spinal cord function adn dysfunction

Question 1

summarise the spinal cord segments

Answer 1

31 spinal segments
31 pairs of nerves - 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal - leave the vertebral column through intervertebral foramen

Question 2

why are there cervical and lumber enlargements *

Answer 2

for innervation of the limbs

there are many more neurons in the cord at these points

Question 3

what does the cervical enlargement innervate and what spinal segments are involved *

Answer 3

upper limbs

C3-T1

Question 4

what does the lumbar enlargement innervate and what spinal segments are involved *

Answer 4

upper limbs

L1-S3

Question 5

describe at what level the nerves leave the vertebral column *

Answer 5

C1-C7 nerve leave above the relevant vertebrae,

C8 leaves between C7 and T1 vertebrae, every nerve after that leaves after the relevant vertebrae

Question 6

describe the discrepancy between the spinal levels and the vertebral levels *

Answer 6

each has the same number as segments - spinal cord segment is shorter
therefore coccygeal segment of spinal cord is at the 2nd lumber vertebrae
where the nerve emerges from the cord is different from where it emerges from the vertebrae - the nerves get more angled lower down

Question 7

what is the clinical relevance of the discrepancy between the spinal and vertebral levels *

Answer 7

the effect of an injury depends on the spinal level and the vertebral level that it occurs

Question 8

describe the meningeal coverings *

Answer 8

dura mater - continuous with inner sheet of dura in cranium, forms dural sac, extends to S2, hard

arachnoid mater - ballooned up against dura, spider like

pia mater - adheres tightly to the surface of the spinal cord - the filum terminale is an extension of the pia mater - tethering the spinal cord to the sacrum

Question 9

describe the epidural space *

Answer 9

true space - between dura and periosteum, filled with fat and venous plexus

Question 10

describe the subarachnoid space *

Answer 10

filled with CSF

continuous with subarachnoid space of cranium

Question 11

describe the posterior root *

Answer 11

carries sensory info
cell bodies in spinal ganglion
enters the spinal cord in the posterolateral sulcus

Question 12

describe the spinal ganglion *

Answer 12

contains the nerve cell bodies or primary sensory afferents, pseudounipolar neurons - there are no synapses

Question 13

describe the anterior root *

Answer 13

carries motor info, exits spinal cord through anterolateral sulcus

Question 14

describe the denticulate ligament

Answer 14

extensions of pia - anchor the spinal cord to the dura

lateral denticulate ligaments separate posterior and anterior roots

Question 15

comparison between the meninges in the brain and in the vertebral column *

Answer 15

no space between the dura and the skull, but tehre is space between the dura and the vertebral column - useful to inject anaesthetics into the epidural space in the spine instead of using a general anaesthetic - eg in C section
also because the spinal cord ends at L2 - unlikely to be damaged
also can take a lumbar puncture of subarchnoid space- sample the CSF that flows down the spinal canal - can see what is happening in brain and if there is a sign of infection and add anaesthetics here
also can add spinal blocks into subarachnoid space - when you know the dose you will need

Question 16

where are the ascending and descending tracts in the spinal cord *

Answer 16

in the white matter

Question 17

define dermatome

Answer 17

area of skin supplied by one single spinal nerve or spinal segment

Question 18

define myotome

Answer 18

collection of muscles innervated by single spinal nerve or segment

Question 19

what are rootlets

Answer 19

they come from the horns of grey matter and join to form roots

Question 20

define roots *

Answer 20

roots only have either sensory or motor fibres
they mix with the other type of root (motor/sensory) to form the spinal nerve
a bundle of nerve fibres at its emergence from the spinal cord

Question 21

what is the spinal nerve *

Answer 21

mix of nerves - going into dorsal horn and out of ventral horn

Question 22

what is a rami *

Answer 22

have anterior and posterior rami
mix of sensory and motor 
branches of the spinal nerve 
anterior innervates most of body 
posterior smaller, innervate skin and muscles of back

Question 23

illustrate where the sulci and fissures are on the spinal cord

Answer 23

….

Question 24

describe the posterior median SULCUS and anterior median fissures *

Answer 24

divide the posterior/anterior surface of the spinal cord in 2 halves respectively

Question 25

describe the posterolateral sulcus *

Answer 25

entry point off the posterior (sensory) root

Question 26

describe the anterolateral fissure *

Answer 26

exit point for the anterior (motor) root

Question 27

illustrate different pathways through the grey matter in the spinal cord*

Answer 27

….

Question 28

describe the path of the discriminative touch and perception fibres *

Answer 28

sensory fibres enter the dorsal horns travel up dorsal column (fasciculus gracilis or fasciculus cuneatus) without synapsing - synapse in the medulla (nucleus gracilis/cuneatus)- cross to the contralateral side

Question 29

describe the path for pain and temp fibres *

Answer 29

enter the dorsal horn may travel up/down 1/2 segments in the Lissauer tract (posterolateral fasciculus) then synapse in the dorsal horn in the nucleus proprius fibres then cross the midline in the anterior commissure and travel in the spinothalamic tract

Question 30

describe the motor pathways *

Answer 30

a-motor neurons located in anterior horn exit spinal cord and travel to target interneurons in anterior horn filter descending motor info and are involved in reflexes

Question 31

what is the substantia gelatinosa

Answer 31

lamina II of grey matter, first modulation for pain and temp

Question 32

illustrate the main tracts of the spinal cord

Answer 32

…

Question 33

describe the spinocerebellar tract *

Answer 33

proprioception (sense of self-movement and body position) from limbs to the cerebellum

Question 34

describe the lateral corticospinal tract *

Answer 34

motor to ipsilateral anterior motor horn (mostly limb musculature) main vol movement pathway 85% fibres

Question 35

describe the spinothalamic tract *

Answer 35

pain and temp from contralateral side

Question 36

describe the anterior corticospinal tract *

Answer 36

motor to ipsi- and contralateral anterior horn (mostly axial musculature) innervate trunk 15% fibres

Question 37

describe the anterior white commissure *

Answer 37

pain and temp fibres cross | anterior corticospinal tract fibres cross

Question 38

describe the fasciculus gracilis *

Answer 38

sensory - fine touch, proprioception and vibration from ipsilateral lower limb

Question 39

describe the fasciculus cuneatus *

Answer 39

sensory - fine touch, proprioception and vibration from ipsilateral upper limb

Question 40

show diagrammatically the corticospinal tract

Answer 40

…

Question 41

describe the generic neuron pathways of the main sensory pathways *

Answer 41

there are 3 neurons from skin to brain primary goes into spinal cord (may synapse here or in the medulla) secondary goes to the thalamus, synapse here for both paths tertiary goes to the cortex when the nerves first synapse they cross to thee other side of the body

Question 42

illustrate the pathway for Discriminative touch, vibration, proprioception *

Answer 42

…

Question 43

why are reflexes important clinically

Answer 43

they can show the integrity of sensory and motor pathways | and show what's happening in the brain - the legion get smaller if peripheral nerve legion and bigger if stroke

Question 44

effect of reflexes

Answer 44

the nerves have many synapses to minimise damage - eg not just lift feet up but enable you to balance

Question 45

where are the sympathetic preganglionic motoneurons located *

Answer 45

the thoracolumbar region of the cord | in the intermediate horn - this is the site of the motor neurons of the SNS

Question 46

what are the factors affecting the severity of the spinal legion *

Answer 46

loss of neural tissue - small if trauma, more if metastasis (invade tracts/surgery damage cord) or degenerative disease vertical level - higher the legion the more disability (more pathways blocked below) transverse plane - complete/partial section, damage to the white matter is more important than damage to the grey matter because it would affect ascending/descending tracts

Question 47

how can you treat legions *

Answer 47

either try and repair below the legion | or bypass the legion - bringing neurons from above to below

Question 48

how does the transverse plane affect severity of spinal legions *

Answer 48

it depends on which tract is affected if legion at back - sensory pathways affected anterior - affect muscle of the trunk lateral - major motor tract for limbs - paralysis spinothalamic - loss of pain/temp

Question 49

describe the effect of injury to the lateral corticospinal tract *

Answer 49

stage 1 - spinal shock, inflammation, loss of reflex activity below legion, lasting for days/weeks - flaccid paralysis - cant move but floppy stage 2 - return of reflexes with graeter vigour - hyperreflexia or spasticity = rigid paralysis - reflex is more excitable - remain after tested

Question 50

summarise brown-sequard syndrome *

Answer 50

incomplete spinal injury - damage to one side of spinal cord lose sense of touch, vibrations and/or position in 3D below level of injury - hemiparalysis sensory loss is strong ipsilaterally - lose pain and temp

Question 51

what is the function of the cells in the dorsal *horn

Answer 51

sensory cell bodies

Question 52

what is the function of the cells in the ventral horn *

Answer 52

motor cell bodies.

Question 53

define nerve *

Answer 53

a bundle of connecting fibres that transmit impulse from the brain to glands/muscles or from the sense organs to the brain and spinal cord

Question 54

where asre transverse vertebral foramina and what are there functions

Answer 54

transmit vertebral arteries up to brain in cervical vertebrae

Question 55

action of the sympathetic preganglionic motoneurons *

Answer 55

their axons control visceral function via ventral roots and spinal nerves

Question 56

what is the lumbar cistern *

Answer 56

the subarachnoid space belwo the end of the spinal cord