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Biological Mind Tracts

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This page is intended to describe set of physically existing tracts connecting set of regions across mind.

Sensory and Motor Root Neurons

(generated)

Motor Endings:

• • Alpha motoneurons (MA): generate large force (extrafusal muscle fibres, voluntary movement)
• FF-type alpha motoneurons (MA-FF): fast-twitch fatigable (run; generate large force, poor efficiency; biggest motoneurons, type IIB extrafusal muscle fibers; affected by static beta motoneurons); FIBERS={A-alpha-Ia-motor}
• FR-type alpha motoneurons (MA-FR): fast-twitch fatigue-resistant (walk; type IIA extrafusal muscle fibers; affected by static beta motoneurons); FIBERS={A-alpha-Ia-motor}
• S-type alpha motoneurons (MA-S): slow-twitch fatigue-resistant (stand; type I muscle fibers; little force, metabolically efficient, affected by dynamic beta motoneurons); FIBERS={A-alpha-Ia-motor}
  • Beta motoneurons (MB): affect both extrafusal and intrafusal muscle fibers (intrafusal/extrafusal muscle fibres, voluntary movement)
• beta dynamic motoneurons (MB-D): slow contracting motor units (type I extrafusal muscle fibers and the intrafusal bag1 fiber); FIBERS={A-beta-motor}
• beta static motoneurons (MB-S): fast contracting motor units (type IIA or IIB extrafusal fibers and the intrafusal bag2 fiber); FIBERS={A-beta-motor}
  • Gamma motoneurons (MG): enforce alpha motoneurons (intrafusal muscle fibers, muscle tonus, additional contracts to maintain sensitivity in stretched state; originate in pontine RF)
• gamma dynamic motoneurons (MG-D): contract muscle spindles from both ends (intrafusal bag1 fiber ); FIBERS={A-gamma-motor}
• gamma static motoneurons (MG-S): contract muscle spindles from both ends (intrafusal bag2 fiber and the nuclear chain fibers); FIBERS={A-gamma-motor}
  • postganglionic autonomic motoneurons (MPG): postganglionic autonomic
• postganglionic parasympathetic motoneurons (MPG-P): visceral activity and repose, short, local (from ganglia in/on wall of organ); FIBERS={C-motor}
• postganglionic sympathetic motoneurons (MPG-S): muscles and skin, pre/post - temporal summation and spatial summation (one-to-many, wide-spread, long and unmyelinated, NE); FIBERS={C-motor}
  • preganglionic autonomic motoneurons (MPA): preganglionic paravertebral/prevertebral sympathetic, spinal/cranial parasympathetic
• preganglionic parasympathetic cranial (MPA-PC): cranial nerves III, VII, IX and X long fibers to parasympathetic ganglia (eye iris, lacrimal/submandibular/subingual glands, thorax, abdomen, GI tract); FIBERS={B-motor}
• preganglionic parasympathetic spinal (MPA-PS): spinal cord long fibers to parasympathetic ganglia (splantic nerves, abdominal organs); FIBERS={B-motor}
• preganglionic paravertebral sympathetic (MPA-SPAV): short to paravertebral sympathetic ganglia (close to vertebral, fibers ascend/descend to reach all spinal cord levels); FIBERS={B-motor}
• preganglionic prevertebral sympathetic (MPA-SPRV): long to prevertebral sympathetic ganglia (celiac, superior/inferior mesenteric ganglia); FIBERS={B-motor}

Sensory Endings:

• • Mechanoreceptors (SMECH)
• Deep tissue mechanoreceptors (SMECH-DEEP)
  • Pacinian corpuscles (SPC): responds to vibration; vibration 60-400 Hz, deep (deep layers of dermis in both hairy and glabrous skin; greater signal from more massive or rapid deformation; deep receptors, subcutaneous tissue, viscera, rapidly adapting, low threshold; transient receptors, connective tissue, vibration, intrafusal muscles, tonic proprioceptive endings, flower-spray type); FIBERS={A-beta-sensory; A-delta-sensory}; TRACTS={fasciculus cuneatus tract; fasciculus gracilis tract; spinopontoreticular tract}
  • Ruffini corpuscles (SRC): responds to pressure on skin; stretching of skin, crude touch (end-bulbs of Krause - dermis of both hairy and glabrous skin and Ruffini - lips, tongue, and genitals; deep receptors, slowly adapting, low threshold; strong position and weak velocity receptors - regular discharge, type II, hairy/hairless skin); FIBERS={A-alpha-Ib-sensory; A-beta-sensory}; TRACTS={cuneocerebellar tract; dorsal spinocerebellar tract; spinocervical tract}
• Skin mechanoreceptors (SMECH-SKIN)
  • Hair follicle receptors (SHF): responds to hair displacement; touch, hairy skin velocity (slowly adapting, low threshold; peritrichial endings - nerve plexus wrapped around hair roots; large hair follicles, slow and rapid movement of hairs and deflection of the skin); FIBERS={A-beta-sensory}; TRACTS={fasciculus cuneatus tract}
  • Meissner corpuscles (SMC): responds to vibration; vibration 20-50 Hz; dynamic touch/pressure (dermis of glabrous skin; tactile, texture, rapidly adapting, superficial papillary receptor, low threshold, especially sensitive to light touch - like fingers and lips); FIBERS={A-alpha-Ia-sensory}; TRACTS={fasciculus cuneatus tract; spinoolivary tract; spinovestibular tract}
  • Merkel disk receptors (SMD): responds to pressure on skin; vibration 5-15 Hz, static (sustained) touch/pressure (epidermis of glabrous skin; respond to slight change in skin surface; high resolution tactile discrimination, mechanoceptors in hairless skin and mucosa, pressure and texture, slowly adapting, sustained response, low threshold; weak position and strong velocity - irregular discharge, type I, hairy/hairless skin); FIBERS={A-beta-sensory}; TRACTS={cuneocerebellar tract; dorsal spinocerebellar tract; spinoolivary tract; spinovestibular tract}
  • Pain and temperature receptors (SPT)
• A-delta fiber nociceptors (SAD): fast/first pain information; FIBERS={A-delta-sensory}; TRACTS={lateral spinothalamic tract; spinomedulloreticular tract; spinomesencephalic tract}
• Cold receptors (SCR): respond to low temperature (channel: TRPM8 (less than 28C), TRPA1 (less than 18C)); FIBERS={A-delta-sensory}
• Nonencapsulated free-nerve endings (SFN): pain and temperature (the only nociceptors); TRACTS={anterior spinothalamic tract; anterior trigeminothalamic tract; dorsal trigeminal tract; lateral spinothalamic tract; spinohypothalamic tract; spinosolitary tract; spinotectal tract; tract of Lissauer}
  • C fiber nociceptors (SFN-CN): responsible for the second, burning pain; FIBERS={C-sensory}
  • C fiber warming-specific receptors (SFN-CW): responsible for warmth; FIBERS={C-sensory}
  • C mechano- and metabo- receptors in muscles or joints (SFN-CM): responsible for muscle exercise, burn and cramp; FIBERS={C-sensory}
  • tactile C fibers (SFN-CT): 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 less than 5 milliNewtons; have moderate adaptation and may exhibit fatigue on repetitive stimulation and after discharges for several seconds after a stimulus); FIBERS={C-sensory}
  • ultra-slow histamine-selective C fibers (SFN-CI): responsible for itch; FIBERS={C-sensory}
  • Proprioceptors (SPROP)
• Golgi tendon organs (SGT): muscle tension (slowly adapting, low threshold); FIBERS={A-alpha-Ib-sensory}; TRACTS={cuneocerebellar tract; dorsal spinocerebellar tract; rostral spinocerebellar tract; spinoolivary tract; ventral spinocerebellar tract}
• Muscle spindles (SMS): skeletal muscle, stretch by muscle length, fast (intrafusal fibers); TRACTS={cuneocerebellar tract; dorsal spinocerebellar tract; fasciculus gracilis tract; spinoolivary tract; ventral spinocerebellar tract}
  • Dynamic nuclear bag fibers (SMS-DN): report rate of change of muscle length (bundle in fiber middle)
  • Nuclear chain fibers (SMS-NC): report static length of muscle (aligned in a single row)
  • Static nuclear bag fibers (SMS-SN): report static length of muscle (bundle in fiber middle)

Fibers by thickness:

• • A-alpha (mixed, 12-22 mcm, 70-120 m/sec): low theshold, 2ms after stimulus (type Ia,Ib; motoneurons, touch, position and velocity); TRACTS={spinocervical tract}
• A-alpha-Ia (mixed); TRACTS={fasciculus cuneatus tract}
  • A-alpha-Ia-motor - alpha motoneurons (motor); ENDINGS={MA-FF,MA-FR,MA-S}
  • A-alpha-Ia-sensory (sensory): skin, two-point discrimination (muscle spindle primary sensory endings; extrafusal muscles, Meissner's corpuscles; annulospiral endings, length and velocity); ENDINGS={SMC}; TRACTS={spinoolivary tract; spinovestibular tract}
• A-alpha-Ib-sensory (sensory): report load being applied to muscle, stretching of skin; ENDINGS={SGT,SRC}; TRACTS={cuneocerebellar tract; dorsal spinocerebellar tract; rostral spinocerebellar tract; spinoolivary tract; ventral spinocerebellar tract}
  • A-beta (mixed, 8-13 mcm, 40-70 m/sec): higher theshold, 4ms after stimulus (type II; fine touch, kinesthesia, muscle spindle secondary endings); TRACTS={fasciculus cuneatus tract; fasciculus gracilis tract; spinocervical tract}
• A-beta-motor - beta motoneurons (motor): skeleto-fusimotor, intrafusal fibers and collaterals to extrafusal muscle fibers, muscle spindles, increase dynamic sensitivity of ending; ENDINGS={MB-D,MB-S}
• A-beta-sensory (sensory): fine touch, kinesthesia (length only; secondary afferents, flower spray endings); ENDINGS={SMD,SRC,SHF,SPC}; TRACTS={cuneocerebellar tract; dorsal spinocerebellar tract}
  • A-delta-sensory (sensory, 1-4 mcm, 5-15 m/sec): noxious, cold, pressure; 20ms after stimulus (type III; thinly-myelinated; noxious receptors - first/fast, sharp, well-localized pain; cold receptors - temperature, high-threshold mechano/heat, phasic; pressure - rapidly adapting mechanosensitive, directional selectivity, crude touch); ENDINGS={SAD,SCR,SPC}; TRACTS={anterior trigeminothalamic tract; lateral spinothalamic tract; spinomedulloreticular tract; spinomesencephalic tract; spinopontoreticular tract; tract of Lissauer}
  • A-gamma-motor (motor, 4-8 mcm, 15-40 m/sec): intrafusal muscle fibers, 6ms after stimulus (skeletal muscle tone, contract muscle spindles from both ends, fusimotor gamma neurons, affect Ia/II); ENDINGS={MG-D,MG-S}
  • B-motor (motor, 1-3 mcm, 3-14 m/sec): preganglionic autonomic (myelinated, ACh, sympathetic only in T1-L3, IML); ENDINGS={MPA-SPAV,MPA-SPRV,MPA-PS,MPA-PC}
  • C (mixed, 0.1-1 mcm, 0.2-2 m/sec): pain, touch, pressure, temperature, postganglionic autonomic (60ms after stimulus)
• C-motor (motor): postganglionic autonomic; ENDINGS={MPG-S,MPG-P}
• C-sensory (sensory): pain and temperature; ENDINGS={SFN-CN,SFN-CW,SFN-CI,SFN-CT,SFN-CM}; TRACTS={anterior spinothalamic tract; dorsal trigeminal tract; lateral spinothalamic tract; spinohypothalamic tract; spinosolitary tract; spinotectal tract}

Tracts Hierarchy

(generated)

Ascending Tracts

TRACT SET: Ascending Tracts

• • TRACT ALS: anterolateral system - pain transfer
• TRACT PSTS: paleospinothalamic system - body pain transfer
  • TRACT ASTT: anterior spinothalamic tract (anterolateral tract) - body slow pain localization
  • TRACT LSTT: lateral spinothalamic tract - body pain perception
  • TRACT LST: tract of Lissauer (fasciculus of Lissauer, tract/zone of Lissauer, dorsolateral fasciculus, posterolateract tract, dorsolateral tract) - body fast pain localization
• TRACT SLS: spinolimbic system - autonomic body pain transfer
  • TRACT SHTT: spinohypothalamic tract - autonomic body pain transfer to hypothalamus
  • TRACT SMST: spinomesencephalic tract - descending modulation of pain
  • TRACT SST: spinosolitary tract - autonomic body pain transfer to parabrachial nucleus
• TRACT SRS: spinoreticular system - automatic body pain reflection
  • TRACT SMRT: spinomedulloreticular tract - automatic body pain spinal reflection
  • TRACT SPRT: spinopontoreticular tract - automatic body pain cortical reflection
  • TRACT STCT: spinotectal tract - automatic body pain spinovisual reflection
• TRACT TTS: trigeminothalamic system (neospinothalamic tract) - head pain transfer
  • TRACT ATTT: anterior trigeminothalamic tract (ventral trigeminothalamic tract) - head pain localization
  • TRACT DTTT: dorsal trigeminal tract (dorsal trigeminothalamic tract, lemniscus) - head pain perception
  • TRACT MLS: medial lemniscus system - conscious body mechanical perception
• TRACT PCS: posterior column system (dorsal column, Reils band, Reils ribbon) - conscious upper body mechanical and lower body cutaneous perception
  • TRACT FCT: fasciculus cuneatus tract (tract of Burdach) - conscious upper body mechanical perception
  • TRACT FGT: fasciculus gracilis tract (tract of Goll) - conscious lower body cutaneous perception
• TRACT SCVT: spinocervical tract (Morin's tract) - conscious lower body proprioception
  • TRACT SCS: spinocerebellar system - automatic activity
• TRACT DSCS: direct spinocerebellar system - automatic activity of body
  • TRACT CSCT: cuneocerebellar tract - automatic activity of upper limbs
  • TRACT DSCT: dorsal spinocerebellar tract (posterior spinocerebellar tract, Flechsigs tract) - automatic activity of lower limbs
  • TRACT RSCT: rostral spinocerebellar tract - automatic activity of upper body
  • TRACT VSCT: ventral spinocerebellar tract (anterior spinocerebellar tract, Gowers tract) - automatic activity of lower body
• TRACT SMTS: spinometencephalic system - automatic activity integration
  • TRACT SOT: spinoolivary tract (Helwegs tract) - automatic activity of head, neck and upper limbs
  • TRACT SVT: spinovestibular tract - automatic activity vestibular integration

Descending Tracts

TRACT SET: Descending Tracts

• • TRACT ATS: autonomic tracts system (descending autonomic fibers) - autonomic control
• TRACT HTST: hypothalamospinal tract - oculomotor autonomic control
• TRACT SSS: solitariospinal system - involuntary breathing control
  • TRACT SSET: solitariospinal expiratory tract - rhythmic expiration
  • TRACT SSIT: solitariospinal inpiratory tract - rhythmic inspiration
  • TRACT ESS: extensor somatic system - extensor control
• TRACT ACST: anterior corticospinal tract (ventral corticospinal tract) - conscious extensor control
• TRACT MLFS: medial longitudinal fasciculus system - automatic control
  • TRACT TCST: tectospinal tract - oculomotor automatic control
  • TRACT VST: vestibulospinal tract - body automatic control
    • TRACT LVST: lateral vestibulospinal tract - maintaining balance via legs extensors
    • TRACT MVST: medial vestibulospinal tract - stabilize visual image on retina
• TRACT RTSS: reticulospinal system - automatic and autonomic control
  • TRACT MRST: medullary reticulospinal tract (lateral reticulospinal tract) - inhibit extensors
  • TRACT PRST: pontine reticulospinal tract (medial reticulospinal tract) - excite extensors
  • TRACT FSS: flexor somatic system - flexor control
• TRACT CBT: corticobulbar tract - cranial flexor control
• TRACT LSTT: lateral corticospinal tract - conscious flexor control
• TRACT RBST: rubrospinal tract - automatic flexor control