Chapter 4 Flashcards
What is the difference between sensation and perception? examples
Sensation is the stimulation of sensory organs (light to eye)
Perception is organizing sensory info into representation of physical stimulus
-qualitative experience
(light of different wavelengths into colour)
Term for translation and the process that link the two
Transduction, the process that links sensation and perception.
- transformation of a physical stimulus into a neural signal
How many senses do we have
More than the 5 standard senses.
- balance, body position, temperature
What is sensory adaptation
-gradual decline in sensitivity to a stimulus over prolonged stimulation
(jumping in a cold lake)
- result of sensory neurons firing less and less
cant redirect stimulus to feel cold again
What is habituation
- decreased response to a repeated stimulus
(clock ticking in the background) - result of simple learning processes in the CNS (not sensory neurons)
can redirect the stimulus if focused on it
Visual adaptation
- all senses adapt to help us concentrate on what is important. we do not notice this in our eyes because they are constantly moving
- tiny involuntary movements in our eyes ensure that the millions of individual receptors in our eyes are always seeing something new or different
Cornea function
- protective bump at the front of the eye
- sharply refracts light
- part of focusing light onto retina
- 80% of focusing power but fixed in place
Pupil function
- hole that allows for light into the eye
- dilation or constriction controlled by muscles in the iris
Pupillary reflex does what
keep the light entering into the eye at optimal level
Iris function
dilates or constricts to allow light into the eye
Lens function
- elastic, crystalline structure that also helps focus light into the retina
- 20% of focus power
- purpose is to focus light precisely onto the retina
- changes shape to accommodate
Shapes of the lens and what muscle controls the shape
thinner lens is to focus distant objects (bends light less)
thicker lens is to focus closer objects (bends light more)
shape is controlled by the ciliary muscles
Function of accomodation
the most important function of focussing light onto the retina
What is the near point of vision and occurs when?
The point at which the image of a close object becomes blurred, occurs when the lens reaches its maximum curvature.
Correct terms for nearsighted and farsighted
- myopia is nearsightedness
- light is focused in front of the retina, elongation of the eye
- hyperopia is farsightedness
- light is focused behind the retina, shortened eye
What is the order of the cells in the retina from the back of the eye
- photoreceptors
- horizontal cells
- bipolar cells
- amacrine cells
- ganglion cells
Do we have more rods or more cones
More rods 120 million per eye
cones 6 million per eye
Are cones or rods more sensitive to light what causes it?
Rods are extremely sensitive to light
- convergence causes more sensitivity, but poor acuity
Which photoreceptor sees in colour
Cones see in colour
- 3 different types, special for different wavelengths
Which photoreceptor is associated with greater acuity and why?
Cones have better acuity because they have no convergence, poorer sensitivity
Which photoreceptors are found in the fovea
only cones
Fovea function 6
small area on centre of the retina
- vast majority of vision is here
- involved in directed looking
- highest density of photoreceptors
- great visual acuity
- ONLY CONES each connecting to one bipolar then 1 ganglion cell
Which photoreceptors are in peripheral vision
mostly rods
Which photoreceptors has faster pigment recovery?
cones (10 min)
What are photo pigments
- proteins that change shape when they absorb light
- changing shape requires action potential
Define dark adaptation
progressive increase in sensitivity to light
Why is there a “blip” in sensitivity to light as we adapt to the dark
- as you enter a dark room a fair number of photo-pigments are used up, the likelihood of a photon hitting a ready photo-pigment is not 100%, not very sensitive to dim light
- after awhile, more and more photo-pigments have regenerated, and more means more sensitive
What is determined by the frequency of wavelengths?
colour
what is determined by amplitude of wavelengths?
brightness
What colour most visible in the dark?
yellow
What are the three colours of light our cones are sensitive to?
blue green red