Tut 2 Completly done !!! Flashcards
The eye exist out of:
- Cornea
- Aqueous Humor
- Lens
- Pupil
- Iris
- Retina
- Fovea
Draw it !
Name the function of cornea :
- Entering of light without interruption (which means Transparent)
- It is transparent because it has no blood vessels which observe light
- serves as protection
- 80 % of focus power
Name the function of aqueous humor :
- fluid which supplies oxygen to cornea and lens and removing waste from cornea and lens.
Name the function of Pupil:
It controls via the pupillary light reflexes how much light reaches the retina trough out expansion or conteraction.
Pupillary light reflexes
Mainly just iris !
- it is just a muscle hole called iris
- it controls the expansion and conteraction
Name the function of retina:
Network of neurons that covers the back of the eye.
- contains photoreceptors (rods and cons) responsible for receiving image from lens and send it to the brain through the optic nerve.
Name the function of Fovea:
Part in the center of retina responsible for producing the highest visual acuity and point of fixation. (cons)
Define Rods which are photorecpetors and contain pigments !
- Rods are in the periphery area
- have high convergence, Low acuity and are high sensitive to light
- slow respone
- Good when it is dark
Define Cons which are photoreceptors which conatin pigments !
- Mainly located in foeva:
- little convergence
High acuity - Low sensitivity to light
- Fast response
- responsible for colour vison
Process of seing: 3 major layers
- Starts at the back of the retina
- Photoreceptor respond to light 1 Layer
- Photoreceptor pass the signal on to bipolar cells 2 Layer
- Which than sends the signal to ganglia cell 3 layer
- which then passes the signal on to the axon of the ganglion cell which then passes the signal to the brain
Describe the direct pathway regarding on center cell:
- photoreceptor gets activated by light
- That leads to hyperpolarization
- which means a decrease of the neurotransmitter glutamate which wil lead to more glutamate on bipolar cell and ganglion cell if these are on center cells !
- If light is off then receptor will produce more glutamate which will lead to less glutamate on bipolar and ganglion cell.
How does the Indirect pathway work ?
- via lateral inhibition and horizonal cells Horizontal cells which inhibit the activity of surronding neurons !
- Now u have the activity of two receptor fields which influence each other. (Lecture example in reality more!)
What is anatagonsim ?
When the activity on a receptor field between on center + and off surrunding crosses each other out. (or visa versa)
Horizontal cells
- 1 intermedate layer
- They make adjustment to the signals form photoreceptors bipolar cells.
- support the activity of neighbouring cells
- they produce gaba
- causes lateral inhibition
What is Presbyopia?
When a person get older they lose the foucisng power gained by the ciliary muscle / iris which becomes weaker so the lens ages.
- Can not focus on close by object
Define transduction:
- light (chemical) is converted into electrical signals (energy) in the rod cells and cone cells.
Descirbe the Dark adaption
- Cones: only need 3-6 minuets to regenrate to light
- Rods cone break by 7 min
- after 7 min rods take over
What is special about our blind spot?
- There are no receptors
- mechansim fill in the missing inofmration which is why we do not recognize our blind spot
Explain the visual pigment bleaching process :
- Retinal seperates from the opsin after being activated from light.
- which leads to colour bleeching
- The activation of the pigment statrts the enzyme cascade
- It is also called isomerization (activation of photopigment)
What does a pigment do and what does it contain ?
- It changes light into electrical energy.
- Contains molecules which is made of by opsin, for determing which wavelength the molecule observes and the retinal which catches light protons.
Definiton of Acuity (regarding cones and rods):
How fine in spatial detail
can you see?
What is sensitivity (regarding cones and rods):
How easily can you see
in very dim light?
What do short wavelengths show for a colour ?
Blue
What do middle wavelength show for a colour ?
Green
What do long wavelength show for a colour ?
Yellow orange and red
What is Myopia ?
Name the 2 differnt types:
Problems to see in a further distance
- Refractive myopia: the cornea and/or the lens bends the light too much
Axial myopia: eyball is to long
What is Hyperopia?
Trouble seeing close by obejcts
- Because eyball is to short
What is the function of the Lens:
- Transparent so light goes directly trough.
Also includes - Accomodation: unconscious tightening or widening of shape in order to adjust eye’s focus by ciliary muscles
- 20% of focusing power
Describe the direct pathway regarding off center cell:
Light is on so less glutamate is produced by receptors.
- which means less glutamate will be produced by bipolar and ganglion cells.
- If light is off everything will be exitotory
What is the enzyme cascade ?
- one visual pigment molecule can cause a chemical effect that is large enough to a activate the entire rod receptor (so thousands of pigments)
How does the visual pigment regenerat ?
In the darkness, retinal re-attaches to the opsin
- Which is why then retina only contains intact pigments at night
What is convergence ?
When a one cell effects a lot of neurons !
- that is why we have high acuity in cones cause they have less convergence
How is a photoreceptor constructed?
- inner and outer segments
- Inner segment just contains the nucleus
- Outer segment Contain disk files with opsin and retinal
What is isomerization?
- the change of the retinal molecule to another molecule when a light comes in.
