L11 - spinal cord and spinal nerves Flashcards
ganglia
grouping of cell bodies in the PNS
nerve
collection of axons
fascicule / tracts / pathways
collection of white matter fibres in the CNS
location of spinal cord
extends from foramen magnum to L1/2
where does the spinal cord terminate
conus medullaris
how do spinal nerves leave
intervertebral foramina
cauda equina
Spinal nerves continue to emerge to leave below the conus medullaris
thicker part of the spinal cord
cervical / lumbar
thinner part of the spinal cord
thoracic
filum terminale
proves an inferior attachment for the spinal cord
what is contained in the dural sac
CSF
how many spinal nerve segments are there
31
lumbar cisterm
region of the dural sac –> most common site for LP
location of conus medullaris
L1-2
cervical enlargement
brachial plexus
C1-C8
lumbosacral enlargement
lumbosacral plexus
L1-S2
why are cervical and lumbar regions thicker
lots of neurones for motor control which innervate the upper and lower limb
where do C- spinal nerves leave
above corresponding spinal level
how many C spinal vertebrae are there
7
how many C spinal nerves are there
8
why are there more spinal nerves than spinal vertebrae
in the C-spine, spinal nerves leave above corresponding spinal level
In the T spine, spinal nerves leave below their corresponding spinal level
there is therefore a gap for spinal nerve C8 to leave above T1 (below C7)
denticulate ligaments
extensions of the Pia which secure the spinal cord as they emerge and attach to the dura
epineurium
a protective outer sheath of connective tissue for each spinal nerve
how is the epineurium formed
spinal nerve and meningeal coverings
what is contained within the real epidural space
fat
location of epidural/extradural space
between dura and vertebrae
explain differential growth between vertebral column and the spinal cord
- vertebral column grows faster compared to spinal cord
- spinal cord regresses and ascends upwards
termination of spinal cord in children
L3
coccyx
filum terminale
where to insert needle in lumbar puncture
anywhere around L3 - lumbar cistern
what structure allows for lumbar puncture at lumbar cistern
Cauda equina
- nerve roots will just move away gently when the needle is inserted
when is a lumbar puncture not indicated
patients with increased inter cranial pressure
- a pressure differential would be created
- CSF would escape
- brain could herniate
why should a patient bend their back when receiving a lumbar puncture
- ligaments will stretch so there is room to insert the needle
what structure are you hitting when you hear a pop in a lumbar puncture
ligamentum flavum
epidural anaesthesia
- Still puncture ligamentum flavum, however, do not go as deep
- Popular to insert at region of sacrum for pregnant women as this will numb the nerves around the perineum
vasculature of spinal cord
anterior and posterior spinal arteries and nerves
how are anterior and posterior spinal arteries enforced
segmental spinal arteries
medullary artery
originates from segmental spinal arteries
- reinforces asa in the anterolateral aspects of the cord
anterior and posterior radicular artery
supplies spinal nerve rootlets
dorsal horn
- many synapses occur
- mainly of sensory neurones
lateral horn
origin of preganglionic visceral motor neurones of the sympathetic and parasmypathetic nervous system
ventral horn
motor neurones which innervate muscles
ventral white commissure
allows for communication / crossing of fibres from hemispheres
peripheral nervous system
connections outside of the brain
afferent fibres
sensory
- sends info TO CNS
efferent fibres
motor
- sends into AWAY FROM CNS
how is CNS connected to PNS
spinal cord is connected to PNS via nerve rootlets
how to nerve rootlets leave the CNS
ventral - leave anterolateral sulcus
dorsal - leave posterolateral sulci
what do ventral and dorsal nerve rootlets combine to form
segmental spinal nerve
what do afferent sensory fibres do once entering the spinal nerve
segregate to the dorsal root ganglia
what happens in the ventral horn
cell bodies of somatic motor neurones leave the cord and join the spinal nerve (via the ventral root)
when does the reflex arc occur
- No time to for info to process properly
- Quick response
- Occurs at level of spinal cord
reflex arc
- sensory afferent fibres travel to CNS using dorsal route
- synapse with interneurones
- interneurones relay information to cel body of efferent neurones
- leave ventral horn and use ventral route of spinal nerve and use the PNS to go to the muscle it is stimulating
which part of the spinal cord has the most white matter
cervical
why does the cervical cord have the most white matter
Increasing fibres relaying information from all over the body
how does white matter change throughout the cord
increases as cord ascends
where in the spinal cord are ventral grey horns enlarged
- where motor fibres to limbs arise
- cervical and lumbosacral enlargements
location of lateral horn
T1-L2
S2-S4
where in the spinal cord are there 2 dorsal columns on either side of the midline
above T6
what are the 2 dorsal columns on either side of the midline
- Gracile fascicle medially
- Cuneate fascicle laterally
dorsal columns below T6
1 or no fascicles
how is grey matter divided into regions
- sites of sensory or motor nuclei
- extends varying length of cord
is the dorsal horn motor or sensory
sensory
is the ventral horn motor or sensory
motor
lissauer’s tract
where sensory fibres enter to synapse to their corresponding lamina of grey matter
role of dorsal columns
sen ascending sensory information
- fine touch
- vibrations
- pressure
- joint position
lateral corticospinal tract
descending motor neurones for voluntary control of muscles
ventral corticospinal tract
descending motor fibres for voluntary movement
spinothalamic tract
ascending sensory fibres
- crude touch
- pain
- temperature
