Anatomy of the Eye
What is the band of contractile tissue that determines the size of the pupil?
Iris
Are there more rods or cones in the retina?
Rods
it is inactive and rod is slightly depolarized; Na+ channels partially open; influx of glutamate
the surface of the visual cortex is a map of the ___
retina
what does the spectral sensitivity curve depict
differential sensitivity to wavelengths
What is the process of translating sensory signals into electrical signals called?
sensory transduction
What does the duplexity theory state?
rods and cones mediate different kinds of vision
Rods transmit signals through ___.
inhibition of excitatory NT, glutamate
Which layers are the magnocellular layers?
The two inner layers
what two kinds of vision does the spectral sensitivity curve depict?
scotopic and photopic vision
What is the process of the lens focusing light on the retina called?
What does photopic vision involve?
Light vision
High acuity
Low sensitivity with few receptors
Low convergence
Fovea
cones
What happens to a rod in the light?
gets bleached; Na+ channels close; reduction of glutamate; rod is hyperpolarized
Which layers are the parvocellular layers?
The four outer layers
Damage to the Primary Visual Cortex results in...
Scotomas (fixed through process of completion)
What are the muscles that are in charge of adjusting shape of the lens? Which muscle does what?
Ciliary muscles give lens cylindrical shape
Ligaments pull lens to flatten it
What does scotopic vision involve?
Dark vision
Low acuity
High convergence
High sensitivity with many receptors
Peripheral vision
Rods
What is the nucleus of the thalamus involved in the visual system?
Lateral geniculate Nucleus
Layers 1, 4, and 6 receive input from ___ cells of the ___ eye.
retinal ganglion cells of the contralateral eye.
What are the Primary and Secondary Visual cortices located?
primary - striate cx of the occipital lobe
secondary - prestriate cx of the occipital lobe
Why do we have a blind spot?
The optic disk at the back of the eye doesn't have an photoreceptors, therefore creates the blind spot.
What is convergence?
when we combine different visual signals from each eye to create one complete visual field.
Explain the process of sensory transduction from organ to association cortex.
organ (eye) --> receptors (cones/rods) --> thalamus (lateral geniculate nuclei) --> primary sensory cx (striate cx) --> secondary sensory cx (prestriate cx) -->association cx (dorsal stream - posterior parietal / ventral stream - inferotemporal)
Layers 2, 3, and 5 receive input from ___ eye.
ipsilateral eye.
What are the dorsal and ventral streams of the association cortex in the visual system responsible for?
dorsal - where (behavior control)
ventral - what (consious perception)