1. A.3 Perception of Stimuli

2. Sensory Receptors Type of receptor Stimuli Detected Examples
Mechanoreceptor
Pressure
Gravity
Detection of sound waves in the ear
Detection of pressure on skin
Chemoreceptor
Dissolved chemicals
Vapor chemicals
Detection of chemicals dissolved in taste buds
Detection of chemicals in vapor (olfactory or smell)
Thermoreceptor
Temperature (hot or cold)
Detection of warm and cold by the skin
Detection of the temperature of blood as it travels through the hypothalamus
Photoreceptor
Electromagnetic radiation (light)
Detection of light (rod cells of the eye)
Detection of color (cone cells of the eye)

3. The Human Eye
Detects electromagnetic radiation in light
Rods
cones

5. Eye Parts and Functions
Sclera: Tough outer layer; protects whites of eyes
Cornea: Front of eye, allows light to pass through; clear
Conjunctiva: outer lining; provides moisture
Eyelid: covers the eye; protection and spreads moisture
Choroid: Dark layer; lots of capillaries to nourish retina
Aqueous humour: Fluid in the front portion of the eye; provides pressure and contains nutrients
Pupil: Opening in the iris; controls amount of light let into the eye
Lens: focuses light on the fovea of the retina

6. Eye Parts Continued
Iris: Colored part of the eye; contracts & relaxes to change size of the pupil
Vitreous Humour: Thick fluid in the back of the eye
Retina: Contains rods & cones (photoreceptors)
Fovea: Location of most of the cones; most accurate visual region
Optic nerve: Contains all the neurons leaving the retina, and carries visual messages to the brain
Blind spot: where the optic nerve leaves the back of the eye

7. The Retina
Contains photoreceptors (rods and cones; more detail on next slides)
Absence of, or defect to either red or green cone cells causes red-green color-blindness

10. Rods Detect black and white Sensitive to all wavelengths of light
Groups of rods connect to one
neuron (nerve fiber) in the optic
nerve (low visual acuity)
More numerous (over 100 million)
spread out in retina

11. Cones Detect bright light (color) Sensitive to 3 wavelengths of
light; red, blue & green
Each cone connects to its own
(one) neuron (nerve fiber) in the
optic nerve (high visual acuity)
Less numerous (less than 10 million)
Mostly in fovea

12. Bipolar Cells Rods and cones synapse with bipolar cells in the retina
Send the impulses from rods and cones to the ganglion cells

13. Ganglion cells
Send messages to the brain via the optic nerve

14. Edge Enhancement & Contralateral Processing
Visual processing
Main Site of Processing
Function
Result of Processing
Edge Enhancement
Retina of the eye
Selectively activates only some of the ganglion cells
Enhances the sharpness of images (where edges are located)
Contralateral Processing
Optic chiasma in the brain
Sends ganglion cells entering brain close to the nose to the opposite side of the brain
Allows the interpretations of distances and sizes of objects

15. Contralateral processing

16. Contralateral Processing

17. The Human Ear Transmit pressure waves into auditory sounds
Brain interprets the information from the receptors

19. Parts & Functions of the Ear
Structure
Function
Pinna
Collects sound waves
Eardrum
(tympanic membrane)
Transmits sound waves to the inner ear bones
Bones of the middle ear
(hammer, anvil, stirrup)
Transmit and amplify (by up to 20 times) the sound waves received from the eardrum
Also known as the malleus, incus and stapes
Oval window
Receives pressure from middle ear bones (stirrup) and transmits pressure waves into the middle ear
Round window
Absorbs pressure waves after they travel through the cochlea, preventing the waves from moving backwards
Semicircular canals
Help maintain balance by sensing position; hair cells
Auditory nerve
Made up of neurons that are activated in the cochlea by pressure waves bending hairs in the inner ear; sends messages to brain
Cochlea
Part of ear that contains hairs that are attached to neurons and activated by pressure waves; transforms the pressure waves into neural impulses

20. Outer Ear
Pinna

21. Middle Ear
Eardrum
3 smallest bones in the body (malleus, Incus and Stapes)

22. Inner Ear Does both auditory and balance
Cochlea and Vestibula or semicircular canals

23. Transmission of Sound
Pinna collects sound waves and passes them to the eardrum
The eardrum vibrates
Vibration of the eardrum puts pressure on the ear bones
Ear bones absorb the vibrations and amplify them
Vibrations reach the stirrup and act like a piston to convert it to mechanical energy
Mechanical energy is passed on to the cochlea via the oval and round windows
As it moves through the cochlea it causes the hair cells to bend

24. Transmission continued
Hair cells are varying heights and are in a jelly-like substance
Larger sound waves vibrate more hair cells
The more hair cells activated (bent) the louder the sound
The more frequent the sound waves the higher the pitch (frequency)