The Senses Flashcards
Receptors
A cell or group of cells that detects a stimulus e.g. heat and light
A Sense Organ
Is an assembly of specialised sensory receptors
Conjunctiva
Protects against infection
Sclera
Keeps the shape of the eye
Cornea
☆ How is it suited to carry out its function? - Curved and Transparent
☆ Function = Bends light towards the retina
Choroid
Has blood vessels to nourish the eye
Iris
☆ Controls the amount of light entering the eye
☆ How? - Muscular contraction
Iris in bright light
Relaxes (gets longer, pupil gets smaller so less light enters the eye)
Iris in dim light
Contracts (gets smaller, pupils gets bigger so more light enters the eye)
Pupil
Allows light into the back of the eye
Lens
☆ Adaptations = Curved, elastic and transparent
☆ Function = To focus light onto the retina
Ciliary Muscle
Surrounds the lens and causes the shape of the lens to change when we look at near or far objects. This is a reflex action known as accommodation.
Suspensory ligaments
Holds the lens in place
Retina
☆ Converts light into nerve impulses
☆ Types = Rods and Cones
Rods
☆ Active in dim light
☆ Black and white vision
☆ Found all over retina
Cones
☆ Active in bright light
☆ Colour vision
☆ Found mostly at fovea
Fovea (Yellow Spot)
Is where most images are focused
Blind spot
☆ Where optic nerve leaves the eye
☆ No rods or cones here
Optic nerve
Brings impulses from the retina to the brain
Aqueous humour
Holds the front of the eye (cornea) in shape
Vitreous humour
Gives shape to the eye and supports the lens
Why are two eyes better than one?
☆ Increased visual field
☆ 3D vision
☆ Can judge distance of objects
Hearing
Detection of vibrations, their frequency and amplitude
Balance
Detection of direction of motion, acceleration and head position related to gravity
Structure
Composed of three sections;
☆ Outer ear = air
☆ Middle ear = air
☆ Inner ear = lymph
Pinna (outer ear)
Collects sound waves
Auditory canal
Tube that carries the sound waves to the eardrum
Eardrum
Vibrates due to the air vibrations that reach it
Ossicles (bones)
Consist of the hammer, anvil and stirrup which transmit vibrations from the outer to the inner ear and amplify the vibrations
Estuchian tube
☆ Connects the middle ear to the pharynx
☆ Equalises pressure
Cochlea
Contains sound receptors that convert sound waves into nerve impulses
Auditory / Cochlear nerve
Carries impulses from the cochlea to the cerebellum of the brain
Semi - circular canals
☆ Controls balance
☆ Their are 3 to control balance in three dimensions
☆ Nerve impulse generated for balance
Vestibular nerve
Carries impulses from the balance structures to the cerebellum of the brain
How do we hear?
☆ Sound is caused by vibrations in the air
☆ Vibrations are collected by the outer ear, pass through the middle ear where they are changed to electrical impulses and sent to the brain which interprets them as sound
Glue ear
☆ Cause = Middle ear fills with sticky fluid instead of air, it can be caused by infection or a blocked eustachian tube
☆ Symptoms = Reduced hearing
☆ Treatment = Nose drops or grommets
Grommets
Tiny ventilation tubes inserted into the ear, they allow air in, which builds up and forces the fluid down the eustachian tube, the tubes fall out naturally
External muscle
Pulls on the eye causing it to change direction
