receptors

Question 1

photoreceptors convert light into electrical impulses

Answer 1

• light enters eye and hits photoreceptors and absorbed by light sensitive pigments
• light bleaches pigments causing a chemical change
• this triggers a nerve impulse along bipolar neuron
• bipolar neuron connects photoreceptors to optic nerve which take impulse to brain
• 2 photoreceptors are rods and cones
• rods are found in peripheral of retina and give information in black and white
• cones are found in fovea and give information in color, they can be red, blue or green sensitive. they are stimulated in different proportions so you see different colors

Question 2

rhodopsin

Answer 2

-it is a light sensitive pigment found in rods
- made of chemicals opsin and retinal

Question 3

rods not stimulated in the dark

Answer 3

• Na+ pumped out actively of the cell
• ions diffuse in back through open Na channels
• inside of cell slightly negative and membrane said to be depolarized
• triggering of neurotransmitter
• neurotransmitter inhibit bipolar neuron which can’t fire as it doesn’t have an action potential so no message go into the brain

Question 4

rods stimulated inn the light

Answer 4

• light energy breaks rhodopsin to retinal and opsin and is called bleaching
• bleaching cause the Na channels to close and ions diffuse out the cells but can’t get back in
• more Na on the outside makes the inside more negative making it hyperpolarized
• when hyperpolarized rod cells stop releasing neurotransmitter so no inhibition of bipolar neuron
• bipolar membrane depolarizes and if potential difference reaches threshold, action potential can be transmitted to brain by the optic nerve