Summary of Somatosensory pathways: lateral & anterior spinothalamic tract and tract of gall and cuneatus

Summary of Somatosensory pathways

The somatosensory system is a part of the sensory nervous system.

It  is a complex system of sensory neurons and neural pathways that responds to changes at the external environment or inside the body.

The axons (as afferent nerve fibers) of sensory neurons has two part peripheral and center part. Terminal portion of peripheral portion of axon of sensory neuron is converted into receptors.

 Sensory receptors are found all over the body including the skin, epithelial tissues, muscles, bones and joints, internal organs, and the cardiovascular system.

Touch is a crucial means of receiving information. This photo shows tactile markings identifying stairs for visually impaired people.

Somatic senses are sometimes referred to as somesthetic senses, with the understanding that somesthesis includes the sense of touch, proprioception (sense of position and movement), and (depending on usage) haptic perception

The mapping of the body surfaces in the brain is called somatotopy. In the cortex, it is also referred to as the cortical homunculus. This brain-surface ("cortical") map is not immutable, however. Dramatic shifts can occur in response to stroke or injury.

Our nervous system deal two types of sensation conscious and unconscious . this article summarized the main somatosensory pathways 

Topics	Lateral spino-thalamic tract	Anterior spinothalamic tract	Tract of gracilis & cuneatus
Sensation	Pain and temperature	Light touch and pressure	Discriminative touch, vibration , conscious muscle joint sense
Receptor	Free nerve ending	Free nerve ending	Meissners corpuscles, pacinian corpuscles, muscle spindles , tendon organ
1st order neuron	Posterior root ganglion	Posterior root ganglion	Posterior root ganglion
2nd order neuron	Substantia getalinosa	Substantia getalinosa	Nuclei gracilis and nuceatus
3rd order neuron	Ventral posterior lateral nucleus of thalamus	Ventral posterior lateral nucleus of thalamus	Ventral posterior lateral nucleus of thalamus
Related with Spinal lamniscus	Present	Present	Absent
Related with Medial lamniscus	Absent	Absent	Present
Destination	Post central gyrus	Post central gyrus	Post central gyrus
Lesion	Contra-lateral loss of pain and thermal sensibilities below the level of the lesion Unable to sense pin prick or recognize hot or cold objects	Contra-lateral loss of light touch and pressure  sensibilities below the level of the lesion. Discriminative touch will be present but unable to feel light touch of cotton placed against the skin	Ipsilateral loss of muscle and joint sensation, two point discrimination and vibration  below the level of lesion but sense of light touch is unaffected Movement are jerky or ataxic