DO NOW:

What do you know about our sense of sight and vision?

What parts of the eye do you know? What do you know about light?

VISIONAP Psychology

Ms. Desgrosellier

11.16.2009

OBJECTIVES:

SWBAT define transduction, and specify the form of energy our visual systems converts into the neural messages our brain can interpret. 

SWBAT describe the major structures of the eye, and explain how they guide an incoming ray of light toward the eye’s receptor cells. 

SWBAT contrast the two types of receptor cells in the retina, and describe the retina’s reaction to light. 

SWBAT discuss the different levels of processing that occur as information travels from the eye’s retina to the brain’s cortex.

VISION

transduction: conversions of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses or brains can interpret.

THE STIMULUS INPUT: LIGHT ENERGY

Light that hits our eyes is not actually in color.

Visible light is part of the electromagnetic spectrum (and it makes up only a tiny part).

The spectrum ranges from gamma rays (shortest) to the long waves of radio transmission.

Some organisms see different parts of the spectrum, like bees.

THE STIMULUS INPUT: LIGHT ENERGY

THE STIMULUS INPUT: LIGHT ENERGY

wavelength: the distance from the peak of one light or sound wave to the peak of the next. electromagnetic wavelengths vary from the short

blips of cosmic rays to the long pulses of radio transmission.

hue: the dimension of color that is determined by the wavelength of light what we know as the color names blue, green,

etc.

THE STIMULUS INPUT: LIGHT ENERGY

intensity: the amount of energy in a light or sound wave, which we perceive as brightness or loudness as determined by the wave’s amplitude.

amplitude: the wave’s height.

THE EYE

cornea: protects the eye and bends light to provide focus.

pupil: the adjustable opening in the center of the eye through which light enters.

THE EYE

THE EYE

iris: a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening.The iris adjusts light intake by dilating and

constricting in response to light intensity and even to inner emotions.

The uniqueness of peoples’ irises enables iris scanning machines to confirm someone’s identity.

THE EYE

THE EYE

lens: the transparent structure behind the pupil that changes shape to help focus images on the retina.

accommodation: the process by which the eye’s lens changes shape to focus near or far objects on the retina.

retina: the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layer of neurons that begin the processing of visual information.

THE EYE

THE RETINA

Images projected on the retina are actually projected upside down.

However, the retina does not read images as a whole.

The receptor cells convert the light energy into neural impulses, which are then sent to the brain and constructed there into a perceived, upright image.

THE RETINA

THE RETINA

Acuity: the sharpness of vision. Normally, the cornea and the lens focus the

image of any object on the retina. nearsightedness: a condition in which

nearby objects are seen more clearly than far objects because the image of near objects is focused behind the retina.

farsightedness: a condition in which far-away objects are seen more clearly than near objects because the image of near objects is focused behind the retina.

NEARSIGHTEDNESS

FARSIGHTEDNESS

THE RETINA

rods: retinal receptors that detect black, white and graynecessary for peripheral and twilight

vision, when cones do not operate. cones: retinal receptor cells that are

concentrated near the center of the retina and that function in daylight or in well-lit conditions.They detect fine detail and give rise to

color sensations.

THE RETINA Optic nerve: the nerve that carries neural

impulses from the eye to the brain. blind spot: the point at which the optic nerve

leaves the eye. fovea: the central focus point in the retina,

around which the eye’s cones cluster (NO RODS) Bipolar cells relay cone’s individual message

to the visual cortex, which devotes a large area of input from the fovea. This retains precise information, which allows them to better detect fine detail.

You pupil dilates in the dark to allow more light to reach your rods in the retina’s periphery.

THE EYE

THE RETINA

VISUAL INFORMATION PROCESSING

Visual information works its way through our visual system through increasingly complex layers. It starts at the retina, then moves to the

thalamus and brain’s cortex.The retina also helps encode and analyze

sensory information. Info from the retina’s 130 million receptor

rods and cones is received and transmitted by the million or so ganglion cells (whose axons make up the optic nerve).

VISUAL INFORMATION PROCESSING

Retinal areas relay its information to the occipital lobe, specifically the visual cortex.

Retinal cells are so responsive that they can be triggered by pressure.

FEATURE DETECTION

Nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement.

Specific cells refer to only one specific thing, like a bar at a 2 o’ clock tilt. When shown a different angle, the cell does not fire.

Feature detection cells in the visual cortex pass information to other areas of the cortex where cells respond only to more complex patterns.

FEATURE DETECTION

The temporal lobe area behind your right ear allows you to perceive faces.

Necker cube: the image on your retina is constant, you can perceive it in two different ways that shift back and forth.