the spinal cord Flashcards
what are the regions in spinal column
cervical, thoracic, lumbar, sacral
where does the cervical region serve
neck
where does thoracic region serve
thorax
where does lumbar region serve
lower back
where does sacral region serve
butt
how many vertebra
30
how can we move if we have vertebra
jelly donuts separate vertebra (tough tissue and thick liquid)
what are the breakdowns for vertebra
7 cervical vertebrae (C1 - C7)
12 thoracic vertebrae (T1 - T12)
5 lumbar vertebrae (L1 - L5)
5 sacral vertebrae (S1 - S5) [fused]
Coccyx (tailbone)
where is c1 attatched to
bottom of skull
how do nerves leave vertebra
through the holes, out both sides
where does SC end
at conus medullaris which is L1 region
what is the cauda equina
the dangling nerves beyond the end of the SC
what holds the dangling nerves in the cauda equina
thecal sac
what is the thecal sac made out of and what is it filled with
dura matter and filled with CSF
what is the spinal nerve breakdown
8 cervical spinal nerves (c1 - c8)
12 thoracic spinal nerves (t1 - 12)
5 lumbar spinal nerves (l1 - l5)
5 sacral spinal nerves (S1 - S5)
1 coccygeal spinal nerve
where do nerves go in relation to vertebra
Nerve goes under vertebra expect for cervical spinal nerves where they go above and 8 is below C7
where do the sacral and coccygeal perforate and where do they go
the sacrum from back to front and go down the legs
where is the spinal cord widest and why
cervical and lumbosacral regions due to increase in LMN for arms/legs
what are the two fissures in the spinal cord and what are the differences in them
anterior median fissure –> shallow but wide separation
posterior median fissure –> deep but thin fissure (tissue adhered to itself)
what are the sulci on the SC and what occurs at these places
anterolateral sulcus –> motor roots exit
posterolateral sulcus –> sensory roots enter
what is the differences between tracts and columns
tracts are fiber bundles with common functions
columns contain multiple tracts
what info is in ascending tracts
sensory
what info is in descending tracts
motor info
how do tracts change throughout the spinal cord
in size and shape but not relative position
what are the descending tracts
corticospinal
rubrospinal
reticulospinal
vestibulospinal
tectospinal
where does the corticospinal tract go to/from
from cerebral cortex to spinal cord
how many corticospinal tracts are there and how do they differ
2 –> lateral (decussates), anterior (no decussation)
how are the axons for each region arranges in corticospinal tract
sacral most lateral, cervical most medial
where does the rubrospinal tract go to/from
from red nucleus to spinal cord
what info does the corticospinal tract carry
main motor movement (UMN to LMN)
how many rubrospinal tracts
1
what does the rubrospinal tract do
regulate large muscle movement (esp arms)
where does the reticulospinal tract go to/from
from reticular formation (part of BS)
to spinal cord
how many reticulospinal tracts are there and what are they
2: lateral and medial
what does the reticulospinal tract do
modify pain perception (analgesic system)
where does the vestibulospinal tract go to/from
from vestibular nuclei (in brain stem)
to spinal cord
how any vestibulospinal tracts are there
1
what does the vestibulospinal tract do
activate quick movements due to body postion changes
where does the tectospinal tract go to/from
from superior colliculus (tectum in midbrain)
to spinal cord
what does the tectospinal tract do
coordinate eye and head movements
how many tetcospinal tracts
1
where do the 1º neurons for sensory live
dorsal root ganglion
what are the ascending tracts
dorsal white column tracts
spinothalamic tracts
spinocerebellar tracts
where do the dorsal columns go to/from
from spinal cord
to medial lemniscus
what is another name for the dorsal column
medial lemniscal system
what info is carried in the dorsal columns
touch, vibration, positon
what are the sides of the dorsal columns and where are they
fasciculus gracilis –> medial
fascilus cuneatus –> lateral
how are the axons for each region arranges in dorsal columns
cervical most lateral, sacral most media
where does the spinothalamic tracts go to/from
from spinal cord
to thalamus
how many spinothalamic tracts are there and what
2: lateral, anterior
what info is carried in spinothalamic tracts
sharp pain, temperature
how are the axons for each region arranges in spinothalamic tract
Sacral most lateral, cervical most medial
where does the spinocerebellar tracts go to/from
from sc
to cerebellum
what info is carried in spinocerebellar tracts
motor control, state, position
how many spinocerebellar tracts and what are they
2: posterior and anterior
how many horns in grey matter and what are they
4
2 sensory in dorsal
2 motor in ventral
what is the difference between spinal nerves and roots
Spinal nerves are combo of dorsal and ventral roots on same side of body
what are ventral roots
Myelinated axons coming from the lower motor neurons that innervate body’s muscles, organs and circulatory system for motor output
what are dorsal roots
myelinated axons that bring sensory input into CNS from receptors
Info about pressure, temperature and pain
what are the spinal nerve types
somatic efferents, visceral efferents, somatic afferents, visceral afferents
what do somatic efferents control
voluntary movment
what do visceral efferents control
involuntary smooth muscle motor movement and secretion from autonomic nervous system
what do somatic afferents do
convey stretch and touch info from skin, joints and muscles
what do visceral afferents do
convey info from internal organs
where do cervical nerves go to
neck, arms, shoulder, upper back
where do thoracic nerves go to
chest, abdomen, back
where do lumbar nerves go to
hips, low back, legs, feet
where do sacral nerves go to
butt, perineum, crotch, back of leg, feet
where does the coccygeal nerve go to
tailbone
what activates mechanoreceptor neutires
all somatic sensations (but tissue damage only activate in extreme conditions)
what somatic sensations are there
pressure, vibration, hair deflection
what activates nociceptors
noxious stimuli (tissue damage)
where do mechanoreceptors decussate
medulla (brain stem)
how do mechanoreceptors ascend in the sc
ipsilaterally
where is the first mechanoreceptor synapse
medulla (brain stem)
where do nociceptive cells decussate
spinal cord
where is the first nociceptive synapse
dorsal horn
how do nocicpetive ascend in the sc
contralaterally
what are the types of 2º nocipetive neurons
Nociceptive specific cells
Wide range dynamic cells
what is the majority 2º nociceptive cell
nociceptive specific cells
where are Nociceptive specific cells located
superficial parts of dorsal horn
what do Nociceptive specific cells respond to
noxious stimuli only
who does Nociceptive specific cells recetive synaptic connections from
1º noci cells
where are wide range dynamic cells located
deep intermediate parts of dorsal horn
what do wide range dynamic cells respond to
noxious stimuli and pressure
what does wide range dynamic cells receptive synaptic connections from
noci cells and mechanoreceptors
where does the spinothalamic tract project to (all steps)
to medial thalamus which projects to both somatosensory and associative cortices
what is the associative cortex
interacts with other parts of brain to get meaning/quality of pain
where does the neospinothalamic tract go
lateral thalamus which projects to somatosensory cortex
what are the differences between UMN and LMN
UMN live in motor cortex and project axons to LMN, they are the origins of motor commands
LMN live in ventral horns and control muscles
what percent of UMN decussate and where
80-90% at pyramidial decussation in lower medulla
what corticospinal tract decussates and what does not
lateral decussate and anterior does not
what are intrafusal fibers
sensory component in muscle that doesn’t contract but contains a sensory stretch receptor
what are extrafusal fibers
bulk of the muscle that is the sensory component which moves the muscle
how do reflexes work
When the intrafusal fibers are stretched, the DRG sensory neuron goes onto the LMN to activate the extrafusal fiber of the same muscle to contract it
Since muscles exist in antagonistic pairs, the sensory afferents also activate inhibitory interneurons that interact with a different LMN to suppress the extrafusal fibers of the opposite muscle
what are signs of lower motor lesions
flaccid paralysis of involved muscles, muscular atrophy (because muscles don’t get activity so it degrades), diminished or absent reflexes
what are signs of upper motor lesions
spastic paralysis (bc LMN are still alive so can act on their own spasms), little/no muscle atrophy, hyperactive reflexes
