Lecture 24 Flashcards
The path through which tears travel….
1.
2.
3.
4.
5.
6.
7.
8.
- lacrimal gland
- ducts
- lacrimal punctum
- lacrimal canaliculus
- lacrimal sac
- nasolacrimal duct
- inferior meatus of nasal cavity
- nostril
Three functions of tears:
- ________ and ________ the eye surface
- deliver ___________ and _________ to the conjunctiva
- _______ from infection
- cleanse; lubricate
- oxygen; nutrients
- protect
The lacrimal apparatus is connected to the nostril which means an abundance of tears from crying or watery eyes can result in a ______________
runny nose
Three layers or tunics of the eyeball
1.
2.
3.
- Fibrous tunic
- Vascular tunic
- Neural tunic
Fibrous tunic:
1. _________: protects the eye and give its shape (white part of the eye) and covered majority of outer surface area
2. _________: located at the front of the eye and covers the central portion
- sclera
- cornea
Vascular tunic:
1. __________
2. __________: muscular ring around lens and secretes aqueous humor
3. _________: high density of blood vessels and provides nutrients & removes waste
- Iris
- Ciliary body
- Choroid
Neural tunic:
1. _________: it lines the back of the eye (inner-most layer)
- retina
Cornea:
- it is a ____________________ membrane that protects the eye
- It allows ______ to enter the eye
- it contains ______ cells which allows for regeneration after injury
- transparent
- light
- stem
refraction: _____________________________
- As light passes through the eye, the ________ (mostly) and _____ bend and focus it on the retina
- These structures make refraction possible because they are _______ structures: cause parallel rays of light to converge (come together)–> essential for focusing light onto the retina
- Result of image on retina: Image (2D) is _____________ (upside down) and _____________
bending of light rays
- cornea; lens
- convex
- inverted; reversed
- Light rays striking the very center of the cornea pass _________ ________
- Light rays striking off center are _____ toward the center (because of the curvature of the cornea)
- straight through
- bent
The ______ is located between the cornea and lens.
- the colored part of the eye because it contains cells with ________ (black, brown, or hazel color)
- Function: adjustable diaphragm that controls pupil __________ (______), thus the amount of light entering- it enlarges and shrinks, depending on how much light is entering the eye
iris; melanin; diameter (size)
_______: aperture through which light enters the eye
Two iris muscles that control pupil diameter:
1. _________:
2. _________: closet to pupil
pupil
1. dilator pupillae
2. sphincter pupillae
Muscles of the iris
- __________ receives sympathetic input
- __________ receives parasympathetic input
- dilator pupillae
- sphincter pupillae
- _____________ stimulation of the dilator pupillae causes the muscle to contract (pupil dilates) which occurs in ______ light
- _____________ stimulation of the sphincter pupillae causes the muscle to contract (pupil constricts) which occurs in ________ light
- sympathetic; dim
- parasympathetic; bright
Response that the pupil has for close-up vision:
- stimulation of _____________ fibers in sphincter pupillae= pupil _________
- this ____________ depth of focus and ____________ spherical aberration
- parasympathetic; constriction
- increases; decreases
Spherical aberration: occurs when light rays passing through the __________ of the cornea and lens come to a focus at a slightly different location than light rays passing through the center of the cornea and lens. This results in ___________ image quality
periphery; decreased
__________ refers to the specific point on the retina where light rays converge after being refracted by the cornea and lens
focal point
The lens: clear, biconvex, and flexible structure suspended within the eye by the__________ ligaments (________)
Function:
- _________ and ________ its width (called ____________) in order to focus light rays
suspensory; zonules
- shorten; widen; accommodation
The __________ muscles controls the lens shape
ciliary
Structures that form the ciliary body:
1.
2.
3.
- ciliary muscles
- ciliary process
- ciliary ligaments or zonules
Aqueous humor:
- transparent fluid produced by the _____________ and it flows out through the _________ ___________ in the drainage angle
Function
- to supply _________ to the avascular structures of the eye, cornea, and lens
- to maintain ___________ ________ within its physiological range
Location
- found in the __________ __________ of the eye which is between the cornea and lens
- ciliary body (specifically ciliary process); trabecular meshwork
- nutrients
- intraocular pressure
- anterior chamber
____________: change in the curvature of the lens which allows for the eye to focus on objects at different distances
accommodation
Close-up vision= ___________
- there is ____________ stimulation of the ciliary muscles which causes the muscles to contract and ____________ of the zonules leading to the _________ (rounding) of the lens
accommodated
- parasympathetic; relaxation; bulging
At rest vision= ______________
- relaxation of the ciliary muscles causes the ____________ of zonules which leads to the lens _____________
non-accommodated
- tightening; flattening
_____________: means normal eye that sees distant objects clearly without using accommodation
emmetropia
- Eye convergence is produced by the contraction of both ____________ muscles
- If the eyes cannot converge accurately= __________
- medial rectus
- double vision (diplopia)
Three processes involved in the adjustment to close-range vision:
1.
2.
3.
- pupil constriction
- Lens thickening (accommodation)
- Inward rotation of the eyes (convergence)
___________ _______ fills the globe of the eyeball
Function:
- it maintains the ______ of the eye
- it helps with vision clarity (it is _____ “glassy” so that light can pass through it)
Located:
- ___________ part of the eyeball between the lens and retina
vitreous humor
- shape; clear
- posterior
___________: region in the retina where the optic nerve leaves the eye
- it is considered a “blind spot” because it does not contain any ____________: leaving a blind spot in the visual field
optic disk
- photoreceptors
The Retina:
- the back surface of the eye
- it receives the image that the cornea focuses through the lens and transforms this image into _________ ________ that are carried by the _______ ______ to the brain
- electrical impulses; optic nerve
____________ (yellow spot): a small area about 1mm in diameter from which we get our ____________ vision. This is because of the high concentration of _______ cells. These cells are responsible for color, vision, sharp acuity and central vision.
Macula; sharpest; cone
Six cell types found in the neural layer of the retina
1.
2.
3.
4.
5.
- photoreceptors (cones and rods)
- bipolar cells
- ganglion cells
- horizontal cells
- amacrine cells
Sequence of light path in neural layer:
______–> _________–>_______
—-> ____________
photoreceptors–> bipolar cells–> ganglion cells–> optic nerve
Horizontal and amacrine cells are ___________ that modify the ______ of electrical firing in __________ cells
- they are NOT apart of the light pathway!
interneurons; rate; bipolar
_________ cells give rise to the axons that from cranial nerve II (OPTIC NERVE)
ganglion
____________ capture light (energy) and converts it into electrical signals (this is called _______________)
photoreceptors (rods and cones); phototransduction
Photoreceptors
- __________: responsible for scotopic (night) vision
- __________: responsible for photopic (day) vision & trichromatic (color) vision
- rods
- cones
Which segment of the rods is specialized to absorb light?
outer segment
The outer segment in rods is made up of approx. 1,000 ___________ _______ inside which all contain visual _____________
membranous discs; pigments
Rhodopsin is a light sensitive protein (visual pigment) found in the disc membrane of the ______ cells. Its main components include a protein called _________ and a light-absorbing molecule called ________
rod; opsin; retinal
- Visual pigments for
rods= _____________
cones= ___________ - Two conformations of retinal moiety = __________
- rhodopsin; photopsin
- cis & trans
Three types of cones
- they are defined by the wavelength of light to which they are most ___________
1. ________- wavelength: detects ______
2. ________- wavelength: detects ______
3. ________- wavelength:
detects ______
- short; blue
- medium; green
- long; red
The trichromatic theory of color vision says that human eyes only perceive THREE colors of light: ______, _______, _______. The wavelengths of these three colors can be combined to create every ________ on the visible light spectrum
red, blue, green; color
Phototransduction in the rods:
- Receptor= ___________
- G protein= __________
- Enzyme= __________
- Secondary messenger= ___________
- rhodopsin
- transducin
- phosphodiesterase
- cGMP
Phototransduction in the rods: The Dark Phase
- form of retinal bound to rhodopsin= ___________
- transducin is ____________
- phosphodiesterase (PDE) is _____________
- _____________ triggers the opening of Na+ channels–> leads to an influx of Na+
- this _____________ the mb potential of the ___________ segment which triggers ___________ release to __________ cells
- 11-cis
- INACTIVE
- INACTIVE
- cGMP
- depolarizes; inner;glutamate; bipolar
Upon light absorption, what happens to 11-cis retinal in rods?
it is converted to all-trans retinal & dissociated from rhodopsin
_____________: refers to the temporary loss of sensitivity to light in rods, where trans retinal needs to be regenerated to 11-cis retinal
bleaching
- ________ _____________ activates transducin and phosphodiesterase (PDE)
- PDE degrades ___________ which leads to the closure of Na+ channels
- this causes ______________ meaning that there is _____ release of glutamate
- light absorption
- cGMP
- hyperpolarization; NO
- The optic nerve starts in the retina ____________ cells (their axons) and finishes in the _________ __________
- The optic tract starts in the _________ _________ and finishes in the _____________
- ganglion; optic chiasm
- optic chiasm; thalamus
______________: point where the optic nerve in both eyes partially (1/2 fibers) cross in the brain, allowing each hemisphere to receive visual information from both the left and right visual field
optic chiasm
- The thalamic nucleus that receives visual information and relays it to the visual cortex is the _________________
- the visual cortex is located in the ______________ lobe
- lateral geniculate nucleus
- occipital
Two other brain regions that receive visual information
1. ____________: in midbrain related to visual reflexes
2. _____________: in hypothalamus (master circadian clock)
- Superior colliculi
- Suprachiasmatic nucleus
