SpinalCordOld

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Spinal Cord

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This page is intended to discover component structure of spinal cord of biological human, sitting in between mind and peripheral organs.

SPINAL CORD STRUCTURE

BASIC INFORMATIOIN

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  • regions - cervical (C1-C8), thoracic (T1-T12), lumbar (L1-L5), sacral (S1-S5), coccygeal (CX = CX1-CX3)
  • width - 1 cm (thoracic/sacral) /2 cm (cervical-lumbar)
  • height - 45 cm (men)/43 cm (women)

SPINAL CORD SENSORY AND MOTOR ROOTS NEURONS

  • Fibers by thickness*:
  • A-alpha motor/sensory (Ia, Ib): 12-22 mcm, 70-120 m/sec, low theshold, 2ms after stimulus (motoneurons, touch, position and velocity, Meissner's corpuscles)
    • A-alpha-Ia motor/sensory:
      • muscle spindle primary sensory endings (skin, two-point discrimination, extrafusal muscles, Meissner's corpuscles)
      • alpha motoneurons (extrafusal muscle fibers, skeletal movements, brainstem/spinal cord)
        • FF-type alpha motoneurons - biggest motoneurons, type IIB extrafusal muscle fibers (generate large force, poor efficiency, affected by static beta motoneurons)
        • FR alpha motoneurons - type IIA extrafusal muscle fibers (affected by static beta motoneurons)
        • S-type alpha motoneurons - type I muscle fibers (little force, metabolically efficient, affected by dynamic beta motoneurons)
    • A-alpha-Ib sensory:
      • sensory Golgi tendon organs
      • sensory Ruffini endings in skin
  • A-beta motor/sensory (II): 8-13 mcm, 40-70 m/sec, higher theshold, 4ms after stimulus (fine touch, kinesthesia, muscle spindle secondary endings)
    • Merkel disks (weak position and strong velocity - irregular discharge, type I, hairy/hairless skin)
    • Ruffini's corpuscles (strong position and weak velocity receptors - regular discharge, type II, hairy/hairless skin)
    • Hairy skin velocity receptors (large hair follicles, slow and rapid movement of hairs and deflection of the skin)
    • Pacinian corpuscles (transient receptors, connective tissue, vibration, intrafusal muscles, tonic proprioceptive endings, flower-spray type)
    • beta motoneurons (skeleto-fusimotor, intrafusal fibers and collaterals to extrafusal muscle fibers, muscle spindles, increase dynamic sensitivity of ending)
      • beta dynamic motoneurons - type I extrafusal muscle fibers and the intrafusal bag1 fiber (slow contracting motor units)
      • beta static motoneurons - type IIA or IIB extrafusal fibers and the intrafusal bag2 fiber (fast contracting motor units)
  • A-gamma motor: 4-8 mcm, 15-40 m/sec, 6ms after stimulus
    • intrafusal muscle fibers (skeletal muscle tone, contract muscle spindles from both ends, fusimotor gamma neurons, affect Ia/II)
      • gamma static motoneurons - intrafusal bag2 fiber and the nuclear chain fibers
      • gamma dynamic motoneurons - intrafusal bag1 fiber
  • A-delta sensory (III): 1-4 mcm, 5-15 m/sec, 20ms after stimulus
    • noxious receptors (first/fast, sharp, well-localized pain)
    • cold receptors (temperature, high-threshold mechano/heat, phasic)
    • pressure (rapidly adapting mechanosensitive, directional selectivity, crude touch)
  • B motor: 1-3 mcm, 3-14 m/sec, preganglionic autonomic, myelinated, ACh (sympathetic only in T1-L3, IML)
    • preganglionic paravertebral sympathetic (short to paravertebral sympathetic ganglia, close to vertebral, fibers ascend/descend to reach all spinal cord levels)
    • preganglionic prevertebral sympathetic (long to prevertebral sympathetic ganglia, celiac, superior/inferior mesenteric ganglia)
    • preganglionic parasympathetic spinal (spinal cord long fibers to parasympathetic ganglia, splantic nerves, abdominal organs)
    • preganglionic parasympathetic cranial (cranial nerves III, VII, IX and X long fibers to parasympathetic ganglia, eye iris, lacrimal/submandibular/subingual glands, thorax, abdomen, GI tract)
  • C motor/sensory (IV): 0.1-1 mcm, 0.2-2 m/sec, 60ms after stimulus (pain, touch, pressure, temperature, postganglionic autonomic)
    • C fiber nociceptors (responsible for the second, burning pain)
    • C fiber warming specific receptors (responsible for warmth)
    • ultra-slow histamine-selective C fibers (responsible for itch)
    • tactile C fibers (sensual touch, includes CT fibres, also known as C low-threshold mechanoreceptors (CLTM), which are unmyelinated afferents found in human hairy skin, and have a low mechanical threshold < 5 milliNewtons. They have moderate adaptation and may exhibit fatigue on repetitive stimulation and "afterdischarges" for several seconds after a stimulus)
    • C mechano- and metabo- receptors in muscles or joints (responsible for muscle exercise, burn and cramp)
    • postganglionic sympathetic C fibers (muscles and skin, pre/post - temporal summation and spatial summation, one-to-many, wide-spread, long and unmyelinated, NE)
    • postganglionic parasympathetic C fibers (from ganglia in/on wall of organ, visceral activity and repose, short, local)
  • Sensory neurons*:

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  • Classification by receptor:
    • proprioceptors: LI,LV, also LII (fast pain/temperature senses), A-delta fibers
    • nociceptors: LII,LI (slow pain/temperature senses, unmyelinated), C fibers
    • mechanoreceptors: LIII,LIV (touch/position/kinesthetic/vibration senses), A-alpha-Ia/A-beta fibers

nrn1073-f1.jpg

  • Proprioception
    • receptors origin: muscle spindle (intrafusal fibers), Golgi tendon organ, A-alpha-Ib/A-beta fibers
    • intrafusal fiber types:
      • nuclear chain fibers - report static length of muscle (aligned in a single row), A-alpha-Ia/A-beta/A-gamma fibers
      • static nuclear bag fibers - report static length of muscle (bundle in fiber middle), A-alpha-Ia/A-beta/A-gamma fibers
      • dynamic nuclear bag fibers - report rate of change of muscle length (bundle in fiber middle), A-alpha-Ia/A-gamma fibers
    • roman number fiber classification:
      • Ia - primary afferents, annulospiral endings, length and velocity, A-alpha-Ia fibers
      • Ib - Golgi tendon organ, report load being applied to muscle, A-alpha-Ib fibers
      • II - secondary afferents, flower spray endings, length only, A-beta fibers
  • Sensory endings
    • mc_ch14_fig01.jpg
    • Hair follicle receptors: touch (slowly adapting, low threshold), A-beta fibers
    • Merkel disk receptors: vibration 5-15 Hz (high resolution tactile discrimination, static touch/pressure, mechanoceptors in hairless skin and mucosa, pressure and texture, slowly adapting, sustained response, low threshold), A-beta fibers
    • Meissner's corpuscles: vibration 20-50 Hz (tactile, dynamic touch/pressure, texture, rapidly adapting, superficial papillary receptor, low threshold, especially sensitive to light touch - like fingers and lips), A-alpha-Ia fibers
    • Pacinian corpuscles: vibration 60-400 Hz (deep receptors, subcutaneous tissue, viscera, rapidly adaptng, low threshold), A-beta fibers
    • Ruffini's corpuscles: stretching of skin (deep receptors, slowly adapting, low threshold), A-alpha-Ib/A-beta fibers
    • Free nerve endings: pain, temperature, crude touch, A-delta/C fibers
    • Golgi tendon organs: muscle tension (slowly adapting, low threshold), A-alpha-Ib fibers
    • Muscle spindles: skeletal muscle, stretch by muscle length (fast), A-alpha-Ia/A-beta
  • Motoneurons*: Motoneurons:

reflexarcs1336087730891.gif

  • alpha-motoneuron: extrafusal muscle fibres (voluntary movement), A-alpha-1a fibers
  • beta-motoneuron: intrafusal/extrafusal muscle fibres (voluntary movement), A-beta fibers
  • gamma-motoneuron: intrafusal muscle fibers (muscle tonus, additional contracts to maintain sensitivity in stretched state), A-gamma fibers
  • preganglionic autonomic: B fibers
  • postganglionic autonomic: C fibers
  • renshaw cell: axon collateral of alpha-motoneuron -> renshaw cell -> alpha-motoneuron (negative feedback)
  • Motor interneurons*:

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  • interneurons of indirect supraspinal connections: primary pathway for alpha-motoneurons
  • renshaw interneurons: interneurons of direct monosynaptic connections with alpha-motoneurons, some fibers of CST/LVST/RST, negative feedback on the same alpha-neurons; stop firing to be ready for next supraspinal signal
  • integrated rhythmic movements of upper and lower extremities like walking and running
    • intersegmental interneurons: reciprocal inhibition (excite agonist muscles/ inhibit antagonist muscles), feedback inhibition (selectively inhibit LMN to proper pattern in agonist muscle group)
    • commissural interneurons: to contralateral neurons (crossed extensor reflexes, alternate rhythms of both upper and lower extremities during running and walking)

SPINAL CORD NUCLEI

spinal-cord-nuclei.jpg

  • outer:* outer:
  • Lateral Cervical Nucleus (LCN) (lateral horn, low-threshold fast-conducting, tactile/pressure relay); sensory, tract of Lissauer/spinocervical tract; A-alpha-Ib/A-beta/A-delta sensory data
  • Lateral Spinal Nucleus (LSN) (lateral horn, relay in unmyelinated pathways between the periphery and brain, intersegmental integrator); sensory, spinohypothalamic tract/spinosolitary tract; A-delta/C sensory data
  • sensory:* sensory:

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  • Marginal Nucleus (MN), Apex of Posterior Horn, Nucleus Posteromarginalis - LI (A-delta/C, somatic sensory, non-modulatable pain and temperature sensations, joint nociception); sensory, tract of Lissauer/spinomesencephalic tract; modulatory, dorsolateral tract (from RVM); interneurons from SG; interneurons to NPR,IML; A-delta/C sensory data
  • Substantia Gelatinosa (SG), Rolando's Substance - LII (C, somatic sensory, short - pain, temperature, long - mechanoreceptors; long inhibits short); sensory, tract of Lissauer; modulatory, dorsolateral fasciculus (from VTA); interneurons to MN, CLN; C sensory data
  • Nucleus Proprius (NPR), Main Sensory Nucleus, Proper Sensory Nucleus - LIII,LIV (A-beta, visceral sensory, crude and pressure, 2-point discrimination, vibration); sensory: lateral spinothalamic tract/spinocervical tract/spinotectal tract/spinoolivary tract; A-alpha-Ib/A-beta/A-delta sensory data
  • Clarke's Nucleus (CLN), Nucleus Dorsalis, Posterior Thoracic Nucleus, Clarke's Column - LV, LVI (A-alpha/A-delta, visceral sensory, secondary visceral afferents, unconscious proprioception): sensory, tract of Lissauer/anterior spinothalamic tract/spinoreticular tract/dorsal spinocerebellar tract; interneurons from SG, NPR; A-alpha-Ia/A-alpha-Ib/A-delta sensory data
  • Central Nucleus (unconscious proprioception)
    • Central Cervical Nucleus (CCN) - LVII (spinocerebellar sensory, relays neck proprioception to cerebellum, locomotion); sensory, spinoolivary tract/spinovestibular tract; A-alpha-Ia/A-alpha-Ib sensory data
    • Centrobasalis Nucleus (CBN) - LVII (spinocerebellar sensory, relays forelimb proprioception to cerebellum); sensory, rostral spinocerebellar tract; A-alpha-Ia sensory data
  • Intermediomedial Nucleus (IMM) - LVII (visceral sensory); sensory, ventral spinocerebellar tract; A-alpha-Ia sensory data
  • motor:* motor:
  • Medial Motor Nuclei (axial muscles motor neurons)
    • Posteromedial Nucleus (PMN), Dorsomedial Nucleus - LIX (axial trunk flexors, T1-L2); flexor motor, lateral vestibulospinal tract/medullary reticulospinal tract; A-alpha-Ia/A-beta/A-gamma motor data
    • Ventromedial Nucleus (VMN), Anteromedial Nucleus - LVIII (axial trunk extensors, inhibit flexors, all segments); extensor motor, ventral corticospinal tract; A-alpha-Ia/A-beta/A-gamma motor data
  • Lateral Motor Nuclei (distal muscles motor neurons)
    • Posterolateral Nucleus (PLN), Dorsolateral Nucleus - LIX (distal flexors, C4-C8/L2-S1, hand/leg, distal muscles of forearm, hand, leg, foot); flexor/extensor motor, lateral corticospinal tract/rubrospinal tract/lateral vestibulospinal tract; A-alpha-Ia/A-gamma motor data
    • Ventrolateral Nucleus (VLN), Anterolateral Nucleus - LIX (distal extensors, C4-C8/L2-S1, shoulder/hip, distal muscles of shoulder girdle, arm, hip, thigh); extensor motor, pontine reticulospinal tract; A-alpha-Ia/A-gamma motor data
    • Spinal Accessory Nucleus (SAN) - LIX (neck, control neck to rotate head); flexor motor, tectospinal tract/medial vestibulospinal tract; A-alpha-Ia/A-beta/A-gamma motor data
    • Phrenic Nucleus (PHN) - LIX (diaphragm, conscious and autonomic control of breathing); visceral motor, ventral corticospinal tract; autonomic motor, solitariospinal tract; A-alpha-Ia/A-beta/A-gamma motor data
    • Retroposterolateral Nucleus (RPL), Retrodorsolateral Nucleus - LIX (fingers, C8-T1/S1-S3, distal large motor neurons to small arm and leg finger muscles); flexor motor, lateral corticospinal tract/rubrospinal tract; A-alpha-Ia/A-gamma motor data
  • Onuf's Nucleus (ONN), Gert's Nucleus, Lumbosacral Nucleus - LIX (dorsomedial: urination, dorsolateral: defecation, external sphincters; orgasmic muscular contractions); flexor motor, dorsolateral tract; interneurons from Sacral Parasympathetic Nucleus; A-alpha-Ia/A-gamma motor data
  • Dorsal Commissural Nucleus (DCN) - LX (integrate direct/indirect excitatory and inhibitory fast inputs, modulate by slow excitatory responses); interneurons from Intermediolateral Nucleus
  • autonomic:* autonomic:
  • Intermediolateral Cell Column, Intermediate Zone:
    • Intermediolateral Nucleus (IML) - LVII (autonomic, visceral structures); sympathetic, visceral motor; dorsolateral tract; interneurons from Marginal Nucleus; B motor data
    • Ciliospinal Center (CSC) - LVII (autonomic, visceral structures); sympathetic motor, tectospinal tract/hypothalamospinal tract; B motor data
    • Sacral Parasympathetic Nucleus (SPS) - LVII (S1-S3, psym. to large intestine; pelvic nerve); sympathetic motor, dorsolateral tract; interneurons to Onuf's Nucleus; B motor data

SPINAL CORD LAMINAE AND LEVELS

(generated)

|| Level/Lamina || LO || LI || LII || LIII || LIV || LV || LVI || LVII || LVIII || LIX || LX || || C1 || LCN || MN || SG || NPR || NPR || || || CCN || VMN || SAN || || || C2 || LCN || MN || SG || NPR || NPR || || || CCN || VMN || SAN || || || C3 || LCN || MN || SG || NPR || NPR || || || CCN || VMN || SAN,PHN || || || C4 || LCN || MN || SG || NPR || NPR || || || CCN || VMN || SAN,PHN,PLN,VLN || || || C5 || LCN || MN || SG || NPR || NPR || || || CBN || VMN || SAN,PHN,PLN,VLN || || || C6 || LCN || MN || SG || NPR || NPR || || || CBN || VMN || SAN,PLN,VLN || || || C7 || LCN || MN || SG || NPR || NPR || || || CBN || VMN || PLN,VLN || || || C8 || LCN || MN || SG || NPR || NPR || CLN || CLN || CBN,RPL || VMN || PLN,VLN || || || T1 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM,RPL,CSC || VMN || PMN || || || T2 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM,CSC || VMN || PMN || || || T3 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN || || || T4 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN || || || T5 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN || || || T6 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN || || || T7 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN || || || T8 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN || || || T9 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN || || || T10 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN || || || T11 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN || || || T12 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN || || || L1 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN || DCN || || L2 || LSN || MN || SG || NPR || NPR || CLN || CLN || IML,IMM || VMN || PMN,PLN,VLN || DCN || || L3 || || MN || SG || NPR || NPR || CLN || CLN || || VMN || PLN,VLN || || || L4 || || MN || SG || NPR || NPR || || || || VMN || PLN,VLN || || || L5 || || MN || SG || NPR || NPR || || || || VMN || PLN,VLN || || || S1 || || MN || SG || NPR || NPR || || || RPL,SPS || VMN || PLN,VLN,ONN || DCN || || S2 || || MN || SG || NPR || NPR || || || RPL,SPS || VMN || ONN || DCN || || S3 || || MN || SG || NPR || NPR || || || RPL,SPS || VMN || ONN || DCN || || S4 || || MN || SG || NPR || NPR || || || || VMN || || DCN || || S5 || || MN || SG || NPR || NPR || || || || VMN || || || || CX || || MN || SG || NPR || NPR || || || || VMN || || ||

SUBCORTICAL SENSORY SYSTEMS

  • subcortical visual system
  • somatosensory system
  • subcortical auditory system
  • gustatory system
  • viscerosensory system
  • humerosensory system

SPINAL CORD CONNECTIVITY

SPINAL CORD TRACTS

image044.jpg 800px-Spinal_cord_tracts_-_English.svg.png

  • ASCENDING*: ASCENDING:
  • DESCENDING*: DESCENDING:

OvyHXzkWIfq4piBE7gtbUw.png

  • INTRASPINAL*: INTRASPINAL:

SpCdFibersNeuronsSmll.gif

SENSORY NUCLEI CONNECTED TO SPINAL CORD

MOTOR NUCLEI CONNECTED TO SPINAL CORD

NUCLEI RECIPROCALLY CONNECTED TO SPINAL CORD

GANGLIA CONNECTED TO SPINAL CORD

FUNCTIONAL GROUPS

SENSORY NUCLEI FROM DRG TO VPL/VPM

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SENSORY NUCLEI FROM SPINAL CORD TO VPL/VPM

SENSORY NUCLEI FROM SPINAL CORD TO CR

INTERSPINAL SENSORY TO MOTOR

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