Sensory System: Vision Flashcards
The eye is lubricated by the ______ apparatus
lacrimal
blinking spreads the fluid of the eye evenly.
true or false
true
The eyes move in order that the object of interest falls onto the fovea of the ______
Retina
The ____ is where the sensivity is greatest
Reina
The 3 extrinsic muscles of the eye that produce movement are:
- superiror and inferior rectus muscles
- medial and lateral rectus muscles
- superior and inferior oblique muscles
The superior and inferior rectus muscles allow the eyes to move ____ and ____
up and down
Medial and lateral rectus muscles allow looking towards the _____ and the ______
nose and ear
The superior and inferior oblique muscles allow the eyes to look ____ and ____ while also producing some _____ and _____
down and up
torsion and rotation
The nervous system produces 2 types of eye movements:
- saccades
- smooth pursuit
What movements do saccades produce
fast voluntary movements to change the point of visual attention
what movements do smooth pursuit produce?
involuntary eye movements to follow the movement of an object
smooth pursuit muscles are autonomic
True or False
True
Where does the convergence of the eye occur for close objects
the fova centrialis of both eyes
The visible spectrum includes electromagnetic wavelengths from ___nm (violet) to _____mn (red)
400nm to 750nm
A prisim will ____ white light according to the wavelength and reveal that white light is a mixture of all wavelengths of colours.
bend
What is reflection
the ability of light to be reflected on a surface. where the colour of the object indicates the colour reflected by the object
what does colour perception depend on?
on the wavelength of the light entering the eyes
Your visual system perceives a white colour when light of all wavelengths enters the eye. It perceives black when no light wavelengths enter the eye.
true or false
true
A blue colour is perceived at ____nm
420nm
what structures does light pass through to reach the photoreceptors:
the cornea
anterior chamber
pupil
posterior chamber
lens
posterior segment
retina
Light will first strike the _____ cells
ganglion
after the ganglion light will strike
bipolar cells and photoreceptors
The white surface of the eyeball and the inner surface of the eyelids contain a delicate mucous membrane known as the _______
conjunctiva
The eye itself has 3 layers (tunics):
- fibrous
- vascular
- sensory (retina)
The cornea is located in the _____ tunic
fibrous
The cornea can be transplanted without worry of rejection because:
it does not have any blood cells to carry an immune response
The ____ forms the white of the eyeball
the sclera
What is used to anchor the occulomotor muscles?
the sclera
The sclera joins the dura matter at the back which forms the envelope of the _____ nerve
optic
The iris and the ciliary body (anteriorly) and choroid (posteriorly) is found in the ___ tunic
vascular
The iris is composed of smooth muscle in a radial and circular layout for the purpose of ____ and _____ the pupils
dilating and constricting
The _____ is the opening of the iris
pupil
The ____ lets light pass through
pupil
Ciliary body is made of smooth muscles for changing the ____ of the lens
shape
The sensory tunic is commonly called the _____
retina
The retina contains a ______ layer and a _____ layer
pigmented layer and a neural layer
The pigmented layer of the retina covers the _____, ____ _____ and ______ surface if the iris
choroid, ciliary body and posterior
The neural layer does not extend beyond the _____ and forms the ora serrata at the junction with the cilliary body
choroid
The yellow spot on the eye is known as the macula lutea. At the center of the macula lutea is the ____ _____
fovea centrialis
the blood vessels of the optic nerve irrigate the posterior ___/___ of the retina
2/3
The anterior 1/3 of the retina is irrigated by the ______
choroid
There are 2 types of photoreceptors:
- cones
- rods
Describe the function of cones
sensitive to colour and are very present in the fovea centrialis but decreases toward the periphery
Decribe the function of rods
Rods are insensitive to colour, but more sensitive to weak light and are found mostly in the periphery
Photoreceptors synapse onto ______ cells
bipolar
The axon of the ganglion cells for the _____ nerves
optic
The _____ divides the eyeball into a posterior segment and an interior segment
lens
The posterior segment od the eye contains ____ humorous, which is a gelatin substance
vitreous
The anterior segment of the eye contains ____ humor
aqueous
The anterior segment is divided by the _____
iris
How is the aqeous humor formed?
filtration through the capillaries at the ciliary process
How is the aqueous humor evacuated?
the scleral venous sinus (Cana of schlemm)
Blockage of the venous sinus can lead to
intraocular pressure and glaucoma
The ___ controls the amount of light entering the eye
pupil
Constriction of the circular muscles produces _____ ______ and contraction of the radial muscles produces pupillar lialation
pupillary constriction
The pupillary reflex is a fast contraction of the circular smooth muscles of the iris in response to _____ _____
excessive light
Light that is transduced by the retina and activates the retinal _______ cells that relat to pretecal nucleus neurons
ganglion
The pretectal nucleus neurons are sent to the ________-______ nucleus on both the left and right sides
Edinger-Westphal
The dinger-westphal projects via the _____ cranial nerve to relay to the ciliary ganglion neurons that innervate the constrictor muscle of the iris
Third
The process of focusing requires the convergence of light from the same point source which is done by _____ of light through the lens
refraction
An object is formed by only one point source.
True or False
False
An object is formed by many point sources and each of these point sources reflect light in all directions
If an object is coming from a single point source the image will be focued.
True or False
False
an object that is coming from one point source will be blurry
What causes refraction
Speed of light lowing in a medium of higher density
The transition between the air and the cornea accounts for ____% of the refraction while the remainder is due to the lens
80
The eye not only focuses light, but causes the image to be _______ on the retina
inverted
The inverted image reamins inverted along the path to the primary ______ _____
Visual cortex
What does the accommodation reflex do?
Bends the light rays toward the focal point of the retina so that the visual field is in focus when we are looking at an object that is close or far away
Relaxation of the ______ body, which forms a ring around the eyeball, will allow the intraocular pressure to increase tension on suspensory ligaments and stretch the lens to promote far vision
ciliary
Contraction of the ciliary body decreases tension of the suspensory ligaments and allows the lens to bulge from its elastic properties. This permits ______ vision
near
An object that is closer than the punctum promimum cannot be seen clearly because accomodation of the lens is already at _____
maximum
(the bulging of the lens is already at maximum)
An object at the punctum remotum or further does not require accommodations of the lens to be seen clearly because the light entering is ____
parallel
What is Myopia
good near vision but poor far vision
Why does someone with myopia have poor far vision and how is it corrected
the image is formed at the front of the retina. This is corrected by concave lenses
What is hyperopia
the person can see well far, but has poor close vision
How is hyperopia corrected
the image tries to form begin the retina, and therefore, correction requires convex lenses
What causes astigmatisim
unequal curvature of the lens or cornea
How is astigmatisim corrected
bifocals: both concave and convex curvature of the lenses
What is Presbyopia? when does this start
When there is a loss of elasticity in the lens due to age. This starts between the ages of 10-50
What are cataracts
an opacity of the lens in which the clouds block vision. It is corrected through surgery
The visible spectrum is caused by ____ ____ and ___ cones
blue, green and red
blue cones are maximally sensitive to light at ____
420 Nm
Green cones are maximally sensitive to light at ____
530 Nm
Red cones are maximally sensitive to light at
560 Nm
Explain the Red-Green perception Test
Used to detect colour blindness
What is the most common form of colour blindness
red-green
what causes red-green colour blindness
a defective X chromosome for the coding of red or green ( either the cone type is absent or defective)
Visual pigment is made up of two molecules
Retinal and Opsin
Rhodopsin is the visual cycle for rods. Explain it
Light + Rhodospin = Scotospin + all trans retinal, Dark + all-trans retinal + isomers + ATP = 11cis retinal and Dark + 11-cis retinal + Scotospin = Rhodospin
