Eye

Sclera: white, tough

• protects inner structures
• provides surface for attachment of eye muscles
• maintains shape of eyeball

Conjunctiva

• protects cornea
• allow light to pass through

Cornea

• ALPT
• Refracts light

Choroid

• contains black pigment to absorb light to reduce reflection to help form sharp image
• contains capillaries which supply nutrients and oxygen to retina, sclera

Iris

• control size of pupil

Pupil : light enter eye

Retina

• rod cells: visual purple, dim light vision and black and white vision
• cone cells: bright light vision and color vision
• yellow spot: concentrated cone cells
• blind spot: no photoreceptors, where optic nerve leaves eyeball

Lens: refracts and focuses light on retina

Ciliary body: change lens thickness by constrict/relax ciliary muscles

Suspension ligament: connects lens to ciliary body

Aqueous humour: supplies oxygen and nutrients to conjunctiva, lens and cornea, reflects light and maintains shape of eyeball

Vitreous humour: reflects light and maintains shape

Seeing

Process

image formed on retina --> light-sensitive cells stimulaed by light, send nerve impulses along optic nerve to visual centre
Brain interprets upright image of object

amount of light

Bright: circular muscles contract, radial muscles relax, pupil contricts
Dim: circular muscles relax, radial muscles contracts, pupil dilates

Eye accommodation

Near objects: Circular ciliary muscles contract, suspensory ligaments becomes slackened, lens become more convex
Distant objects: circular ciliary muscles relax, suspensory ligaments are pulled, lens become less convex

Ear

Outer ear

Pinna: connects sound wavecs of sound vibrations
auditory canal: directs sound waves to the eardrum
eardrum: converts sound waves to sound vibrations

Middle ear

Ear bones: amplify and transmit vibrationsfrom eardrum to the oval window
Oval window:trnasmits vibrations from ear bones to inner ear
Eustachian tube: equalizes pressure between the middle ear and atmosphere

Inner ear

Semicircular canals: detect direction of head movement
Cochlea

• upper, lower canals --> perilymph
• central canal --> endolymph, sensory hair cells
  When endolymph vibrates, hairs bent, stimulate sensory hair cells, nerve impulses to auditory nerve to auditory center

Light detection by plants

Phototropism

Unilateral light
shoots grow towards light - positively phototropic: leaves obtain max amt of light
roots grow away from light - negatively phototropic: better anchorage