Spinal Cord Anatomy Flashcards
Case of the jellyfish
–Has a neural net •Diffuse •Radial organization •Reflex Pathways
Case of the lamprey
–Has a nerve cord (iespinal cord) •Central •Segmented •Reflex Pathways, Conduit, Central Pattern Generators
Segmented
why you can move in multiple directions at once
Case of mammals
–Have Brain and Spinal Cord •Central •Spine and spinal cord are segmented and specialized •Reflex Pathways, Conduit, Central Pattern Generators
Reflex Pathways, Conduit, Central Pattern Generators
walking breathing, etc, things you dont have to think about
Spinal cord segments have distinct anatomical features
•Cervical enlargement •Lumbosacral enlargement •Peripheral organization •Conusmedullaris, cauda equina, filumterminale
Cervical enlargement
reason for enlargement is bc of our hands and feet, more neurons also, white matter serves as conduit so axons in cervical cord have the axons that go all the way down to the bottom
Conus medullaris
between l1-l2, goes down to s5
cauda equina
horses tail
filum terminale
ligament, can cause tethered cord system, cause back pain, pelvic floor function and incontinence
Gray matter
dendrites, cell bodies, and axon terminals –Located in dorsal and ventral horns
White matter
myelinatedaxonsof ascending and descending information
MS
starts with spinal cord, macros around peripheral white matter
lissuaers tract
this tract has unmyelinated axons in it, how pain info gets into spinal cord
somatosensory small fibers
go to dorsal horn and synapse related to pain takes longe rto turn on and off
somatosensory fat axons
nonpainful and mechanoreception faster
sensory
demratome
motor
myotome
brachial plexus sections
randy - roots travis - trunks drinks - divisions cold - cords beer -
why sensory doesn’t match myotome
plexus that mix nerves up
cervical cross section
a lot of white matter dorsal horns are skinny thicker looks like lower medulla
lumbar
big cord a lot of gray matter toward bottom big ventral
thoracic
a lot of white matter both horns smaller skinny imll
sacral
mostly gray matter skinnier than lumbar big ventral and dorsal horn
white rami
carry sympathetic info from the lateral horn of the spinal cord to the ganglia.
gray rami
ramicarry sympathetic info from the ganglia to viscera
chiari type I
cerebellum drooping down teeny hole (central canal) trying to let all the csf down because there is pressure so it creates a fluid filled sac called spherinx and it presses against horns on both sides and you get seringromylia…..weakness, paralysis, diminished snese or hyper sense and in a lot of pain
lumbar puncture
nerves lfoating in water, the displacement causes it to float up and it moves, terrible injector can cause problems
afferent tracts
all sensory going up, fat fibers go posterior funiculi, thin fibers go into dorsal horn
primary neuron
neuorn coming from dorsal root ganlia has a psuedounipolra axon, transduces signal from periphery insto electrochemical that the neuron can interpret and then shares it
secondary
number 2 in chain
motor neurons
ventral horn and root - motor neuron
lmn
a neuron directly innervating muscle basic weakness
umn
a neuron in a series of neurons in the brain that will innervate a LMN spasticity
Renshaw cells
provide negative feedback on LMNs at level of spinal cord •Constant inhibition •Glycinergic –Large amounts in jaw and facial musculature •Blocked by strychnine –Convulsions
renshaw cells secrete
glycine
interneurons
constant twerking to enhance signal
propriospinal
sub class of interneuron, sits between border of white and gray matter connect diff levels on interneurons to each other tracer to figure out where all fibers that uptake….
rexed lamina
represent histologically and morphologically similar groups of neurons in the gray matter •10 layers
lamina I
marginal zone - pain fibers
lamina II
substantia gelitinosa of rolando - pain a lot of converging input to let you know if you should ignore pain
lamina III-IV
nucleus proprius - mechanoreceptive
lamina V
mix of pain, temp, and itch, no special name
lamina VI
pain, mchanoreceptive and proprioreceptive
Lamina overview
1-6 are dorsal horn, 7-10 are ventral horn layer 10 dont worry it is right around central canal, will go with cerebralmalinga
mechanoreceptive
light touch and 2 point discrimination
nucleus proprius
lamina 3 and 4
lamina VII
big thoracic cord imll sacral cord autonomic nucleus of sacral cord (para) propriorective synapses clarks nucleus - proprioreceptive nucleus
Lamina VIII and IX
8 and 9 are related lower motor neurons make ventral horn motrom horne 8 proximal muscles (trunk) 9 is distal muscles (extremities)
lower motor neuron pools
a bunch of cell body pools, innervate the same muscles
onuf’s nucleus
ventral horn of s2-s4 lamina 8 and 9 pudendal nerve
Clarke’s nucleus
dorsal nucleus and clark somehow mixed
accessory nucleus
upper cervical ventral horn lamina 9 sticks out and it is the spinal accessory nucleus traps and scm
phrenic nucleus
c3-c5/6 innervate diaphragm
nucleus caudalis
spinal trigeminal nucleus from brain stem down to c4? basis for cervicogenic headaches because it shares dorsal horn with all these cerical nerves, so you get pain in a demratone and interpret it as a headache
IML
love handles T1-L2
Somatotopic
flexors - dorsal extensors - ventral lateral to medial Hand>Forearm>arm>shoulder>trunk
more neurons per unit area
smaller receptive field=more sensitive
nociceptors
more dorsal bad noxious any type of irritation
mechanoreceptors
touch
proprioceptors
more ventral
free nerve endings
most basic light touch temp pain chemical acidity cold capsacin have everything but nothing else can detect pain and temp
merkels disk
unencapsulated two cell types together fine touch
ruffinis corpuscle
encapsulated free nerve ending pressure
pacinian corpuscle
vibration onion skin wrapped many times around free nerve ending
meissners corpuscle
fine touch condensed free nerve ending encapsulated in dermal papillae
different types of free nerve endings
•Nociceptoris umbrella term for “noxious” receptor •Thermal, mechanical, chemo •Silent/sleeping nociceptors •Polymodalnociceptors
pain
psychological pheomenon in your head
GTOs
cant detect if someone else raises up only detect if there is a strain gto causes you to drop weight sits at muscle and tendon intersection
intrafusal fibers
passively contract muscle spindle sends signal out thatis interpreting change
extrafusal fibers
contract
nuclear chain
fibers have single row of nuclei in center of fiber only moves when muscle is moving
nuclear bag
fibers have nuclei collected in bundle in center of fiber signals during moevment and when passive
two types of bag fibers
one to signal staticmuscle length and one to signal changesin muscle length
Type Ia
–Wrap around allspindle types at the center of spindle –Annulospiralendings –Provide info on length and velocity Fast
type II
–Innervate nuclear chain and only STATIC nuclear bag fibers –Flower spray endings –Provide info only on length
GTO sit at muscle-tendon junction
•GTOs are more responsive to active muscle stretch than muscle spindles •Use Ibaxons •Often used in negative feedback circuits
A Fibers
Myelinated sensory and motor fibers, fastest Alpha Beta Gamma Delta •*In “A” fibers, the “A” is often omitted and only the greekletter is used to describe the subtype
Alpha
fastest lower motor neurons extrafusal
Beta
fibers from somatosensory receptors
Delta
slowest of the A sharp pain cold
B fibers
Myelinated visceral fibers preganglionic autonomic lightly myelinated
C Fibers
unmyelinated fibers postganglionic autonomic slow pain heat itch slowest
Another way to classify PNS axons, from largest to smallest
•I –Ia: Muscle Spindles –Ib: Golgi Tendon organs •II—Same as A-Beta or A-Gamma Fibers •III—Same as A-Delta or B Fibers •IV—Same as C Fibers
myotactic reflex
works within spinal circuits
Steps for myotactic reflex
descending facilitation and inhibition alpha motor neuron muscle force required to hold glass & disturbance (addition of liquid to glass) length change in muscle fiber spindle receptor increase spindle afferent discharge (positive on alpha motor neuron)
more complex reflex arc: crossed extension reflex
Most of our activity is controlled by microcircuits that are activated in sequences both in the brain and spinal cord phillisons reflex: doing opposite things on each side
locomotion and the spinal cord: central patter generators
reflex arc but do the same thing over and over
fasciculus cuneatus
vibration and 2 point discriminations
ventral spinocerebellar tract
carry unconscious proprioreception
anterolateral system
pain heat itch
fasciculus proprius
proprial spinal nerves complicated stuff happens
lateral corticospinal tract
descending
ascending and descending around spinal cord
ascending - around edges descending - middle
clarkes nucleus
