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gray matter

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centrally placed H or butterfly shaped region surrounding the central canal -neuronal somata and processes, glial cells, and capillaries three subdivisions: posterior (dorsal) horn, anterior (ventral) horn, and intermediate gray

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white matter contains?

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myelinated and unmyelinated axons arranged in longitudinal tracts

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one of the three major regions/funiculi (bilaterally) of white matter: dorsal/posterior funiculus

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medial border is the dorsal medial sulcus and septum, lateral border is the dorsal gray horn and Lissauer's tract (dorsolateral fasciculus) -divided by dorsal intermediate sulcus and septum into two major ascending tracts above T6 (below T6 is only fracilis) -fasciculus gracilis -fasciculus cuneatus

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Ventral/anterior funiculus

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lateral border is ventrolateral sulcus, medial border is ventral medial sulcus

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lateral funiculus

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located between the dorsolateral sulcus (dorsal root entry) and the ventrolateral sulcus (ventral root exit)

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changes in shape of spinal cord at different levels

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oval at cervical circular at lumbar quadrangular at sacral

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proportion of white matter to gray matter at different levels

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progressively increasing from below up

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size of anterior horn

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enlargement at cervical and lumbar segments

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posterior intermediate sulcus is present at what levels of the spinal cord

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cervical and thoracic

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lateral horn is most well marked at what segment

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thoracic

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nerve roots most prevalent at what segments

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lumbar and sacral

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cell types in spinal gray matter

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root cells: axons exit CNS at ventral roots, cell bodies in the ventral horn, intermediolateral and intermediomedial cell columns tract cells: projection neurons, axons project to supraspinal regions of the CNS interneurons: axonal projections remain in spinal cord, classified according to the projections (intrasegmental, intersegmental, commissural)

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spinal cord gray matter is arranged longitudinally in columns and lamina known as

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nuclear columnar organization laminae of Rexed

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Posterior Horn have what nuclei present at all levels? (Rexed Laminae I-VI)

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postero-marginal nucleus (marginal zone), substantia gelatinosa, nucleus proprius (principle sensory nucleus)

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Anterior horn (Rexed's Laminae VIII and IX) column organization

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-Medial motor column: extends entire length of spinal cord and innervates axial musculature -Lateral motor columns: located in cervical and lumbar enlargements, innervates muscles of their respective extremities

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Anterior horn Rexed Lamina IX organization

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axial musculature is medial and distal musculature is lateral

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Organization of intermediate gray (Rexed's laminae VII)

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-Dorsal Dark nucleus of Clark:spinal segments C8-T1 to L2-L3, it is the nucleus of origin for the dorsal spinocerebellar tract (DSCT) -Interomediolateral nucleus: thoracic and lumbar vertebrae, forms pointed lateral horn at T1-L3, contains preganglionic sympathetic GVE neurons -Intermediomedial nucleus: visceral motor reflexes, preganglionic parasympathetic neurons (Sacrovisceromotor cell column) -central gray matter/gray commissure

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spinal cord is divided into how many laminae

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10

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Rexed laminae in the posterior horn involved in receiving sensory inputs

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most of posterior horn (I-VI) I: marginal zone II: substantia gelatinosa III and IV: nucleus proprius I and II involved in modulating incoming activity Nucleus proprius transmits info and reflex connections

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Rexed laminae V and VI involved in?

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base of posterior horn -areas important for integration of somatic motor info and as reflex centers

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Rexed laminae VII

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dorsal nucleus of Clark, intermediolateral and intermediomedial columns -source of spinocerebellar fibers (DSCT), important for motor reflex activity and the is the location of autonomic preganglionic neurons

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Rexed laminae VIII

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contains interneurons and tract cells

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Rexed lamina IX

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lateral and medial motor columns

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Rexed lamina X

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gray commissure

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Functional overview of posterior horn

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receives sensory info from exterocepters (GSA terminate in I-V), proprioceptors (GSA terminate in V-VI), interoceptors (terminate in I, V-VI) -receives descending input from supraspinal centers (cerebral cortex and subcortical areas) -activity is integrated and relayed to motor neurons (IX), interneurons, and projection neurons

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functional overview of intermediate gray

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receives inputs from dorsal root fibers, posterior horn, interneurons, cortical, and subcortical areas -integrates info and relays it to other spinal zones via projection neurons -contains preganglionic autonomic neurons

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functional overview of anterior horn

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inputs include dorsal root fibers (monosynaptic reflex connections), intermediate zone, cortical, and subcortical descending pathways outputs via alpha and gamma motor neurons to muscle

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white matter tracts: Fasciculus gracilis (present entire spinal cord) and fasculus cuneatus (T6 and above)

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collectively=dorsal posterior columns -ipsilateral relay of primary sensory info (proproception, tactile position, vibratory sense, and deep touch) -Gracilis relays sensory info from below T6, Cuneatus above T6 -Damage produces ipsilateral loss below lesion -septomarginal fasciculus: in lower half of cord, where fibers making up the fasciculus gracilis enter -interfascicular fasciculus: levels of cord where fibers making up the cuneate fasciculus enter

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white matter tract: anterolateral system

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contralateral pathway in ventrolateral area of spinal cord -spinothalamic, spinomesencephalic, spinoreticular, and spinohypothalamic tracts -relay pain, temp, touch info to higher levels of CNS -damage-->loss of sensation in contralateral side of body 1-2 segments below lesion

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white matter tract: dorsal spinocerebellar tract (DSCT)---L2 or L3 and above

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located at the dorsolateral edge of spinal cord, contains fibers originating from the dorsal nucleus of Clark, so found only above level L2 or L3 because the nucleus is only present above that level -ipsilateral pathway that carries unconscious proprioceptive info from the spinal cord to cerebellum

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white matter tract: Vental spinocerebellar tract

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arises from laminae V-VIII and has large neurons along the border of the anterior horn -contralateral to its cells of origin, some fibers cross the midline twice, the second time in the cerebellum, before terminating -relays unconscious proprioceptive information

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descending pathway: lateral corticospinal tract

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largest and most prominent pathway in spinal cord, crosses midline in pryamidal decussation of brainstem and descends in the contralateral spinal cord -function is to control fine movements of distal musculature -damage produces ipsilateral spastic paralysis below lesion

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descending pathway: ventral corticospinal tract

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in venral funiculus -ipsilateral pathway that contains fibers that dont cross midline in the decussation of pyramids

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descending pathway: rubrospinal tract

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anterior to lateral corticospinal tract, contralateral tract that arises from the red nucleus -controls various musculature

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descending pathway: lateral (medullary) and medial (pontine) reticulospinal tracts

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located in lateral and ventral funiculi respectively -arise from nuclei of medullary and pontine reticular formation respectively -mostly ipsilateral and terminate on motor neurons in the gray matter

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descending pathway: raphespinal tract

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just below and overlapping LCST, arises from nucleus raphe magnus in medulla and ends in external laminae of posterior horn -inhibits transmission of entering sensory signals at level of spinal cord

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descending pathway: vestibulospinal tract

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ipsilateral pathway in ventral funiculus, originates in lateral vestibular nucleus in brainstem -modulates lower motor neuron activity in response to vestibular sensory info

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descending pathway: medial longitudinal fasciculus, medial and lateral tectospinal tracts

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small tracts located in the ventral funiculus that arise in the brain stem and alter motor function

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fasciculus proprius

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intersegmental fibers that ascend and descend immediately adjacent to spinal cord gray matter

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Lissauer's fasciculus

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primary sensory fibers carrying pain, temp, touch info -bifurcate upon entering spinal cord -branches ascend and descend for several segments before terminating in posterior horn

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anterior white commissure

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contains crossing intersegmental (commissural) and ascending fibers

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opiates involved in pain pathways?

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methionine and leucine enkephalin

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what neuropeptides are present in dorsal root ganglion cells and in the dorsal horn

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substance P, calcitonin gene-related peptide (CGRP)

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glutamate, GABA, and glucine are present where in the spinal cord?

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glutamate: dorsal columns, dorsal and ventral horn, dorsal root ganglion GABA: dorsal horn glycine: ventral horn

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monoaminergic terminals of supraspinal origin

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dopamine, serotonin, and noradrenalin

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acetylcholine is present

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in the ventral horn, efferent fibers in spinal nerves

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spinal nerve

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union of dorsal root and ventral root

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Bell-Magendie law

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ventral roots largely efferent, dorsal roots largely afferent

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Afferent classification: GSA and GVA

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General somatic afferents: body surface, muscles, tendons, and joints General visceral afferents: visceral structures

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Efferent classification: GSE and GVE

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GSE: arise from ventral horn cells, fibers innervate skeletal muscles (alpha) and muscle spindles (gamma) GVE: -arise from intermediolateral cell column (T1-L2), sympathetic preganglionic neurons that leave spinal nerve via white communicating ramus to synapse in the sympathetic trunk -arise from sacrovisceromotor nucleus (S2-S4), parasympathetic preganglionic neurons

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posterolateral herniation of disc

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-->spinal root/nerve compression, sensory and motor symptoms may occur depending on dorsal and ventral root involvement

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if spinal nevers are involved in both sensory and motor disturbances then, either will affect

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the stretch refelx

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effects of compression of spinal nerve can present as

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pain in the muscles supplied by the nerve, parasthesia along the dermatome, cutaneous sensory loss, motor weakness, or loss of a tendon reflex

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traction (compression) of a spinal nerve will stretch and irritate nerve to produce

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radicular pain

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segmental levels for reflexes biceps triceps knee ankle

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c5, c6 c7 L3, L4 S1

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spinal cord disorders are classified as?

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focal: can be segmental (symptoms and signs at only one level) or combinatorial (segmental and longitudinal symptoms and signs) diffuse: may involve single system or multiple systems

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example of focal spinal cord disorders include

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demyelinating and degenerative diseases due to the selective involvement of specific functional-anatomical systems

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subacute combined degeneration

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diffuse spinal cord disorder -combined motor and sensory related symptoms -loss of position, vibration sense, discriminative touch (demyelination of dorsal columns) -ataxia of sensory type due to loss of dorsal columns and spinocerebellar tracts -spastic paresis (demyelination of LCST)

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complete transverse lesion of spinal cord results in

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sudden loss of sensation and voluntary movements below level of injury

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signs of upper cervical spinal cord damage

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long tract signs in the upper and lower extremities for motor and sensory modalities and a reflex bladder dysfunction

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signs of middle and lower cervical spinal cord damage

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segmental signs of motor and sensory dysfunction in the upper extremities, and long tract signs in the lower extremities with bladder dysfunction

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signs of thoracic spinal cord damage

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long tract signs in the lower extremities with segmental sensory finding in the trunk and bladder dysfunction

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signs of lumbar and upper sacral spinal cord damage

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segmental motor and sensory signs in lower extremities with bladder dysfunction

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signs of conus medullaris damage

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segmental signs appear in lower extremities with nonreflex bladder disturbance

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signs of cauda equina damage

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pain and asymmetric motor and sensory involvement of multiple roots with or without nonreflex bladder

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