rods and cones

1. light

2. optic nerve

3. ganglion (sensory neurone)

4. bipolar neurones

5. first line rod second line cone

6. pigmented retina

what is a photoreceptor

these are receptors that detect light

what are the 2 types of photoreceptors

rods and cones

1. rod

2. inner segment

3. outer segment

4. synapse

5. nucleus

6. mitochondria

7. membrane disks

1. cone

2. inner segment

3. outer segment

4. synapse

5. nucleus

6. mitochondria

7. membrane disks

which has enables colour vison and which is only in black or white

rods= black or white

cones= colour vison

what is the pigment in rods

rhodopsin

what is the pigment in cones

iodopsin

In what type of cell does retinal convergence occur

rods

define retinal convergence

several rod cells converge and form a synapse with a single bipolar cell

what is the benefit of retinal convergence

In order for a generator potential to be produced in the bipolar cell a certain threshold value must be exceeded. If there are several rod cells that are stimulated at once there is a much greater chance that this threshold is reaches even in low light therefore there more sensitive

what is the process of all the stimulation from all rod cells adding together to produce a generator potential called.

spatial summation

what are other factors which make rods more sensitive

1. retinal convergence

2. the pigment rhodopsin breaks down even at low light intensity where as iodopsin is more stable

what is a limitation of retinal convergence

as many rods converge to one bipolar neurone generating a single impulse were unable to work out exactly where on the retina stimulation occurred resulting in low acuity where as each cone synapes with one individual bipolar neurone

what are the 3 types of cone

red green blue

1. fovea = were light focused in centre of retina

2. blind spot = were the optic nerve is

yellow = rods

green = cones