The sense of hearing also comes into play. Sight is yet another important sensory response in readying the body for a meal. Light from an object, such as a glass of juice, strikes the lens of the eye and is directed to the retina. The impulse generated by the retina travels along the optic nerv e to the brain, where it is perceived. If the image shows a favorite food, our appetite center and digestive system will be further stimulated.
Touch is also involved in eating.
As the food touches nerve endings in the tongue and palate, its texture and temperature further stimulate circulation of blood in the entire digestive system and also help increase the secretion of digestive enzymes. In a marvelously coordinated, highly complex process that requires little or no conscious effort aside from chewing or swallowing, our breakfast is transformed into the fuel and other nutrients required by all of our individual cells. Along the way, ou r food passes through distinctive body structures. The actual digestive process begins with chewing, a conscious effort involving the skeletal muscles of the jaw, mouth, and tongue, coordinated by the nervous system. In the mouth, food is broken into small pieces and mixed with saliva and other digestive juices.