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The Senses Chapter 35 5 senses --- touch , taste, smell, sight & hearing TOUCH The skin is the organ of touch Touch is a combination of pain, pressure, hot & cold TASTE The tongue is the organ of taste Receptors for taste are located in the taste buds Sweet--- tip of tongue Salt--- sides of tongue near front Sour--- sides of tongue near back Bitter--- 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 Eye PART FUNCTION conjunctiva protection sclera Lets no light through Holds 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 light Cones 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 contract the size of the pupil decreases Less light enters the eye DIM LIGHT The circular muscles relax The size of the pupil increases More light enters the eye Hearing 1. 2. 3. The function of the ear is hearing and balance There are 3 sections to the ear Outer ear Middle ear Inner ear The Ear PART FUNCTION Auditory canal Collects vibrations & carries vibration to eardrum Carries vibration to the middle ear Eardrum Ossicles– hammer, anvil, stirrup Eustachian tube Increases the vibrations & passes them to the oval window Connects the middle ear & pharynx Equalises pressure between the middle & outer ear Cochlea Organ of Corti 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 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)
