MindTracts

Biological Mind Tracts

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

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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

* [ALS]: *anterolateral system* - pain transfer

• [PSTS]: *paleospinothalamic system* - body pain transfer

* [ASTT]: *anterior spinothalamic tract* (anterolateral tract) - body slow pain localization
* [LSTT]: *lateral spinothalamic tract* - body pain perception
* [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

* [SHTT]: *spinohypothalamic tract* - autonomic body pain transfer to hypothalamus
* [SMST]: *spinomesencephalic tract* - descending modulation of pain
* [SST]: *spinosolitary tract* - autonomic body pain transfer to parabrachial nucleus

• [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
* [STCT]: *spinotectal tract* - automatic body pain spinovisual reflection

• [TTS]: *trigeminothalamic system* (neospinothalamic tract) - head pain transfer

* [ATTT]: *anterior trigeminothalamic tract* (ventral trigeminothalamic tract) - head pain localization
* [DTTT]: *dorsal trigeminal tract* (dorsal trigeminothalamic tract, lemniscus) - head pain perception
* [MLS]: *medial lemniscus system* - conscious body mechanical perception

• [PCS]: *posterior column system* (dorsal column, Reils band, Reils ribbon) - conscious upper body mechanical and lower body cutaneous perception

* [FCT]: *fasciculus cuneatus tract* (tract of Burdach) - conscious upper body mechanical perception
* [FGT]: *fasciculus gracilis tract* (tract of Goll) - conscious lower body cutaneous perception

• [SCVT]: *spinocervical tract* (Morin's tract) - conscious lower body proprioception

* [SCS]: *spinocerebellar system* - automatic activity

• TRACT DSCS: *direct spinocerebellar system* - automatic activity of body

* [CSCT]: *cuneocerebellar tract* - automatic activity of upper limbs
* [DSCT]: *dorsal spinocerebellar tract* (posterior spinocerebellar tract, Flechsigs tract) - automatic activity of lower limbs
* [RSCT]: *rostral spinocerebellar tract* - automatic activity of upper body
* [VSCT]: *ventral spinocerebellar tract* (anterior spinocerebellar tract, Gowers tract) - automatic activity of lower body

• TRACT SMTS: *spinometencephalic system* - automatic activity integration

* [SOT]: *spinoolivary tract* (Helwegs tract) - automatic activity of head, neck and upper limbs
* [SVT]: *spinovestibular tract* - automatic activity vestibular integration

Descending Tracts

TRACT SET: Descending Tracts

* TRACT ATS: *autonomic tracts system* (descending autonomic fibers) - autonomic control

• [HTST]: *hypothalamospinal tract* - oculomotor autonomic control
• [SSS]: *solitariospinal system* - involuntary breathing control

* [SSET]: *solitariospinal expiratory tract* - rhythmic expiration
* [SSIT]: *solitariospinal inpiratory tract* - rhythmic inspiration
* TRACT ESS: *extensor somatic system* - extensor control

• [ACST]: *anterior corticospinal tract* (ventral corticospinal tract) - conscious extensor control
• [MLFS]: *medial longitudinal fasciculus system* - automatic control

* [TCST]: *tectospinal tract* - oculomotor automatic control
* [VST]: *vestibulospinal tract* - body automatic control
 * [LVST]: *lateral vestibulospinal tract* - maintaining balance via legs extensors
 * [MVST]: *medial vestibulospinal tract* - stabilize visual image on retina

• [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

• [CBT]: *corticobulbar tract* - cranial flexor control
• [LSTT]: *lateral corticospinal tract* - conscious flexor control
• [RBST]: *rubrospinal tract* - automatic flexor control