1.6 Vision Sense
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The eyes work like a camera..
It retracts and focuses light rays to form image on retina
Which portion of the eye is the part that retracts & focuses?
Which portion of the eye is the part that transduces the image?
The eye can detect wavelengths from which range?
What occurs when light rays hit a curved surface?
The light rays will bend
Light rays AND convex surface
Light rays hit convex surface and they will bend inwards creating a focal point then spread out creating an upside down image
Light rays AND Concave Surface
- Light rays hit the concave surface and do not create a focal point, instead they end up diverging further more.
- *not useful for human eye
Which surface is useful for human eye?
2 structures that retract light
What type of surface does cornea contain?
Why does the cornea contain low water content? And how does this occur?
If it has a high water content then it would blur the image.
The lower water content is maintained by a sodium pump
Which structure bends the light more?
What type of surface does the lens have?
Does the lens have low water content or high?
Low water content
What are the lens held by?
suspensory ligaments that surround the lens In a circle
What are the suspensory ligaments attached to?
Focusing on something is the active process of ..
Bending the light in a way to properly view it
What occurs when ciliary muscles contract? (3)
-ciliary muscles pull forward
-causes lens to become more globular
What occurs when ciliary muscles relax? (2)
-pulls on suspensory ligaments
- -puts tension on lens causing it lengthen
- *straighten out
What occurs if we are trying to focus on distant objects
-lens are flat
-ciliary muscles are relaxed
- -suspensory ligaments are pulled tightly
- **20 ft
What process occurs when we are trying to focus on nearby object
-ciliary muscles contract
-release tension on ligaments
-lens becomes more spherical
*bending light rays more
As you move towards something,
Pupillary constriction occurs giving us greater depth of focus by light passing through lens center to make it easier to see
When does convergence of pupils occur?
When objects are too close to the nose our eyes rotate medially
Retinal transduction of image
-the inverted image must be translated from photons of light to AP in order for the CNS to understand it
What is the pigmented retina?
- Cells with melanin that reduce light scatter
- *single layer
What are the 2 receptor cells in sensory retina?
Rods and cones
When are rods activated/
When are cones activated?
which are the 2 relay cells in sensory retina?
What are the 2 interneurons in sensory retina?
What are the relay cells going to do?
Will carry AP from rods/cones toward CNS
2 functions of interneurons
-synapse with different rods/cones
-help provide integration in retina itself
With what are rods/cones embedded in?
Where will transduction take place in rods/cones?
What does the rods dendritic end contain?
Unfolding of plasma membrane which forms discs.
What is within the unfolding of plasma membrane that forms discs?
A protein called rhodopsin
What 2 components make up rhodopsin ?
opsin and retinal
What is rhodopsin important in?
Initial step & transduction
How does transduction process begin in rods?
Bleaching, meaning when light hits rhodopsin it splits it into its 2 components (opsin and retinal)
What is rhodopsin near?
In the dark, the rod membrane is normally
When light hits the rod membranes,
NA channels close and hyperpolarization begins resulting in GP
What does the dendritic end of cones contained?
PM folded into membranous discs
What do the membranous discs of cones contain?
What are the 3 different iodopsin?
What are the 2 components that make up iodopsin?
What is the process of initiating transduction in cones called?
What does the fovea centtralis contain/
- Concentration of only cones
- *it is located within macula lutea
What does having cones/rods embedded in pigmented layer do?
Allows for less scatter of light
When we are focusing on something, what are we doing to fovea centrallis?
Placing it directly to it
What is the pathway in which the GP (then AP) has to travel to get realized?
-Rod/cone to Bipolar cells to ganglion cells to optic disc to optic nerve to visual pathway in brain
Which are the only cells to generate APs?
Visual diagram summary
The medial of the Left and right eyes will pick up their own side ( left eye to left visual) but will be processed on the opposite side (left visual field to right visual cortex). The lateral points of eyes will process the middle area but will not cross and be processed on that same side (lateral left eye to center will not cross and be process on left visual cortex ).
Which structure focuses and retracts?
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