“Psychological factors, both situational and emotional factors exist when we experience pain and can profoundly alter the strength of these perceptions. Also, attention, understanding, control, expectations, and the aversive significance can affect pain perceptions.” Pubmed.ncbi.nlm.nih.gov
“Physiological signs of pain may include: dilation of the pupil and/ or wide opening of the eyelids. Change in blood pressure and heart rate. Increased respiration rate and/or depth.” Www.vet.ed.ac.uk
“This theory suggest that the spinal cord contains a neurological “gate” that either blocks pain signals or allows them to continue on to the brain.” Www.verywellmind.com