Receptors That Detect Cold & Heat

Written by tony oldhand
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Receptors That Detect Cold & Heat
Receptors are nerve cells that send out signals. (Comstock Images/Comstock/Getty Images)

Thermoreceptors are individual nerve cells that receive temperature information and put forth an electrical pulse, or "fire," when activated. The process occurs on the microscopic level, so hundreds of thousands of receptors are constantly being activated. The brain processes all the information. Thermoreceptors are tied to other receptors, such as pain receptors that are activated when extreme heat or cold is detected, sending pain signals to the brain alongside temperature information.

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Thermoreceptor Characteristics

Thermoreceptors are a specialised group of nerve cells that sense heat and cold. When a thermoreceptor is activated, or "fires," it sends an electrical pulse to the spinal cord. The pulse travels up the spinal cord, where it eventually reaches the brain. Because electricity travels at the speed of light, the transference of information is almost instantaneous. According to Dawn A. Tamarkin of Springfield (Mass.) Technical Community College, heat receptors fire around 25 degrees Celsius up to 45 degrees Celsius and higher. Cold receptors fire from 10 degrees C to about 20 degrees Celsius. Notice that the temperature range of heat receptors is a lot wider than cold receptors. The exact mechanism of reception and information transference, as of 2011, is not fully understood.

Interconnection to Other Receptors

Thermoreceptors do not work by themselves.The are interconnected with other receptors. For example, when heat or cold become too great, thermoreceptors stop firing. The signal is taken over by pain receptors, called nocireceptors, which fire and transmit pain signals. Other examples are taste and smell. Thermoreceptors are interconnected to taste (lingual) and smell (olfactory) receptors. An example of this by "New World Encyclopedia" is that cold lemonade tastes good but cold gravy does not.

Method of Transferance

Receptors transmit their signals through nerves, which act like wires. Think of a receptor being like a small signal output device. When it puts out an electric current, the current travels down a nerve to the spinal column. Bear in mind billions of receptors are constantly firing and turning off, sending signals down billions of nerves. The nerves are bundled into channels. The current output of the channels is inversely proportional to the input temperature signal. The stronger the signal output by the receptor, the weaker the final output and vice versa.

Locations of Thermoreceptors

Thermoreceptors are located in various parts of the body. Some areas are the nasal cavity, tongue, bladder and skin. The cornea also has cold receptors that trigger blinking and tear formation. The study of the locations of thermoreceptors is ongoing. Some thermoreceptors were found in certain areas of the intestinal tract. Some animals, such as snakes, have specialised heat receptor areas that can detect very low infrared heat levels.

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