The Nervous System: VISION Flashcards
what is VISION?
VISION:
uses of VISIBLE LIGHT (part of the ELECTROMAGNETIC SPECTRUM)
- has wavelengths between 400-700 nm
(range from violet —red)
define WAVELENGTHS
distance between TWO CONSECUTIVE PEAKS of an electromagnetic wave
what are the eye’s ACCESSORY STRUCTURES?
ACCESSORY STRUCTURES:
- eyelids
- eyelashes
- eyebrows
- lacrimal glands
- extrinsic eye muscles
describe accessory structure; EYELASHES
- helps with the PREVENTION of foreign matter from entering the eye
- root of eyelash hair; has important NERVE ROOT PLEXUSES + reflex of blinking
- has SEBACEOUS GLANDS
describe accessory structure; LACRIMAL GLANDS
FUNCTION:
- production of tears
- reduces friction + removes DEBRIS + prevention of BACTERIAL INFECTION
- has specific ANTIBODIES
ANATOMY:
- specific TEAR DUCTS; has continuous tears being produced
- draining system between LACRIMAL PUNCTA
(drainage through LACRIMAL CANALICULI, LACRIMAL SAC, then lastly the NASOLACRIMAL DUCT)
describe accessory structure; EYEBROWS
- continuous with the skin (integumentary sys.)
function of PALPEBRAL MUSCLES
helps control eyelid movement and extrinsic eye muscles
EXTRINSIC EYE MUSCLES
- responsible for moving the eyeball itself in all directions
CONJUNCTIVA, what are its layers?
DESCRIPTION;
a thin, protective mucous membrane
- formed from stratified squamous tissue
- shaped like a culdesac; FORNIX
- has several layers;
1. PALPEBRAL CONJUNCTIVA
2. OCULAR CONJUNCTIVA/BULBAR CONJUNCTIVA
(does not cover cornea area–transparent)
FUNCTION;
helps line the eyelids and covers the sclera
TARSAL PLATE
DESCRIPTION;
- fold of connective tissue
- has row of SEBACEOUS GLANDS (TARSAL GLANDS/MEIBOMIAN GLANDS)
FUNCTION:
- helps prevent eyelids from sticking together
what are our EXTRINSIC/EXTRAOCULAR MUSCLES?
we have SIX EXTRINSIC EYE MUSCLES:
- SUPERIOR RECTUS
- controlled by CN III
- pulled eye up - INFERIOR RECTUS
- controlled by CN III
- pulls eye down - LATERAL RECTUS
- controlled by CN VI
- pulls eye laterally/abducts - MEDIAL RECTUS
- controlled by CN III
- pulls eye medially/adducts - SUPERIOR OBLIQUE
- controlled by CN IV
- depresses & abducts the eye - INFERIOR OBLIQUE
- controlled by CN III
- elevates & abducts the eye
what are our eye TUNICS?
we have TWO TUNICS (COATS):
- FIBROUS TUNIC
- seen in cornea & sclera - VASCULAR TUNIC
- seen in choroid, ciliary body, & iris
- contains the intrinsic muscles - **RETINA (NEURAL TUNIC)
describe SCLERA
DESCRIPTION:
- the “white” of our eyes
- made up of dense irregular connective tissue
- penetrated by blood vessels
- consists of the fibrous tunic
FUNCTION:
provides shape and protects inner parts
describe CORNEA
DESCRIPTION:
the transparent area of the FIBROUS TUNIC
- receives nutrients and oxygen from the chamber from being (the aqueous humor)
- nourished by oxygen and tears
FUNCTION:
- admits and refracts light
describe IRIS
- functions to help constrict and dilate the pupil through AUTONOMIC REFLEXES
- the “colored” part of the eye
PUPIL CONSTRICTION
- reaction to bright light
PUPIL DILATION
- reaction to dim light
describe CILIARY BODY
- attaches to the iris and stringlike projections to the lens
- aids in ACCOMMODATION;
the eye’s ability to reshape the lens to aid in controlling/viewing objects at various distances
describe the CHOROID
- an extensive network of capillaries
(supplies nutrients to the retina) - contains an abundance of blood vessels
describe the RETINA (aka NEUTRAL TUNIC)
DESCRIPTION:
has a pigmented layer
- attached to the choroid
- the lining of the post. 3-quarters of the inner layer of the eyeball
- can see the optic (II) nerve + OPTIC DISC/BLIND SPOT
FUNCTIONS:
- serves as a “dark room” (pigmented blac)
this allows light to be absorbed specifically by photoreceptors)
- light absorbed through the neural layer (NEURAL SIGNALS) + PHOTORECEPTORS (rods + cones)
- specific image is ACTUALLY INVERTED :O due to refraction
describe the MACULA LUTEA
- the CENTER of the retina
- absorbs UV light
describe the FOVEA CENTRALIS
- the CENTER of the MACULA LUTEA
- area of the HIGHEST VISUAL ACUITY
describe the PHOTORECEPTORS within our eye :)
DESCRIPTION:
- found within the retina, specific sensors
- known as RODS + CONES
RODS:
- aid to see the DIM light
- contains only photopigment RHODOPSIN
CONES:
- production of COLOR VISION
- contains three different photopigments; RED, GREEN, BLUE
PHOTOPIGMENTS:
- helps ABSORB LIGHT and produces RECEPTOR POTENTIALS
- response through CYCLICAL PROCESS
- this converts the light energy into NEURAL IMPULSES
what is the PHOTORECEPTOR SENSORY FLOW?
- Outer synaptic layer
- Bipolar cells
- Innter synaptic layer
- Ganglion cells
- Optic (II) Nerve
describe the EYE DIVISIONS
ANTERIOR CHAMBER
- between the iris & cornea
- filled with AQUEOUS HUMOR
POSTERIOR CHAMBER
- behind the iris and front of the lens
- filled with AQUEOUS HUMOR
VITREOUS CHAMBER/POSTERIOR CAVITY
- behind the posterior chamber
- filled with VITREOUS HUMOR (more gelatinous in texture)
describe REFRACTION
where light can bend when passing through various transparent substances with varying densities
describe the LENS
FUNCTION:
use of accommodating to properly focus on specific object
- able to accommodate during short or long distances
describe the CENTRAL FOVEA
area of where the image is projected onto; sharpest/highest visual acuity
describe the typical EYE CONDITIONS:
EMMETROPIC EYE:
- our “normal” eye
- refraction of light is correct
- clear image on retina
MYOPIA (NEARSIGHTEDNESS):
- eyeball is “longer”
- image is CONVERGING in FRONT of the retina
- CONCAVE LENS used to correct
HYPEROPIA (FARSIGHTEDNESS)/HYPERMETROPIA:
- eyeball is shorter
- image is CONVERGING BEHIND the retina
- CONVEX LENS used to correct
ASTIGMATISM:
- a condition where CORNEA/LENS has IRREGULAR CURVES
- causes blurred or distorted vision
describe VISION ADAPTATION (and LIGHT + DARK ADAPTATION)
VISION ADAPTATION:
- rates of BLEACHING + REGENERATION of photopigments within rods and cones
LIGHT ADAPTATION:
- decreases the release of inhibitory neurotransmitter GLUTAMATE
(from dark to light –takes SECONDS)
DARK ADAPTATION:
- RELEASES the inhibitory neurotransmitter GLUTAMATE
(from light to dark–takes MINUTES)
- stops transmission signals from BIPOLAR CELLS to GANGLION CELLS (stops signal from retina to brain)
describe the NEURAL PATHWAY
PATHWAY:
- beginning of where RODS + CONES start CONVERSION of light energy into neural signals
- Optic (II) Nerve
- Optic chiasm
- Optic Tract
- Lateral geniculate nucleus of thalamus
- Optic radiation
- allows info to be received in primary visual areas
- Primary visual area of the cerebral cortex (area 17) in the occipital lobe
describe our VISUAL FIELDS + BINOCULAR VISION
BINOCULAR VISION:
- The anterior location of our eyes leads to our visual fields to OVERLAP
VISUAL FIELDS:
- NASAL (MEDIAL)
- TEMPORAL (LATERAL)
these fields work similarly in OPPOSITES
*visual info from RIGHT of each field – LEFT SIDE of brain
*vice versa
describe the EYE DEVELOPMENT
- typically begin to develop around 22 DAYS after fertilization
- ECODERM of the FOREBRAIN [PROSENCEPHALON]:
- formation of the optic grooves (which will eventually become the optic vesicles)
- OPTIC VESICLES:
- thicken into the lens placodes
- also form distally into optic cups
- continue being attached to the prosencephalon through the optic stalks
describe clinical condition; PRESBYOPIA
difficulty focusing on close objects due to loss of elasticity in lens
describe clinical condition; PINK EYE
inflammation of the conjunctiva from infection or allergies
**bacterial infection specifically for pink eye
describe clinical condition; CHAAZION vs. STYE
CHALAZION
- build of secreted sebum from tarsal glands (inflamed)
STYE
- pimple on the eye
describe clinical condition; CORNEAL TRANSPLANT
where the cornea is surgically removed from a donor
