1. What are Stimuli? How do we sense them? How do we respond to them?
Responding to Stimuli
What are Stimuli?
How do we sense them?
How do we respond to them?

2. Figure 46-00 2

3. Responses to Stimuli
Tactile Senses

4. DB34040.jpg 4

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6. Pictogram of Brain Sensitivity and Responsiveness
sensory
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motor

8. Responses to Stimuli
Tactile Senses
Chemical Senses

9. Olfactory bulb of brain
Figure 46-16
Brain
Action potentials
Olfactory bulb of brain
Glomeruli
Bone
Nasal cavity
Olfactory receptor neuron
Mucus
Odor molecules 9

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Mammalian Tongue
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14. Figure 46-15
Taste bud
Pore
Taste cells (salt, acid, sweet, bitter, meaty, etc.)
(umami)
Afferent neuron (to brain) 14

15.  mannitol sucrose sucralose sorbitol sodium cyclamate xylitol
saccharin
(alitame) 
truvia/purevia
lead acetate

16. All sensors are broadly distributed
A Bogus Tongue Map
bitter
sour
sour
salt
salt
sweet
All sensors are broadly distributed

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19. Responses to Stimuli
Tactile Senses
Chemical Senses
Wave Senses

20. Sound Perception Do the wave application here!
Do the wave beats (tuning) application here!
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21. Loudness in Decibels

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23. malleus incus stapes Figure 46-4 Outer ear Middle ear Inner ear
Auditory neurons (to brain)
Cochlea
Ear canal
Ear ossicles
malleus
incus
Oval window
Sound waves (in fluid)
stapes
Sound waves (in air)
Cochlea
Middle ear cavity
Tympanic membrane (eardrum) 23

24. The middle chamber of the fluid-filled cochlea contains hair cells.
Figure 46-5
     The middle chamber of the fluid-filled cochlea contains hair cells.
Cochlea
Auditory nerve
Three fluid- filled chambers
Tectorial membrane
Neurons (to auditory nerve)
Hair cells
Hair cells are sandwiched between membranes.
Stereocilia
Tectorial membrane
Outer hair cells
Axons of sensory neurons
Inner hair cells
Basilar membrane 24

25. 1. Arrival of pressure wave bends stereocilia.
Figure 46-3
Hair cells have many stereocilia and one kinocilium.
WHEN STEREOCILIA BEND, A SEQUENCE OF EVENTS RESULTS IN THE RELEASE OF NEUROTRANSMITTER.
Kinocilium
1. Arrival of pressure wave bends stereocilia.
Pressure wave
Stereocilia
Potassium channels joined by threads K+
2. Potassium channels open in response to bending. K+
3. Membrane depolar-izes due to influx of K+.
Nucleus
Depolarization
Hair cell
Synaptic vesicle
4. Depolarization triggers inflow of calcium ions.
Afferent sensory neuron
Calcium channel
5. Ca2+ causes synaptic vesicles to fuse with plasma membrane.
Ca2+
Ca2+
Efferent sensory neuron
6. Neurotransmitter is released and diffuses to afferent neuron.
Neurotransmitter released into synapse
Afferent neuron (to brain) 25

26. Sound-receptor cells depolarize in response to sound.
Figure 46-2
Sound-receptor cells depolarize in response to sound.
Sound stimulus
Depolarized
Sound-receptor cells respond more strongly to louder sounds.
Highest response occurs at a characteristic frequency
Louder sound
Softer sound 26

27. Uncoiled cochlea (to show basilar membrane)
Figure 46-6
Semicircular canals
Cochlea
Wide part of basilar membrane is flexible— vibrates in response to low frequencies
Oval window
Uncoiled cochlea (to show basilar membrane)
500 Hz
1 kHz
Basilar membrane)
Human Hearing ranges from 20 Hz to 20 kHz
2 kHz
4 kHz
Base of cochlea (near oval window)
16 kHz
Narrow part of basilar membrane is stiff— vibrates in response to high frequencies 27

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30. Responses to Stimuli Tactile Senses Chemical Senses Wave Senses
Vestibular Senses

31. The middle chamber of the fluid-filled cochlea contains hair cells.
Figure 46-5a
     The middle chamber of the fluid-filled cochlea contains hair cells.
Semicircular canals
Cochlea
Auditory nerve
Three fluid- filled chambers
Tectorial membrane
Neurons (to auditory nerve)
Hair cells 31

32. Semicircular Canals Contain Statoliths (Otoliths)
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SemiCircular Canals
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34. Responses to Stimuli
Tactile Senses
Chemical Senses
Wave Senses

35. Light: An Energy Waveform With Particle Properties Too
wavelength
violet
blue
green
yellow
orange
red nm
wavelength (nm)
10-9 meter
meter!

36. Light: An Energy Waveform With Particle Properties Too
wavelength
visible spectrum nm
wavelength (nm)
10-9 meter
meter!

37. White light: all the colors humans can see at once

38. Which side of our brains are we using?
Which side of our brains are we using?

39. Leaf Pigments Absorb Most Colors
White Light
Green is reflected!
Leaf Pigments Absorb Most Colors

40. Light: An Energy Waveform With Particle Properties Too
amplitude
brightness
intensity
Many metric units for different purposes
We will use an easy-to-remember English unit: foot-candle
0 fc = darkness
100 fc = living room
1,000 fc = CT winter day
10,000 fc = June 21, noon, equator, 0 humidity

41. Light wavelength demonstration:

42. Ommatidia are the functional units of insect eyes.
Figure 46-7
Ommatidia are the functional units of insect eyes.
      Ommatidia contain receptor cells that send axons to the CNS.
Ommatidia
Lens
Receptor cells
Axons 42

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Human vs Insect Vision
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Vertebrate Eye
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blind spot

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52. Normal Cornea
Astigmatic Cornea

54. blind spot
CD jpg 54

55. Figure 46-8 55 The structure of the vertebrate eye.
In the retina, cells are arranged in layers.
Pigmented epithelium
Ganglion cells
Connecting neurons
Photoreceptor cells
Sclera
Retina
Iris
Direction of light
Pupil
Cornea
Fovea
Lens
Optic nerve (to brain)
Axons to optic nerve 55

56. Figure 46-9
The Cephalopod Eye
Retina (photoreceptors are on the inside surface)
Cornea
Lens
Sensory nerves to brain
This “design” is “more intelligent” than that of mammals (humans) because it lacks the blind spot and maximizes light exposure to receptors 56

57. Eye Evolution

58. Vertebrate Retina
rod
cone
light

59. Rods and cones contain stacks of membranes.
Figure 46-10
Rods and cones contain stacks of membranes.
Rhodopsin is a transmembrane protein complex.
Opsin (protein component)
Retinal (pigment)
Cone
Rod
0.5 µm
Rhodopsin
Light
Light
The retinal molecule inside rhodopsin changes shape when retinal absorbs light.
trans conformation (activated)
cis conformation (inactive)
Opsin
Opsin
Light 59

60. The disk of a photoreceptor cell (a rod) before stimulation
Figure 46-11
The disk of a photoreceptor cell (a rod) before stimulation
cGMP-gated sodium channel (open)
Rhodopsin
GDP
cGMP
cis
Transducin (inactive)
Phosphodiesterase
Plasma membrane of rod
Disk membrane
The same disk after stimulation (light)
cGMP-gated sodium channel (closed)
Rhodopsin (activated)
GTP
trans
Lack of Na+ current hyperpolarizes membrane
Transducin (activated)
Light 60

61. Figure 46-13
Visible spectrum
S opsin 420
M opsin 530
L opsin 560 61

62. Red-green color deficiency
Figure 46-12
No color deficiency
Red-green color deficiency 62

63. The Eye-Brain Connection
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65. Responses to Stimuli Tactile Senses Chemical Senses Wave Senses
Vestibular Senses
Positional Senses

66. Ball-and-socket joints swivel
Figure 46-17
Ball-and-socket joints swivel
Hinge joints hinge

67. Endoskeleton Extensor (quadriceps) contracts
Figure 46-18a
Endoskeleton
Extensor (quadriceps) contracts
Flexor (hamstring) contracts

68. Figure 46-19
Sarcomere
Myofibril
Muscles
Dark band
Light band
Muscle fiber (one cell) contains many myofibrils
Relaxed
Bundle of muscle fibers (many cells)
Contracted
Muscle tissue

69. Thick filament (myosin) Myofibril
Figure 46-20
Thin filament (actin)
Thick filament (myosin)
Myofibril
Relaxed
Z disk A B C D
Contracted A B C D

70. Colors indicate protein subunits
Figure 46-21
Myosin head
Colors indicate protein subunits
ATP binding site
Actin binding site

71. CHANGES IN THE CONFORMATION OF THE MYOSIN HEAD PRODUCE MOVEMENT.
Figure 46-22
CHANGES IN THE CONFORMATION OF THE MYOSIN HEAD PRODUCE MOVEMENT.
1. ATP bound to myosin head. Head releases from thin filament.
Myosin head of thick filament
Actin in thin filament
4. ADP released. Cycle is ready to repeat.
2. ATP hydrolized. Head pivots, binds to new actin subunit.
3. Pi released. Head pivots, moves filament (power stroke).

72. Thick filaments (myosin) Thin filaments (actin)
Figure 46-24
Motor neuron
Muscle cell
HOW DO ACTION POTENTIALS TRIGGER MUSCLE CONTRACTION?
Motor neuron
Action potential
1. Action potential arrives; acetylcholine (Ach) is released.
ACh
ACh receptor
Action potentials
2. ACh binds to ACh receptors on the muscle cell, triggering depolari-zation that leads to action potential.
3. Action potentials propagate across muscle cell’s plasma membrane and into interior of cell via T tubules.
T tubule
4. Proteins in T tubules open Ca2+ channels in sarcoplasmic reticulum.
Sarcoplasmic reticulum
5. Ca2+ is released from sarcoplasmic reticulum. Sarcomeres contract when troponin and tropomyosin move in response to Ca2+ and expose actin binding sites in the thin filaments (see Figure 46.23).
Thick filaments (myosin)
Thin filaments (actin)
Ca2+ ions