VISION Flashcards
(30 cards)
What is Sensation?
How cells detect stimuli in our environment and transduce them for neurotransmitter release
What two things combined result in sensation?
Detection and transduction
What is perception?
Interpretation of external stimuli
What two things create perception?
Experience and sensory interpretation
What is Sensory Transduction (before perception)
Sensory stimuli to receptor potentials
Receptor Potential (Before perception)
Graded changes in membrane potential
Sensory Neuron (Before perception)
Specialized neuron detecting a specific types of sensory stimuli
4 OPSIN PROTEINS
RHODOPSIN (RODS) - Dark
RED CONE OPSIN
GREEN CONE OPSIN
BLUE CONE OPSIN
What are the 4 OPSIN PROTEINS sensitive to?
Light!
from binding to retinal, the molecule absorbing photon energy
What kind of receptors do the 4 OPSIN PROTEINS have? (Excitatory? Inhibitory?)
They all have inhibitory metabotropic receptors
How many of each type of 4 OPSIN PROTEINS do we have. Ex. How many rods? How many cones?
We have two types of photoreceptors: rods (x1) and cones (x3: Red, green, and blue cones). They each have their own opsin proteins for sensory transduction.
What’s the difference between visible light mixing and paint mixing?
Visible light: Red, Blue and Green.
Converges as white
Painting: Blue, Yellow and Pink
Converges as black
What is colourblindness with No functional blue cone opsins? (* – visual acuity is not noticeably reduced since blue cones are not very sensitive to light)
Tritanopia
What is colourblindness where No functional red cone opsins?* (X-linked, more common in males)
Protanopia
What is colourblindness with No functional green cone opsins?* (X-linked, more common in males)
Deuteranopia
What is colourblindness with No functional cones at all?
Achromatopsia
What are the two types of eye movements?
Saccadic:
Rapid, jerky shifts
Pursuit:
Follows moving objects
What do photoreceptors do?
No action potentials
Graded glutamate release at between -40mV and-70mV
Leaky sodium ion channels are open In dark and already depolarized
Release more glutamate in the dark than In the light
What do horizontal cells do?
Regulates adjacent photoreceptor and bipolar cells
What do bipolar cells do?
There are ON Bipolar cells and OFF bipolar cells
No action potential
Graded glutamate release depending on membrane potential
Amacrine cells
Regulate excitability of adjacent bipolar and ganglion cells
What do Ganglion cells do?
Have action potentials and are excited by glutamate
Have on-off receptive fields for light and colour
What are Receptive Fields (these are in ganglion cells)?
Area of the visual space (relative to a fixation point) where light is capable of changing the activity of a neuron.
How does visual information get to the cortex?
Lateral Geniculate Nucleus: a nucleus in the thalamus: man RGCs project here and then LGN neurons project to the visual cortex
• Left visual field goes to the right hemisphere
•Right visual field goes to the left hemisphere
• Each hemisphere gets inputs from both eyes!
• Superior Colliculus: involved in controlling fast reflexive movements in response to light
• Hypothalamus: regulates sleep/wake cycles
