(2) Spinal Cord Flashcards
what system is the spinal cord a part of?
central nervous system
where does the spinal cord continue form
the medulla oblongata (of the brainstem)
sympathetic vs parasympathetic nervous system
sympathetic= fight or flight (spinal cord)
parasympathetic= rest and digest (brainstem/spinal cord)
dorsal vs ventral spinal cord
dorsal/posterior= sensory INTO spinal cord
ventral/anterior= motor OUT OF spinal cord
function of the foramen magnus
defines the border of the brainstem and spinal cord
- part of occipital bone
4 main functions of the spinal cord
motor functions
reflex integration
autonomic functions
impulse conduction
motor functions of the spinal cord
- enable us to move and interact with environment
- location of lower motor neurons controlling muscle function in limbs/torso
reflex integration of the spinal cord
specific pathways originating from periphery allow for reflexive movements rather than those initiated by brain
(e.g. involuntary movement)
autonomic functions of the spinal cord
sympathetic and part of the parasympathetic NS (ANS)
- internal organ function
impulse conduction of the spinal cord
provides means of neural communication to and from the brain
- ascending tracts and descending tracts
ascending vs descending tracts of the spinal cord
ascending= conduct impulses from peripheral sensory receptors to the brain
descending= conduct motor impulses from brain to muscles and glands
where does the spinal cord start and end
start: foramen magnum
end: filum terminale
2 enlargements of the spinal cord
cervical and lumbar enlargement
- contain network that control arm/leg movement
cervical enlargement location
C5 – T1
controls arm movements
lumbar enlargement location
L2 – S3
controls leg movements
- ends at conus medullaris
central canal of the spinal cord function
filled with CSF
- nurtures spinal cord
- carries material
dorsal and ventral roots pass through
dorsal= dorsal lateral sulcus
ventral= ventral lateral sulcus
how many spinal cord segments?
31 in total
8- cervical 12- thoracic 5- lumbar 5- sacral 1- coccygeal
where is dorsal root ganglia and what does it contain?
DRG is in the PNS
contains cell bodies of sensory neurons
spinal cord segments give rise to ….
one exception
segments give rise to spinal nerves
exception: No C8 vertebrae
cervical plexus and brachial plexus control what??
arm and neck movements
dorsal rootlets enter where
enters posterolateral sulcus
- bears dorsal root ganglia (contain cell bodies of primary sensory neurons)
ventral rootlets leave where?
leave from anterolateral sulcus
what is a dermatome?
area of skin supplied by nerves from single spinal root
C1 and C3 segment dermatomes
C1 segment= no dermatome
C3= neck
does the face have a dermatome?
NO
face is innervated by cranial nerves (not spinal!)
spinal cord is located within… (why?)
vertebral canal
provides protection
3 protective sheets of the spinal cord are called?
Meninges
1) dura mater
2) Arachnoid mater
3) pia mater
dura, arachnoid and pia mater
dura= outer, toughest
arachnoid= middle, spiderweb
pia= inner, wrap spinal cord tissue
what is between the arachnoid and pia mater?
CSF
what goes between pia mater and dura mater?? (what is the function)
denticulate ligaments
- position spinal cord (centres it in meninge tube)
what segments does the spinal cord end?
L1/L2
how long is the spinal cord and vertebral column?
spinal cord= 42-45 cm
vertebral column= ~70 cm
caudal/lower end of the cord is anchored to…
end of dural tubal by filum terminal
structures at the end of the spinal cord
conus medullaris (L1)
lumbar cistern (L2)
filum terminale internum (L3)
dura mater (continues farther than spinal cord) – (L4)
filum terminal externum (coccygeal ligament) – (S2)
what and where is the cauda equina?
from L1/L2 –> S2
(above the filum terminale externum)
filled with dorsal and ventral roots
cauda equina is also called
horses tail
where to inject epidural needle? Why?
dural sac= filled with spinal nerves
able to insert needle without damaging spinal cord
(in lumbar region)
grey matter and white matter in spinal cord
grey= cell bodies of interneurons and motor neurons (surrounded by white matter)
white= heavy myelinated axons projecting too and form spinal cord (surrounds grey)
grey matter and white matter are divided into
grey= horns
white= funiculi
Lissauer’s tract location and what does it contain
between substantia gelatinosa and surface of the cord
contains finely myelinated/unmylinated fibers
left side of body
at what levels is the posterior intermediate sulcus found
cervical and upper thoracic levels
anterior median fissure
extend almost to centre of cord
- at apex a thin zone of white matter (anterior white commissure) and thin grey matter zone separates central canal from subarachnoid space
posterior median sulcus
(less distinct)
glial septum extend from it all the way to grey matter surrounding central canal
location and function of substantia gelatinosa
distinctive region of grey matter, caps the posterior horns
- deals with finely myelinated and unmyelinated SENSORY fibres that carry PAIN and TEMPERATURE information
2 spinal reflexes
patellar (knee-jerk) reflex
flexor and crossed extensor reflex
patellar reflex
- cell body of afferent is in DRG
- tapping patellar tendon, stretches quadriceps
- quad muscle spindles excited and excite quad alpha motor neurons
- causing muscle to contract (completing reflex)
flexor and crosses extensor reflex
- initiated by cutaneous receptor
- involves whole limb
- caused by specific network in spinal cord
ex: withdrawal from pain stimuus
somatic nervous system afferents in the spinal cord
- what is the boss?
afferents and info from body goes INTO spinal cord
innervates muscles, causes contraction
Boss= cerebral cortex (generate decisions about how to move, what to do)
autonomic nervous system afferent fibers in spinal cord
- what is the boss?
ANS= control gut movements, heart, and internal organs (unaware)
afferent fibers (visceral= internal)- info goes into spinal cord through dorsal root - innervate interneurons and motor neurons, and project to target organs (muscle/endocrine organs)
Boss= hypothalamus
general visceral sensory neurons monitor what 4 sensations in visceral organs
stretch
temperature
chemical changes
irritation
cell bodies of visceral sensory neurons are located where?
dorsal root ganglion
visceral pain
- no pain results when visceral organs are cut
- pain results from chemical irritation or inflammation
- often perceived to be of somatic origin (referred pain)
ex: gall bladder pain
visceral pain
- feel pain in arm, shoulder and stomach
where are sympathetic and parasympathetic preganglionic neurons segregated?
symp= thoracic and lumbar (intermediate horn)
para= brain stem and sacral
radicular vs medullary arteries
radicular= posterior/anterior, don’t touch main arteries
- run dorsal and ventral spinal nerve roots
medullary= supply main arteries
3 major longitudinal arteries of the spinal crd
1 anterior spinal
2 posterior spinal arteries
- originate from vertebral arteries
- run length of cord
major longitudinal arteries are supplemented by:
segmental arteries
- derived from vertebral, deep cervical, intercostal and lumbar arteries
large radicular artery arises from…. and supplies what?
arises from intercostal artery on left between T9 and T11
- often supplies blood for lower spinal cord
6 veins in venous drainage
3 anterior
3 posterior spinal veins
venous drainage
- 3 anterior, 3 posterior spinal veins
- drained by medullary and radicular veins
- join internal vertebral venous plexuses in epidural space
3 types of nerve fibers in white matter of spinal cord
& where do they project to/from
1) long ascending fibers: project to thalamus, cerebellum or brainstem nuclei
2) long descending: project from cerebral cortex or from brainstem nuclei in grey matter
3) shorter propriospinal= interconnecting different spinal cord levels, mostly remain in propriospinal tract
what is the fasciculus proprius?
thick shell surrounding grey matter
in white matter
where are the ascending and descending tracts in the spinal cord located
white matter
white matter is divided into 3 parts
posterior, lateral, anterior fasciculus
ascending tracts in spinal cord.. found… function
found in all 3 funiculi
bring info TO brain (Right side)
descending tracts in spinal cord… found… function
found primarily in lateral or anterior funiculi (not posterior)
- bring info TO BODY (left side)
are descending tracts sensory or motor?
MOTOR
are ascending tracts sensory or motor?
SENSORY
what do descending motor tracts represent
functional pathways that convey signals from brain to periphery/body
generate movement
name of descending motor tracts (all similar)
ends in spinal
cells of origin of descending motor tracts
cells of origin (upper motoneurons) are in cerebral cortex
- e.g lateral corticospinal tract
or in brainstem (e.g. rubrospinal tract)
- and innervate lower motoneurons in brainstem or spinal cord (final target)
descending motor tracts can be grouped into….
conscious (2) and subconscious tracts (4)
2 conscious motor tracts (descending)
lateral corticospinal tract
anterior corticospinal tract
– used to consciously move something
4 subconscious motor tracts (descending)
vestibulospinal tract
tectospinal tract
reticulaspinal tract
rubrospinal tract
conscious descending tracts begin where?
both in primary motor cortex
precentral gyrus
8 parts to the lateral corticospinal tract pathway
descending, motor, conscious
1) fibers in cerebral cortex (precentral gyrus/motor cortex)
2) upper motor neuron descends through internal capsule
3) corticospinal tract
4) cerebral peduncle (midbrain)— crux cerebri
5) basal pons
6) CROSS pyramids of medulla oblongata (cross to right)
7) lateral fasciculus
8) terminate in motor neurons in anterior horn (skeletal muscle) – contraction occurs
8 parts to the anterior corticospinal tract pathway
descending, motor, conscious
1) fibers in cerebral cortex (precentral gyrus/motor cortex)
2) upper motor neuron descends through internal capsule
3) corticospinal tract
4) cerebral peduncle (midbrain)— crux cerebri
5) basal pons
6) medulla oblongata (white matter)
7) CROSS at final segments of spinal cord (anterior white commissure)
8) terminate in motor neurons in anterior/ventral horn (skeletal muscle) – contraction occurs
anterior corticospinal tract important for
fine movement
corticospinal tracts are involved in
skilled motor activity, particularly in the limbs
cells of origin of corticospinal tracts
aka upper motor neurons
- they are pyramidal cells located in motor, premotor and supplemental motor cortices
upper motor neuron controls …
lower motor neuron
if lose upper motor neuron then what happens?
don’t lose all control because still have lower motor neurons
if lose lower motor neuron then what happens?
lose all control on muscles, cannot contract, lose tone, no reflex
upper vs lower motoneuron lesion effect on strength
upper lesion= decreased strength
lower lesion= decreased stength
upper vs lower motoneuron lesion effect on muscle tone**
upper lesion= increase tone*
lower lesion= decreased tone
upper vs lower motoneuron lesion effect on reflexes**
upper lesion= increased reflex*
lower lesion= decreased reflex
upper vs lower motoneuron lesion effect on atrophy**
- decrease in mass of muscle
upper lesion= mild atrophy
lower lesion= increased atrophy *
upper vs lower motoneuron lesion effect on other signs
upper lesion= clonus (large involuntary muscle contractions usually initiated by reflex)
lower lesion= fasciculations (small, spontaneous twitching)
what is brachial monoparesis
patient cannot move right arm
brachial monoparesis locations rule out
unlikely anywhere along corticospinal tract (internal capsule/brainstem)
- b/c the face and lower extremities would be involved
brachial monoparesis locatiosn ruled in
- arm area of primary motor cortex
- or peripheral nerve supplying arm
brachial monoparesis common causes (3)
- infarct of a small cortical branch of middle cerebral artery
- compression injury
- diabetic neuropathy of the peripheral nerve
what is hemiparesis?
lost control of entire side of body
has control of face
hemiparesis locations ruled out (2)
- unlikely corticospinal tract below motor cortex, above the medulla because the corticobulbar fibers are nearby (face would be involved)
- unlikely peripheral nerve neuropathy (odd entire side is affected)
hemiparesis locations ruled in (2)
- arm and leg area of primary motor cortex
- or corticospinal tract lower than the medulla
hemiparesis common causes (3)
- watershed infarct of the anterior cerebral artery
- medial medullary infarct
- compression of the cervical spinal cord
ascending sensory tracts represent
functional pathway that convey sensory information from periphery/body to brain
name of ascending sensory tracts (all similar)
begins with spino
ascending sensory tracts usually consist of …
3 neurons
- 1st, 2nd and 3rd order neurons
first order neurons of ascending sensory tracts are located…
always in dorsal root ganglia (DRG)
ascending sensory tracts can be grouped into (3)
conscious (2) and unconscious (2) tracts
2 ascending conscious tracts
posterior/dorsal column-medial lemniscus system
anterolateral system (spinothalamis tract)
3 ascending unconscious tracts
dorsal/posterior spinocerebellar tract
anterior/ventral spinocerebellar tract
cuneocerebellar tract
small and large diameter sensory fibers in the ascending conscious tracts
small= enter cord laterally, through Lissauer’s tract
- terminating in substantia gelatinosa
large= enter through medial division of white matter, join posterior/dorsal columns
posterior/dorsal column medial lemniscus tract transmits what type of information (4)
proprioception ***
fine touch *
pressure
vibration
2 fasciculi in posterior/dorsal column-medial lemniscus pathway
fasciculus gracilis
fasciculis cuneatus
fasciculus gracilis vs cuneatus
gracilis= more lateral, transmit info coming from areas inferior to T6 segment
- lower limbs to brain (nucleus)
cuneatus= more medial, upper limbs to brain
damage to posterior/dorsal column-medial lemniscus pathway
- causes impairment of tactile perception
- results in ataxia (incoordination of movement)
- brain unable to direct motor activity properly without sensory feedback of position of limbs/body parts
10 parts to posterior/dorsal column-medial lemniscus pathway
ascending, sensory, conscious
1) 1st order neuron (cell body DRG)
2) dorsal column spinal cord (Lissauer’s tract)
3) fasciculis gracilis (lower) & cuneatus (upper) in spinal cord axons project to
4) medulla oblongata (reaches nucleus gracilis/cuneatus)
5) 2nd order neuron (cell body medulla oblongata)
6) axons CROSS as internal arcuate fibers in medial lemniscus (medulla)
7) project to thalamus, synapse with VPL nucleus
8) 3rd order neurons (cell bodies VPL nucleus)
9) internal capsule
10) project to somatosensory cortex (postcentral gyrus)
2 components of anterolateral/spinothalamic tract
each responsible for
- crude touch, pressure, pain and temperature
lateral spinothalamic tract= crude touch, pressure
anterior spinothalamic tract= pain, temperature
10 parts to anterolateral/spinothalamic tract
ascending, sensory, conscious
1) 1st order neurons (cell bodies DRG)
2) dorsal column spinal cord
3) branches ascend/descend via Lissauer’s tract
4) synapse interneurons in substantia gelatinosa/nucleus proprius
5) CROSS via anterior white commissure in spinal cord
6) 2nd order neurons (cell bodies nucleus proprius)
7) spinal lemniscus
8) project to thalamus (VPL nucleus)
9) 3rd order neurons (cell bodies thalamus)
10) somatosensory cortex (postcentral gyrus)
anterolateral/spinothalamic tract reach out to PAG and spinoreticular trac
PAG–> provide natural analgesics (don’t feel pain while panicking)
spinoreticular–> when pain info reaches tract, prepares us to react (inc heart beat, become anxious/nervous)
transverse cord lesion results in loss of
(lesion whole cord)
- vibration, position
- pain, temperature
- motor
LOWER BODY (waist down)
transverse cord lesion common causes (3)
- trauma
- tumors
- transverse myelitis (inflammation)
hemicord lesions results in loss of
(lose right side of spinal cord)
- lose control fine movement, fine touch/position on RIGHT side LOWER body
- lost pain info contralaterally, LEFT side LOWER body
hemicord lesion aka
brown-sequard syndrome
hemicord lesion common causes (2)
- penetrating injuries
- lateral compression from tumors
posterior cord syndrome results in
- lose dorsal part of spinal cord
- lose fine sensation of touch info (vibration and position) in WHOLE BODY, not face
posterior cord syndrome common causes (4)
- trauma
- tumors
- MS
- vitamin B12 deficiency tabes dorsalis (tertiary syphilis)
anterior cord syndrome results n
- lose ventral/lower part of spinal cord
- lose pain/temperature and motor loss of muscles in WHOLE BODY, not face
