Noelle Branch Senses Article

VISION

From Light in the Eye to Image in the Brain!

The visual process our eyes go through begins with light entering the eye through the cornea. The cornea protects the eye and bends light. Next, the light passes through the pupil. The amount of light that enters through the eye is regulated by the iris. The iris is the colored portion of the eye and controls the size of the pupil opening. The lens, located behind the pupil, focuses the incoming rays into an image.

Color

Hue: the dimension of color (blue, red, etc.) determined by wavelength of light

Intensity: the amount of energy in a light wave determined by the wave's amplitude; influences brightness

Saturation: the ratio of the dominant wavelength to the other wavelengths in the color 

Nearsightedness & Farsightedness

Nearsightedness is a condition that affects ones ability to focus on distant objects, because distant objects focus in front of the retina. In contrast, farsightedness is a condition in which faraway objects are seen more clearly than those near, due to the focus of the retina on objects behind the retina. 

          

  Opponent Process Theory

Is the theory that opposing retinal processes such as red-green, blue-yellow, etc. enable color vision. This theory explains afterimages, as demonstrated by the image on the right. Stare at the white dot in the middle for about a minute and then shift your eyes to a white space. After tiring your eyes to the given colors you should see their opponent color! 

Photoreceptors: Rods and Cones

Rods are retinal receptors that detect black, white and gray. They are vital in peripheral vision and twilight vision, which is when cones don't respond. In contrast, cones are receptor cells that function in daylight; they detect fine detail and give rise to color sensations.

HEARING

Frequency: the number of complete wavelengths that pass point in a given time

Pitch: the highness or lowness of a tone; depends on frequency

Amplitude: amount of energy in a wave

Middle and Inner Ear

The middle ear is the chamber between the eardrum and cochlea. It contains the three tiny bones: the hammer, anvil, and stirrup. These bones concentrate the vibrations of the eardrum on the cochlea's oval window. The inner ear is the innermost part of the ear. It contains the semicircular canals, vestibular sacs, and the cochlea.

Conduction Hearing Loss: caused by damage to the eardrum and tiny bones
Sensorineural Hearing Loss:caused by damage to the cochlea's receptor cells

How Sound Is Turned Into Information

We hear by converting sound waves into neural activity. This is done in a detailed "mechanical chain reaction."  The outer ear first channels the sound waves through the auditory canal to the eardrum. The eardrum is a tight membrane that vibrates with the waves. Then, the middle ear transmits the vibrations through the three tiny bones (hammer, anvil, and stirrup) to the cochlea in the inner ear. The vibrations cause the oval window, which is the cochlea's membrane, to vibrate the fluid filling the tube.  This motion causes ripples in the basilar membrane which contains hair cells. The rippling bends the hair cells, triggering impulses in adjoining  nerve fibers, which converge to form the auditory nerve. Sound waves cause the hair cells to send neural messages up the temporal lobe's auditory cortex. Through this complicated process we are able to hear! 

TOUCH AND OTHER SENSES

The Four Skin Senses and Their Interaction

The four skin senses are warmth, cold, pressure, and pain. Pressure is the only one that has identifiable receptors. Within the skin there different types of nerve endings. Some spots are especially sensitive to one skin sense. However, there is no simple relationship between what we feel at a given spot and the specialized nerve ending found there.

Pain

Pain is extremely important because it lets the body know if something has gone wrong. Pain usually results from damage to the skin and other tissues. There are three influences on pain: biological, psychological, and social cultural. Biological influences are activity in spinal cord's large and small fibers along with genetic differences in endorphin production. Psychological influences are attention to pain, learning based on experience, and expectation of pain relief. Lastly, Social-cultural influences include the presence of others, empathy for others pain, and cultural expectations. 

Gate Control Theory 

Theory proposed by Ronald Melzak and Patrick Wall, suggesting that the spinal cord contains a neurological "gate" that either blocks pain signals or allows them to pass onto the brain. The spinal cord consists of small nerve fibers which conduct most pain signals, and then larger fibers that conduct other sensory signals. Therefore, when the tissue is injured the small fibers are activated and open the neural gate. This is enables you to feel pain. The large fibers when activated turn pain off. So the neurological "gates" either block pain or allow it to be sensed, suggesting that chronic pain can be treated by"gate closing" activity in the large neural fibers. This can be done electrically, by massage, or by acupuncture.

 Other Senses:

Vestibular Sense: the sense of body movement and position; balance

Kinesthetic Sense: the sensing of the position and movement of body parts individually

Temperature: temperature sense receptors of hot and cold 

Time: body's perception of time; time can appear to pass faster if you are enjoying yourself

SMELL

Olfaction

Olfaction is the process in which chemicals are turned into smell information. You are able to smell when the molecules of the substance carried through the air has reached a cluster of 5 million receptor cells at the top of the nasal cavity. The olfactory receptor cells selectively respond to the aroma in the air. Olfactory receptors recognize scents individually.
The olfactory bulb is a neural instructor involved in sense of smell along with Olfaction.

The Link Between Smell and Memory

Memories with emotional links can be associated with certain smells. These are long lasting and very vivid.

TASTE

The Five Taste Sensations

• Sweet
• Sour
• Salty
• Bitter
• Umami (recently discovered)

There are five basic tastes but the tongue is not mapped into regions for each taste. The entire tongue can sense these tastes equally.

Sensory Interaction: when one sense affects another sense. For example, the smell of coffee interacts with the taste of it

Gustation

Gustation is the tasting process in which food is turned into taste information. There are nearly 200 taste buds on every bump in your tongue. Each taste bud contains a pore that catches food chemicals. These are sensed by taste receptor cells protecting hairs into the pore. The molecules to respond to the different taste sensations differently. Taste receptors reproduce relatively fast (every week or so) therefore if you burn your tongue they will come back. 

Works Cited

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Wanjek, Christopher. "The Tongue Map: Tasteless Myth Debunked." LiveScience. TechMedia Network, 29 Aug. 2006. Web. 20 Oct. 2014.