When the body experiences an injury, pain is almost always involved. Although a person usually feels the pain in the part of the body that experienced the injury, there is a lot going on in the nerves, spinal cord, and the brain as well. Scientists continue to examine the complex processes that answer the question of how is pain interpreted by the brain.
When a person gets a cut or other physical injury, body tissue is damaged. The skin contains tiny pain receptors, which pick up on the tissue damage. These tiny pain receptors make up one end of nerve cells, which in turn are connected by means of long nerve fibers to the spinal cord. The tissue damage activates one or more pain receptors, and electrical signals are transmitted to the connecting nerve fiber.
There are many small pain receptors, as well as many nerve fibers. The nerve fibers are bundled together into groups, referred to as peripheral nerves. The electrical signals travel via the peripheral nerves until they reach the spinal cord.
From the spinal cord, the electrical signals are transmitted from one neuron to the next, via neurotransmitters, which are basically chemical messengers. The electrical signals then travel by means of the spinal cord, until they reach the brain.
The thalamus portion of the brain is tasked with sorting and relaying the signals appropriately. Different areas of the brain process different types of signals. Physical sensations are handled by the somatosensory cortex, the thinking process takes places in the frontal cortex, and emotions are processed by the limbic system.
These various signals, sorted and processed by the various sections of the brain, are what produce the usual response to a bodily injury. The pain itself is processed by the somatosensory cortex, the cognitive realization of the injury is processed by the frontal cortex, and the emotional reaction to getting hurt is processed by the limbic system. This complex process happens quickly, and as such, it is hard to imagine the complexities that are happening throughout the body.
Other bodily reflexes are activated upon experiencing pain. For example, when a person hurts his or her hand, the activation of motor neurons causes muscles to contract. The result is the automatic reaction of pulling one’s hand away from the cause of the pain. This happens extremely fast – faster than even the relay of the pain signals to the brain. This automatic reaction helps to protect the body, allowing it to automatically pull away to avoid further injury.
Of course, not all pain is the same, and as such, not all pain is conveyed by the same type of fibers. For example, a sharp sudden pain is transmitted by one type of fiber, much more quickly than other fiber types transmit deeper, throbbing pain.
The central nervous system also has methods by which it can block pain messages from getting to the brain under certain circumstances. This would explain how an athlete may be able to continue playing, barely feeling pain, after sustaining an injury. The brain, busy with other processes, does not register the pain until it has time to focus on it.