Unit 7: Visual System Flashcards
Visual System
Detects light converts it into APs and sends them to the primary visual area for processing.
The visual system consists of….
The eyes (contains photoreceptores that convert the light into action potentials)
the visual pathways which transmits the action potential
primary visual area in the occipital lobe of the brain (which process incoming sugnals)
After passing through the ______ the amount of light is regulated by the _____ which can constrict w/ bright light or dilate in lowlight.
Cornea
Iris.
____ flips the light upside down and backwards and focuses it onto the ___ at the back of the eye.
Lens
Retina
The Retina Contains photoreceptors called ____ and _____.
rods and cones.
the cones and rods point towards the back of the head.
The center of your vision is focused onto a part of the retina called the _______.
Fovea
Fovea
highest concentration of cone cells.
Rod Cells
extremeley sensitive to light.
function best under low light conditions.
contain one type of photopigment
do not detect colour.
located in the region of the retina outside and around the fovea.
Cones
Function best under bright light
ideal for detecting detail
three types of cone cells:
each contain a different photoreceptor.
located in the region of the fovea
found in large concentrations.
Rods and cones do not have….?
Axons.
Neither generate APs.
Rods and cones generate ______ ______ that cause the release of an _______ ______ from their _______ ______.
Receptor Potentials
Inhibitory Neurotransmitters.
synaptic ending.
Other cells of the retina (5)
The retina contains a pigment layer at the very back of the eye that absorbs excess light.
Bipolar
Ganglion
Horizontal
Amacrine
responsible for the integration of information from teh rods + cones and the production of APs.
Transduction of Light into APs
Visual system works backwards:
- light striking the retina has been flipped upside down + backwards due to the lens
- when depolarized the rod + cone cells releaese inhibtory neurotransmitter shutting off the bipolar cell.
- when light strikes the retina it hyperpolarizes the rod and cone cells shutting them off.
- Bipolar cells are switched on (no more inhibtory neurotransmitter)
- bipolar cells spontaneously depolarize (by themselves).
- this depolarization leads to an AP in the ganglion cell.
How is light transformed into action potentials
- In the dark Na+ are flowing into the photoreceptors producing a depolarization
- release of inhibitory neurotransmitter
- when light trikes the rod/cine cells it closes the Na+ channels
- less Na+ coming in and K+ leaking out hyperpolarizes the cell.
-rods/cones are hyperpolarized no inhibitory neurotransmitter is released and the bipolar cell depolarizes.
Types of eye movements.
-Allow us to focus on objects.
