Human Eye Flashcards
what does the sensory input of the eye involve?
- light detecting cells
- conduction of signals from the sensory receptors to the integration centre
what are the light detecting cells found in the retina?
rods and cones
what is integration?
- process where information from the environmental stimulation of the sensory receptors is interpreted
- associated with appropriate responses of the body
- carried out in the central nervous system CNS
what is motor output?
- the conduction of signals from the central nervous system
- conduction of signals to the effectors
- carry out the body’s responses to the stimulus
where does the tear sac empty into?
nasal cavity
structure of the conjunctiva?
- thin mucous transparent membrane
- covers the sclera in front
- continuous with the skin of the eyelids
function of the conjunctiva?
- protects the cornea at the front of the eyeball against friction
- keeps the eyeball moist
structure of the cornea?
- anterior end of the sclera that forms a small bulge in front of the eye
- transparent portion of the sclera
function of the cornea?
- allows light to pass through to reach the retina
- refracts light into the pupil
structure and function of the sclera?
tough white outer layer of the eyeball that protects it against mechanical injury
structure and function of the choroid?
- contains blood vessels to supply the retina with oxygen and nutrients
- pigmented black to prevent internal reflection of light
structure and function of the retina?
innermost layer that contains photoreceptors that detect stimuli
function of cones?
concerned with colour vision in bright light
function of rods?
concerned with vision in dim light
function of the optic nerve?
transmits nerve impulses from the photoreceptors to the brain
structure of the iris?
- anterior end of the choroid
- consists of the circular and radial muscles
function of the iris?
- controls the size of the pupil, and hence the amount of light that enters the eye
- contains pigments to give the eye its colour
are the circular and radial muscles voluntary or involuntary?
involuntary
what is the pupil?
hole in the centre of the iris that allows light to enter the eye
structure of the lens?
- transparent biconvex structure
- elastic
function of the lens?
focuses light rays by changing thickness onto retina
function of the suspensory ligaments?
holds the lens in position by attaching the lens to the ciliary body
function of the ciliary body?
- supports the lens
- contains muscles which control the curvature of the lens
structure of the vitreous humour?
- transparent
- jelly-like
function of the vitreous humour?
- supports the lens
- refracts light rays onto the retina
- keeps the eyeball firm
structure of the aqueous humour?
- transparent
- watery fluid
function of the aqueous humour?
- refracts light onto the retina
- keeps the eyeball firm
- maintains the shape of the anterior chamber of the eyeball
what does the fovea contain?
densely-packed cones
function of the fovea?
- part of the retina most sensitive to light
- has acute colour vision in bright light
what is the blind spot?
- found immediately over the optic nerve
- no photoreceptor cells
what are the difference between the rods and cones?
- sensitivity to light
- ability to distinguish colours
- concentration in what part of the retina
- images provided
what are the three types of cones?
- red cones
- blue cones
- green cones
- the cones come together to enable a spectrum of colours to be seen
how do we see images in the eye?
- refracted light rays from the object enter the eye through the pupil
- light rays are refracted by the cornea, aqueous and vitreous humour, and the lens to focus on the retina
- the lens make fine bending adjustments to focus the rays
- an image formed on the retina stimulates the photoreceptors
- nerve impulses generated are transmitted to the brain via optic nerve
- the brain interprets the impulses to see the object the right way
properties of the image formed on the retina
- inverted - upside down
- back to front - inverted
- diminished
what is the pupil reflex?
an immediate involuntary change in the diameter of the pupil in response to the intensity of light that falls on the photoreceptor cells
what happens during high light intensity?
- circular muscles of the iris contract
- radial muscles relax
- pupil size constricts
- reduces the amount of light that enters the eye, preventing damage to the rods and cones
what happens during low light intensity?
- circular muscles of the iris relax
- radial muscles contract
- pupil size dilates
- allows as much light as possible to enter the eye, for us to see more clearly
what is focusing?
the adjustments of the lens of the eye so clear images at different distances can be formed on the retina?
what happens when we focus at a distant object?
- light rays reflecting off the object are almost parallel when they enter the eye
- ciliary muscles relax
- suspensory ligaments are pulled taut
- lens become thinner and less convex and refractive for image to be focused on the retina
- an image formed on the retina stimulates the photoreceptors
- nerve impulses generated are transmitted to the brain via optic nerve
- the brain interprets the impulses to see the object the right way
what happens when we focus at a near object?
- light rays reflecting off the object are divergent when they enter the eye
- ciliary muscles contract
- suspensory ligaments slacken
- lens become thicker and more convex and refractive for image to be focused on the retina
- an image formed on the retina stimulates the photoreceptors
- nerve impulses generated are transmitted to the brain via optic nerve
- the brain interprets the impulses to see the object the right way
