spinal cord anatomy and receptors Flashcards
lumbar cistern clinical landmarks
L1-L2, S2-S3
lumbar puncture landmark
L3, S1
common vertebral injuries
- impact to head = C1-C2, C4-C6
- industrial accidents = T1-L2
dermatome references (C2, C6, T4, T10, L3, S1)
C2 - back of head C6 - thumb and index finger T4 - nipples T10 - umbilicus L3 - kneecap S1 - pinky toe
if you cut the root….sensation? if you cut the peripheral nerve…?
root => don’t knock out all sensation
peripheral => knock out
sympathetic nerves
- exit from IML
- continue from sympathetic chain as splanchnic to prevertebral ganglion
- synapse to paravertebral ganglion
- white rami - myelinated; goes into paravertebral ganglion
- grey ramus - unmyelinated; goes out of paravertebral ganglion
dorsal funiculus
- white matter
- ascending axons from DCP
- fasciculus gracilis and cuneatus
lateral funiculus
ascending and descending tracts
dorsolateral fasciculus
- zone of lissauer
- between lateral fasciculus and dorsal funinculus
- sensory modulation
- contains axons from substantia gelatinosa
substantia gelatinosa
- present at all cord levels
- sends axons to NP
- receives dorsal root afferents
- spinal trigeminal nucleus
- pain reception
nucleus proprius
- present at all cord levels
- chief sensory nucleus
- receives dorsal root afferents
- project contralaterally as the STT
dorsal root afferents
lateral = lightly myelinated; GSA; ascends/descends in dorsolateral fasciculus
medial = much myelinated; sends to medulla; 2 point touch, proprioception, and muscle stretch
Nucleus Dorsalis/Clarke’s Nucleus
- located from C8-L3
- accessory cuneate nucleus of medulla
- receives muscle afferents from spindles
- projects ipsilaterally as DSCT
- coordination, proprioception
intermediolateral nucleus (IML)
- located lateral to CN at T1-L3
- projects cholinergic sympathetic efferents
- GVE
intermediomedial (IMM)
- present at all levels
- receives visceral afferents
- projects to intermediolateral nucleus
medial and lateral motor neurons
- largest in cervical/lumbosacral enlargements
- alpha motor = cholinergic, LMN, final common pathway, innervate skeletal muscle
- inhibitory GABA neurons
- gamma motor neurons - innervate spindles
ventral horn nuclei
receive input from descending tracts
project axons between cervical and lumbar levels
phrenic nucleus
medial ventral horn at C3-C5
spinal accessory nucleus
lateral ventral horn at C1-C6
differences in spinal cord levels
- gray matter increases at C8, L3, and S2 due to enlargements
- ventral expansions at enlargements
GSA
general somatic afferent
- pain, vibration, proprioception, touch
- dorsal horn
GVA
general visceral afferent
- pain, stretch
- from gut
- dorsal horn
GVE
general visceral efferent
- motor innervation to viscera, glands, and blood vessels
- autonomics
- lateral horn
GSE
general somatic efferent
- motor innervation to skeletal muscles
- ventral horn
SSA
special somatic afferent
- vision
- hearing
- balance
SVA
special visceral afferent
- taste
- smell
SVE
special visceral efferent
- motor innervation to branchial muscles (gills, mastication)
- motor innervation to facial expression
free nerve endings
- nonencapsulated
- slow adapting
- pain/temp
- deep skin/viscera
merkel’s disk
- nonencapsulated
- slow adapting
- touch
- feet, hands, genitalia
hair follicle
- nonencapsulated
- fast adapting
- touch
meissner’s corpuscle
- sheath surrounding epithelial cells
- encapsulated
- fast adapting
- 2 point discrimination
pacinian corpuscle
- afferent nerve ending surrounded by concentric circles of epithelial cells
- encapsulated
- fast adapting
- vibration
ruffini ending
- encapsulated
- slow adapting
- stretch, pressure
joint receptor
- encapsulated
- slow adapting
- joint position
neuromuscular spindle
- encapsulated
- slow adapting
- stretch/length
- important for proprioception
golgi tendon organ
- encapsulated
- slow adapting
- muscle tension
muscle spindles vs GTOs
- spindles fire when muscles are stretched
- GTOs fire when muscles are tense; during isometric contraction
muscle reflex arc
- stretching alerts afferent neurons
- signal travels to dorsal horn
- signal travels to ventral horn
- alpha motor neuron signals muscle to shorten to resist overstretching
- muscle becomes saggy
- gamma motor neurons signal muscle to reset the spindle length
