The Senses

Chapter 35

5 senses --- touch , taste, smell, sight & hearing TOUCHThe skin is the organ of touchTouch is a combination of pain, pressure, hot & cold TASTEThe tongue is the organ of tasteReceptors for taste are located in the taste budsSweet--- tip of tongueSalt--- sides of tongue near frontSour--- sides of tongue near backBitter--- across back of tongue

•SMELL

The nose is the organ of smell

The Olfactory neurons in the nose detect smell

•SIGHT

The eye is the organ for sight

The EyePART FUNCTION

conjunctiva protection

sclera Lets no light throughHolds the eye in shape

cornea Lets light into the eye

choroid Nourishes eye & prevents reflection of light with in eye

Fovea (yellow spot) Contains cones only– region of sharpest vision

Blind spot Where optic nerve leaves the eye

Optic nerve Carries impulses from the eye to the brain

Lens Changes shape to focus light on the retina

Ciliary muscle Cause the lens to change shape

Iris (coloured part) Controls the amount of light entering the eye

Pupil Lets light into the eye

Aqueous Humour Holds the front of the eye in shape

Retina Contains rods & cones (the light receptors)Rods for black & white vision & work in dim lightCones for colour vision & work in bright light

Vitreous Humour Holds the back of the eye in shape

Long Sightedness--Hypermetropia Person with long sight can see distant

objects clearly, but cannot see near objects

Cause: eyeball is too short To Fix: use CONVEX lens

Short sightedness--- Myopia Person can see near objects clearly, but

cannot see distant objects Cause: the eyeball is too long To Fix: use CONCAVE lens

Accommodation Is the ability of the eye to focus light from

objects at different distances by altering the focal length of the retina

Response of Iris to light BRIGHT LIGHT

the circular muscles contractthe size of the pupil decreasesLess light enters the eye

DIM LIGHT

The circular muscles relaxThe size of the pupil increasesMore light enters the eye

Hearing The function of the ear is hearing and

balance There are 3 sections to the ear1. Outer ear2. Middle ear3. Inner ear

The Ear

PART FUNCTION

Auditory canal Collects vibrations & carries vibration to eardrum

Eardrum Carries vibration to the middle ear

Ossicles– hammer, anvil, stirrup

Increases the vibrations & passes them to the oval window

Eustachian tube Connects the middle ear & pharynxEqualises pressure between the middle & outer ear

Cochlea Hearing– contain receptors which are stimulated by pressure waves in lymph. Receptors cause electrical impulses to be sent to the brain along the auditory nerve which interprets them as sound

Organ of Corti Contains receptors for hearing

Pinna Collect and channel vibration into the auditory canal

Vestibular apparatus Balance

How we hear Sound waves enter the ear Eardrum vibrates Three bones amplify the sound Oval window vibrates Liquid in cochlea moves hair cells stimulated Auditory nerve carries impulses to the

brain Brain interprets the sound

Glue Ear Is a hearing disorder Caused: by too much sticky fluid in the

middle ear Corrected: by decongestants or grommets(

small tubes inserted into the eardrum)