Wednesday, April 21, 2010

The five general categories of sensory receptors found in animals


Sensory receptors are how the body recognizes stimuli in the environment. An example is Pacinian corpuscles in the skin, which can feel pressure from the outside, and relay the information, via dendrites to the central nervous system. Enough pressure causes an action potential to travel down the dendrite, until the body gets
used to the pressure, and we no longer sense the pressure.

(Above: cross section through dendrite of Pacinian corpuscle)
http://faculty.stcc.edu/AandP/AP/AP2pages/Units14to17/unit15/sensory.htm

The five general categories of sensory receptors in animals:

1. Mechanoreceptors
These receptors allow us to detect touch. We can also monitor the position of our joints, muscles and bones with mechanoreceptors. A Pacinian corpuscle is an example of this, which allows us to detect pressure in our skin. Mechanoreceptors are mostly found in the skin (cutaneous), but others also exist, such as in hair cells.
http://en.wikipedia.org/wiki/Mechanoreceptor
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mechanoreceptors.html

2. Thermoreceptors
These sensory receptors detect changes in temperature. For example, when we put our hand into hot water, or the shower is too cold. Other examples of where these receptors would come in handy would be in knowing when it is too cold outside without a jacket.

http://www.wisegeek.com/what-are-thermoreceptors.htm

The speed in which an action potential fires and reaches the brain is directly related to the level of the temperature stimulus. Also, different types of myelinated fibers have different speeds in which they travel to the brain.
http://en.wikipedia.org/wiki/Thermoreceptor

3. Nociceptors
These receptors detect pain. Somatic (skin and deep tissues) and visceral pain receptors are located throughout the body, and send signals for pain to the central nervous system until the pain has stopped.
http://pain.about.com/od/typesofchronicpain/g/nociceptors.htm

4. Electromagnetic receptors
These sensors detect electric currents. (electromagnetic waves)
http://medical-dictionary.thefreedictionary.com/electromagnetic+receptors
http://en.wikipedia.org/wiki/Sensory_receptor

Examples of electromagnetic waves are x-rays, TV, and radio. However, the best example of how humans perceive these waves is by sensing, or seeing light. These waves are visible (within the visible spectrum).
http://en.wikipedia.org/wiki/Electromagnetic_radiation

5. Chemoreceptors
These receptors respond to taste (taste buds) or smell (Olfactory cells) or other chemical stimuli. There are also chemoreceptors in the body which help the brain maintain homeostasis by measuring concentration of certain chemicals in the body.
http://medical-dictionary.thefreedictionary.com/Chemoreceptors

http://www.cliffsnotes.com/study_guide/Sensory-Receptors.topicArticleId-22032,articleId-21950.html