11.5 The Senses Tuesday January 7, Wednesday, 8 January, 14

Transcription

1 11.5 The Senses Tuesday January 7, 2014.

2 TEST ON ALL OF HOMEOSTASIS (FOCUS ON REPRODUCTIVE AND NERVOUS SYSTEM) ON FRIDAY.

3 Structure of the Eye

4 Eye Anatomy and Function v=0hzwmldldhi&feature=related

5 Structure of the Eye cornea: transparent, highly sensitive layer of tissue which refracts as it passes through pupil: the hole in your eye that allows light to pass through iris: circular band of muscle which controls the size of the pupil and therefore controls the amount of light coming into the eye retina: the light-sensitive inner lining in the back of the eye containing photoreceptors (rods and cones)

6 Structure of the Eye lens: allows you to change your focus to see objects at any distance adjustments to focal length is done by muscles that change the lens shape when the lens becomes more spherical in shape, you can see things that are close up when the lens becomes flatter in shape, you can see things that are distant

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8 Visual Defects Glaucoma is a buildup of aqueous humour normally fluid is drained each day by ducts blockage of ducts causes fluid pressure to collapse blood vessels in the retina this means the eye does not receive nutrients and neurons die = blindness

9 Visual Defects Lens problems: 1. cataract: lens becomes opaque and lets less light in Solution: remove lens and get very strong glasses 2. astigmatism: lens irregularly shaped and image is seen above and below retina Solution: an angled lens

10 Optical Illusions Can you get to the centre? Start at the red dot and try to follow the spiral to the centre. Where do you end up?

11 What happened? Most people see this as a spiral although they are in fact a series of circles. Cells in your brain become active when they see lines at different tilts. Some respond to lines like this / others to this \ and still others to or _. The activity from all these brain cells is put together, allowing us to see the huge variety of shapes and forms in the natural world. When you look at this image, your eyes send electrical messages to your brain and activate the appropriate brain cells. Because of the way this image is drawn, the segments that make up the circles appear to tilt more than they actually do. Your brain makes a best guess of what is there and decides it is a spiral.

12 Optical Illusions Are these lines straight and parallel?

13 What happened? Although barely believable, all these lines are straight, and parallel to one another. This illusion comes about because the black and white rectangles do not sit directly above one another. You clearly see the horizontal grey space between the black and the black, and accentuate this difference. However, the horizontal grey between the white and the black rectangles is not so clear. Your visual system decides this space is not real, so shrinks it. This has the effect of producing lots of wedges, which your brain puts together and decides you are looking at non-parallel wavy lines.

14 Optical Illusions What do you see?

15 What happened? Most people see a triangle in front of three circles. Your brain tries to make sense of this pattern by going for the most likely explanation. In this case it is a white triangle in front of 3 coloured circles. Even when you know that the white triangle does not really exist, your brain still opts for it as the most likely explanation.

16 Can you trust your eyes?

17 DEMONSTRATING THE BLIND SPOT To draw the blind spot tester on a piece of paper, make a small dot on the left side separated by about 6-8 inches from a small + on the right side. Close your right eye. Hold the image (or place your head from the computer monitor) about 20 inches away. With your left eye, look at the +. Slowly bring the image (or move your head) closer while looking at the +. At a certain distance, the dot will disappear from sight...this is when the dot falls on the blind spot of your retina. Reverse the process. Close your left eye and look at the dot with your right eye. Move the image slowly closer to you and the + should disappear. Repeat the test for the left eye. This time close the right eye and focus the left eye on the dot.

18 Who do these ears belong to?

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20 Ear Anatomy and Function v=tkpj4igbmqq&feature=related

21 Ear Anatomy ossicles

22 Function of the Ear sound hits the outer ear and the auditory canal funnels sound waves in the middle ear, the eardrum transfers vibrations to the inner ear in the inner ear, the vestibule (not on diagram) controls head movement and balance (static equilibrium) semicircular canals also control body movement and balance (dynamic equilibrium) cochlea contains specialized hair cells that respond to sound waves in fluid and convert sound waves into electrical signals which are sent through the auditory nerve to the brain

23 TESTING YOUR BALANCE 1) Knee Flexion a. Stand straight; hold onto table with one hand b. Slowly bend knee as far as possible, so foot lifts up behind you; hold this position c. Now, use one fingertip to hold onto the table d. Next, no hands e.finally, with your eyes closed if you are steady 2) Hip Extension a. Stand inches from table b. Bend at hips; hold onto table c. Slowly lift one leg backwards (like an ice skater); hold this position d.now hold onto the table with one fingertip, then no hands, Finally with eyes closed!

24 Taste chemoreceptors on taste buds bind with particular molecules signals are relayed to the brain pleasant vs. unpleasant tastes cause different responses (salivation, nausea, vomiting...) humans have about 10,000 taste buds that cover the tongue, mouth and throat

25 Smell airborne molecules dissolve in the mucus of the nose and are detected by chemoreceptors the message is relayed to the brain and interpreted as pleasant or unpleasant

26 Touch mechanoreceptors in the skin, skeletal muscles and the walls of blood vessels detect touch and pressure these receptors are concentrated in the fingertips and lips and on the tip of the tongue, giving greater sensitivity

27 TESTING YOUR TOUCH RECEPTORS 1) Cutaneous (Skin) Sensations a. Have your partner rest comfortably with his/her eyes closed and both forearms resting on the table. One arm should have the hand up, the other with hand facing down. Hair or clothing from the back of the neck should be pinned back so the surface of the neck is exposed. Do not allow your partner to open his/her eyes at any time during this part of the lab! b. Perform the tests with the caliper in a random order. Measure the distance between the points, when your partner indicates he/she can feel only one stimulus instead of two. Which areas of the skin are most sensitive to the two-point discrimination test? Which areas of the skin are least sensitive to the test?

28 To do: Read page What is the sixth sense? How are the three kinds of thermoreceptors different? What types of changes happen in the body in response to varying temperatures? What is the purpose of pain receptors? What part of the nervous system do pain receptors belong to? What is SPD? Give some examples.