Special Sensory (vision) Flashcards
Which part of the eye has the highest number of cones?
- Fovea
- deals with color
Which part of the eye deals with the control of light?
Iris
The iris is divided into what 2 muscles?
- Outer radial muscle
- inner circular muscle
How does the pupil react when bright light and low light hits it?
- bright light=pupil constriction
- low light=pupil dilation
How does bright light affect the iris? Which part of the autonomic nervous system is activated?
- inner circular muscles contract (thickens) = pupil constriction
- activates parasympathetic nervous system
How does low light affect the iris? Which part of the autonomic nervous system is activated?
- outer radial muscles contract = pupil dilation
- activates sympathetic system
What determines the color of someones eye?
-pigments and other components of the iris
Define the accommodation of vision
-lens ability to focus image on the retina
How does distant vision affect how the eye is set to accommodate?
-cilliary muscles relax, suspensory ligaments tighten = lens thin and flat
How does near vision affect how the eye is set to accommodate?
-cilliary muscles contract, suspensory ligaments relax= lens thicken and round
Explain what Presbyopia is and why it is caused?
- the loss of accommodation (near or distant vision)
- lens is not flexible
What is visual acuity?
-vision sharpness
Define emmetropia
-normal eye ball shape
What are the characteristics of Myopia (near sightedness)?
- abnormally curved cornea or eye ball longer than normal
- image falls before retina
- corrected with concave lens
What kind of lens is needed to correct myopia (near sightedness)
-concave
What are the characteristics of Hyperopia (farsightedness)?
- eye ball shorter than normal
- image falls after retina
- correction with convex lens
What type of lens is needed to correct hyperopia (farsightedness)?
-convex lens
What are the characteristics of an Astigmatism?
- asymmetry of the cornea
- corrected with uneven lenses
How can an astigmatism be corrected?
-the use of an uneven lens
What part of the eye is the light sensitive lining that contains photoreceptors?
-retina
What are the types of photoreceptors of the retina? (2)
-rods and cones
What makes up the rods of the retina?
-contain rhodopsin
What is rhodopsin and what is it made of?
- photopigment that detects light
- contains opsin and retinal
What are the cones of the retina made of?
-contains trichromatic rhodopsins (red, green, blue)
Where do the photoreceptors send the light info to?
-bipolar cells
The bipolar cells received light info from what source?
-photoreceptors
Where do bipolar cells send their info?
-ganglion cells
What are ganglion cells?
-axons that form the optic nerve
What is the optic disk?
- the location of neurons of the visual pathway form the optic nerve (cranial nerve II) and exit the eye
Explain the phototransduction of the eye in the dark
- High ICF (cGMP)
- keeps cyclic nucleotide-gated channels open
- Ca+/Na+ influx
- depolarization (dark current)
-Release neurotransmitter onto bilpolar cells
Explain the phototransduction of the eye when light is present
- Light hits rhodopsin -> opsin will dissociate
- Low ICF (cGMP)
- cyclic nucleotide-gated channels close
- K+ efflux continues
- hyperpolariztion
-Stop/decrease neurotransmitter release onto bipolar cells
What is the step by step process of the phototransduction pathway?
1) photoreceptor neurotransmitter excites or inhibits bipolar cells
2) bipolar cells excite or inhibit ganglion cells
3) excited ganglion cells generate action potential
4) action potential travels along optic nerves
After the phototransduction pathway, what is the pathway of the signal that is being transducted?
5) optic chiasm
6) optic tract
7) lateral geniculate nuclei (thalamus)
8) optic radiation
9) visual cortex
