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The Sensory system Lesson 1 • OB 28 recall five sense organs in the human (eyes, ears, nose, skin, and tongue) and understand how these enable humans to gather information from their surroundings Lesson 2 • OB 29 describe the role of the central nervous system and the sensory and motor functions of nerves Lesson 3 • OB 30 locate the main parts of the eye on a model or diagram and describe the function of the cornea, iris, lens, pupil, retina, optic nerve and ciliary muscle The Sensory system The Senses • What are the senses? • Why do we need our senses? • Helps us to avoid danger • Allows us to appreciate nice objects The Senses Animals have 5 senses: 1. Sight 2. Hearing 3. Taste 4. Smell 5. Touch The Senses The senses respond to stimuli: • Light: sense of sight • Sound: sense of hearing • Pressure and Heat: Senses of touch • Chemical substances: Sense of taste and smell Sense Organs • • • • Eye: Organ of sight Ear: Organ of hearing Skin: Organ of touch Tongue: Organ of taste • Nose: Organ of smell Sense Organs • Eyes: Detect light • Ears: Detect sound • Skin: Detects pressure + heat • Tongue: Detects taste • Nose: Detects smell Nervous system • System of communication • Two Parts: – Central nervous system: consists of the brain and spinal cord – Peripheral nervous system: consists of the nerves or neurons Brain • Is the centre of our intelligence • Contains 100 billion nerve cells • Electrical signals or impulses pass through these cells • Gives us our ability to think, make decisions • Protected by the skull Spinal cord • Is an extension of the brain • Nerves branch off from it • Most signals pass from the senses and go through the spinal cord • Most signals that pass from Sensory Neurons the brain go through the spinal cord • Protected by the backbone Motor Neurons Nerves • Nerves cell = neuron • Two types: • Sensory neurons: carry signals from the senses to the CNS • Motor neurons: carry signals away from the CNS to the muscles The Eye • • • • • • Organ of sight Detects light and distinguishes colour Made up of three parts Sclera Choroid Retina The Eye Sclera Iris Choroid Pupil Aqueous humour Retina Cornea Vitreous humour Lens Sclera & Cornea • The sclera is the outer coating – protects the eye. • The cornea is the transparent bump on the front of the eye; it bends the light, producing an image on the retina. (The lens provides fine adjustment of the focus to match the distance to the object.) Choroid • • • • • Darkly coloured Front part – iris – coloured part of eye Pupil – centre of the iris Allows light to enter the eye Function of the iris is to control the amount of light that enters the eye Retina • Part of the eye that detects light • Cells are light sensitive • Optic nerve carries nerve impulses from the eye to the brain • Blind spot – has no light sensitive cells • Lens – adjusts the focus (depending on the distance to the object) to form a sharp image on the retina. • Ciliary muscles – change the shape of the lens to change the point of focus The Eye Sclera Iris Choroid Pupil Aqueous humour Retina Cornea Vitreous humour Lens Part of The Eye Function Cornea Provides most of the focussing of light. Iris Controls the amount of light that enters the eye. Pupil The hole in the middle of the iris; allows light to enter the eye Retina Detects light and produces nerve impulses. Provides fine focus of the image on the retina Lens Ciliary muscle Optic nerve Changes the shape of the lens Carries nerve signals from the eye to the brain The Eye Sclera Iris Choroid Pupil Aqueous humour Retina Cornea Vitreous humour Lens
