Senses & Sensory Relationships

1. Senses & Sensory Relationships • All of our senses respond to stimuli in the environment/ • ________________________________________ • ________________________________________________________________________________ • The role of sense receptors is to ______________ ________________ and to provide the other parts of the body with information about these stimuli.

3. Sense organs(Fill out the following table)

4. 1. The Eye • The eye is the organ of sight. • Our eyes enable us to appreciate: • __________________ • __________________ • _____________________ • ____________________________________ • The eye is made up of a system of 4 _________ and 3 ___________ substances

6. Anatomy of the Eye Membranes: - 1 membrane covers the front part of the eye .  __________________ - it is transparent - under the cornea are: 1) _________: the coloured ring of the eye 2) __________: the central portion of this ring (black dot)

7. Anatomy of the Eye - the other 3 membranes line the posterior (back) of the eye They are all different: • ________________________________________ - rigid, gives the eye its shape • ___________________________ - provides nourishment for the eye • ___________________________ - active nervous membrane = receiver of stimuli

8. Anatomy of the Eye Transparent Substances: Found inside the eye • _________________ • ________________________ - located between the cornea and lens - a liquid made up of water and minerals • _________________________ - located between the lens and the retina - jelly like substance

9. What path does light take as it travels through the eye? 1) Light must pass through a number of transparent media before it reaches the nerve cells of the eye. Where are these located?  __________________ 2) Label these different structures in the order that light passes through: vitreous humour, lens, retina, cornea, aqueous humour 1st _____________  2nd _____________  3rd ______________ 4th ______________ 5th ______________.

10. The Path Light Takes in the Eye • Light passes through and is bent by the cornea and then the lens. WHY? ________________________________________________________________________ • Images appear inverted(______________) on the retina • When looking at near-by objects = the lens curves and thickens. • When looking at far object = the lens flattens. • The reflex that causes the lens to change shape is called the _____________________ near-far sightedness

11. Flattened lens thickened lens ugh THE PROPERTY OF REFRACTION (BENDING IF LIGHT), we are able to focus an image at the back of our eye, in the Retina. The image for which we see from the outside environment is actually upside down on our retina. The Brain flips it back so we can see right-side-up.

12. Light rays enter the eye and focus on the retinal nerve cells (neurons) • These retinal nerve cells then change the light waves that strike them into nerve impulses that are carried along the optic nerve to the visual center of the brain • Optic nerve • Nerve tissue formed by the axons of the retinal cells • Transmits nerve impulses form the retina to the optical centre of the brain • Examples of retinal nerve cells: • Rods = detect light and dark • Cones = detect colour

13. Visual pathway

14. Visual Sensory Mechanics 1. Stimuli = Light 2. Receptor = Retina 3. Processor = Rods and Cones 4. Nerve Impulse = Action Potential from Axons 5. Conductor = Optic Nerve 6. Analyzer = Brain (Occipital Lobe) • It is only when the center for vision in the brain (in the occipital lobe) is stimulated that a person has any visual sensation • Therefore, it is not only the eyes alone that allow us to “see” but also the brain.

15. Lenses • Convex lenses • Also called converging • Cause light to converge on a focal point • This is like the actual lens inside your eye • Concave lenses • Also called diverging lens • Cause light to diverge from a focal point

16. Eye Disorders • Hyperopia (far-sighted): • The image is focused behind the retina • Close objects are blurred • Requires CONVEX lenses • Myopia (near-sighted): • The image is focused in front of the retina • Distant objects are blurred • Requires CONCAVE lenses • Presbyopia: • loss of elasticity of the lens (usually in old age) Long eyeball Myopia Short eyeball Hyperopia

17. Common visual defects