We have sense organs. They are the eyes, nose, ears, tongue and skin.
The sense organs — eyes, ears, tongue, skin, and nose — help to protect the body. The human sense organs contain receptors that relay information through sensory neurons to the appropriate places within the nervous system.
Each sense organ contains different receptors.
General receptors are found throughout the body because they are present in skin, visceral organs (visceral meaning in the abdominal cavity), muscles, and joints.
Special receptors include chemoreceptors (chemical receptors) found in the mouth and nose, photoreceptors (light receptors) found in the eyes, and mechanoreceptors found in the ears.
OOOH, THAT SMELL: OLFACTION
Olfactory cells line the top of your nasal cavity. On one end, olfactory cells have cilia — hair-like attachments — that project into the nasal cavity. On the other end of the cell, are olfactory nerve fibers, which pass through the ethmoid bone and into the olfactory bulb. The olfactory bulb is directly attached to the cerebral cortex of your brain.
As you breathe, anything that is in the air that you take in enters your nasal cavity: hydrogen, oxygen, nitrogen, dust, pollen, chemicals. You don’t “smell” air or dust or pollen, but you can smell chemicals. The olfactory cells are chemoreceptors, which means the olfactory cells have protein receptors that can detect subtle differences in chemicals.
The chemicals bind to the cilia, which generate a nerve impulse that is carried through the olfactory cell, into the olfactory nerve fiber, up to the olfactory bulb and to your brain. Your brain determines what you are smelling. If you are sniffing something that you haven’t experienced before, you need to use another sense, such as taste or sight, to make an imprint in your brain’s memory.
MMM, MMM, GOOD: TASTE
The senses of smell and taste work closely together. If you cannot smell something, you cannot taste it, either. Taste buds on your tongue contain chemoreceptors that work in a similar fashion to the chemoreceptors in the nasal cavity. However, the chemoreceptors in the nose will detect any kind of smell, whereas there are four different types of taste buds, and each detects different types of tastes: sweet, sour, bitter, and salty.
A common misconception is that the little bumps on your tongue are the taste buds. As with all misconceptions, this idea is wrong, too. The little bumps on your tongue are called papillae, and the taste buds actually lie down in the grooves between each papilla.
Foods contain chemicals, and when you put something into your mouth, the taste buds in your tongue can detect what chemicals you are ingesting. Each taste bud has a pore at one end with microvilli sticking out of the pore, and sensory nerve fibers attached to the other end. Chemicals from food bind to the microvilli, generating a nerve impulse that is carried through the sensory nerve fibers and eventually to the brain.
NOW HEAR THIS: SOUND
The ear not only is the organ of hearing, but it also is responsible for maintaining equilibrium — or balance. To maintain equilibrium, the ear must detect movement. To hear, the ear must respond to mechanical stimulation by sound waves.
The outer ear is the external opening to the ear canal. Sound waves are shuttled through the ear canal to the middle ear. The eardrum sets the mechanics in motion: