Dermatome

[scilearner]

wiki-A dermatome is an area of skin that is mainly supplied by a single spinal nerve. There are eight cervical nerves, twelve thoracic nerves, five lumbar nerves and five sacral nerves. Each of these nerves relays sensation (including pain) from a particular region of skin to the brain.

 

My understanding is that one spinal nerve contains bothe afferent and efferent fibers. So shouldn't a dermatome have an efferent compartment as well. Do dermatomes only have afferent fibres or is it simply that we consider only the afferent part as the dermatome of that spinal nerve.

 

Thanks!!

[Mokele]

My understanding is that one spinal nerve contains bothe afferent and efferent fibers. So shouldn't a dermatome have an efferent compartment as well. Do dermatomes only have afferent fibres or is it simply that we consider only the afferent part as the dermatome of that spinal nerve.

 

Dermatomes are purely sensory. Motor innnervation in the body doesn't correspond to the dermatome map.

[scilearner]

Thanks a lot for your help. So is dermatome the afferent component of that spinal nerve. I mean every never has both efferent and afferent parts right. Can you explain a bit more. Thank you!!

[stb]

A nerve is made up of bundles of smaller nerves these individual nerve cells can be either efferent or afferent - they don't do both. So a nerve that takes sensory from the skin ( afferent) can not motor component at the skin. In the spinal nerve (the bundle of a bunch of nerve axons) there are many nerve cell axons that end up at a muscle (efferent) - they split off before it gets to the skin. A spinal nerve is really only a couple of cm's long before it splits into a rami which further split into anterior/posterior/muscle nerves/etc. There are no muscles in the skin (except for the muscle that gives you goose bumps - which is under sympathetic control not motor).

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A nerve is made up of bundles of smaller nerves these individual nerve cells can be either efferent or afferent - they don't do both. so a nerve that takes sensory from the skin ( afferent) does not have to have any motor component at the skin, even though in the spinal nerve (the bundle of a bunch of nerve axons) there are many nerves cell axons that end up at a muscle (efferent) - they split off before it gets to the skin. A spinal nerve is really only a couple of cm's long before it splits into a rami which further split into anterior/posterior/muscle nerves/etc. There are no muscles in the skin (except for the muscle that gives you goose bumps - which is under sympathetic control not motor).

Edited November 12, 2009 by stb