Hearing relies on the auditory system, beginning with the ears. Sound waves are captured by the outer ear and channeled into the ear canal. These vibrations cause the eardrum to vibrate, and this energy is transferred to the small bones in the middle ear, known as the ossicles. These bones amplify the sound and transmit the vibrations to the cochlea in the inner ear. The cochlea, filled with fluid, converts the mechanical vibrations into electrical signals, which are then sent to the brain for processing. The materials involved here include the bones, fluid, and hair cells within the cochlea, which are vital to hearing.
The sense of touch involves a variety of sensory receptors in the skin, such as mechanoreceptors, thermoreceptors, and nociceptors. These receptors detect pressure, temperature, and pain. When these receptors are stimulated, they send electrical signals via the nervous system to the brain, allowing us to feel sensations like texture, heat, and pressure. The material aspect of touch lies in the intricate network of nerve endings in the skin and the sensory pathways they form to relay information. Similarly, taste and smell rely on chemical receptors: taste buds on the tongue detect flavor molecules, while olfactory receptors in the nose detect odor molecules. Together, these senses rely on specialized biological materials — from cells in the skin to the complex tissues in the sensory organs — to relay information to the brain and contribute to our perception of the world.