Sensory pathways include serially connected neurons. Higher order neurons are in the thalamus and cortex.
Skin contains mechanoreceptors, thermoreceptors, and nociceptors.
Mechanoreceptors may be rapidly or slowly adapting. Thermoreceptors include cold and warm receptors. A d and C nociceptors may be sensitized by release of chemical substances from damaged cells. Muscle, joints, and viscera have mechanoreceptors and nociceptors. Trigeminal primary afferent fibers supply the face, oral and nasal cavities, and dura.