Spinal Cord Anatomy and Organization Flashcards
spinal cord length
foramen magnum to L2
general function of spinal cord
sensory processory
- primary afferents enter spinal cord
- local - for simple reflexes (w/in level and side)
- ascending tracts
motor neurons
efferents
LMN’s - cell bodies in ventral horn
axons for motor neurons
go to periphery
ventral horn cells
location of lower motor neurons
“final common pathway
descending tracts
axons of upper motor neurons
from brainstem and cerebral cortex
segmentation of spinal cord
based on vertebrae
8 cervical 12 thoracic 5 lumbar 5 sacral 1-3 coccygeal
conus medullaris
around L2
end of spinal cord
each segment of spinal cord
gives rise to pair of spinal nerve
-each has axons of dorsal root and anterior root
spinal cord segment = ?
gives rise to 1 pair of spinal nerves
dorsal root
has dorsal root ganglion
each segment ?
innervates a dermatome
2 enlargements of spinal cord
due to increased number of neurons
-associated with limbs
cervical enlargement - brachial plexus
lumbar enlargement - lumbosacral plexus
cervical enlargement
brachial plexus
lumbar enlargement
lumbosacral plexus
gray matter
inner - butterfly shape
-has cell bodies
white matter
outer
has cell processes (myelin)
clinical orientation
looking up from feet as patient lies on back
blood supply to spinal cord
differences will lead to different lesions depending on location of occlusion
sacral cross section
round
mostly gray
very little white
lumbosacral enlargement cross section
enlarged ventral horns - motor to lower limb
round shape
little white matter
thoracic cross section
very little gray matter - not a lot of musculature
lots of white matter - lots of somatosensation
lateral horn - first presence
dorsal nucleus of clarke - central portion of gray
lateral horn
T1-L2
- preganglionic sympathetic cell bodies
aka IMLCC
dorsal nucleus of clarke
center of gray matter - thoracic cross section
proprioception to cerebellum
cervical enlargement cross section
oval shape
enlarged dorsal and ventral horns
lots of white matter
flexors
more posterior in ventral horn
extensors
more anterior in ventral horn
proximal muscles
more medial in ventral horn
distal muscles
more lateral in ventral horn
three general types of white matter in SC?
long ascending
long descending
propriospinal (short)
long ascending tracts
thalamus
cerebellum
brainstem
long descending tracts
upper motor neurons - to lower motor neurons
from cortex
from brainstem
propriospinal fibers
short - within spinal cord
-connect different cord levels
coordinate reflexes
posterior funiculus below T6
below T6 - known as fasciculus gracilus
somatosensation from lower limb
fasciculus gracilus
posterior funiculus caudal to T6
somatosensation from lower limb
posterior funiculus above T6
fasciculus gracilus
and also fasciculus cuneatus
fasciculus cuneatus
posterior funicullus above T6
primary afferents
somatosensation from upper limb
anterolateral system
anterior and lateral funiculus
- somatosensory fiber tracts
- ascending secondary, tertiary, quarternary neurons
- carrying axons from contralateral side**
spinocerebellar tracts
somatosensation to cerebellum (not conscious)
up lateral funiculus
-ascending secondary and third order neurons
corticospinal tracts
descending tract
lateral funiculus
descending upper motor neurons
final synapse - ventral horns - to LMNs
spinal cord reflexes
motor event driven by sensory stimulus
ex/ withdraw, pupil constriction
local - can operate without UMN input (from cerebrum)
program pattern generators
reflex arc
1 receptor 2 afferent neuron 3 interneurons (s) 4 efferent neuron 5 target organ
local circuits
can still operate with lesion in spinal cord above or below
brainstem
continuation of the spinal cord
performs spinal cord like functions for head
- gives rise to cranial nerves
- initial processing for sensory from head
- LMNs for muscles of head
vital reflexes
relay for all info
conduit functions of brainstem
ascending tracts to thalamus and cerebellum
descending tracts to SC
many relay nuclei in brainstem
cranial nerve functions of brainstem
afferent and efferent info
special sensation
integrative functions of brainstem
complex motor patterns (chewing, swallowing)
cardiovascular and respiratory functions
rostral medulla
open fourth ventricle
caudal medulla
closed fourth ventricle (central canal)
pyramidal decussation
level of inferior edge of medulla
-outcropping of cells - location of crossing of corticospinal tract fibers
pyramids
left and right on medulla
- location of corticopsinal fibers
- UMNs - to voluntary movement
olives
laterally on medulla
pre and post olivarry sulcus
on medulla aorund olives
pons division
basal pons
tegmentum
basal pons
does NOT connect two hemispheres
cerebellar peduncles
fibers from pons to cerebellum
superior
middle
inferior
midbrain
cerebral peduncles
-fiber bundles from cerebral cortex
colliculi
colliculi
two superior
two inferior
cranial nerve 4
right below the inferior colliculi
brainstem
tectum
tegmentum
tegmentum
reticular formation - nuclei throughout brainstem
cranial nerve nuclei (LMNs)
tracts (ascending and descending)
substantia nigra
makes it easy to pick out midbrain
-dopaminergic cell bodies
