The Senses Flashcards
Conjunctiva
Transparent outer layer
Protects sclera
Sclera
White of the eye
Opaque and tough
Holds eye in shape
Cornea
Transparent part of sclera
Lets light in and bends it towards the retina
Choroid
Dark coloured layer
Contains melanin to absorb light and blood vessels to nourish eye
Ensures no internal reflection
Retina
Where the light receptors are located
Function of rods
Detect b and w
Work in dim light
Most common
Function of cones
Detect colours
Work in bright light
Least common, found mostly at fovea
Fovea
Only contains cones
Focuses images
Blind spot
Where the nerves and fibres leave the eye
Not sensitive to light due to lack of cones and rods
Optic nerve
Carry impulses from rods and cones to the cerebrum of the brain
Pinna
Cartilage
Channels vibrations into auditory canal
Auditory canal
Carries vibrations to eardrum
Wax secreted to trap dust and protect inner ear
Eardrum
Separates outer and middle ear
Vibrates
Ossicles
Hammer anvil and stirrup
Smallest bones
Transmit and amplify vibrations
Eustachian tube
Runs to throat
Equalises pressure on either side of eardrum
Cochlea
Converts pressure waves to electrical impulses
Describe in four steps how the cochlea works
- Vibrations from stirrup arrive at cochlea
- Pass through oval window and form pressure waves in the lymph in the cochlea
- These waves stimulate receptors in cochlea which are attached to sensory cells called Organ of Corti
- Cause electrical impulses to go to the brain
What controls balance
The three semicircular canals - vestibular apparatus
Hearing disorder
Glue ear
Cause of hearing disorder
Surplus sticky fluid in middle ear, possibly due to infection
Prevents movement of eardrum and ossicles
Correction for hearing disorder and how it works
Grommets inserted into ear
Allow air in and force fluid down the Eustachian tube
