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Spinal Cord
Spinal Cord
What is the spinal cord?
Together with the brain, the spinal cord is a key part of the central nervous system. It contains many neuron bundles, or tracts, allowing for information from the peripheral nervous system (i.e., neurons that communicate with organs and limbs) to travel to the brain and vice-versa.
Different spinal cord tracts receive and send information about either movement (including reflexes and planned actions) or sensations (like touch, temperature, and pain).
There are also tracts dedicated to proprioception, or our ability to know where our limbs/body are in space — it’s why you can normally touch your nose without looking in a mirror, but might struggle after a few alcoholic drinks.
Weirdly-shaped bones, called vertebrae, protect the spinal cord from minor injuries, but major injuries
might cause long-lasting to permanent impact on movement, sensation, and/or proprioception, depending on which tracts are damaged.
Regions of the Spinal Cord
There are 5 regions of the spinal cord. Each region has a different shape and place where their motor and sensory functions map onto in the body (e.g., legs vs. arms). In total, there are 31 levels that are divided into cervical, thoracic, lumbar, sacral, and coccygeal regions. The coccygeal region only has one level, but the rest contain multiple levels.
Cervical
There are 8 cervical spinal cord levels. Cervical spinal cord level 1 (C1) does not map on to areas of the skin. C2 and C3 are associated with the head and neck, where as C4 and C5 are associated with the neck only. C6 is associated with the thumb, whereas C7 and C8 are associated with the middle finger an pinky, respectively.
Thoracic
There are 12 thoracic spinal cord levels. Thoracic spinal cord levels 1 and 2 (T1, T2) are associated with the inner forearm. T3 is associated with the middle of the back. T4 is associated with the top of the chest. T5 is associated with the middle of the chest. T6 is associated with the bottom of the feet. T7-T10 are associated with the middle to bottom of the torso. T11 is associated with the area between the belly button and the groin. T12 is associated with the midpoint of the groin.
Lumbar
There are 5 lumbar spinal cord levels. Lumbar spinal cord level 1 (L1) is associated with the hip and groin area. L2 is associated with the inner thigh. L3 is associated with the knees. L4 is associated with the inside of the ankle. L5 is associated with the bottom of the feet and your inner 3 toes on each foot.
Sacral
There are 5 sacral spinal cord levels. Sacral spinal cord level 1 (S1) is associated with the outer 2 toes on each food and outer ankle. S2 is associated with the outer part of the heel. S3 is associated with the middle of the buttocks and genitals. S4-S5 are associated with the genitals.
Spinal Cord Tracts
Coming soon!
References
[1] Purves, D., Augustine, G. J., Fitzpatrick, D., Hall, W. C., LaMantia, A. S., McNamara, J. O., & White, L. E. (2008). Neuroscience. 4th. Sunderland, Mass.: Sinauer. xvii, 857, 944.
[2] Haines, D. E. (2004). Neuroanatomy: An atlas of structures, sections, and systems (Vol. 153, No. 2004). Lippincott Williams & Wilkins.
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