Responding to Stimuli
What are Stimuli?
How do we sense them?
How do we respond to them?
Figure 46-00
Responses to Stimuli
Tactile Senses
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sensory
motor
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Pictogram of Brain
Sensitivity and
Responsiveness
Responses to Stimuli
Tactile Senses
Chemical Senses
Figure 46-16
Action potentials
Brain
Glomeruli
Nasal cavity
Olfactory
bulb of
brain
Bone
Olfactory
receptor
neuron
Mucus
Odor molecules
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Mammalian Tongue
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Figure 46-15
Taste bud
Pore
Taste cells
(salt, acid,
sweet, bitter,
meaty, etc.)
(umami)
Afferent neuron (to brain)
http://upload.wikimedia.org/wikipedia/co
mmons/d/db/Monosodium_glutamate.svg
mannitol
sucrose
sucralose
sorbitol
saccharin
sodium cyclamate
xylitol
(alitame)

truvia/purevia
lead acetate
A Bogus Tongue Map
http://www.getgreatcodes.com/graphics/funny/18/funnypic227.jpg
bitter
sour
sour
salt
salt
sweet
All sensors are broadly
distributed
Responses to Stimuli
Tactile Senses
Chemical Senses
Wave Senses
Sound Perception
Do the wave
application here!
http://www.frontiernet.net/
~imaging/
Do the wave beats
(tuning) application here!
http://library.thinkquest.org
/19537/
Loudness in Decibels
http://science.pppst.com/sound.html
Figure 46-4
Middle Inner
ear
ear
Outer
ear
Auditory
neurons
(to brain)
Cochlea
Ear canal
Ear ossicles
malleus
Oval
window
incus
stapes
Sound
waves
(in air)
Sound
waves
(in fluid)
Cochlea
Middle
ear cavity
Tympanic membrane
(eardrum)
Figure 46-5
The middle chamber of the fluid-filled cochlea contains hair
cells.
Cochlea
Auditory
nerve
Three
fluidfilled
chambers
Tectorial
membrane
Neurons
(to auditory
nerve)
Hair
cells
Hair cells are sandwiched between membranes.
Stereocilia
Outer
hair cells
Axons of
sensory
neurons
Inner
hair cells
Tectorial
membrane
Basilar
membrane
Figure 46-3
Hair cells have many stereocilia and one kinocilium.
Kinocilium
WHEN STEREOCILIA BEND, A SEQUENCE OF EVENTS
RESULTS IN THE RELEASE OF NEUROTRANSMITTER.
1. Arrival of pressure
Pressure wave
Stereocilia
wave bends stereocilia.
K+
Potassium
channels
joined by
threads
2. Potassium channels
open in response to
bending.
K+
Nucleus
Hair cell
Afferent
sensory
neuron
Efferent
sensory
neuron
3. Membrane depolarizes due to influx of K+.
Depolarization
4. Depolarization triggers
Synaptic
vesicle
inflow of calcium ions.
Calcium
channel
5. Ca2+ causes synaptic
Ca2+
Neurotransmitter
released into
synapse
Ca2+
Afferent
neuron
(to brain)
vesicles to fuse with
plasma membrane.
6. Neurotransmitter is
released and diffuses to
afferent neuron.
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
Figure 46-6
Semicircular canals
Cochlea
Oval
window
Base of
cochlea
(near oval
window)
Wide part of basilar
membrane is flexible—
vibrates in response to
low frequencies
500 Hz
1 kHz
2 kHz
Human Hearing ranges
4 kHz
from 20 Hz to 20 kHz
16 kHz
Narrow part of basilar membrane is stiff—
vibrates in response to high frequencies
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Responses to Stimuli
Tactile Senses
Chemical Senses
Wave Senses
Vestibular Senses
Figure 46-5a
The middle chamber of the fluid-filled cochlea contains
hair cells.
Semicircular canals
Cochlea
Three
fluidfilled
chambers
Tectorial
membrane
Hair
cells
Auditory
nerve
Neurons
(to auditory
nerve)
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Semicircular Canals Contain Statoliths
(Otoliths)
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SemiCircular Canals
Responses to Stimuli
Tactile Senses
Chemical Senses
Wave Senses
Light: An Energy Waveform With Particle Properties Too
wavelength
violet
400
blue
green yellow orange red
500
600
wavelength (nm)
700 nm
10-9 meter
0.000000001 meter!
Light: An Energy Waveform With Particle Properties Too
wavelength
visible spectrum
400
500
600
wavelength (nm)
700 nm
10-9 meter
0.000000001 meter!
White light: all the colors humans can see at once
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
http://www.alanbauer.com/photogallery/Water/Rainbow%20over%20Case%20Inlet-Horz.jpg
http://www.chez.com/uvinnovation/
site/images/introduction/apple_logo.
gif
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Which side of our
brains are we using?
Qui ckTi me™ and a
TIFF (Uncompressed) decompr essor
are needed to see this pictur e.
http://jojoretrotoybox.homestead.com/files/Rainbow_Brite_Logo_2.jpg
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Qui ckTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this pictur e.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
http://www.astrostreasurechest.n
et/websmurfclub/images/pinsmur
foncloudrainbow.jpg
http://www.tvtome.com/images/shows/4/8/40-11946.jpg
http://www.coreywolfe.com/NOV%202004/mlp.jpg
White Light
Green is reflected!
Leaf Pigments
Absorb Most
Colors
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
Light wavelength demonstration:
http://micro.magnet.fsu.edu/primer/java/wavebasics/index.html
Figure 46-7
Ommatidia are the functional units of insect eyes.
Ommatidia
Ommatidia contain receptor
cells that send axons to the CNS.
Lens
Receptor
cells
Axons
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Human vs Insect Vision
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Vertebrate Eye
blind spot
http://www.cagle.com/working/100427/cagle00.gif
http://www.visionassociates.net/picts/Refractive%20errors.JPG
http://www.childrenshospital.org/az/Site1517/Images/myopia_big.gif
http://www.childrenshospital.org/az/Site1517/Images/hyperopia_big.gif
http://www.vision-and-eyes.com/images/img-presbyopia.jpg
Normal Cornea
Astigmatic Cornea
blind spot
Figure 46-8
The structure of the vertebrate eye.
In the retina, cells are arranged in layers.
Ganglion cells
Sclera
Iris
Retina
Direction of light
Pupil
Cornea
Fovea
Lens
Optic nerve
(to brain)
Axons to optic nerve
Connecting neurons
Pigmented
Photoreceptor cells epithelium
Figure 46-9
The Cephalopod Eye
Cornea
Lens
Retina
(photoreceptors
are on the inside
surface)
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
http://upload.wikimedia.org/wikipedia/commons/thumb/b/b6/Diagram_of_eye_evolution.svg/350px-Diagram_of_eye_evolution.svg.png
Eye Evolution
Vertebrate Retina
rod
cone
light
Figure 46-10
Rods and cones contain stacks of membranes.
Rhodopsin is a transmembrane protein complex.
Opsin
(protein
component)
Cone
Retinal
(pigment)
0.5 µm
Rod
Light
Rhodopsin
Light
The retinal molecule inside rhodopsin changes shape when retinal absorbs light.
trans conformation
(activated)
cis conformation
(inactive)
Opsin
Opsin
Light
Figure 46-11
The disk of a photoreceptor cell (a rod) before stimulation
cGMP-gated sodium
channel (open)
Rhodopsin
GDP
cGMP
cis
Transducin Phosphodiesterase
(inactive)
Plasma
membrane of
rod
Disk membrane
The same disk after stimulation (light)
Rhodopsin
(activated)
GTP
trans
Light
Transducin
(activated)
Lack of Na+ current hyperpolarizes membrane
cGMP-gated sodium
channel (closed)
Figure 46-13
Visible spectrum
S opsin
420
M opsin L opsin
530
560
Figure 46-12
No color deficiency
Red-green color deficiency
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The Eye-Brain Connection
Responses to Stimuli
Tactile Senses
Chemical Senses
Wave Senses
Vestibular Senses
Positional Senses
Figure 46-17
Ball-and-socket
joints swivel
Hinge
joints
hinge
Figure 46-18a
Endoskeleton
Flexor
(hamstring)
contracts
Extensor
(quadriceps)
contracts
Figure 46-19
Sarcomere
Muscles
Myofibril
Dark band Light band
Bundle of
muscle fibers
(many cells)
Muscle fiber
(one cell)
contains many
myofibrils
Relaxed
Contracted
Muscle tissue
Figure 46-20
Thin filament (actin)
Myofibril
Thick filament (myosin)
Relaxed
Z disk
A
B
C
D
Contracted
A
B
C D
Figure 46-21
Myosin
head
Colors indicate
protein subunits
ATP binding site
Actin binding site
Figure 46-22
CHANGES IN THE CONFORMATION OF THE MYOSIN HEAD PRODUCE MOVEMENT.
1. ATP bound to myosin head.
Myosin head
of thick filament
Head releases from thin filament.
Actin in thin filament
4. ADP released.
2. ATP hydrolized.
Cycle is ready to
repeat.
Head pivots, binds to
new actin subunit.
3. Pi released. Head pivots,
moves filament (power stroke).
Figure 46-24
Motor neuron
Muscle cell
HOW DO ACTION POTENTIALS TRIGGER
MUSCLE CONTRACTION?
Motor neuron
Action
potential
1. Action potential
ACh
arrives; acetylcholine
(Ach) is released.
ACh receptor
Action
potentials
2. ACh binds to ACh
receptors on the muscle
cell, triggering depolarization that leads to
action potential.
3. Action potentials
propagate across muscle
cell’s plasma membrane
and into interior of cell via
T tubules.
4. Proteins in T tubules
open Ca2+ channels in
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 Ca2+
(actin)
ions