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Despite its unpleasantness, pain is a critical component of the body's defense system. It is part of a rapid warning and defence relay instructing the motor neurons of the central nervous system to minimize detected physical harm.
The gate control theory of pain, offers insight into how cognitive and emotional factors might dramatically influence painful sensations. Developed by Ronald Melzak and Pat Wall, it focuses on different pain states at the brain, rather than at the perceived site of injury.
Nociception, is the physiological sense for perception of physiological pain. Nociception does not describe psychological pain.
Nociceptors are the free nerve endings of neurons that have their cell bodies outside the spinal column in the dorsal root ganglion and are named based upon their appearance at their sensory ends. These sensory endings look like the branches of small bushes.
The interpretation of pain occurs when the nociceptors are stimulated and subsequently transmit signals through sensory neurons in the spinal cord, which releases glutamate, a major exicitory neurotransmitter that relays signals from one neuron to another and ultimately to the thalamus, in which pain perception occurs. From the thalumus, the signal travels to the cerebrum, at which point the individual becomes fully aware of the pain.
Interestingly, the brain itself is devoid of nociceptive tissue, and hence cannot experience pain (thus a headacheA headache is a condition of mild to severe pain in the head; sometimes upper back or neck pain may also be interpreted as a headache. Headaches have a wide variety of causes, ranging from eyestrain to inflammation of the sinus cavities to life-threatenin is not pain in the brain itself). Some evolutionary biologists have speculated that this lack of nociceptive tissue might be due to the fact that any injury of sufficient magnitude to cause pain in the brain has a sufficiently high probability of being fatal that development of nociceptive tissue therein would have little to no survival benefit.
If pain is defined as a signal of present or impending tissue damage effected by a harmful stimulus then the ability to experience pain or irritation is observable in most multi- cellularstained for keratin The cell is the structural and functional unit of all living organisms. Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, are multicellular, (humans have an estimated 100,0 organismIn biology and ecology, an organism is a living being. The origin of life and the relationships between its major lineages are controversial. Two main grades may be distinguished, the prokaryotes and eukaryotes. The prokaryotes are generally considered tos. Even some plantGreen algae land plants (embryophytes non-vascular embryophytes Hepatophyta liverworts Anthocerophyta hornworts Bryophyta mosses vascular plants (tracheophytes seedless vascular plants Lycopodiophyta clubmosses Equisetophyta horsetails Pteridophyta "true"s have the ability to retract from a noxious stimulus. Whether this sensation of pain is equivalent to the human experience is debatable.