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examples of physical stimuli
-wavelengths of light
-sound waves
-chemicals
-pressure, heat
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examples of psychological experiences
-painting
-nirvana song
-general tsos chicken
-smell of a skunk
-someone holding your hand
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Light is essential for vision...which means?
without light there can be no visual perception
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Light behaves both as a particle...
photon and waves of energy
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What does amplitude mean?
brightness
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Whats the iris?
-contractile tissue
-dictates opening of the pupil
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In bright light the pupil...
contricts
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in dim light the pupil...
dilates
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Dilation of pupil- Sensitivity
-larger the pupil size, the more light permitted in.
- *normal circumstances is good for dimly lit environments
- **increases sensitivity
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Dilation of pupil- Acuity
- -In bright light, pupils contrict
- * image is now sharper, more detailed
- **Acuity is improved
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Opening of Iris- Sympathetic system
activation leads to pupil dilation
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Opening of the Iris- Parasympathetic system
activation leads to pupil contruction
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Atropine
is an acetycholine receptor antagonist
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How do pupils contricts?
acts via acetycholine receptor
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Peple under the influence of mushrooms..
- have hard time focusing and seeing.
- ** poor acuity
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Lens
- focuses incoming light
- **permitted in by the pupil
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Contraction of cillary muscle...
- allows the lens to take its normal cylindrical shape
- *in this position we are able to focus our vision on objects close
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When cillary muscle relaxes...
- lens lay more flat
- *able to focus our vison on objects close to us
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Retina
contains the sense organs for vision
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Animals that have both eyes in front of their heads...
can see depth much better than animals that have them on their sides
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BInocular disparity
- difference in the position of the same image on the 2 retinas is greater for close objects than for distant objects
- *helps us contruct a 3D image
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Retina composed of 5 layers of neurons
- -receptors
- -horizontal cells
- -bipolar cells
- -amacrine cells
- -ganglion cells
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retina layers- Receptors
- -light receptors
- -located at the back of the retina
- *not a NT
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retina layers- Horizontal cells
commmunicate between receptors
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retina layers- Amicrane cells
communicate between ganglion cells
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retina layers- Ganglion cells
send information out of the eye and to the brain
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Problems of retina contrcution: Light is filtered throughout the neuronal cell layers to the receptors
Solution: Fovea
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What is Fovea?
- specialized area of the retina with a thinning of the retinal ganglion layer.
- *area of hihg acuity
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Problem: how do axons exit out of the eye
- blind spot
- *visual system fills over the blank
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COmpletion
visual system uses information from the receptors around the blind spot to complete broken images
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description of rods (4)
-rod-mediated vision dominates in dim light
-more sensitive to light than cones
-poor acuity
-referred as scotopic vision
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description of cones (4)
-cone-mediated vision dominates in ample light
-high acuity
-color
-referred as photopic vision
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Why dont we see the world with gray in the center?
-saccades
-temporal intefgration
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Rhodospin
- absorbs light and when enough light hits rhodospin it bleaches into white.
- *when light is turned off it turns back to red
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AP happen in order for....
information to be passed
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4 steps of rod in the dark
- 1. Rhodospin molecules inactive
- 2.sodium channels are kept open by cyclic GMP3. Soium ions flow inside, partially depolarizing the rod
- 4.Rods continuously release Glutamate
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4 processes of rods in light
- 1.light bleaches rhodospin molecules
- 2. as a result cGMP is broken down and sodium channels close
- 3. sodium ions cannot enter rods, rodes become hyperpolarized
- 4. glutamate release is blocked
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saccades
fast movement of eye to move the fovea around and prevent gray spots
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