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perception basics
procces of perception and the structures involved
19
Psychology
Undergraduate 2
12/04/2014

Additional Psychology Flashcards

 


 

Cards

Term

 

 

 

 

 

Perception is dependent on what?

 

Definition

 



detection of electromagnetic spectrum

 

Visible spectrum for humans ranges from 400-700 nanometers (blue on 400 side (short side), red on 700 side (long side)

 

Term

 

 

 

 

 

What is the process of perception relative to the eye? What happens if  light is unfocussed?

 

Definition

 

 

Light enters the eye through the pupil and is focused by the cornea and lens to a sharp image on the retina

 

Rods and cones are visual receptors in the retina that contain visual pigment that responds to light

 

The optic nerve carries information from retina to the brain

 

The cornea (which is fixed) accounts for about 80% of focusing

 

The lens automatically adjusts shape for object distance to maintain focus and accounts for the other 20% of focusing

 

Light must be focused or objects will be blurry

 

Term

 

 

 

 

 

What is accommodation and why does it occur?

 

Definition

 

Automatic adjustment of the lens to maintain focus

 

Accommodation results when ciliary muscles are tightened which causes the lens to thicken

 

ability of accommodation is lost with age.

 

Occurs when the lens can no longer adjust for close objects loses flexibility

 

Lens begins to harden and ciliary muscles weaken

 

Term

 

 

 

 

 

What is an effect of loss of accommodation, and what is a solution?

 

Definition

 

 

 

 

presbyopia “old` eye” the increasing of near point along with age

 

Near point is the closest distance to you at which the image can be sharpened on the back of the eye

 

Corrective lenses needed for close sight activities such as reading

 

Term

 

 

 

 

 

What two defects are associated with bad vision?

 

Definition

 

Myopia and hyperopia

Myopia or nearsightedness is the inability to see distance objects clearly

 

Image is focused in front of retina

 

Caused by refractive myopia or axial myopia

 

In refractive myopia the cornea or lens bends too much light

 

In axial myopia the eyeball is too long

 

Solutions for myopia

 

Move stimulus until it lies within the far point

 

LASIK surgery

 

Distance when light becomes focused is called the far point

 

Hyperopia or farsightedness is the inability to see nearby objects clearly

 

Focus is behind the retina

 

Usually caused by an eyeball that is too short

 

Constant accommodation for nearby objects can lead to eyestrain and headaches

 

corrected with lenses

 

Term

 

 

 

 

what is isomerization and how does it fit into transduction?

 

Definition

 

 

 

isomerization is when the  Retinal changes shape a due to light absorption

 

transduction occurs when the retinal absorbs one photon of light

 

Receptors have outer segments which contain visual pigment molecules that have two components

 

Opsin and Retinal

 

Term

 

 

 

 

 

How are rods and cones distributed in the eye and how does this effect vision (blind spots)?

 

Definition

 

 

 

 

 

Rods are large and cylindrical approximately  120 million rods

 

Cones are small and tapered approximately 6 million cones

 

Fovea consists solely of cones

 

Peripheral retina has both rods and cones (majority rods)

 

Blind spot is located at edge of visual field and the brain “fills in” the blind spot

 

blind spot exists where the optic nerve leaves the eye We don’t see the blind spot as one eye covers the blind spot of the other

 

Term

 

 

 

 

name the 2 diseases that effect  vision

 

Definition

 

Macular degeneration and Retinitis pigmentosa

 

 

Macular degeneration

 

affects cones only

 

Creates a blind spot on the retina

 

Most common in older people

 

 

 

Retinitis pigmentosa

 

Genetic disease

 

Rods are destroyed first, destroying peripheral vision

 

Severe cases result in complete blindness

 

Term

 

 

 

 

What is an effect of isomerization and what methods does it emoloy?

 

Definition

 

dark adaptation is caused by isomerization

 

Dark adaptation occurs following extended exposure to the dark

 

Three different types of experiments have been used: cone adaptation experiment,  rod adaptation experiment and cone and rod adaptation experiment

 

To assess both rods and cones

 

[image]Observer looks at a fixation point but pays attention to a test light to the side

 

Results show a dark adaptation curve (rapid drop, slight curve/leveling followed by rapid fall again)

 

rod-cone break is the point in the adaptation curve where there is a gradual improvement in sensitivity (the leveling of the curve)

 

Dark adapted sensitivity is about 100,000 times greater than light adapted sensitivity

 

Experiment for cone adaptation

 

Place light at fovea so test light only stimulates cones

 

Results show that sensitivity increases for three to four minutes then levels off

 

Experiment for rod adaptation

 

Must use a rod monochromatic (people born without cones)

 

Results show that sensitivity increases for about 25 minutes and then levels off

 

Term

 

 

 

 

 

Define spectral sensitivity

 

Definition

 

 

 

 

 

Spectral Sensitivity is the sensitivity of rods and cones to different parts of the visual spectrum

 

monochromatic light used  to determine threshold at different wavelengths

 

Thresholds for light is lowest in the middle of the spectrum

 

Term

 

 

 

 

 

How is rod and cone sensitivity determined?

 

Definition

 

 

 

 

To determine separate sensitivity of rod and cones to light wavelengths similar methods to dark adapation are used

 

For cone sensitivity stimuli is presented solely to the fovea Most sensitive at 560 nm

 

For rod sensitivity the observers dark adapt for 30 minutes an wavelength sensitivity is then tested (as only rods would be utilized at this point)more sensitive to short-wavelength light at 500nm

 

Term

 

 

 

 

 

What is the absorption length for rods and cones?

 

Definition



rod pigments absorbs best at 500nm

cone pigments absorb best at 419nm (short) 531nm  (medium) and 558nm (long)

Term

 

 

 

 

 

what has occurred when things blue in color are more visible than things that are red in color?

 

Definition

 

 

 

Purkinje shift-enhanced

 

sensitivity to short wavelengths during dark adaptation when the shift from cone to rod vision occurs

 

due to cones being more sensitive to longer wavelengths than rods

 

Term

 

 

 

 

what is the structure and function of neurons?

 

Definition

 

three key components of neurons

 

cell body

 

dendrites

 

axons or nerve fiber

 

function is transmission of electrical signals

 

Term

 



Describe how neurons transmit data

 

Definition

 

through action potential and synapses

 

action potentials

 

have a  propagated response (travels without decreasing in size) and a refractory period of 1ms and firing rate up to 800 impulses per second

 

spontaneous activity can occur without stimulation which permits inhibitory effect

 

the resting the  potential negative charge of the neuron relative to its surrounding

 

the action potential is the peak from the jump of an electrical impulse

 

Synapses is the small space between neurons and the jump of information between neurons is achieved using neuro transmitters

 

Neurotransmitters are                                   

 

Released by the pre-synaptic neuron from the vesicles

 

Received by the  postsynaptic neuron on the receptor sites

 

Specific receptor sites have a “key/lock” match

 

 

Term

 

 

 

 

How many types of Neurotransmitters are there? what are they?

Definition

 

two types of transmitters: Excitatory and inhibitory transmitters

 


Excitatory transmitters cause depolarization in post-synaptic neuron

 

Neuron becomes more positive

 

Increases the likelihood of an action potential

 

Inhibitory transmitters cause a hyper-polarization

 

Neuron becomes more negative

 

Decreases the likelihood of an action potential

 

Term

 

 

 

 

What is the structure of the retinal and how does it proccess light?

 

Definition

 

Retinal composition consists of (in ascending order)

 

Ganglion cells               

 

Amacaine cells

 

Bipolar cells

 

Horizontal Cells

 

Rod and cone receptors

 

Light rays must pass through all receptors and is then sent back along the same

 

done this way to reduce light scatter and image degradation

 

Rods and cones send signals vertically through

 

Bipolar cells

 

Ganglion cells and axons

 

Signals are sent hotizontally

 

Between receptors by horizontal cells

 

Between bipolar and ganglion cells by amacrine cells

 

Term

 

 

 

 

 

Explain convergence

 

Definition

 

126 million rodes and cones converge to one million ganglion cells

 

Higher convergence of rods then cones

 

Average 120 rods to one ganglion

 

Six cones to one ganglion

 

Cones in the fovea have a one to one relation to ganglion cell

 

Rods have greater convergence increasing likelihood of response

 

Rods cannot distinguish details very well

 

foveal vision results in high visual acuity

 

One to one wiring leads to ability to discriminate small details

 

More convergence = better sensitivity to light but a loss of resolution/discrimination

 

Term

 

 

 

 

What is a sinusoid?

Definition

 



Sinusoid is the shape of electromagnetic light waves

 

The distance between the peaks of sinusoids is what we call wavelength

 

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