5: Spinal Cord

do all fiber tracts of the spinal cord decussate

yes, so that left brain controls right body and vice versa

what is the first interface of the CNS and PNS

spinal cord

where does the spinal cord receive somatosensory info from

limbs and body

where are all of the motor neurons that supply the muscles

in the spinal cord

how long (in cm) is the spinal cord

42-45 cm

how much does the spinal cord weigh

35 g

how wide is the spinal cord at the widest point

1 cm

what forms the cauda equina

spinal root fibers

what anchors the spinal cord to the coccyx

cauda equina

what type of dermatome innervation does C1 have

rudimentary dorsal root

what does the spinal cord look like at the cervical level

has an enlargement, dense sensory and motor innervation to the upper extremities, (middle amount of grey matter)

what does the spinal cord look like at the thoracic level

little grey matter, lots of white, chest and back area

what does the spinal cord look like at the lumbar level

dense sensory and motor innervation with an enlargement, fairly equal amounts of grey and white

what does the spinal cord look like at the sacral level

contains the cauda equina, mostly grey matter, much smaller

where are the two spinal cord enlargements

cervical and lumbar

what are the two filum terminale made of

pia mater and dura mater

what is cauda equina syndrome

pressure on cauda equina causes bladder retention, bowel incontinence and paralysis

what is the treatment for cauda equina syndrome

emergency surgery

what will pt's with cauda equina syndrome present with (4 symptoms)

* low back pain
* saddle anesthesia
* bilateral sciatica
* sexual dysfunction

what are two causes of cauda equina syndrome

* lumbar disc herniation
* hematoma

where in the tract is the cauda equina

L1 to L2

what are the layers (meninges and spaces) of the spinal cord from outside in

* epidural space
* dura
* subdural
* arachnoid
* subarachnoid
* pia

what does the grey mater consist of in the spinal cord

soma, unmyelinated processes and neuroglia

what does the grey commissure connect of the spinal cord

masses of grey matter, encloses the central canal

what do the posterior dorsal horns contain

interneurons

what do the anterior ventral horns contain

interneurons and somatic motor neurons

what do the lateral horns contain

contain sympathetic nerve fibers

what do the dorsal and ventral rootlets indicate

the borders of the spinal cord

what forms the spinal nerve in the intervertebral foramen

dorsal and ventral rootlets

what are funiculi

bundle of white matter tracts

what type of fibers does the anterior white commissure contain

decussating

does the dorsal gray matter horn reach the dorsal side

yes

does the ventral gray matter horn reach the ventral side

no

what does the grey commissure contain

central canal, debris of macrophages

what are the 4 zones evident within the grey matter

* somatic sensory
* visceral sensory
* somatic motor
* visceral motor

what is Lissauer's tract

the fine dorsal root fibers that enter at the dorsolateral fasciculus

what type of input does the Lissauer's tract

exteroceptive input such as pain, temp and tactile info

what are Rexed Laminae

clusters of spinal cells arranged in 10 layers

which Rexed Laminae layers are in the dorsal horn

I-VI

what are the functions of layers I-IX (Rexed Laminae)

* pain and temp (I & II)
* tactile (III)
* Muscle spindle afferents (VI, VII, IX)

where is pain and temp processed

* Lissauer's tract that carries nociceptive fibers
* II is Substantia Gelatinosa (spinothalamic tract)

what layers have the nucleus proprius

III-VI

what type of synapses does the proprius nucleus contain

synapses from the mechanoreceptors

what layers form the intermediate zone

VII and X

what layers contain the motor neurons columns

VIII through IX

what layer contains motor neurons that innervate limb muscles

layer IX

what is the func. of Lissauer's tract

exteroceptive input (pain, temp, tactile)

what is the name for lamina I

postero-marginal nucleus

what is the func of lamina I

dorsal root fibers mediating pain, temp, touch, spinothalamic tract

what is the name for lamina II

substantia gelatinosa

what is the func of lamina II

modulate pain and temp (release substance P and glutamate)

what is the name for lamina III and IV

lamina propria

what is the func of lamina III and IV

proper sensory nucleus that receives input from substantia gelatinosa. pain, temp, crude touch

what is the function of lamina V

\
descending fibers: of the corticospinal and rubrospinal tract

Ascending: spinothalamic tract

where is lamina VI present

cervical and lumbar segments

what is the function of lamina VI

integrate somatic motor processes, lateral segment receives descending corticospinal and rubrospinal fibers

what is the role of lamina VII at C8-L2/L3

contains Nucleus Dorsalis of Clark (dorsal cerebrospinal tract and info to cerebellum)

what is the role of lamina VII at T1-L2

sympathetic preganglionic neurons that make up the Intermediolateral Cell Column

what is the role of lamina VII at S2-S4

parasympathetic neurons and interneurons, Renshaw cells

how do Renshaw cells make inhibitory synapses

glycine

how do Renshaw cells make excitatory synapses

acetylcholine

what horns form the intermediate zone

dorsal and ventral horns overlapping

what is the other name of the Dorsal Nucleus of Clarke

Dorsal Thoracic Nucleus

where is the Dorsal Nucleus of Clarke located

lamina VII fromC7/8 to L2/3

where is the Dorsal Nucleus of Clarke more prominent

thoracic levels

do axons of the Dorsal Nucleus of Clark ascend crossed or uncrossed

either

what is a role of the Dorsal Nucleus of Clark

unconscious processing

what is the location of lamina VIII and IX

the ventral horn

what is the func of Lamina VIII and IX

Alpha and Gamma innervating skeletal muscles in somatotropic arrangement, Vestibulospinal and Reticulospinal tracts for posture

what is the func. of lamina X

Gray matter surrounding canal, joins w/ lamina VII to form intermediate zone

what levels are the lateral horn visible on

C7/C8/T1- L2/L3

what does the lateral horn contain

preganglionic sympathetic neurons for entire body (intermediolateral cell column)

how does the synapse travel if on the same level of the sympathetic chain

leaves via ventral root via white ramus to sympathetic paravertebral ganglion, synapses at same level, post-ganglionic neuron innervates organ

how does the synapse travel if on a different level of the sympathetic chain

leaves via ventral root, via white ramus to symp. paravertebral ganglion, up or down symp. chain, synapses on ganglion then to the gray ramus

what are deep touch and fine touch supplied by

myelinated Alpha-Beta fibers

what do Pacinian receptors encode for

rate and force of repeated stimuli

what is the detection of joint position

proprioception

what is kinesthesia

sensing small changes in limb position, direction, force and speed

what is pain mediated by

nociceptors

what triggers itching

chemical irritation, response to inflammatory agents

what provides info about maintaining body temp

thermal sensors

what sensations provides info regarding BP, breathing, fullness, nausea, and arterial pressure

visceral sensations

what are the 3 types of ascending and descending nerve fibers

* long ascending
* long descending
* short propriospinal interconnections

where do long ascending nerve fibers go

to thalamus, cerebellum and brainstem

where are long ascending nerve fibers present (which funiculi)

in all 3 funiculi

where do long descending nerve fibers go

spinal grey matter

where are long descending nerve fibers present (which funiculi)

lateral and anterior funiculi

what do shorter propriospinal interconnections serve to do

coordinate flexor reflexes

where are shorter propriospinal nerve fibers present (which funiculi)

fasciculus proprius

what are the 3 major white matter pathways

* dorsal column medial lemniscus
* spinothalamic
* corticospinal

where does the Gracile Fasciculus originate in the DCML pathway

lower limbs and trunk

where does the cuneate fasciculus originate in the DCML pathway

upper limbs, trunk, neck

what info does the cuneate fasciculus send

unconscious proprioceptive info from upper limbs

what does the spinocerebellar tract carry info regarding

unconscious proprioceptive info

Where does the DCML cross?

gracile nuclei

what is the 3 neuron chain of the DCML

* primary: peripheral ganglia in dorsal root ganglion
* secondary: decussate and ascend fascicle
* third: ventro-posteriomedial nucleus of thalamus (to postcentral gyrus)

sensitive mechanoreceptors in the DCML may

* synapse at the spinal cord for reflex action
* ascend ipsilaterally synapse with 2nd order in medulla

what is the two neuron arc

monosynaptic reflex with

* knee-jerk reflex
* deep tendon

how are axons added in ascending first order neurons of the DCML

medial to lateral

do dorsal columns become broader or more specific as the ascend

broader