Sensation and Perception: Chapter 3

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the saga continues as the race to study for this test makes me hate my life....

Electromagnetic spectrum

A continuum of electromagnetic energy that is produced by electrical charges and is radiated as waves

wavelength

distance BETWEEN the peaks of the electromagnetic waves

range from short-wavelength gamma rays to long-wavelength radio waves.

Light enters the eyes through the ______?

pupil. Then, the light is focused by the cornea and the lens to form sharp images of the objects on the retina, which contains the receptors for vision.

What are the two kinds of visual receptors?

Rods and cones - which contain light-sensitive chemicals called visual pigments that react to light and trigger electrical signals
cones: responsible for high levels of illumination and for color and detail vision
rods: responsible for low levels of illumination, extremely sensitive in the dark but can't resolve fine details

What are visual pigments and where are they located?

light-sensitive chemicals that react to light and trigger electrical signals. they are located in the two visual receptors of the eyes - the rods and cones.

What are cones?

One of the two visual receptors located in the retina of the eye. Composed of light sensitive chemicals that react to light and trigger electrical signals called visual pigments. Cones are in charge of high illumination, color and detail vision.

What are rods?

One of the two visual receptors located in the retina of the eyes. In charge of dark illumination, not much detail vision though. Help you in a movie theater, in a ROD-mantic comedy :)

Optic nerve

After signals go through the pupil and retina, they emerge from the back of the eye in the optic nerve which conducts signals toward the brain.

Accommodation

focus. Bringing objects located at different distances into focus by changing the shape of the lens. Kind of like a camera lens being altered for objects at different distances...only you turn it whereas the eyes changes the shape of its own lens.

What technique of the eye helps you bring near and far objects into focus?

Accommodation

What is the distance at which your lens can no longer adjust/accommodate to bring a close object into focus?

near point

What is presbyopia?

A condition that happens as you get older where the distance of the near point increases. That means that the distance at which your lens can no longer adjust to bring a close object into focus gets farther and farther away from your face as you get older.

Fovea

contains only cones. (cones in charge of high illumination, color and details)

blind spot

the place where the optic nerve leaves the eye. An area in the retina where there are no receptors.

dark adaptation

visual adaptation that occurs in the dark, during which the sensitivity to light increases. This increase in sensitivity is associated with regeneration of the rod and cone visual pigments.

dark adaptation curve

the function that traces the time course of the increase in visual sensitivity that occurs during dark adaptation

Ganglion cells

A neuron in the retina that receives inputs from bipolar and amacrine cells. The axons of the ganglion cells travel out of the eye in the optic nerve.

Amacrine cells

neurons that transmit signals laterally in the retina. Amacrine cells synapse with bipolar cells and ganglion cells

What is a Hermann grid?

A geometrical display that results in the illusion of dark areas at the intersection of two white "corridors." This perception can be explained by lateral inhibition.

horizontal cells

neurons that transmit signals laterally across the retina. Horizontal cells synapse with receptors and bipolar cells

bipolar cell

a retinal neuron that receives inputs from the visual receptors and sends signals to the retinal ganglion cells

What kinds of cells does the bipolar cell send signals to?

Ganglion cells

lateral inhibition

inhibition that is transmitted laterally across a nerve circuit. In the retina, lateral inhibition is transmitted by the horizontal and amacrine cells

What are Mach bands?

perception of a thin dark band on the dark side of light-dark border and a thin light band on the light side of the border. These band are an illusion because they occur even though corresponding intensity changes do not exist

monochromatic light

light that contains only a single wavelength.

mono=one, chromo ....wavelength

neural convergence

synapsing of a number of neurons onto one neuron

simultaneous contrast

the effect that occurs when surrounding one color with another changes the appearance of the surrounded color

spectral sensitivity curve

the function relating to a subject's sensitivity to light to the wavelength of the light. The spectral sensitivity curves for rod and cone vision indicate that the rods and cones are maximally sensitive at 500nm and 560 nm respectively

visual acuity

the ability to resolve small details

Give all the characteristics of rods:

rod shaped, 120 million in the eye, there are none in the fovea (only cones in the fovea), 30 min. dark adaptation time, grayscale, high sensitivity, and low acuity

Give all the characteristics of cones:

cone shaped, 6 million/eye, located everywhere - dense in fovea, 4 min adaptation time, color vision, low sensitivity (helps with illuminated light) and high acuity

What is functional specialization?

Different parts of the visual system are specialized to carry out specific functions

What is an example of functional specialization?

Cones - daylight, detailed color vision
Rods - night grayscale, poorly detailed vision

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