FIGURE 4.24 Touch Receptors Specialized sensory neurons form groups of haptic receptors that detect pressure, temperature, and vibrations against the skin; their long axons enter the brain via the spinal or cranial nerves. Pain receptors populate all body tissues that feel pain; they are distributed around bones and within muscles and internal organs as well as under the skin surface. Different types of pain receptors transmit immediate, sharp pain sensations or signal slow, dull pain that lasts and lasts.