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The primary visual pathway:
Optic nerves meet at the _____ ______ forming the ____ _____. Most axons go to the ________ ________ ________, which then sends its axons to the visual cortex.
- Optic Chiasm
- Optic Tract
- Lateral Geniculate Nucleus
The pathways for the visual system starts with light. Light enters the Retina and is exposed to _____ & ______ then _______ cells, then ______ cells, the signal is then carried by the optic tract, courses through the ______ ______ ______ in the thalamus, and continues on in the _______ _______ to the visual cortex and visual association cortex.
- Cones & Rods
- Lateral Geniculate Nucleus
- Visual Pathway
What transduces light energy to electrical energy (action potentials)?
Light enters the eye via the _____, and then lens focuses light to the ____ of the eye. Light coming in from the right hits the _____ half of the retina. Light coming in from the left hits the _____ half of the retina. Light from the top hits the _______. Light from the bottom hits the _____.
What does the fovea specialize in?
Detailed, acute vision
There are three main cell layers in the retina, ____ ____ ____, through which light must pass to reach the ________. The ______ cells axons band together to form the optic nerve. The _____ _____ is the only area without photoreceptors.
- Blind Spot
What are the two types of photoreceptors?
What are these stimulated by?
- Rods: stimulated by faint and periphery light that is seen in black and white.
- Cones: Stimulated by bright light. More light is needed to activate the cones. Red, Green, or blue is received by the cones, and then the optic nerve mixes these stimuli together to get complex colors. The fovea aid in this.
The receptors for light are actually _______ _____ that do not have ______ or _______. The neuron consists of (5):
- Modified Neurons
- Inner segment: Synaptic endings, Nuclei, Mitochondria
- Outer segment: place of phototransduction (photons interact here to create an electrical signal)
Rods and cones contain ______ _______ which, when struck by light, will release chemicals. ___________ occurs when light reaches the photo receptors. This causes the _____ channels to close and _____________ occurs, which decreases neurotransmitter release. The NT release here _____ the bipolar cell. Since the bipolar cell is not inhibited, it releases excitatory NT into the ________ cell which forms the information pathway for the _____ ______.
- Photo pigments
- Optic Nerve
What is Color Vision Deficiency?
Lacking of one or more of the different types of cones. It is the inability to perceive some colors.
Visual fields: _____ portions decussate and _______ portions remain _______ at the optic chasm.
*Make sure to understand the visual of the visual field!!!
What are the Visual Pathways in the cortex?
Lateral Geniculate Nucleus: Primary visual cortex: Secondary visual cortex
- Ventral stream: identifying and recognizing objects, "what" pathway, connects to temporal lobe
- Dorsal stream: finding objects and determining how to move toward and grasp them, "where/how" pathway, connects to parietal lobe.
What is seen when the ventral stream is damaged?
Visual agnosia, difficulty identifying objects visually, but they are able to copy images without problems (visual acuity is fine)
What happens when the inferior part of the temporal lobe is damaged?
Prosopagnosia. Difficulty identifying/discriminating faces. These individuals can determine facial features though.
Damage to the Dorsal Stream may result in:
Difficulty in moving towards an object they can see (have no problem moving towards an object they can hear though)
What occurs if the parietal cortex is damaged?
inability to convert vision into action (can walk towards something they hear, but not see)