Spinothalamic tract

Brain: Spinothalamic tract
Spinothalamic tracts are grouped, in blue at bottom right.
Diagram of the principal fasciculi of the spinal cord. (Anterior and posterior spinothalamic fasciculus is labeled at bottom left.)
Gray's	subject #185 760
NeuroNames	ancil-114

The spinothalamic tract is a sensory pathway originating in the spinal cord. It transmits information to the thalamus about pain, temperature, itch and crude touch. The pathway decussates at the level of the spinal cord, rather than in the brainstem like the posterior column-medial lemniscus pathway and corticospinal tract.

Contents 1 Tracts 2 Information transmitted 3 Sub-systems 4 Path of sensation 5 Lesions 6 See also 7 External links

Tracts

There are two main parts of the spinothalamic tract (STT):

• The lateral spinothalamic tract transmits pain and temperature.
• The anterior spinothalamic tract (or ventral spinothalamic tract) transmits crude touch.

Information transmitted

The types of sensory information transmitted via the spinothalamic tract are described as affective sensation. This means that the sensation is accompanied by a compulsion to act. For instance, an itch is accompanied by a need to scratch, and a painful stimulus makes us want to withdraw from the pain.

Sub-systems

There are two sub-systems identified:

• Direct (for direct conscious appreciation of pain)
• Indirect (for affective and arousal impact of pain). Indirect projections include
  • Spino-Reticulo-Thalamo-Cortical (part of the ascending reticular arousal system, aka ARAS)
  • Spino-Mesencephalic-Limbic (for affective impact of pain).

Path of sensation

The Spinothalamic Tract, like the Dorsal Column-Medial Lemniscus Tract, use three neurons to convey sensory information from the periphery to conscious level at the cerebral cortex.

Pseudounipolar neurons (those with only one long process) in the dorsal root ganglion have axons that lead from the skin into the dorsal spinal cord where they ascend or descend one or two vertebral levels via Lissauer's tract and then synapse with secondary neurons in either the substantia gelatinosa or the nucleus proprius. These secondary neurons are called tract cells.

The axons of the tract cells cross over (decussate) to the other side of the spinal cord via the anterior white commissure, and to the anterolateral corner of the spinal cord (hence the spinothalamic tract being part of the anterolateral system). The axons travel up the length of the spinal cord into the brainstem, specifically the rostral ventromedial medulla.

Traveling up the brainstem, the tract moves dorsally. The neurons ultimately synapse with third-order neurons in several nuclei of the thalamus -- including the medial dorsal, ventral posterior lateral, and ventral medial posterior nuclei. From there, signals go to the cingulate cortex, the primary somatosensory cortex, and insular cortex respectively.

Lesions

Unilateral lesion usually causes contralateral anaesthesia (loss of pain and temperature). Anaesthesia will normally begin 1-2 segments below the level of lesion, affecting all caudal body areas. This is clinically tested by using pin pricks.

See also

• Rostral ventromedial medulla
• Periaqueductal gray

External links

Nervous system, receptors: somatosensory system (GA 10.1059) Medial lemniscus Touch/mechanoreceptors: Lamellar/Pacinian corpuscles – vibration • Tactile/Meissner's corpuscles – light touch • Merkel's discs – pressure • Bulbous/Ruffini endings - stretch • Free nerve endings – pain • Hair cells • Baroreceptor Proprioception: Golgi organ – tension/length • Muscle spindle – velocity of change (Intrafusal muscle fiber • Nuclear chain fiber • Nuclear bag fiber) Spinothalamic tract Pain: Nociception and Nociceptors Temperature: Thermoreceptors M: PNS anat(h/r/t/c/b/l/s/a)/phys(r)/devp/prot/nttr/nttm/ntrp noco/auto/cong/tumr, sysi/epon, injr proc, drug(N1B)

Anatomy of torso (primarily): the spinal cord (TA 14.1.02, GA 9.749) External, dorsal Posterior median sulcus · Posterolateral sulcus Grey matter/ Rexed laminae I–VI: Posterior horn I: Marginal nucleus · II: Substantia gelatinosa of Rolando · III+IV: Nucleus proprius · Spinal lamina V · Spinal lamina VI VII: Lateral horn Intermediolateral nucleus · Posterior thoracic nucleus VIII–IX: Anterior horn Interneuron · Alpha motor neuron (Onuf's nucleus) X: Other Central gelatinous substance · Gray commissure Central canal White matter somatic/ ascending (blue) Posterior/PCML: touch: Gracile · Cuneate Lateral: proprioception: Spinocerebellar (Dorsal, Ventral) · pain/temp: Spinothalamic (Lateral, Anterior) · Posterolateral (Lissauer) · Spinotectal Spinoreticular tract · Spino-olivary tract motor/ descending (red) Lateral: Corticospinal (Lateral) · Ep (Rubrospinal, Olivospinal) Anterior: Corticospinal (Anterior) · Ep (Vestibulospinal, Reticulospinal, Tectospinal) both Anterior white commissure External, ventral Anterior median fissure · Anterolateral sulcus External, general Cervical enlargement · Lumbar enlargement · Conus medullaris · Filum terminale · Cauda equina M: CNS anat(n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp noco(m/d/e/h/v/s)/cong/tumr, sysi/epon, injr proc, drug(N1A/2AB/C/3/4/7A/B/C/D)

Human brain: rhombencephalon, myelencephalon: medulla (TA A14.1.04, GA 9.767) Dorsal Surface Posterior median sulcus · Posterolateral sulcus · Area postrema · Vagal trigone · Hypoglossal trigone · Medial eminence Grey: Cranial nuclei afferent: GVA: VII,IX,X: Solitary/tract/Dorsal respiratory group · SVA: Gustatory nucleus · GSA: VIII-v (Lateral, Medial, Inferior) efferent: GSE: XII  · GVE: IX,X,XI: Ambiguus · SVE: X: Dorsal · IX: Inferior salivatory nucleus Grey: other Gracile nucleus · Cuneate nucleus · Accessory cuneate nucleus White: Sensory/ascending Sensory decussation  · Medial lemniscus · Inferior cerebellar peduncle (Juxtarestiform body) · Ascending dorsal longitudinal fasciculus · MLF, III, IV and VI White: Motor/descending Descending dorsal longitudinal fasciculus · MLF, III, IV and VI Ventral White: Motor/descending Motor decussation · Olivocerebellar tract · Rubro-olivary tract Grey matter Ventral respiratory group · Arcuate nucleus of medulla · Inferior olivary nucleus · Rostral ventromedial medulla Surface Anterior median fissure · Anterolateral sulcus · Olive · Pyramid Grey: Raphe/ reticular Reticular formation (Gigantocellular, Parvocellular, Ventral, Lateral, Paramedian) · Raphe nuclei (Obscurus, Magnus, Pallidus) M: CNS anat(n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp noco(m/d/e/h/v/s)/cong/tumr, sysi/epon, injr proc, drug(N1A/2AB/C/3/4/7A/B/C/D)

Human brain, rhombencephalon, metencephalon: pons (TA A14.1.05.101–604, GA 9.785) Dorsal/ (tegmentum) Surface Cerebellopontine angle · Superior medullary velum · Sulcus limitans · Medial eminence · Facial colliculus White: Sensory/ascending Trapezoid body/VIII · Trigeminal lemniscus (Dorsal trigeminal tract, Ventral trigeminal tract) · Medial lemniscus · Lateral lemniscus MLF, III, IV and VI: Vestibulo-oculomotor fibers Anterior trigeminothalamic tract · Central tegmental tract White: Motor/descending ICP (Vestibulocerebellar tract) MLF, III, IV and VI: Vestibulospinal tract (Medial vestibulospinal tract, Lateral vestibulospinal tract) Grey: Cranial nuclei afferent: GSA: Principal V/Spinal V · VIII-c (Dorsal, Anterior)/VIII-v (Superior) efferent: SVE: Motor V  · VII · GSE: VI · GVE: VII: Superior salivary nucleus Other grey Apneustic center · Pneumotaxic center (Medial parabrachial nucleus) · Lateral parabrachial nucleus · Superior olivary nucleus · Caerulean nucleus Ventral/ (base) Grey Pontine nuclei White: Motor/descending Corticospinal tract · Corticobulbar tract · Corticopontine fibers MCP (Pontocerebellar fibers) Surface Basilar sulcus Other grey: Raphe/ reticular Reticular formation (Caudal, Oral, Tegmental, Paramedian) · Raphe nuclei (Median) M: CNS anat(n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp noco(m/d/e/h/v/s)/cong/tumr, sysi/epon, injr proc, drug(N1A/2AB/C/3/4/7A/B/C/D)

Human brain: mesencephalon (midbrain) (TA A14.1.06, GA 9.800) Tectum (Dorsal) Surface Corpora quadrigemina: Inferior colliculi (Brachium of inferior colliculus), Superior colliculi (Brachium of superior colliculus) Grey matter Pretectal area White: Sensory/ascending Spinotectal tract · Central tegmental tract White: Motor/descending Tectospinal tract Peduncle (Ventral) Tegmentum White: Sensory/ascending lemnisci (Medial, Lateral) · Ascending MLF (Vestibulo-oculomotor fibers) · Spinothalamic tract · Anterior trigeminothalamic tract · Dentatothalamic tract White: Motor/descending Rubrospinal tract · Rubro-olivary tract · Descending MLF Grey: cranial nuclei GSA (V: Mesencephalic) - GSE (III: Oculomotor, IV: Trochlear) - GVE (III: Edinger-Westphal) Grey: other Periaqueductal gray/Raphe nuclei (Dorsal raphe nucleus) Ventral tegmental area • Pedunculopontine nucleus • Red nucleus riMLF Ventricular system Cerebral aqueduct Base White: Motor/descending Cerebral crus: Corticospinal tract · Corticobulbar tract · Corticopontine tract/Frontopontine fibers/Temporopontine fibers Grey: Substantia nigra Pars compacta · Pars reticulata Surface Superior cerebellar peduncle (Decussation of superior cerebellar peduncles) · Interpeduncular fossa M: CNS anat(n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp noco(m/d/e/h/v/s)/cong/tumr, sysi/epon, injr proc, drug(N1A/2AB/C/3/4/7A/B/C/D)

Human brain: diencephalon (TA A14.1.08, GA 9.807) Epithalamus Surface Pineal body · Habenula · Habenular trigone · Habenular commissure Grey matter Pretectal area · Habenular nuclei · Subcommissural organ Thalamus Surface Stria medullaris of thalamus · Thalamic reticular nucleus · Taenia thalami Grey matter/ nuclei paired: AN · Ventral (VA/VL, VP/VPM/VPL) · Lateral (LD, LP, Pulvinar nuclei) · Metathalamus (MG, LG) midline: MD · Intralaminar (Centromedian) · Midline nuclear group · Interthalamic adhesion White matter Mammillothalamic fasciculus · Pallidothalamic tracts (Ansa lenticularis, Lenticular fasciculus, Thalamic fasciculus) · PCML (Medial lemniscus, Trigeminal lemniscus) · Spinothalamic tract · Lateral lemniscus · Dentatothalamic tract · Acoustic radiation · Optic radiation · Subthalamic fasciculus · Anterior trigeminothalamic tract Medullary laminae Hypothalamus Surface Median eminence/Tuber cinereum · Mammillary body · Infundibulum Grey matter Autonomic zones Anterior (parasympathetic/heat loss) · Posterior (sympathetic/heat conservation) Endocrine posterior pituitary: Paraventricular (magnocellular, parvocellular)/Supraoptic (oxytocin/vasopressin) other: Arcuate (dopamine/GHRH) · Preoptic (GnRH) · Suprachiasmatic (melatonin) Emotion Lateral · Ventromedial · Dorsomedial White matter afferent (SN → Medial forebrain bundle) · efferent (Mammillothalamic fasciculus → AN, Stria terminalis → Amygdala, Dorsal longitudinal fasciculus → SC) Pituitary Posterior is diencephalon, but anterior is glandular Subthalamus Subthalamic nucleus · Zona incerta Ventricular system: Third ventricle recesses: (Optic recess, Infundibular recess, Suprapineal recess, Pineal recess) Hypothalamic sulcus · Tela chorioidea of third ventricle Subfornical organ Apertures: Interventricular/Monro Posterior commissure M: CNS anat(n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp noco(m/d/e/h/v/s)/cong/tumr, sysi/epon, injr proc, drug(N1A/2AB/C/3/4/7A/B/C/D)

Brain and spinal cord: neural tracts and fasciculi Sensory/ ascending PCML 1°: Pacinian corpuscle/Meissner's corpuscle → Gracile fasciculus/Cuneate fasciculus → Gracile nucleus/Cuneate nucleus 2°: → sensory decussation/arcuate fibers (Posterior external arcuate fibers, Internal arcuate fibers) → Medial lemniscus/Trigeminal lemniscus → Thalamus (VPL, VPM) 3°: → Posterior limb of internal capsule → Postcentral gyrus Anterolateral/ pain Fast/lateral 1° (Free nerve ending → A delta fiber) → 2° (Anterior white commissure → Lateral and Anterior Spinothalamic tract → Spinal lemniscus → VPL of Thalamus) → 3° (Postcentral gyrus) → 4° (Posterior parietal cortex) 2° (Spinotectal tract → Superior colliculus of Midbrain tectum) Slow/medial 1° (Group C nerve fiber → Spinoreticular tract → Reticular formation) → 2° (MD of Thalamus) → 3° (Cingulate cortex) Motor/ descending Pyramidal flexion: Primary motor cortex → Posterior limb of internal capsule → Decussation of pyramids → Corticospinal tract (Lateral, Anterior) → Neuromuscular junction Extrapyramidal flexion: Primary motor cortex → Genu of internal capsule → Corticobulbar tract → Facial motor nucleus → Facial muscles flexion: Red nucleus → Rubrospinal tract extension: Vestibulocerebellum → Vestibular nuclei → Vestibulospinal tract extension: Vestibulocerebellum → Reticular formation → Reticulospinal tract Midbrain tectum → Tectospinal tract → muscles of neck Basal ganglia direct: 1° (Motor cortex → Striatum) → 2° (GPi) → 3° (Lenticular fasciculus/Ansa lenticularis → Thalamic fasciculus → VL of Thalamus) → 4° (Thalamocortical radiations → Supplementary motor area) → 5° (Motor cortex) indirect: 1° (Motor cortex → Striatum) → 2° (GPe) → 3° (Subthalamic fasciculus → Subthalamic nucleus) → 4° (Subthalamic fasciculus → GPi) → 5° (Lenticular fasciculus/Ansa lenticularis → Thalamic fasciculus → VL of Thalamus) → 6° (Thalamocortical radiations → Supplementary motor area) → 7° (Motor cortex) nigrostriatal pathway: Pars compacta → Striatum Cerebellar Afferent Vestibular nucleus → Vestibulocerebellar tract → ICP → Cerebellum → Granule cell Pontine nuclei → Pontocerebellar fibers → MCP → Deep cerebellar nuclei → Granule cell Inferior olivary nucleus → Olivocerebellar tract → ICP → Hemisphere → Purkinje cell → Deep cerebellar nuclei Efferent Dentate nucleus in Lateral hemisphere/pontocerebellum → SCP → Dentatothalamic tract → Thalamus (VL) → Motor cortex Interposed nucleus in Intermediate hemisphere/spinocerebellum → SCP → Reticular formation, or → Cerebellothalamic tract → Red nucleus → Thalamus (VL) → Motor cortex Fastigial nucleus in Flocculonodular lobe/vestibulocerebellum → Vestibulocerebellar tract → Vestibular nucleus Bidirectional: Spinocerebellar Unc. prop. lower limb → 1° (muscle spindles → DRG) → 2° (Posterior thoracic nucleus → Dorsal/posterior spinocerebellar tract → ICP → Cerebellar vermis) upper limb → 1° (muscle spindles → DRG) → 2° (Accessory cuneate nucleus → Cuneocerebellar tract → ICP → Anterior lobe of cerebellum) Reflex arc lower limb → 1° (Golgi tendon organ) → 2° (Ventral/anterior spinocerebellar tract→ SCP → Cerebellar vermis) upper limb → 1° (Golgi tendon organ) → 2° (Rostral spinocerebellar tract → ICP → Cerebellum) M: CNS anat(n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp noco(m/d/e/h/v/s)/cong/tumr, sysi/epon, injr proc, drug(N1A/2AB/C/3/4/7A/B/C/D) M: PNS anat(h/r/t/c/b/l/s/a)/phys(r)/devp/prot/nttr/nttm/ntrp noco/auto/cong/tumr, sysi/epon, injr proc, drug(N1B)