Senses makes us aware of what is happening around us. It provide information about the things around. Humans have different kinds of senses. Each of this senses picks up information from the environment through their specific receptors.
The sense organ will send impulses to different regions of the brain. The brain then will receive the transmitted impulses and interpret a sensation according to the specific impulse received.
The Sense of Touch (Skin)
In the end of the terminal branches of dendrites of sensory neurons in the skin is a special sensory structures called receptors. There are receptors for different kinds of stimulus namely; the receptor for touch, the receptors for pain the receptors for pressure, for heat and for cold.
The pain receptors are distributed through out the human skin and said to be 27 times more abundant than does of the receptors of cold. Deeper, lies the receptors that detects pressure and touch.
There are three tiny bones that form a chain across the middle ear; the hammer, the anvil, and the stirrup.
The middle of the eardrum was connected to the hammer (also called malleus). The anvil (also called incus) bridges the hammer and the stirrup (also called stapes). Finally, the stirrup connects to the oval window, the opening to inner ear part.
The third part of the ear is the inner ear. It has a special passage called cochlea which is filled with liquids. Cochlea was lined with nerve endings that reserve sound impressions. An auditory nerve leads from the cochlea and connects to the brain.
The Sense Of Vision (Eye)
The eye gathers light through lens. It is protected by the cornea, a tough covering on its outer layer. It has a curved surface which makes the incoming light rays bends.
The eye has a colored area, it is called the iris and lies just behind the cornea The iris makes the color of the eye blue, green or brown. It regulates its opening and closing through its smooth muscles.
The opening of the iris is called pupil. The pupil is the black portion of the eye. Pupil expands to allow more light to enter when it is dim. It also contracts to reduce light amount that enter the eye when it is bright.
Light are focused at the retina. It contains sensitive receptors. The retina is a thin membrane located in the back portion of the eye.
The light rays that enters the eye will be bent by the cornea and lens. The light then focus on the retina.
Nerve impulses are created and transmitted to the brain through the optic nerve when the light strike the receptor.
The Sense of Taste (Tongue)
The sense of taste is within the taste buds. This is unevenly distributed over the surface of the tongue and contains taste receptors. Taste is a result of the chemical stimulation of certain nerve endings.
Sweet and salt can be detected in the tip of the tongue. Sour taste is detected in both sides, bitter taste is sense at the back and spicy although has no distinct flavor, irritate the entire tongue and produce burning sensation.
The Sense of Smell (Nose)
The sense of smell results from chemical stimulation of nerves except that odors are in the gases form. There are nasal passages that are found in three layers of cavities. This is separated by bony layers called the turbinates. The turbinates (particularly the upper turbinates) contains the branched endings of the olfactory nerve. This is a sensory cranial nerve.
Odors stimulates this endings and will result in the sensation of smell. The smell receptors are neurons. This neurons was embedded in the lining of the nose. Axons of the neurons compose the nerves in the nose.
The Sense of Hearing and Balance (Ear)
The ear not just provide us with hearing but it also provide us with balance. The three main parts of the air are the external ear, the middle ear and the inner ear.
The external ear is composed of an ear flap. It also has an external auditory canal.
The middle ear, through the Eustachian tube, the middle ear connects with the throat. The connection of the middle ear and the throat equalizes the pressure in the middle ear with the pressure of the atmosphere and make it balance.