examples of physical stimuli
-wavelengths of light
examples of psychological experiences
-general tsos chicken
-smell of a skunk
-someone holding your hand
Light is essential for vision...which means?
without light there can be no visual perception
Light behaves both as a particle...
photon and waves of energy
What does amplitude mean?
Whats the iris?
-dictates opening of the pupil
In bright light the pupil...
in dim light the pupil...
Dilation of pupil- Sensitivity
-larger the pupil size, the more light permitted in.
- *normal circumstances is good for dimly lit environments
- **increases sensitivity
Dilation of pupil- Acuity
- -In bright light, pupils contrict
- * image is now sharper, more detailed
- **Acuity is improved
Opening of Iris- Sympathetic system
activation leads to pupil dilation
Opening of the Iris- Parasympathetic system
activation leads to pupil contruction
is an acetycholine receptor antagonist
How do pupils contricts?
acts via acetycholine receptor
Peple under the influence of mushrooms..
- have hard time focusing and seeing.
- ** poor acuity
- focuses incoming light
- **permitted in by the pupil
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
When cillary muscle relaxes...
- lens lay more flat
- *able to focus our vison on objects close to us
contains the sense organs for vision
Animals that have both eyes in front of their heads...
can see depth much better than animals that have them on their sides
- 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
Retina composed of 5 layers of neurons
- -horizontal cells
- -bipolar cells
- -amacrine cells
- -ganglion cells
retina layers- Receptors
- -light receptors
- -located at the back of the retina
- *not a NT
retina layers- Horizontal cells
commmunicate between receptors
retina layers- Amicrane cells
communicate between ganglion cells
retina layers- Ganglion cells
send information out of the eye and to the brain
Problems of retina contrcution: Light is filtered throughout the neuronal cell layers to the receptors
What is Fovea?
- specialized area of the retina with a thinning of the retinal ganglion layer.
- *area of hihg acuity
Problem: how do axons exit out of the eye
- blind spot
- *visual system fills over the blank
visual system uses information from the receptors around the blind spot to complete broken images
description of rods (4)
-rod-mediated vision dominates in dim light
-more sensitive to light than cones
-referred as scotopic vision
description of cones (4)
-cone-mediated vision dominates in ample light
-referred as photopic vision
Why dont we see the world with gray in the center?
- absorbs light and when enough light hits rhodospin it bleaches into white.
- *when light is turned off it turns back to red
AP happen in order for....
information to be passed
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
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
fast movement of eye to move the fovea around and prevent gray spots