1. Special Senses

2. Sensory Receptors Stimuli are forms of energy
Sensory receptors convert incoming energy to another form of energy
Ex. TASTE receptors convert chemical energy to electrical energy)
Have modified ends specific to their function
Are grouped within sensory organs
Sensory organs enhance and amplify the stimuli to ensure minimum threshold levels are met
Types of receptors: photoreceptors, chemoreceptors, mechanoreceptors, thermoreceptors,

3. Sensory Adaptation
Occurs one a sensory receptor becomes “used to” the stimulus
The neuron fails to be stimulated even though the minimum threshold has been attained
Once the body realizes it is not in danger, and is used to the stimulus, the sense adapts the stimulus and quits responding to it
Ex. Perfume “fades” ten minutes after you put it on but when you walk by someone they can smell it

4. Taste Able to differentiate between edible and non-edible food
Taste receptors are found in 4 different locations in the tongue
Sweet, Bitter, Salty, Sour
Once dissolved, the specific chemical stimulates the receptors on the tongue, and the message is sent to the brain

5. Smell Olfactory cells are located in the nasal cavity
Airborne chemicals combine with these specialized receptor cells to create an action potential
May be millions of different receptors specific to certain scents, allowing us to smell a variety of smells
** TASTE AND SMELL WORK TOGETHER**
** Both work by chemical stimulation

6. Senses Review Student Text, pp. 466-467
Eye Pop

7. The Eye

8. How we “see”
Rods and cones are the light sensitive cells (humans have many more rods than cones)

9. The rods contain a light-sensitive pigment called rhodopsin which breaks down in the presence of light to produce the action potential
In bright light, rhodopsin breaks down faster than it can be restored. The opsins used for colour vision are much less sensitive to light and, therefore, operate best with greater light intensity
Rods work best during low light
Cones work best during intense light

10. Focussing and Image
Light strikes the eye and is bent by the cornea toward the pupil
Light is bent to a focal point, because the cornea is thicker in the middle than out the outer edges
An inverted image is projected on to the retina to stimulate both rods and cones

11. The shape of the lens is controlled by ciliary muscles
When CLOSE objects are viewed, the ciliary muscles CONTRACT, causing the lens to THICKEN, bending the light more
When FAR objects are viewed, the ciliary muscles RELAX, causing the lens to THIN, causing the light to bend less
THIS IS KNOWN AS ACCOMODATION

12. Eye Defects Glaucoma Caused by an increased build up of aqueous humor
Blood vessels are blocked, thus cutting off a constant supply of blood, carrying oxygen and other nutrients to the eye

13. Eye Defects
Cataract
Caused when the lens of the eye becomes opaque which prevents maximum amount of light from entering the eye
Cured by removing the lens and fitting the patient with strong eye glasses, or to replace the lens with a plastic one

14. Eye Defects Astigmatism
The cornea and lens are not symmetrical, which blurs the focal point

15. Eye Defects Near Sighted (myopia) Eyeball is too long
Image is focused before the retina
Cannot focus on far objects, only near
Far Sighted (hyperopia)
Eyeball is too short
Image is focused behind the retina
Can see far objects, not close

16. Assignment 2 – Eye and Ear

17. Friday
Write your name on the piece of paper and place in the “YAY ITS FRIDAY” box

18. The Ear

19. Ear Functions The ear is associated with TWO functions:
Hearing
Equilibrium and Balance
Sensory cells for both functions are found within the ear
Cells respond to mechanical stimuli produced by movement or by sound waves, which create the action potential

20. http://www. mcgrawhill
Hearing
Sound waves push against the tympanic membrane, which transfers sound to the ossicles
The bones concentrate and amplify the vibrations, passing sound onto the oval window, pushing it inward
The oval window’s force causes the round window to push out
This triggers the fluid in the inner ear to move – also causing vibration of the basilar membrane
Fluid causes hair cells (stereocilia) in the cochlea, specifically the organ of Corti, to bend, thus stimulating nerve cells
Action potential is carried to the brain via the auditory nerve

21. Stereocilia

22. Pitch and Loudness Pitch (frequency) Loudness (amplitude)
Pitch (frequency)
Longer waves move hair structures within the cochlea differently than short waves, thus helping you determine differences in pitch and loudness
Close to oval window is high frequency (short waves)
Loudness (amplitude)
Louder the noise = more pressure fluid puts on hair cells

23. How can hearing loss occur? How is hearing loss corrected?
Two types of hearing loss
Conduction deafness (damage to outer or middle ear)
Nerve deafness (damage to hair cells – permanent)

24. Equilibrium and Balance
Vestibule (gravitational equilibrium - static)
Connects to oval window
Contains two small sacs – utricle and saccule
Lined with tiny hairs suspended in a jelly like material containing crystals (otoliths – calcium carbonate)
When head is in normal position, crystals do not move
When head is tilted, gravitational force acts on the crystals, moving the jelly and thus the hairs

25. Equilibrium and Balance
Semicircular Canals (rotational equilibrium – dynamic)
3 canals, arrange at different angles
Filled with fluid
Movement causes fluid to move, moving the hair within the canal, thus stimulating nerves
Brain then interprets movement

27. What now?!?! “YAY ITS FRIDAY” Relay Race (choose teams)
Choose “mascot” from specimen containers
Rules (outside)