Vision. Rods and Cones of the Retina. Flashcards
What part of the rods and cones of the retina absorbs incoming light?
The photopigmented areas.
What kind of receptors are found in the photopigmented areas of the rods and cones of the retina?
G protein coupled receptors.
What are the rods and cones both made up of?
An opsin and a retinal derivative of vitamin A.
What opsin is found in the rods of the retina?
Rhodopsin.
What opsin is found in the cones of the retina?
Photopsins.
How many types of photopsin are found in the cones of the retina?
3 types each of which can each pick up their own light frequency.
What happens to the rods and cones when light is absorbed?
They undergo a conformational change.
What is the conformation of the rods and cones while the eye is in the dark?
The cis-retinal derivative of vitamin A fits into the opsin binding site and no information travels to the brain.
What position is the cis-retinal derivative of the rods and cones in if the eye is in the dark?
It is inside the opsin binding site.
What position is the cis-retinal derivative of the rods and cones in if no information can travel to the brain?
It is inside the opsin binding site.
What is the conformation of the rods and cones while the eye is stimulated by light?
The cis retinal becomes a trans-retinal derivative and detaches from the opsin.
What happens when the retinal derivative detaches from the opsin?
There is enzyme activation and information can travel to the brain.
What happens to the retinal derivative once it has undergone its conformational change to the trans form?
An enzyme converts the derivative back to the cis form allowing it to absorb more light.
Will the retinal derivatives of cones or rods regenerate quicker?
Cones regenerate much faster than rods.
What enzyme converts the active trans form of the retinal derivative to the inactive cis form?
Retinal isomerase.
Is the cis form or the trans form of the retinal derivative the active form?
The trans form is the active form.
How long does it take the photopsins of cones to regenerate?
Around 90 seconds for 50% tio regenerate.
How long does it take the rhodopsins of rods to regenerate?
50% in 5 minutes.
100% in 30-40 minutes.
What activates the enzymes that change the membrane potential in photoreceptors?
The structural change that follows light absorption in the opsin?
What happens once the enzymes of the retina are activated following light absorption in the rods and cones?
Graded potentials and depolarisation which then allows information to travel to the brain.
What enables animals to see different colours?
Different areas of opsins are programmed to see different wavelengths/colours of light.
What colours are rhodopsins best at picking up?
Blues and greens.
Is it the cones or rods that enable colour vision?
The cones.
How many different opsins are found in the rods?
1.
How many different opsins are found in the cones?
3.
What are the 3 different opsins in the cones?
Type 1. Blue light.
Type 2. Green light.
Type 3. Red light.
What kind of vision do primates have?
Trichromatic vision as they have 3 different opsins in their cones.
Most mammals have what kind of vision?
Bichromatic vision as they only have 2 different opsins in their cones.
Birds have how many kinds opsins?
4 different opsins in their cones.
What animals are capable of seeing UV light?
Birds.
What colour can cattle not see?
Red.
What colours can horses not see?
Blue.
Are rods or cones stimulated by wide wavelengths of light?
Rods.
What part of the retina allows us to differentiate between colours?
The cones.
Do rods or cones contain more photopigment?
Rods contain more photopigment than cones.
How does the amount of photopigment in rods make them differ from cones?
They are much more sensitive to light and can be stimulated by a single photon.
Do we tend to use rods or cones for night vision?
We use rods as they are much more sensitive to light.
What is the regeneration time (trans retina to cis retina) of rods?
It is very slow meaning it takes a long time before the rod can be used again.
What happens to rods when they are exposed to bright light?
All rods are stimulated and then go into regeneration.
What part of the retina gives us day vision?
Cones.
Do cones have a quicker regeneration time than rods?
Yes.
What initiates the pupillary light reflex?
Changes in light intensity as the main function of the pupil is to control the amount of light that shines on the retina.
What name is given to the constriction of the pupil when there is too much light coming in?
Miosis.
What name is given to the dilation of the pupil when there not enough light coming in?
Mydriasis.
What cranial nerves carry out miosis (pupil constriction)?
Cranial nerves 2 and 3.
What cranial nerves carry out mydrasis (pupil dilation)?
Cranial nerves 2 and 5.
What nervous system controls miosis and mydrasis?
Miosis is parasymapthetic.
Mydriasis is sympathetic.
What is the function of the tapetum lucidum?
It intensifies light sensitivity and is useful for animals that are active at night.
