The nose also has a structure called the vomeronasal organ whose function has not been determined, but which is suspected of being sensitive to pheromones that influence the reproductive cycle. The smell receptors interact with the molecules of these vapors and transmit the sensations to the brain. The smells themselves consist of vapors of various substances. The cavity of the nose is lined with mucous membranes that have smell receptors connected to the olfactory nerve. The nose is the organ responsible for the sense of smell. As in the case of color blindness, some people are insensitive to some tastes. Women, in general, have a greater number of taste buds than men. The number of taste buds varies substantially from individual to individual, but greater numbers increase sensitivity. The sense of taste functions in coordination with the sense of smell. At the base of each taste bud there is a nerve that sends the sensations to the brain.
The taste buds on top and on the side of the tongue are sensitive to salty and sour tastes. Generally, the taste buds close to the tip of the tongue are sensitive to sweet tastes, whereas those in the back of the tongue are sensitive to bitter tastes. The tongue also can detect a sensation called “umami” from taste receptors sensitive to amino acids. They are able to detect four basic tastes: salty, sweet, bitter, and sour. The receptors for taste, called taste buds, are situated chiefly in the tongue, but they are also located in the roof of the mouth and near the pharynx. The brain combines the input of our two ears to determine the direction and distance of sounds. The inner ear, or cochlea, is a spiral-shaped chamber covered internally by nerve fibers that react to the vibrations and transmit impulses to the brain via the auditory nerve. The outer ear protrudes away from the head and is shaped like a cup to direct sounds toward the tympanic membrane, which transmits vibrations to the inner ear through a series of small bones in the middle ear called the malleus, incus and stapes.
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