plexus which can lead to the hematogenous spread of cancer