1. Option A.3 Perception of Stimuli
IB BIOLOGY HL
Option A.3 Perception of Stimuli

2. Sensory Receptors Diversity of Stimuli Detect changes in environment
Mechanoreceptors:
Stimulated by mechanical force or pressure
Touch
BP detectors in arteries
Stretch receptors in lungs
Proprioceptors in muscles, tendons joints, ligaments
Inner ear- balance

3. Sensory Receptors, cont.
Chemoreceptors:
Respond to chemical substances
Taste and smell
Monitor pH of blood
Respond to damaged tissues as pain receptor
Located at the top of the nasal passage
Genes recognize smells, no gene for a substance, you can’t smell it.

4. Sensory Receptors, cont.
Thermoreceptors
Respond to change in temperature
Located in skin in humans
Photoreceptors
Respond to light energy
Found in eyes
Rods- black and white
Dim light
Cones-color vision
Bright light

5. Structure of the Human Eye

6. Retinal Arrangement

7. Retinal Arrangement, cont.

8. The Retina Lightrods and conesoptic nerve brain
Rods and cones synapse with own bipolar cells
Bipolar cells synapse with ganglion cell
Axons of ganglion cell make up optic nerve
Rod cells- dim light Synapse in groups onto bipolar neurons
Cone cells- bright light
Have 1 to 1 relationship with bipolar neurons
Bipolar neurons- carry impulse from rods and cones to ganglion cell
Ganglion cells- synapse with bipolar neurons, send impulse to brain via optic nerve

9. Red- Green Color Blindness
Three classes of cones in normal color vision: red, green, blue
Some people have red-green color vision defects
Sex-linked trait
Rare in females

10. Field of Vision
Right field from both eyes sent to left visual cortex, vice versa
Contra-lateral processing

11. Structure of the Ear

12. Structure of the Ear, cont.
The Middle Ear
Transmits and amplifies sound
Air filled chamber
Eardrum separates outer ear from middle ear
Ossicles: Malleus, incus and stapes articulate to transmit vibrations

13. Structure of the Ear, cont.
The cochlea
Sensory hairs detect wavelengths of sound
Tubular, coiled, fluid-filled
Has layers of tissue with sensory cells (hair cells) attached
Round window-separates middle and inner ear

14. Structure of the Ear, cont.
The auditory nerve
Impulses caused by sound perception transmitted to brain via auditory nerve
Action potential sound
Cranial nerve to brain

15. Semi-Circular Canals Three semi-circular canals
Contain fluid and hair cells
Movement of fluid detects orientation of the head
Hair cells vestibular nerve brain

16. Cochlear Implants Convert sound into electrical signals brain Pg. 258