spinal cord Flashcards
spinal cord cross-sectional anatomy: demonstrate on a diagram the main areas of grey matter, and the main ascending and descending tracts
spinal cord sections
grey matter medially containing cell bodies and rami, white matter laterally containing tracts
pattern of grey and white matter
grey matter is butterfly shape; white matter fills rest
define dermatome and what innervates it; trunk vs limbs
area of skin innervated by one single pair of spinal nerves or spinal segment; posterior root; trunk is segmental as in strips, limbs are not as simple as when limbs grow and rotate, segmental organisation becomes less organised
define myotome and what innervates it
muscles innervated by one single pair of spinal nerves or spinal segment; anterior root
cross section of spinal cord: pathway of posterior and anterior horns
2 posterior (dorsal) and 2 anterior (ventral) horns of grey matter -> posterior and anterior rootlets -> posterior (sensory) and anterior (motor) root -> spinal (sensory) ganglion following posterior (sensory) root -> join together to form mixed spinal nerve -> posterior ramus (branch supplying muscle and skin at back) and anterior ramus (everything else)
what ligament anchors spinal cord to dura mater
denticulate ligament
cross section of spinal cord: white matter from posterior median sulcus to anterior median fissure
posterior median sulcus (divides posterior surface into two halves) -> posterior column -> posterolateral sulcus (entry point of posterior - sensory - root) -> lateral column -> anterolateral sulcus (exit point for anterior - motor - root) -> anterior column -> anterior median fissure (divides anterior surface into two halves)
cross section of spinal cord: grey matter: main pathway 1: discriminative touch and proprioception sensory neurones pathway
sensory fibres enter dorsal horn and travel in dorsal columns without synapsing in posterior horn
cross section of spinal cord: grey matter: main pathway 2: pain and temperature sensory neurones pathway
fibers enter dorsal horn, may travel up or down 1-2 segments in posterolateral fasciculus (Lissauer tract), then synapse in nucleus proprius of dorsal horn (dorsal root ganglion); fibers then cross midline in anterior commissure and travel in spinothalamic tract
cross section of spinal cord: grey matter: location and function of substantia gelatinosa
lamina II of grey matter: first modulation for pain and temperature just before dorsal horn
cross section of spinal cord: grey matter: main pathway 3: motor neurones pathway and other contents
a-motor neurones located in anterior horn; exit spinal cord and travel to target muscles; interneurone circuits in anterior horn filter descending motor information and are part of localised reflex circuits
7 major tracts of spinal cord from dorsal medial laterally to anterior medial
anterior white commisure, fasciculus gracilis, fasciculus cuneatus, spinocerebellar tract, lateral corticospinal tracts, spinothalamic tracts, anterior corticospinal tract
function of anterior white commisure
pain and temperature fibers cross; anterior corticospinal tract fibers cross
function of fasciculus gracilis
sensory (fine touch, vibration, proprioception) from ipsilateral lower limb
function of fasciculus cuneatus
sensory (fine touch, vibration, proprioception) from ipsilateral upper limb
function of spinocerebellar tract
proprioception from limbs to cerebellum
function of lateral corticospinal tracts
motor from brain to ipsilateral anterior horn (mostly limb musculature; main voluntary movement pathway)
function of spinothalamic tracts
pain and temperature from contralateral side of body
function of anterior corticospinal tract
motor from brain to ipsi- and contralateral anterior horn (mostly axial musculature)
corticospinal tract constituents
cerebral cortex gyrus -> descending motor fibers -> 15% [anterior corticospinal tract -> motor nuclei; trunk] or 85% [decussation of lateral corticospinal tract -> lateral corticospinal tract; arms and legs]
main sensory pathways: pair of dorsal column pathways - fasciculus gracilis and fasciculus cuneatus: discrimative touch, vibration, prociception from upper and lower limbs
primary sensory neurone -> dorsal root ganglion -> spinal cord -> posterior column medial lemniscus system -> synapse onto medulla to secondary sensory neurone then crosses -> pons -> midbrain -> synapses onto thalamus -> third sensory neurone to cortex
main sensory pathways: pair of spinothalamic tract: pain and temperature
primary sensory neurone -> dorsal root ganglion -> enters and synapses onto spinal cord via Lissauer tract -> secondary sensory neurone crosses in spinal cord -> anterolateral system to medulla then pons then midbrain -> synapses onto thalamus -> third sensory neurone to cortex
reflex pathways: patellar tendon jerk reflex and painful stimulus e.g. plug on floor reflex
sensory muscles stretch -> signal back to spinal cord -> motor response to muscle -> muscle contracts; also synapse into brain to bring in responses and sense pain; reflexes can get bigger if stroke and smaller if peripheral nerve lesion; response to same limb, different limb, core etc. to remove stimulus, maintain stability etc.
in thoracolumbar segments, size of grey matter and what ANS branch does the lateral horn consist of
grey matter small, lateral horn (site of motor neurones: intermediate horn between dorsal and ventral) sympathetic visceomotor
in sacral segments, size of grey matter and what ANS branch does the lateral horn consist of
grey matter big, lateral horn (site of motor neurones: intermediate horn between dorsal and ventral) parasympathetic visceromotor
parasympathetic outflow segments
brainstem cranial nerves III, VII, IX, X; S2-S4
sympathetic outflow segments
T1-L2
directions in neuroanatomy
superior = rostral, inferior = caudal, posterior = dorsal, anterior = ventral
define root
contains nerve fibres of only one type (motor or sensory)
define ramus
contains mixture of motor and sensory nerve fibres
