Intro | A-Delta Fiber | C Fiber | Somatosensory Cortex | Midbrain | Midline Nucleus of the Thalamus | Ventrobasal Nucleus of the Thalamus | Descending Neural Pathway | Spinal Cord | Thalamus
Part 1: Image-Mapped Tutorial
Part 2: Matching Self-Test
Part 3: Multiple-Choice Self-Test
The A-Delta Fiber pain pathway carries information away from damaged skin tissue at a rapid rate. This information reflects the sharp pain experienced almost immediately following damage to the skin.
The C Fiber pain pathway carries information away from damaged skin tissue at a slow pace. This information reflects the burning and aching sensation associated with prolonged pain following damage.
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Recent research has discovered a new neurotransmitter, called substance P, which is responsible for the transmission of pain signals from the receptors to the first synapse point in the spinal cord. When this substance P is injected into the spinal cord of animals, they behave as though they are experiencing pain in the region of the body that projects to the region of injection. Substance P is found concentrated in the same areas of the brain containing the analgesic endorphin receptors. The endorphin opiate receptors play an important role in inhibiting the pain-inducing effects of substance P.
Pain is also induced by injections of capsaicin, a chemical that causes the sudden release of substance P. The intense pain and release of substance P following capsaicin injection is often followed by prolonged periods of pain insensitivity, sometimes for as long as months. Capsaicin occurs naturally in jalapeno peppers, thus the hot pain inducing qualities of these spicy vegetables typically followed by numbness! This substance may be used for pain relief by rubbing into the skin close to an area of discomfort. Capsaicin, however, is not absorbed into the blood stream in quantities sufficient to relieve pain when eaten.