The Human Senses

Topics: Sense, Olfaction, Eye Pages: 8 (1836 words) Published: April 24, 2014

What are the human senses and how do they work?
The human senses are faculties by which the human body perceives external stimulation. Humans have senses to help them experience the world around them. The five main senses are sight, hearing, taste, smell and touch. Each of these five senses consists of organs with a specialized structure that has receptors for specific stimulation. These receptors are linked to the nervous system and therefore the brain.

Sight is the sense by which humans have the capability to detect images and distinguish objects. According to Zamora, A (n.d.), sight is probably the most developed sense in humans, followed by hearing.

In the front of the eye, a transparent structure called the cornea can be found. The cornea helps to focus incoming light. Behind the cornea lays the iris, which is a colored ring-shaped membrane. The space behind between the cornea and the iris is filled with a fluid called the aqueous humor. Within the iris there is an opening called the pupil, which can adjust its size depending on the amount of light entering the eye. Behind the pupil is structure containing a lens and muscles. When the muscles relax, the lens flattens, allowing the eye to see object far away. In contrary, to see closer objects, the muscle contracts, which thickens the lens. The eye itself is made up out of three tissue layers. The outer layer is called the sclera, which gives the eye its white color. The middle layer, called the choroid, contains blood vessels that supply the inner eye with nutrients and oxygen. Lastly, the inner layer of the eye is called the retina. This layer is filled with light sensitive cells that can be divided into two main varieties: rods and cones. The rods are for good vision in poor light, while cones are mainly for detection of color or detail. When light comes through the pupil and strikes either the rods or the cones, the light is converted into an electric signal that is connected to the brain via the optic nerve. Once the signal reaches the brain, the brain converts the signals into the images we see. (Than, K., 2005)

Hearing is the sense that perceives sound. This sense is all about vibration.

The ear consists of three basic parts: the outer ear, the middle ear and the inner ear. The outer ear serves to collect sound in to the middle ear. The human ear is capable of amplifying sounds with frequencies of approximately 3000 Hz. The middle ear transforms the energy of a sound wave into the internal vibrations of the bone structure within the middle ear and furthermore transforms these vibrations into a compressional wave in the inner ear. The inner ear then transforms this wave into nerve impulses that can be sent to the brain.

The sense of taste refers to the capability for humans to detect the taste of substances such as food.
The tongue contains many taste receptors, which test things such as food and beverages. These receptors are found in the taste buds. This is where the sensory cells pick up the chemical substances that are responsible for taste. These sensory cells will send the information to the brain. Based on the information that the tongue gives the brain, there are five basic types of taste. These basic tastes are: sweet, sour, salty, bitter and savory.

Taste is a bundle of different sensations. Not only does it imply the information the tongue sends to the brain but also the smell, texture and temperature of the food are important. For example, when someone eats while having a cold, and is not able to smell the food, the taste will not be optimal.

The sense of smell refers to the ability to perceive odor.

The human smelling function is carried out by two small odor-detecting patches, which are placed at the back of the nasal cavity. These patches contain five or six million sensatory cells. In comparison, a dog has 220 million of these sensatory...
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