<prompt> In case a small stimulus causes more pain, it is called:HypersensitivityCausalgiaHyperalgesiaAllodynia  <response>: - Increase in sensitivity of pain receptors is called hyperalgesia mostly due to inflammatory mediators - Small Noxious stimulus giving exaggerated pain sensation - Causes Excessive sensitivity of pain receptors primary hyperalgesia Facilitation of sensory transmission secondary hyperalgesia mainly due to lesions of spinal cord and thalamus Hypersensitivity - Undesirable reactions produced by normal immune system - E.g. allergies autoimmunity Allodynia - Non - noxious stimulus gives pain - E.g. trigeminal neuralgia Causalgia - Burning type of pain caused by crushing, injuries to nerves. neuropathic pain Nociceptive pain: - Noxious stimulus leads to corresponding degree of pain 