ICL 2.2: Introduction to the Spinal Cord & Internal Organization Flashcards
what are the components of the central vs. peripheral nervous systems?
CNS = brain and spinal cord
PNS = all neural tissue not brain nor spinal cord
this includes cranial nerves, spinal nerves, autonomic ganglia and plexuses
where does the spinal cord end?
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
where do the afferent and efferent neurons enter/exit the spinal cord?
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
where are the cell bodies of afferent neurons located?
dorsal root ganglion
dorsal root ganglion is a cluster of neurons
what are the arteries that supply the spinal cord?
2 posterior arteries that travel down the posterior intermediate septums
there is also an anterior vertebral artery that enters through the anterior media fissure
what are rexed lamina?
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
what is the substantial gelatinosa? which rexed laminae is it found in?
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
what is the nucleus proprius?
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
what is the DCML pathway?
DCML = dorsal column-medial lemniscus pathway found in the white matter of the spinal cord
it conveys localized sensations from skin and joints:
- fine touch
- two-point touch discrimination
- vibration
- joint position (proprioception)
what is the 1st, 2nd, and 3rd order of the DCML pathway?
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
what is the spinothalamic system?
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:
- pain
- temperature (Hot/Cold)
- crude touch
what is the 1st, 2nd, and 3rd order of the spinothalamic system?
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
what are the two ascending afferent pathways through the spinal cord?
- dorsal column-medial lemniscal pathway
fine touch, vibration, proprioception
- spinothalmic tract
pain, temperature, crude touch
what is the corticospinal tract?
conveys:
- motor impulses from cortex to the end organ (skeletal muscle)
- voluntary movement for limbs and trunk
what is the 1st, 2nd, and 3rd order of the corticopsinal tract?
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)
what is the somatotopy of the grey and white matter of the spinal cord? aka where are all the different pathways?
SLIDE 14 GO LOOK AT IT
what is the succession of the parts of a nerve coming into the spinal cord?
anterior primary ramus or posterior primary ramus –> mixed spinal nerve –> dorsal root ganglion –> posterior root –> posterior rootlets –> posterior horns of the gray matter
what is the succession of the parts of a nerve exiting the spinal cord?
anterior horn of the gray matter –> anterior rootlets –> anterior root –> mixed spinal nerve –> anterior primary ramus or posterior primary ramus
in what position do the spinal nerves exit?
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
what is the location of the two spinal cord enlargements?
- cervical enlargement
- lumbosacral enlargement
they are due to the plexuses arising from those levels
what is the cervical enlargement of the spinal cord?
innervates pectoral girdle & upper limb
anterior primary rami of the C5-T1 spinal cord segments contribute to brachial plexus
what is the lumbosacral enlargement of the spinal cord?
innervates pelvic girdle & lower limb
anterior primary rami of the L1-S4 spinal cord segments contribute to lumbar plexus and sacral plexus
what are the layers of the spinal cord meninges?
OUTSIDE
1. dura mater
- arachnoid mater
- pia mater
INSIDE
where is the CSF found?
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
what is the filum terminale interna?
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
what is the cauda equina?
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)
what is the artery of Adamkiewicz?
the major arterial supply of the anterior spinal artery supplying arterial blood to the spinal cord from T8 to the conus medullaris
what is the origin of the artery of Adamkiequiwz?
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
what is the vertebral venous plexus of Batson?
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
what disease is the vertebral venous plexus of Batson associated with?
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
