Photoreceptor
- Created by: tumblrgirl96
- Created on: 22-05-15 23:01
View mindmap
- Photoreceptors
- Cones
- Allow colour vision in bright light
- Found in the centre of the retina
- Synapse with bipolar neurones
- Synapse with ganglion neurones
- Rods
- Only give black and white vision
- Also work in dim light
- Found in the retina
- Synapse with bipolar neurones
- Synapse with ganglion neurones
- Rhodopsin (purplish pigment) absorbs light and results in a chemical change
- Located in membranes of vesicles found in the outer segments of the rod
- In the dark
- Na+ ions flow into the outer segment through open cation channels
- Na+ moves down the conc. gradient into the inner segment
- Na+ actively pumped out of the cell
- Membrane slightly depolarised (-40 mV)
- Triggers the release of a neurotransmitter
- Neurotransmitter binds to the bipolar cell
- Stops the bipolar cell from depolarising
- Neurotransmitter binds to the bipolar cell
- Triggers the release of a neurotransmitter
- Membrane slightly depolarised (-40 mV)
- Na+ actively pumped out of the cell
- Na+ moves down the conc. gradient into the inner segment
- Na+ ions flow into the outer segment through open cation channels
- In the light
- Rhodopsin broken down into retinal and opsin
- Na+ channels close
- No/less Na+ entering the rod
- Inner segment still pumps out Na+ ions
- Cell hyperpolarised
- Neurotransmitter is no longer released
- Bipolar cells depolarised
- Optic nerve neurones depolarised
- Bipolar cells depolarised
- Neurotransmitter is no longer released
- Cell hyperpolarised
- Inner segment still pumps out Na+ ions
- No/less Na+ entering the rod
- Retinal = non-protein
- Opsin = protein component
- Leads to the hydrolysis of a molecule attached to the cation channel in the outer segment
- Results in the closure of the cation channels
- Na+ channels close
- No/less Na+ entering the rod
- Inner segment still pumps out Na+ ions
- Cell hyperpolarised
- Neurotransmitter is no longer released
- Bipolar cells depolarised
- Optic nerve neurones depolarised
- Bipolar cells depolarised
- Neurotransmitter is no longer released
- Cell hyperpolarised
- Inner segment still pumps out Na+ ions
- No/less Na+ entering the rod
- Na+ channels close
- Results in the closure of the cation channels
- Leads to the hydrolysis of a molecule attached to the cation channel in the outer segment
- Has to be quickly converted back into rhodopsin once broken down
- Dark adaptation
- Na+ channels close
- Rhodopsin broken down into retinal and opsin
- Cones
Comments
No comments have yet been made