Answer: Aspirin is a cyclooxygenase inhibitor, which decreases the peripheral nervous system response to painful stimuli.
The skin has specialized receptors which detect pain and noxious temperature. The information from these cells are sent centrally into the dorsal horn of the spinal cord. From here, that information ascends via the anterolateral tract into the thalamus, before going to the somatosensory cortex.
When an injury occurs at the skin, a number of chemical signals contribute to the pain signal. One of them is the prostaglandins. Prostaglandins sensitized the primary sense neuron to further pain stimuli, meaning that they respond more to an equally painful stimuli. They are also involved in the body’s natural inflammation response. The prostaglandins are created by the enzyme cyclooxygenase, which are inhibited by aspirin. When cyclooxyegenase is inhibited, the body experiences analgesia, the decreased sensation of pain.
There are two forms of the cyclooxygenase enzyme, called COX-1 and COX-2. Both are responsible for synthesizing prostaglandin molecules from arachidonic acid, which comes from the lipid membrane.