Spinothalamic tract

Spinothalamic tract
Spinothalamic tract
Decussation	Anterior white commissure
Parts	Anterior and lateral tracts
From	Skin
To	Thalamus
Artery	Anterior spinal artery
Function	Gross touch and temperature
Identifiers
Latin	tractus spinothalamicus
MeSH	D013133
NeuroNames	2058, 810
TA98	A14.1.04.138
TA2	6102
FMA	72644
	Anatomical terms of neuroanatomy [edit on Wikidata]

The spinothalamic tract is a part of the anterolateral system or the ventrolateral system, a sensory pathway to the

somatosensory cortex of the postcentral gyrus

.

The spinothalamic tract consists of two adjacent pathways: anterior and lateral. The anterior spinothalamic tract carries information about

crude touch. The lateral spinothalamic tract conveys pain and temperature

.

In the

thoracic, lumbar, and sacral

components, which is arranged from most medial to most lateral respectively.

The pathway crosses over (

dorsal column-medial lemniscus pathway and lateral corticospinal tract

. It is one of the three tracts which make up the anterolateral system.

Structure

There are two main parts of the spinothalamic tract:

The
lateral spinothalamic tract transmits pain and temperature
.

The

anterior spinothalamic tract

(or ventral spinothalamic tract) transmits crude touch and firm pressure.

The spinothalamic tract, like the

dorsal column-medial lemniscus pathway

, uses three neurons to convey sensory information from the periphery to conscious level at the cerebral cortex.

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

anterolateral system). Decussation usually occurs 1-2 spinal nerve segments above the point of entry. 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 posterior medial nuclei. From there, signals go to the cingulate cortex, the primary somatosensory cortex, and insular cortex respectively.

Anterior spinothalamic tract

The anterior spinothalamic tract (Latin: tractus spinothalamicus anterior) or ventral spinothalamic fasciculus situated in the marginal part of the

gray matter of the opposite side. Aβ fibres carry sensory information pertaining to crude touch from the skin. After entering the spinal cord the first order neurons synapse (in the nucleus proprius), and the second order neurons decussate via the anterior white commissure

. These second order neurons ascend synapsing in the VPL of the thalamus. Incoming first order neurons can ascend or descend via the Lissauer tract.

This is a somewhat doubtful fasciculus and its fibers are supposed to end in the thalamus and to conduct certain of the touch impulses. More specifically, its fibers convey crude touch information to the VPL (ventral posterolateral nucleus) part of the thalamus.

The fibers of the anterior spinothalamic tract conduct information about pressure and crude touch (protopathic). The fine touch (epicritic) is conducted by fibers of the medial lemniscus. The medial lemniscus is formed by the axons of the neurons of the gracilis and cuneatus nuclei of the medulla oblongata which receive information about light touch, vibration and conscient proprioception from the gracilis and cuneatus fasciculus of the spinal cord. This fasciculus receive the axons of the first order neuron which is located in the dorsal root ganglion that receives afferent fibers from receptors in the skin, muscles and joints.

Lateral spinothalamic tract

The lateral spinothalamic tract (or lateral spinothalamic fasciculus), is a bundle of

posterior horn of the spinal cord (one of the three grey columns

).

Together with the anterior spinothalamic tract, the lateral spinothalamic tract is sometimes termed the secondary sensory fasciculus or spinal lemniscus.

Anatomy

The neurons of the lateral spinothalamic tract originate in the

somatosensory cortex, Brodmann areas

3, 1, and 2.

Function

The types of sensory information 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.^[citation needed]

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
  , also known as ARAS)
- Spino-Mesencephalic-Limbic (for affective impact of pain).

Anterolateral system

In the

crude touch from the periphery to the brain

. It comprises three main pathways:

Name	Destination	Function
spinothalamic tract ( anterior )	thalamus	important in the localization of painful or thermal stimuli
spinoreticular tract	reticular formation	causes alertness and arousal in response to painful stimuli
spinotectal tract	tectum	orients the eyes and head towards the stimuli

Clinical significance

In contrast to the axons of second-order neurons in

dorsal column-medial lemniscus pathway, the axons of second-order neurons in the spinothalamic tracts cross at every segmental level in the spinal cord. This fact aids in determining whether a lesion is in the brain or the spinal cord. With lesions in the brain stem or higher, deficits of pain perception, touch sensation, and proprioception are all contralateral to the lesion. With spinal cord lesions, however, the deficit in pain perception is contralateral to the lesion, whereas the other deficits are ipsilateral. See Brown-Séquard syndrome

.

Unilateral lesions usually cause contralateral

anaesthesia

(loss of pain and temperature). Anaesthesia will normally begin 1-2 segments below the level of lesion, due to the sensory fibers being carried by dorsal-lateral tract of Lissauer up several levels upon entry into the spinal cord, and will affect all caudal body areas. This is clinically tested by using pin pricks.

References

This article incorporates text in the public domain from page 760 of the 20th edition of Gray's Anatomy (1918)

^ "Chapter 25:Neural Mechanisms of Cardiac Pain: The Anterolateral System". Archived from the original on 2010-08-11. Retrieved 2009-11-26.

External links

[urlChapter_25:Neural_Mechanisms_of_Cardiac_Pain:_The_Anterolateral_System-1] "Chapter 25:Neural Mechanisms of Cardiac Pain: The Anterolateral System". Archived from the original on 2010-08-11. Retrieved 2009-11-26.

v t e Sensory receptors
Touch	Mechanoreceptor Vibration Lamellar corpuscle Light touch Tactile corpuscle Pressure Merkel nerve ending Stretch Bulbous corpuscle
Pain	Free nerve ending Nociceptors
Temperature	Thermoreceptors
Proprioception	Golgi organ Muscle spindle Intrafusal muscle fiber Nuclear chain fiber Nuclear bag fiber
Other	Hair cells Baroreceptor

1° :		Cuneate nucleus
2° :	→ Posterior external arcuate fibers, Internal arcuate fibers) → Medial lemniscus/Trigeminal lemniscus → Thalamus (VPL, VPM )
3° :	→ Posterior limb of internal capsule → Postcentral gyrus

Fast/lateral	1° ( Anterior Spinothalamic tract → Spinal lemniscus → VPL of Thalamus) → 3° (Postcentral gyrus) → 4° (Posterior parietal cortex ) 2° ( Midbrain tectum )
Slow/medial	1° (Group C nerve fiber → Spinoreticular tract → Reticular formation) → 2° (MD of Thalamus) → 3° (Cingulate cortex)