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quote:The smooth muscle that is responsible for "goose bumps" is called arrector pili or pilimotor muscles. The are attached to the hair follicle and when contacted, raise the hair and pull the skin down in an "attempt" to insulate us from cold via trapping air between the hair. The "bumps" are really the indentions due to the muscle pulling the epidermis down and we notice the difference in height along the skin. Since these muscles are smooth, they are innervated by the Autonomic Nervous System (ANS). The sympathetic branch of the ANS is the only branch that is connected to these muscles. When activated by the ANS, contraction occurs. In the dermis of the skin, there are at least 2 types of temperature receptors, one for hot & one for cold. Both of these are "phasic", meaning that they react to a range of temperatures. For example, the cold receptors, sometimes called Bulbs of Krause, reach threshold between 12 and 35 degrees C whereas the hot receptors (Ruffini organs) are activated between 25 & 47 degrees C. Below 12 and above 47, pain receptors reach threshold. Both the cold and hot receptors use the same sensory pathway to the brain called the lateral spinothalamic tract. This tract goes through the thalamus and terminates in the appropriate location of the post central gyrus of the cerebrum. This helps us to locate the area of the body that is being stimulated. Temperature changes are mediated by nuclei in the hypothalamus which has connections to the thalamus and which then sends messages to the medulla. From there, impulses go down the spinal cord and out spinal nerves, which make up the sympathetic division or thoracolumbar outflow. These send a nerve impulse to the arrector pili muscles and they contract. It would therefore seem to me that if one gets "goose bumps" from hot temps it is due to this pathway being stimulated by a temperature that is an overlapping one so that both hot and cold receptors are being activated.