spinal cord Flashcards
spinal cord in v.canal
-from C1-L2
-um 45 cm lenght, 1 cm diameter
-pia mater, arachnoid and dura mater
Diameter varies, 2 enlargements:
-lumbar enlargement
-cervical enlargement
–> provide innervation for upper/lower limbs
Caudal end spinal cord:
-tapers to form conus medullaris (oftast L1 in adults)
-filum terminale desc. from conus to coccyx (fibrous band to fixate distal spinal cord)
spinal cord
flattened anteroposteriorly
surface marked by:
-anterior/ventral median fissure
-posterior/dorsal median sulcus
-anterolateral sulcus (ventral fibers leave spinal cord)
-posterolateral sulcus (posterior nerve roots are attached)
*sulci divide white matter into funiculi:
-anterior funiculus: desc+asc tracts
(including anterior corticospinal tract)
-lateral funiculus: desc+asc tracts
(including lateral corticospinal tract and pain pathways like spinothalamic tract)
-posterior funiculus: subdiv. in upper p of spinal cord into
a) fasiculus gracilis
b) fasiculus cuneatus
spinal cord
ventral + dorsal roots spring from sides
(anterolateral og posterolateral sulci)
—> forming spinal nerves
lower spinal nerves (lumbar, sacral)
desc. below the lower end of spinal cord
(to reach their exit foramina) in a wisp like arrangement —> cauda equina
dorsal og ventral roots
dorsal root: afferent sensory fibers
(primary afferent neurons)
-somatosensory (from skin, mm, joints)
-viscerosensory (from inner organs)
ventral root: efferent motor fibers
-somatomotor (somatic)
-visceromotor (splanchnic, visceral + autonomic)
*spinal segment:
portion of sp.cord to which a pair of spinal nerves is att.
-31 spinal nerves/segments
(8, 12, 5, 5, 1)
internal structure spinal cord
grey matter centrally w spinal canal surr. by white matter
grey matter subdiv into:
-ventral horn: broad and short
-dorsal horn: slender and long
-intermediate substance
-lateral horn: in thoracic part.
-reticular formation: in cervical part
structure of grey matter
ventral horn w motor neuron supply voluntary mm.
-motor neurons arranged in columns:
a) rexed laminae - motor nuclei
b) rexed laminae VIII - medial gr. - innervation of mm of trunk
c) rexed laminae IX - lateral gr - innervation of mm of limbs
d) in cervical segments: phrenic nucleus
lateral horns
m preganglionic autonomic neurons
(lower autonomic centers)
-interomedial lateral nucleus
–> rexed laminae VII
-in the thoracic and sacral segments
*from 1st thoracic to 2nd lumbar segments
–> preganglionic symp. neurons
*In 2nd to 4th sacral segments
—> preganglionic parasymp. neurons
dorsal horn
cells represent 2nd order sensory neurons
-are grouped to form sensory nuclei
(lower sensory centers) Rexed laminae I-VI
Rexed laminae I-V:
-substantia gelatinosa
-nucleus proprius (rec. afferent pain, pressure and tactile fibers)
Rexed lamina VI:
-Clarkes column (thoracic nucleus)
in thoracic segments
-rec. aff. from receptors in skin, mm + tendons
(info sent to cerebellum)
white matter, surr grey matter
n. fibers of white matter consist of:
1) fibers to post. horns and fibers from ant horns.
2) commisural fibers: interconnect right + left halves of spinal cord
3) intersegmental fibers: interconnect adjacent or distal spinal segments
(ensure intersegmental cordination)
4) fibers interconnecting spinal cord and other parts of cns:
-ascending sensory n. tracts
-descending motor n. tracts
ascending sensory tracts
carry impulses from pain, tactile, thermal, mm + joint receptors to brain
asc. sensory tracts
1) fasiculus gracilis og fasiculus cuneatus:
-carry impulses w proprioception from mm og discriminative (fine) touch sensibility
-pathway for epicritic sensibility
-fg og fc m axons of primary afferent neurons (cell bodies loc. in spinal nerves ganglia)
-axons of spinal ganglia enter sp.cord,
ascend uncrossed in post. funiculi,
to terminate in nucleus gracilis
and nucleus cuneatus of oblongata (2nd order neurons)
asc. sensory tracts
2) spinothalamic tract:
-protopathic sensibility pathway
-pain and thermal sensation
-discriminative = course touch/pressure
-m axons of 2nd-order neurons
-in rexed lamina I-V
(subst. gelatinosa + nucleus proprius)
-fibers decussate to opposite side
and asc as the spinal lemniscus to terminate in thalamus
anterior spinothalamic tract:
-thermal sensation, course touch + pressure
lateral spinothalamic tract:
-pain
asc. sensory tracts
3) spino-reticulo-thalamic tract:
viscerosensory tract
(splanchestic sensibility)
from inner organs, mainly pain, ache
4) spino-reticular tract:
-part of reticular formation connections
asc. sensory tracts
5) spinotectal tract:
-m crossed fibers
-from nucleus proprius to tectum of midbrain
-asc pathway for spinovisual reflexes
(reflexive turning of eyes/head toward a stimulus)
6) spino-olivary tract:
from spinal cord indirectly to cerebellum
asc. sensory tract
7) spinocerebellar tract:
-ventral og dorsal
-carry info from mm + tendons +
tactile receptors to cerebellum
-control of poisture
-m fibers frá clarkes column
(nucleus thoracicus) - rexed lamina VI
descending motor tracts
O: from cortex + brainstem
(cortical og subcortical motor centers)
-control movement
-mm tone
-spinal reflexes
-autonomic functions
desc. motor tracts
1) corticospinal (pyramidal) tracts:
-start in primary motor cortex
(precentral gyrus)
-terminate in ventral horns in spinal cord to synapse w motor neurons
-lateral corticospinal tract:
m crossed fibers
(they cross in the pyramidal decussation)
-ventral corticospinal tract:
m uncrossed fibers
(they decussate near to their termination)
MAIN PATHWAY FOR VOLUNTARY MOVEMENT
extrapyramidal tracts
subcortical centers:
1) red nucleus
2) tectum of midbrain
3) vestibular nuclei
4) reticular formation
extrapyramidal tracts
pathways for involuntary movements:
-maintain mm tone
-eqilibrium
-mm coordination
-reflexes
1) rubrospinal tract
-m crossed fibers
-from red nucleus to ant. horn
(motor neurons)
F: influence mm. tone
extrapyramidal tracts
2) tectospinal tracts:
-m crossed n. fibers
-from tectum of midbrain (sup. colliculi)
to ant. motor horn
F: spinovisual reflexes (in response to visual stimuli)
3) vestibulospinal tracts:
-from vestibular nuclei to ant horns
F:pathway for eqilibrium control
extrapyramidal tracts
4) reticulospinal tract:
-crossed + uncrossed fibers
-from the reticular formation to ant horn
F: influences mm tone
reticulospinal tract also contains
desc. autonomic fibers, ext. from higher autonomic centers (diencephalon)
terminating on the interomediolateral nuclei
(autonomic nuclei)
5) olivospinal tract:
from cerebellum
(unimportant in humans)
