The Eye and Ear Flashcards
Role of Eyelids
To cover and protect the eye
Role of Conjunctiva
Transparent thin lining that protects the cornea
Role of Cornea
Focus light on the retina
Role of Sclera
Tough fibrous outer layer; the white of the eye: it maintains the eyes shape
Role of Choroid
Contains blood vessels to supply food and oxygen to the cells of the eye
Role of Retina
Innermost layer of the eye that contains receptor cells
Role of Fovea
Where vision is best (mostly cones)
Role of Iris
Contains blood vessels and melanin (gives colour of the eye), Controls amount of light that enters the eye through the pupil.
Contraction and expansion is a reflex
Role of Pupil
In bright light the pupil constricts
In dim light the pupil dilates
Role of Ciliary Body/Muscle
Thickened end of choroid that controls the shape of lens
Role of Suspensory Ligaments
Hold the lens in place
Role of Lens
Acts as a magnifying glass, it focuses light rays on the retina for very sharp images
Role of Aqueous Humour
Watery liquid that supplies the lens and cornea with nutrients and helps keep the shape of the cornea and lens
Role of Vitreous Humour
Gel that helps maintain the shape of the eye
Define Blind Spot
Where the optic nerve passes through the retina and there is no room for receptors
Role of Optic Nerve
When light rays focus on retina receptor cells are stimulated and impulses are carried along the optic nerve to the brain
Outline the role of Rods in the eye
Receptor cells that see black and white
Only work in dim light
Better peripheral vision at night due to this
Outline the role of Cones in the eye
Less numerous than rods
They are for colour vision
3 types in humans red, green and blue
How do images form on the retina
Light reflects from object into the eye
The cornea and lens refract (bend) the light rays
Image is formed upside down on the retina
Define Accommodation
The ability of the lens to change its shape to form a clear image
Describe the eye during close vision
For close vision the ciliary muscle contracts, the suspensory ligaments relax and the lens becomes thicker
Describe the eye during distant vision
When the eye is at rest, the lens is thin, has a long focal length and is adapted for seeing distant objects
Name 2 eye defects and the method of treatment
Long sighted or hypermetropia and can be solved with Convex lens glasses
and
Short sighted or myopia and can be solved with concave lenses
Role of Pinna
Funnels sound into the ear
Role of Ear Canal
Has hairs and wax glands to trap dirt and germs
Role of Eardrum
Vibrates when sound waves hit it
What is the middle ear
Air filled cavity containing 3 small bones and Eustachian tube
Role of Ossicles
3 small bones the hammer, anvil and stirrup; they amplify sound
Role of Eustachian Tube
Keeps air pressure equal on each side of the eardrum, opens when we swallow and cough
What is the Inner Ear
Contains coiled fluid filled tube called the cochlea and semi circular canals
Role of Cochlea
Contains nerves that convert sound vibrations into electrical impulses
Semi-Circular Canals
Help us keep balance and posture
Explain how human being hear
The pinna channels sound vibrations towards eardrum which then vibrates
This vibrates the hammer, anvil and stirrup which amplify sound
The stirrup pushes on the oval window which pushes liquid inside the cochlea
Special hairs on 30,000 receptor cells detect the movement and send signals along auditory nerve
The brain interprets these as sound and we hear
Explain how human beings balance
Head movements are detected by nerves in canals
Vestibular nerve send messages to brain
Brain responds by sending messages through the cerebellum which trigger reflexive actions in our muscles
This helps keep the body balanced as we move
Name 2 ear defects the causes and treatment
Otitis Media; caused by bacterial infection; treat with antibiotics
and
Glue Ear in children; build up of fluid in middle ear; install grommet to drain fluid, which then falls out
Draw a diagram of the eye
Draw a diagram of the ear
