Dark Adaptation Flashcards
(20 cards)
What is dark adaptation?
Dark adaptation refers to how the retina recovers its sensitivity in the dark after exposure to various intensities of light.
This process involves a series of biochemical changes in the photoreceptors.
What factors affect dark adaptation?
- Intensity and duration of pre-adaptation light
- Size and position of the retina
- Wavelength of light
- Rate of rhodopsin regeneration
These factors influence how quickly the retina can adjust to darkness.
What are the three types of vision?
- Photopic vision
- Mesopic vision
- Scotopic vision
These types correspond to different lighting conditions: bright, twilight, and dark respectively.
Define photopic vision.
Photopic vision occurs during brighter conditions.
Define scotopic vision.
Scotopic vision occurs during darker conditions.
Define mesopic vision.
Mesopic vision occurs during twilight conditions.
What is illuminance?
Illuminance refers to the amount of light that is incident on a surface.
What is luminance?
Luminance refers to the amount of light that is emitted or reflected from a surface in a specific direction.
What are the components of a photoreceptor?
- Outer Segment
- Inner Segment
- Cell Body
- Synaptic terminal
- Discs
- Nucleus
- Organelles
Photoreceptors include rods and cones, which play distinct roles in vision.
What is the role of guanylyl cyclase in dark adaptation?
Guanylyl cyclase converts GTP to cGMP, which binds to channels in the outer membrane.
What happens to channels in the dark?
In the dark, positive ions come in and keep the cell depolarized.
What is the sequence of events when a photon is absorbed by rhodopsin?
- Photon absorbed by Rhodopsin
- cis retinal converted to trans retinal + opsin
- Opsin activates transducin
- Transducin activates phosphodiesterase
- Phosphodiesterase hydrolyzes cGMP
- Less cGMP = channels close
- Rod synapses reduce glutamate excretion
This cascade is crucial for phototransduction in the retina.
What are the types of bipolar cells?
- Rod Bipolar Cells
- Flat Bipolar Cells
- Midget Bipolar Cells
- On Centre Bipolar Cells
- Off Centre Bipolar Cells
These cells play a key role in processing visual information from photoreceptors.
What neurotransmitter is released by bipolar cells in the dark?
Glutamate.
Fill in the blank: Dark adaptation involves the recovery of the retina’s sensitivity in the dark after exposure to various _______.
intensities of light.
True or False: Longer wavelengths of light take less time to adapt from during dark adaptation.
False.
What is the relationship between the intensity of light and dark adaptation time?
The brighter the light, the longer it takes to adapt.
What is the significance of the dark adaptation curve?
It shows the threshold sensitivity over time in darkness.
How long does it typically take to reach maximum rod sensitivity during dark adaptation?
30 minutes.
How can one measure dark adaptation?
By assessing the retina’s sensitivity changes after exposure to light.
