- _____________ 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

Lecture 24 Flashcards by Priscilla Gallardo

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

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Three functions of tears:
- ________ and ________ the eye surface
- deliver ___________ and _________ to the conjunctiva
- _______ from infection

cleanse; lubricate
oxygen; nutrients
protect

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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

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Three layers or tunics of the eyeball
1.
2.
3.

Fibrous tunic
Vascular tunic
Neural tunic

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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

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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

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Neural tunic:
1. _________: it lines the back of the eye (inner-most layer)

retina

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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

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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

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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

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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)

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_______: 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

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Muscles of the iris
- __________ receives sympathetic input
- __________ receives parasympathetic input

dilator pupillae
sphincter pupillae

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_____________ 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

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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

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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

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__________ refers to the specific point on the retina where light rays converge after being refracted by the cornea and lens

focal point

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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

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The __________ muscles controls the lens shape

ciliary

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Structures that form the ciliary body:
1.
2.
3.

ciliary muscles
ciliary process
ciliary ligaments or zonules

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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.

1. pupil constriction 2. Lens thickening (accommodation) 3. 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.

1. photoreceptors (cones and rods) 2. bipolar cells 3. ganglion cells 4. horizontal cells 5. 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 ______

1. short; blue 2. medium; green 3. 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)

1. Superior colliculi 2. Suprachiasmatic nucleus