Which of your five senses would you be willing to give up? Would you give up your sight? Would you be willing to go deaf for the rest of your life? The fact is that all our senses play an important role in the life we live. Aristotle identified five senses which we still recognize today – sight, hearing, smell, taste and touch (Pfaffmann, 1980). These senses are made possible by sensory receptors which detect stimuli and send nerve impulses to the brain to be interpreted. If we are to understand how our senses work we must familiarize ourselves with the functions of the structures within our sense organs.
Sense of Sight
Our sense of sight is made possible by our eyes. These sensory receptors detect light within our surroundings and convert the light into nerve impulses to be sent to the brain. During this process, many structures in the eyes adjust to allow light to enter the eye through the pupil. Thus, when we look at an object an inverted image of this object is formed on the retina. From here, nerve impulses are sent through the optic nerve to the brain. The brain then translates the impulses forming an image, thus enabling sight (Mackean, 1995). Figure 1 below retrieved from Pass My Exams (2012), demonstrates how light enters the eye and allows the image to be formed upside down on the retina so that nerve impulses can be sent to the brain. To explore more about the functions of the structures in the eyes, click here.
Figure 1. Structure of the eye.
Sense of Hearing
Our ears are the sensory receptors which make hearing possible. Hearing results from the production of sound through vibrations in the air. These vibrations enter the tube of the outer ear, causing the ear drum to vibrate back and forth with these vibrations. The vibrations then move to the structures in the middle ear which also vibrate back and forth. The vibrations are then passed on to the inner ear, where the vibrations are passed to a liquid in the cochlea. The cochlea “transforms sound into nerve impulses that travel to the brain” (WebMD, LLC, 2009). Figure 2 below, retrieved from Heinemann Explore (2002), illustrates the structures in the ear. To learn more about the structures in the ear and their functions, click here.
Sense of Taste
The senses of taste and smell are closely connected. The nasal cavity and the tongue contain sensory cells referred to as chemoreceptors (Mackean, 1995).
On the tongue, sensory cells connect to nerves that lead to the brain (WebMD, LLC, 2010). These sensory cells are known as taste buds, which detect chemicals that produce sensations of sweet, salty, sour, bitter and the fifth category referred to as umami. Figure 3 below, retrieved from Institute for Quality and Efficiency in Health Care (IQWiG), (2012), depicts the tastes perceived by the taste buds.
Figure 3. Tastes perceived by taste buds.
Sense of Smell
The nose is the sense organ responsible for detecting smell. Zamora (2013), explains that receptors found within the nasal cavity interact with airborne chemicals and sends nerve impulses to the brain. Figure 4 below, retrieved from Amsel (2005-2013), illustrates the structure and location of the sensory receptors in the nasal cavity.
For a more in-depth explanation of how the senses of taste and smell work, click here to view and add to my wiki.
If you would just like to peruse this information, click here to visit my taste and smell website.
If you would just like to peruse this information, click here to visit my taste and smell website.
Sense of Touch
The skin is responsible for the sense of touch. The receptors for the sense of touch are distributed all over the body. Within the skin are many sensory nerve endings which “respond to the stimuli of touch, pressure, heat and cold, and some which cause a feeling of pain” (Mackean, 1995, p. 171). Upon receiving a stimulus, the nerve endings send nerve impulses to the brain. Various receptors react to specific stimuli. Some areas have a higher concentration of these receptors, such as the finger-tips which are extremely sensitive to touch.
References:
Amsel, S. (2005-2013). [Illustration the location and structure of sensory receptors in the nose]. Retrieved from http://www.exploringnature.org/db/detail.php?dbID=25&detID=49
Heinemann Explore. (2002). [Illustration the structures in the ear]. Retrieved from http://lvp.lockyersmid.dorset.sch.uk/pluginfile.php/3230/mod_resource/content/0/content/html/portal_ks2science/pg000677.htm
Institute for Quality and Efficiency in Health Care (IQWiG). (2012). [Illustration all tastebuds perceive all tastes]. Retrieved from http://www.informedhealthonline.org/how-does-our-sense-of-taste-work.802.en.html
Mackean, D. G. (1995). GCSE Biology. (2nd ed.). London: John Murray Publishers.
Pass My Exams. (2012). [Illustration the structure of the eye]. Retrieved from http://www.passmyexams.co.uk/GCSE/physics/use-of-lenses-for-correcting-vision-eyesight.html
Pfaffmann, C. (1980). Sensory Receptor, Human. In The encyclopedia Britannica: macropedia (15th ed.).
Web MD, LLC. (2009, July). Brain and nervous system health centre. Retrieved from http://www.webmd.com/brain/picture-of-the-ear
Web MD, LLC. (2010, May). Oral care. Retrieved from http://www.webmd.com/oral-health/picture-of-the-tongue
Zamora, A. (2013). Anatomy and structure of human sense organs. Retrieved from http://www.scientificpsychic.com/workbook/chapter2.htm
