Spinal Cord Flashcards
Spinal cord stability
Denticulate ligaments and filum terminale which arises from tip of conus
Spinal nerve pattern
C1-C7 exit above
C8 and rest are below
Enlargements of spinal cord and significance
Cervical (C4-T1) - brachial plexuses
Lumbar (L2-S3) - lumbosacral
Cauda equina syndrome
Impaired function of multiple nerve roots below L1 or L2…in addition, may affect bladder and bowel
Blood supply of spinal cord
Anterior 2/3 - anterior spinal artery
Posterior 1/3 - posterior spinal artery
Segmental arteries supplement the longitudinal
Great radicular artery is around T10-T12 and supplies lower thoracic and lumbosacral regiions of spinal cord
Difference between radiculopathy, CNS injury, and single nerve
CNS - will affect everything below the lesion
Radiculopathy - entire dermatome
PNS - single nerve
White vs. Gray matter in spinal cord
White - myelinated nerve fibers
Gray - neruonal cell bodies and glial cell bodies
Dorsal horn
Recieve synaptic input from affarent fibers and may ascend many levels
Lateral horn
Preganglionic sympathetic nerves of the intermediolateral cell column (IML)
Ventral horn
Somatomotor neurons
Substantia gelatinosa
Every level
At posterior horn and site of nociceptive termination
Nucleus proprius
In posterior horn
Every level
General sensory fiber termination and interneurons
Medial nucleus of ventral horn
Somatomotor neurons for axial skeletal muscles
All levels
Dorsal nucleus of clarke
C8-L2
Proprioception (noncon) to the cerebellum
Intermediolateral cell column
T1-L2
First neurons for sympathetic nervous system
Lateral nucleus of ventral horn
C5-T1 (upper)
L1-S3 (lower)
Innervation of skeletal limb muscles
Spinal border neuorons
T12-S2
Prorpioception to the cerebellum
Sacral parasympathetic nucleus
Neurons for caudal portion of PS fibers
S2-S4
Lamina 7
8
9
10
7 - contains dorsal nucleus of clarke and IML cell column
8 - mostly interneurons that receive input from primary motor cortex
9 - somatomotor of the anterior horn
10 - encircles central canal and gets visceral affarent fibers
Lamina 1 and 2
1 - gray matter cap of posterior horn…receive nociceptive and thermal from primary afferents…contributesd to spinothalamic tract
2 - corresponds to substantia geltinosa…mostly interneurons…involved with local spinal cord circuits
Lamina 3,4,5
3 - together with 4 creates nuecleus proprius involved in local cord circuits
4 - more of the same
5- multimodal neurons that get direct inputs from adelta fibers and dendrites extend into lamina 3 and 4 so also pain
Also contributes to spinothalamic tract
Interneuons and pain
Interneurons in the dorsal horn (lamina 1) contain enkephalins that inhibit neurons that are transmitting via spinothalamic pathway
Activated by Large diameter Abeta fibers OR descending reticular fibers from periaqueductal grey and Raphe nuceli of brainstem
Local reflex circuit
Sensory terminate at same level that it entered and directly synapse with the motor neuron
Myotatic reflex
1a fibers from spindle synapse directly with motor neurons on the ventral horn to elicit contraction…also synapse with interneurons in nucleus proprius to inhibit antagonistic muscles
Withdrawl reflex (ibsilateral)
Ipsilateral flexors contract and antagonistic relax
Sent through type C fibers to lamina 1,2, and 5
Crossed extensor reflex
Affarents cross the anterior white commissure to activate excitatory and inhibitory on the contralateral side
Dorsolateral fasciculus
Myelinated nad unmyelinnated primary affarent fibers ONLY for pain
Fasciulus proprius
Comprised of interneuron fibers that can ascend or descend…not limited to pain
Central overlap and pain
Can ascend one or two levels so pain cna be felt even if one level is lost
Lower motor neurons do NOT overlap
