PSYC 211 - Chapter 6

PSYC 211 - Chapter 6 - CHAPTER 6 - VISION The brain...

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CHAPTER 6 - VISION The brain performs two major functions: 1. It controls the movements of the muscles producing useful behaviors. 2. It regulates the body’s internal environment. To perform these tasks, the brain must be informed about what is happening both in the external environment and within the body. Such information is received through the sensory systems. SENSORY RECEPTORS – A specialized neuron that detects a particular category of physical events. (Not to be confused with receptors for neurotransmitters, neuromodulators, and hormones.) Sensory receptors = specialized neurons Other types of receptors = specialized proteins that bind with certain molecules SENSORY TRANSDUCTION – The process, by which sensory stimuli are transduced into slow, graded receptor potentials. RECEPTOR POTENTIAL – A slow, graded electrical potential produced by a receptor cell in response to a physical stimulus. THE STIMULUS Our eyes detect the presence of light. Electromagnetic radiation with a wavelength of between 380 and 760 nanometers is visible to humans. (Fig 6.1, pg. 170) The perceived color of light is determined by 3 dimensions: HUE – One of the perceptual dimensions of color; the dominant wavelength . The visible spectrum displays the range of hues that our eyes can detect. BRIGHTNESS – One of the perceptual dimensions of color; intensity. If the intensity of the electromagnetic radiation is increased, the apparent brightness increases, too. SATURATION – One of the perceptual dimensions of color; purity . If all the radiation is of one wavelength, the perceived color is pure, or fully saturated. Conversely, if the radiation contains all wavelengths, it produces no sensation of hue – it appears white. (Fig 6.2, pg. 171) ANATOMY OF THE VISUAL SYSTEM THE EYES: The eyes are suspended in the orbits, the bony pockets in the front of the skull. They are held in place and moved by 6 extraocular muscles attached to the tough, white outer coat of the eye called the sclera. (Fig 6.3, pg. 171) The eyes make 3 Types of Movements: VERGENCE MOVEMENT – The cooperative movement of the eye, which ensures that the image of an object falls on identical portions of both retinas. SACCADIC MOVEMENT – The rapid, jerky movement of the eyes used in scanning a visual scene.
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PURSUIT MOVEMENT – The movement that the eyes make to retain an image of a moving object on the fovea. The pathway of light entering the eye: The outer layer of most of the eye, the sclera, is opaque and does not permit the entry of light. However, the cornea , the outer layer of the front of the eye, is transparent and admits light. The amount of light that enters is regulated by the size of the pupil, which is an opening in the iris , the pigmented ring of muscles situated behind the cornea. The changes in shape of the lens
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This note was uploaded on 02/13/2011 for the course PSYC 211 taught by Professor Yogitachudasama during the Winter '09 term at McGill.

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PSYC 211 - Chapter 6 - CHAPTER 6 - VISION The brain...

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