Eyes
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Eye
Sense organ that contains receptors that are sensitive to light wavelength and light
Retina
Layer of tissue in back of the eye that detects light from environment (cones and rods)
Fovea
Area where most light falls ( Where cone cells are present)
Where are rod cells present
around edges of fovea
Cone cells strcuture
Nucleus Membrane folds Mitochondria
Cone cell optical pigments
Iodopsin
Types of cone cells
Red blue and green each containing diff type of iodopsin to allow it so see that wavelength of light
Advantages of having different cone cells
Enable us to see the whole spectrum of colours as each cone is sensitive to a different wavelength of light. Different colours will excite different numbers of these optical pigments. (Overlapping wavelengths)
Visual acuity
the ability to distinguish between two separate points when viewing an image
Cone cells have ____ visual acuity and why
Cone cells have high visual acuity because each cone cell is connected to one bipolar neurone cell each allowing each cell to send separate action potential to brain
Advantage of cones having high visual acuity
Information from each individual cone cell will be interpreted as separate points when the brain generates images. Light from two points which hits two cones together send separate action potentials to the brain.
Cones have ___ sensitivity and why
Each cone cell connects to its own bipolar neurone Only produces generator potentials in high light intensities as there is only one cone per bipolar neurone. This means it takes more light to reach the threshold and generate an action potential.
Where are rods located
Outside of retina
Pigment for rods
rhodopsin which is broken down by light
In strong light rhodopsin is broken down how is that useful
In strong light, rhodopsin is broken down faster than it can be resynthesised, so rod cells become bleached and do not function. This prevents overstimulation of rods and ensures that vision in bright light is mediated by cone cells.
Retinal convergence
Many rod cells connect to one bipolar neruone THEN, multiple bipolar cells connect to one gangion cells
Why do rods have low visual acuity
Rod cells have low visual acuity As multiple rod cells bind to one single bipolar neurone Light not processed as seperate points and signals combine into one action potential
Rods have high sensitivity
Many weak generator potentials can combine to reach threshold and activate action potential in single bipolar neurone Summation
Optic nerve
Carries impulses from brain to eye