Spinal Cord Flashcards
What is the arterial supply of the sp. cord?
branches of the ant. spinal a.
post. spinal a.
(also gets supply from multiple radicular aa.)
What is the sp. cord derived from?
embryonic neural tube
Where do the ant. & post. spinal aa. branch from?
vertebral arteries
The spinal cord extends from the _________ to the _________.
medulla at the foramen magnum; lower border of L1
What are the 2 enlargements? What are their functions?
Cervical - innervate upper extremities
Lumbar - innervate lower extremities
Conus medullaris
L1 & L2 vertebrae
Site for lumbar puncture:
L4-L5 vertebrae
Filum terminale
pia mater from the conus medullaris to the coccygeal ligament
Cauda equina
lumbosacral roots surrounding the filum terminale
How is the sp. cord segmented?
31 pairs of spinal nerves in 31 segments: 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal
All spinal nerves innervate a single dermatome except?
C1
What is referred pain?
convergence of somatic and visceral afferents
Spinal nerves exit the _________ via the ____________ (location of ______).
vertebral canal; intervertebral foramina; DRG
Spinal cord indentations:
Anterior median fissure
posterior median sulcus/septum
posterolateral sulcus
posterior intermediate sulcus
What lies in the ant. median fissure?
ant. spinal artery and vein
____________ (entry of dorsal roots)
____________ (exit of ventral roots)
posterolateral sulcus
anterolateral sulcus
The ______________ is found in the ______________ only and is the separation of between 2 major ascending tracts
posterior intermediate sulcus; cervical and thoracic
What is the largest area of the spinal cord? The smallest?
cervical enlargement
sacral level
White matter is subdivided into:
Posterior funiculus (dorsal column) Lateral funiculus (column) Anterior funiculus (column)
Posterior funiculus:
Ascending somatosensory fibers:
1) Fasciculus gracilis (sacral & lumbar)
2) Fasciculus cuneatus (thoracic & cervical)
What is the function of ascending somatosensory fibers?
fine touch
vibration
two-point discrimination
proprioception
Lateral funiculus:
Descending tracts to the spinal cord:
lateral corticospinal tract
rubrospinal tract
What is the largest and most important tract? What will happen if this tract is lesioned?
lateral corticospinal tract
if lesioned, spastic paralysis will occur on the ipsi lateral side at the spinal cord level
The rubospinal tract is a(n) ____________ tract
contralateral
The posterior funiculus is a(n) __________ tract.
ipsilateral
What will happen if the posterior funiculus is lesioned?
There will be loss of somatosensory sensation on the ipsi side below the level of the lesion
Ascending tracts from the spinal cord:
spinothalamic tracts = anterolateral tract
posterior spinocerebellar tract
Spinothalamic tracts:
contralateral tract
pain, temp., crude touch
if lesioned: loss of sensation on the contralateral side
Posterior spinocerebellar tract:
ipsilateral tract (from spinal cord to cerebellum) stretch, touch and pressure sensation
if lesioned: loss of sensation on the ipsilateral side
Anterior funiculus:
smaller ascending and descending tracts
crossing of the spinothalamic tracts
Gray matter is subdivided into:
dorsal horn
ventral horn
lateral horn
Dorsal horn:
Sensory:
receives sensory input
mediates synapses
gives rise to ascending sensory pathways
Ventral horn:
Motor: • α motoneurons • γ motoneurons • interneurons • Neurons innervate extrafusal & intrafusal muscle fibers
Lateral horn:
Intermediolateral cell column (T1-L2/L3)
Thoracolumbar sympathetic outflow (preganglionic)
There are ____ cellular laminae
9
Dorsal horn: I - VI
All sensory:
I - marginal zone (pain & temp)
II - substantia gelatinosa (interneurons)
III - V - mechanical visceral and noxious stimuli
VI - prominent only at enlargements
Which laminae give rise to the anterolateral tract?
I, V and some VII
Intermediate zone: dorsal VII
Medial: Clarke’s nucleus (C8-L3)
• gives rise to dorsal spinocerebellar tract
Lateral:
• Intermediolateral cell column (T1-L2/L3) - preganglionic sympathetic
• Sacral autonomic nuclei (S2-S4) - preganglionic parasympathetic
Ventral horn:
ventral VII, VIII & IX
• Motor neuronal groups in lamina IX: innervate truncal & limb muscles
General functional significance of the spinal cord:
1) receives the primary sensory afferent inputs from the DRG; relays them to the brain stem, cerebellum or the thalamus; may or may not synapse within the spinal cord
2) α & γ motorneurons that innervate extrafusal & intrafusal muscles
3) mediates spinal reflexes
4) intermediolateral cell column from T1 to L2/L3 that gives rise to preganglionic sympathetic fibers; synapse in the paravertebral & prevertebral ganglia
5) preganglionic parasympathetic neurons in S2-S4; synapse in terminal ganglia within walls of the pelvic viscera
6) major sensory & motor ascending and descending tracts run through it
Lesions of the spinal cord:
dorsal root lesions ventral root lesions spinal cord hemisection (Brown-Sequard syndrome) spinal cord transection syringomyelia
Dorsal root lesions:
hypesthesia or anesthesia
Ventral root lesions:
weakness/flaccid paralysis & atrophy of muscles
involvement of autonomic preganglionic fibers may result in autonomic dysfunction
Spinal cord hemisection:
loss of fine touch, vibration and propioception ipsilateral to & below lesion
loss of pain & temp. contralateral to & below lesion
spastic paralysis ipsi to & below lesion
Spinal cord transection:
destruction of ascending and/or descending tracts produces sensory, motor & mixed deficits
Syringomyelia:
damage crossing fibers around the central canal
