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Free nerve endings can detect temperature, mechanical stimuli (touch, pressure, stretch) or danger (nociception). Thus, different free nerve endings work as thermoreceptors, cutaneous mechanoreceptors and nociceptors. In other words, they express polymodality.
In mammals, nociceptors are found in any area of the body that can sense noxious stimuli. External nociceptors are found in tissue such as the skin (cutaneous nociceptors), the corneas, and the mucosa. Internal nociceptors are found in a variety of organs, such as the muscles, the joints, the bladder, the
Nociceptors respond to potentially damaging stimuli by sending signals to the spinal cord and brain. This process, called nociception, usually causes the perception of pain. [16] They are found in internal organs, as well as on the surface of the body. Nociceptors detect different kinds of damaging stimuli or actual damage.
Nociceptors have a certain threshold; that is, they require a minimum intensity of stimulation before they trigger a signal. Once this threshold is reached, a signal is passed along the axon of the neuron into the spinal cord. Nociceptive threshold testing deliberately applies a noxious stimulus to a human or animal subject to study pain.
If these nerves do not detect stretching, the body determines perceives low blood pressure as a dangerous stimulus and signals are not sent, preventing the inhibition CNS action; blood vessels constrict and the heart rate increases, causing an increase in blood pressure in the body. [4]
Activation of nociceptors is not necessary to cause the sensation of pain. [12] Damage or injury to nerve fibers that normally respond to innocuous stimuli like light touch may lower their activation threshold needed to respond; this change causes the organism to feel intense pain from the lightest of touch. [ 12 ]
Nociceptors respond to potentially damaging stimuli by sending signals to the spinal cord and brain. This process, called nociception , usually causes the perception of pain . [ 23 ] [ 24 ] They are found in internal organs as well as on the surface of the body to "detect and protect". [ 24 ]
Later studies on the responses of leech neurones to mechanical, chemical and thermal stimulation motivated researchers to write "These properties are typical of mammalian polymodal nociceptors". [4] A sea hare. There have been numerous studies of learning and memory using nociceptors in the sea hare, Aplysia.