The flavor of food also involves smell, texture, and appearance Cranial nerves VII, IX, and X send taste sensations to the gustatory nucleus of the medulla oblongata. These have binding sites for odor molecules, and lie in a thin layer of mucus. Olfactory cells are the only sensory neurons that lie in direct contact with the outside environment, and are replaced about every 60 days. To be detected, chemicals must be volatile and water soluble. When an odor molecule binds with a specific receptor, a second messenger is produced, opening ion channels in the membrane.
Olfactory receptors are quick to adapt.
Some odors, such as the ammonia smell of smelling salts, stimulate nociceptors that trigger the trigeminal nerve Olfactory axons pass through the cribriform plate to the olfactory bulbs to the olfactory tracts. These tracts follow a complex pathway that involves the medial temporal lobes. Hearing and Equilibrium Hearing is a response to vibrating air molecules. A vibrating object sets up vibrations in nearby air molecules, which travel to the eardrum and cause it to vibrate. Pitch Pitch is determined by the frequency of vibration.