2. Sensory Transduction Olfaction Chemoreceptors Photoreceptors Vision
Olfactory
bulb
Olfaction
Chemoreceptors
Photoreceptors
Vision
Mechanoreceptors
Audition
Sensory Transduction

3. Direction of retinal visual processing
Anatomy of the Retina
Direction of light
Pigment layer
Choroid layer
Direction of retinal visual processing
Sclera
Front of
retina
Back of
retina
Fibers of
the optic
nerve
Ganglion
cell
Amacrine
cell
Bipolar
cell
Horizontal
cell
Cone
Rod
Photoreceptor
cells

4. Rhodopsin in the light: retinene changes shape
Back of retina
Cells of
pigment layer
Phototransduction
Cone
Rod
Outer
segment
Discs
Disc
Outer
segment
Mitochondria
Inner
segment
Inner
segment
Nuclei
Light
absorption
Retinene
Dendrites
of bipolar
cells
Opsin
Synaptic
terminal
Synaptic
terminal
Enzymes
Rhodopsin in the dark:
retinene in 11-cis form
(inactive)
Rhodopsin in the light:
retinene changes shape
to all-trans form
(active)
Front
of retina
Direction of
light
11-cis form
of retinene
all-trans form
of retinene

5. LIGHT DARK Cells of pigment layer Cone Rod Discs
(Absorption)
DARK
Activation of photopigment
High concentration
of cyclic GMP
Cells of
pigment layer
Activation of transducin (G protein)
Activates PDE
(Reaction cascade)
Cone
Rod
Takes
place in
outer
segment
Takes
place in
outer
segment
Na+ channels open
in outer segment
Decrease in cyclic GMP
Discs
Closure of Na+ channels
in outer segment
Membrane
depolarization
Outer
segment
(Spreads to synaptic terminal)
Membrane hyperpolarization
(the receptor potential)
Takes
place in
retina
Opens Ca2+ channels
in synaptic terminal
Inner
segment
(Spreads to synaptic terminal)
Takes
place in
synaptic
terminal
Takes
place in
retina
Nuclei
Closure of Ca2+ channels
in synaptic terminal
Takes
place in
synaptic
terminal
Release of inhibitory
transmitter
(inhibition)
Synaptic
terminal
Release of inhibitory transmitter
Bipolar cells inhibited
Bipolar
dendrites
(Removal of inhibition)
Bipolar cells disinhibited
(or, in effect, excited)
Front of retina
Graded potential change
in bipolar cell
No action potential
in cell ganglion cell
(If of sufficient magnitude to bring ganglion cell to threshold)
Action potential in
ganglion cell
No action potential
propagation to
visual cortex
Propagation of AP to visual cortex (occipital lobe)
visual perception

6. Rods versus Cones What about adaptation?
Properties of Rod and Cone Vision RODS CONES
100 M per retina 3 M per retina
Vision in shades of gray Color Vision
High Sensitivity Low Sensitivity
Low Acuity High Acuity
Night vision Day vision
Much convergence in retina Little convergence in retina
More numerous peripherally Concentrated in fovea
What about adaptation?

7. Color Vision

8. Anatomy of the Auditory System

9. The Middle Ear and Cochlea
APEX: Wider, more flexible end of basilar membrane (vibrates best with low-freq)
BASE: Narrower, stiffer end of BM near oval window (vibrates best with hi-freq)

10. The Traveling Wave

11. The Organ of Corti (Stereocilia) Outer hair cells Tectorial membrane
Inner hair cells
Supporting cell
Nerve fibers
Basilar membrane

12. The Hair Cell Potential

13. SOUND WAVES Vibration of round window Energy dissipates
Tympanic Membrane Vibrates
Ossicles Vibrate
Oval Window Vibrates
Fluid Movement within Cochlea
Vibration of
round window
Basilar Membrane Vibrates
Energy dissipates
(no sound perception)
Takes
place in
ear
Closure of Ca2+ channels
in synaptic terminal
Hair cell stereocilia bend as the movement of the basilar membrane displaces them in relation to the overlying tectorial membrane in which they are embedded.
Graded potential change
in bipolar cell
Graded potential change
in hair cell
Action potentials generated in
auditory nerve
Propagation of AP to auditory cortex
(temporal lobe)
sound perception

14. The Transduction Channel

15. What about Adaptation?

16. What about the Outer Hair Cells?

17. What about the Outer Hair Cells?

18. Cochlear Implants