1. Senses I: Light And Vision Flashcards
What is the tough outer coat that protects the entire eyeball
The sclera
What contains blood vessels that nourish the inner eye
The choroid
Light enters the eye through the
Cornea
What is the function of the iris
To adjust the size of the pupil in order to control the amount of light entering
The pupil decreases in size when exposed to
High intensity light
The pupil increases in size when exposed to
Low intensity light
The ability of the eye to focus on distant and nearby objects by changing the focal length is known as
Accommodation
What prevents the the eye from collapsing due to changes in atmospheric pressure
Aqueous humor
Retina contains what type of cells
Light sensitive cells
What are the two types of light sensitive cells
Rod and cone cells
Rod cells
Respond to light intensity
Cone cells
Respond to Color of objects
What is the location of most perception in the eye and is the area of sharpest vision
Fovea centralis (think central=focused)
Where are a maximum number of cones present
Fovea (most are of Color perception the more Color perception= more cones present)
When object is viewed it becomes ___ at the retina
Inverted
After objects are inverted at retina an electrical signal is formed and then sent to the brain via the
Optic nerve
The blind spot is known as the
Optic disk
There are no rods or cones on the
Optic disk (insensitive to light)
The optic nerve enters the eye at the
Optic disk
When an individual is hit by a light beam the process goes
Posterior retina- photoreceptors- bipolar cells- innermost ganglion cells
Those innermost ganglion cells generate
Action potentials
The axons on those innermost ganglion cells weave together to form the
Optic nerve
The second cranial nerve is the
Optic nerve
The impulses from those action potentials generated by the ganglions are carried to the ___ via the optic nerve then into the ____ ___ ___
Thalamus, brain visual cortex
The thalamus (limbic system) is located in the?
Forebrain
Midbrain
Hindbrain
Forebrain
Function of thalamus
Gathers/relaying sensory signals like visual and pain perception
The primary visual cortex of V1 is found in the
Occipital lobe (associated with visual processing and may receive these visual signals from the thalamus)
2 types of light sensitive cells or in other words PHOTORECEPTORS
RODS AND CONES
Peripheral vision is associated with the
Rods
__ only hit their activation thresholds in bright conditions
Cones (less sensitive to light- takes a bright light)
___ response time to stimuli is faster than __
Cones, rods
3 types of cones
S (blue) M (green) L (red) cones
S cones are sensitive to
Short-wavelength
M cones are sensitive to
Medium-wavelength
L cones are sensitive to
Long wavelength light.
Humans have ___ vision
Trichromatic (unmutated- normal red green blue cone shades)
The three cone pigments of blue green and red for detecting light have been shown to vary in their exact chemical composition due to a genetic mutation. This means
The shades may differ and those individuals will have cones with different Color sensitivity
Colour blindedness is
Mostly inherited and rarely acquired
Not being able to tell apart certain colours is
Colour blindness
The most common colours confused in colourblind people are
Red and green (daltonism)
The most usual form of colourblindness is known as
Daltonism
Seeing red as grey is
Daltonism
The most unusual form of colourblindness is known as
Monochromacy
Monochromacy is when
People see the world in black and white (rare)
Colourblindness is rarer in
Women
- this is due to genetics because men have 1 X chromosome and women have 2 X chromosomes- in women they have shot at not having the gene since one X chromosomes may have it and the other wont; therefore, overriding the mutation. However in men they either have it or don’t in that X chromosome and can’t override it since they only have one X chromosome or they don’t have it at all
When 2 or more light sense cones don’t work this results in
Monochromacy (condition term: achromatopsia)
People with four or more types of cones are known to have (RARE: only some verified reports)
Tetrachromatic vision
- almost always female
- more intense colour vision
