Chapter 5 pt.2 Flashcards
What happens to Light after it hits the Retina
It passes through 5 layers of cells to get to the photosensitive cells/photoreceptors, where it it converted to chemical energy
what are the two types of photosensitive cells and what do they do
Rods- most responsive to low levels of light (animals have a lot which is why they cans see in the dark)
Cones - most responsive to bright lights and communicating information about colour
both covert the energy into a chemical message
What happens after the chemical reaction/change caused by the photosensitive cells
They send the message to the adjacent neuron, then sent to the brain
How many photosensitive cells does the retina contain
126 million
When is it easier to see in the dark
when the light is on the side of the fovea (cluster of cones)
What is visual acuity
when cones transmit information about fine detail
What is dark adaptation
when rods and cones adapt to changes in light
Whats the first stage of dark adaptation
the cones rapidly respond to the change of light and after 8 minutes they aren’t sensitive to it anymore
what’s the second stage of dark adaptation
the rods increase their sensitivity for an additional 20 mins
Why do we first see vision upside-down
we see up side down but the lens inverts it
What are Bipolar Cells
They add together the firing of the photoreceptive cells and send different kinds of messages to the Ganglion cell
What are Diffuse Bipolar Cells
They receive signals from the rods (about 50 rods) and send it to the large ganglion cells
What are midget bipolar cells
receive signals from a single cone and send it to a single/small ganglion cell
What are characteristics about Small Ganglion Cells (Parvo cells)
- receive information from the midget bipolar cells
- make up 70percent go Ganglion cells
- send signals to the brain about colour and detail
What are characteristics about Lange Ganglion cells (mango cells)
- found in the periphery
- receive signals from diffuse bipolar cells
- send information about motion in the periphery
What happens when small point of light falls in the centre of the eye
the centre cell increase their firing rate and the centre-off cells (on the edge) decrease their rate of firing
what happens when a small portion of light hits the peripheral
the centre will decrease its firing rate and the center off cells will increase its firing rate
What happens when the entire receptive field is illuminated
both cells fire off at the same rate
What happens when the message finally leaves the eye
it enters the brain through the optic nerve which is made up of axons from the P and M cells
Why do we have a blindspot in our vision
because there is a gap/spot in the retina with no photoreceptor axons (the ganglion)
What is the Optic Chasim
An “X” shaped structure where the optic nerves from each eye cross before the message is sent to the thalamus
How does the information from both eyes travel
information from the right side of both eyes are sent to the left hemisphere and information from the left side of both eyes are sent to the right hemisphere
What is the lateral geniculate nucleus
The 6 layered portion of the thalamus that processes and organizes visual information
-each layer deals with specific types of information
What is the Visual Striate Cortex
its located in the optical lobe and is where features of the visual lobe are identified
