Responding to Stimuli
What are Stimuli?
How do we sense them?
How do we respond to them?
Figure 46-00
Responses to StimuliTactile Senses
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sensory
motor
Pictogram of Brain Sensitivity and Responsiveness
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Responses to StimuliTactile Senses
Chemical Senses
Figure 46-16
Brain
Nasal cavity
Odor molecules
Glomeruli
Action potentials
Olfactory bulb of brain
Bone
Olfactory receptor neuron
Mucus
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Mammalian TongueC
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Figure 46-15
Taste bud
Pore
Taste cells (salt, acid, sweet, bitter, meaty, etc.)
Afferent neuron (to brain)
(umami)
http://upload.wikimedia.org/wikipedia/commons/d/db/
Monosodium_glutamate.svg
sucrose sucralose
saccharin sodium cyclamate
lead acetate
mannitol
sorbitol
xylitol
(alitame)
truvia/purevia
A Bogus Tongue Map
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bitter
sweet
salt
sour
salt
sour
All sensors are broadly distributed
Responses to StimuliTactile Senses
Chemical SensesWave Senses
Sound Perception
Do the wave application here!
http://www.frontiernet.net/~imaging/
http://library.thinkquest.org/19537/
Do the wave beats (tuning) application here!
Loudness in Decibels
http://science.pppst.com/sound.html
Figure 46-4
Outer ear
Middle ear
Inner ear
Auditory neurons (to brain)
Cochlea
Ear ossiclesEar canal
Sound waves (in air)
Tympanic membrane (eardrum)
Middle ear cavity
Cochlea
stapesSound waves (in fluid)
Oval window
malleus
incus
Figure 46-5
Cochlea
Auditory nerve
Neurons (to auditory nerve)
Three fluid-filled chambers
Tectorial membrane
Hair cells
Tectorial membrane
Stereocilia
Outer hair cells
Axons of sensory neurons
Inner hair cells
Basilar membrane
The middle chamber of the fluid-filled cochlea contains hair cells.
Hair cells are sandwiched between membranes.
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
Stereocilia
Potassium channels joined by threads
Nucleus
Hair cell
Afferent sensory neuron
Efferent sensory neuron
Pressure wave
K+
K+
Depolarization
Synaptic vesicle
Calcium channel
Neurotransmitter released into synapse
Afferent neuron (to brain)
Ca2+Ca2+
1. Arrival of pressure wave bends stereocilia.
2. Potassium channels open in response to bending.
3. Membrane depolar-izes due to influx of K+.
4. Depolarization triggers inflow of calcium ions.
5. Ca2+ causes synaptic vesicles to fuse with plasma membrane.
6. Neurotransmitter is released and diffuses to afferent neuron.
Figure 46-2
Sound stimulus
Depolarized
Louder sound
Softer sound
Highest response occurs at a characteristic frequency
Sound-receptor cells depolarize in response to sound.
Sound-receptor cells respond more strongly to louder sounds.
Figure 46-6
Cochlea
Oval window
Base of cochlea (near oval window)
Wide part of basilar membrane is flexible—vibrates in response to low frequencies
Narrow part of basilar membrane is stiff—vibrates in response to high frequencies
500 Hz
1 kHz
2 kHz
4 kHz
16 kHz
Uncoiled cochlea
(to show basila
r membrane)
Basilar m
embrane)
Human Hearing ranges from 20 Hz to 20 kHz
Semicircular canals
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Responses to StimuliTactile Senses
Chemical SensesWave Senses
Vestibular Senses
Figure 46-5a
Cochlea
Auditory nerve
Neurons (to auditory nerve)
Three fluid-filled chambers
Tectorial membrane
Hair cells
The middle chamber of the fluid-filled cochlea contains hair cells.
Semicircular canals
Semicircular Canals Contain Statoliths (Otoliths)
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SemiCircular CanalsC
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Responses to StimuliTactile Senses
Chemical SensesWave Senses
Light: An Energy Waveform With Particle Properties Too
wavelength (nm)10-9 meter
0.000000001 meter!
400 500 600 700 nm
wavelength
violet blue green yellow orange red
Light: An Energy Waveform With Particle Properties Too
wavelength (nm)10-9 meter
0.000000001 meter!
400 500 600 700 nm
wavelength
visible spectrum
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
http://www.alanbauer.com/photogallery/Water/Rainbow%20over%20Case%20Inlet-Horz.jpg
White light: all the colors humans can see at once
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QuickTime™ and aTIFF (Uncompressed) decompressor
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http://www.coreywolfe.com/NOV%202004/mlp.jpg
QuickTime™ and aTIFF (Uncompressed) decompressor
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http://www.astrostreasurechest.net/websmurfclub/images/pinsmurfoncloudrainbow.jpg
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
http://jojoretrotoybox.homestead.com/files/Rainbow_Brite_Logo_2.jpg
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
http://www.chez.com/uvinnovation/site/images/introduction/apple_logo.gif Which side of our
brains are we using?
White Light
Leaf Pigments Absorb Most
Colors
Green is reflected!
Light: An Energy Waveform With Particle Properties Too
amplitudebrightnessintensity
Many metric units for different purposesWe 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 contain receptor cells that send axons to the CNS.
Lens
Receptor cells
Ommatidia
Axons
Human vs Insect VisionC
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Vertebrate Eye
blind spot
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http://www.childrenshospital.org/az/Site1517/Images/hyperopia_big.gif
http://www.childrenshospital.org/az/Site1517/Images/myopia_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 Connecting neurons Photoreceptor cellsPigmented epithelium
Retina
Direction of light
Fovea
Optic nerve (to brain)
Sclera
Iris
Pupil
Cornea
Lens
Axons to optic nerve
Figure 46-9
Cornea Lens
Retina (photoreceptors are on the inside surface) Sensory
nerves to brain
The Cephalopod Eye
This “design” is “more intelligent” than that of mammals (humans) because it lacks the blind spot and maximizes light exposure to receptors
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Eye Evolution
Vertebrate Retina
cone
rod
light
Figure 46-10
Rods and cones contain stacks of membranes. Rhodopsin is a transmembrane protein complex.
Cone Rod
Light Light
Rhodopsin
Retinal (pigment)
Opsin (protein component)
The retinal molecule inside rhodopsin changes shape when retinal absorbs light.
Light
trans conformation (activated)
Opsin
cis conformation (inactive)
0.5 µm
Opsin
Figure 46-11The disk of a photoreceptor cell (a rod) before stimulation
The same disk after stimulation (light)
RhodopsinGDP
Transducin (inactive)
cGMP-gated sodium channel (open)
Phosphodiesterase
cGMP
Plasma membrane
of rod
Disk membrane
cGMP-gated sodium channel (closed)
Rhodopsin (activated)
GTP
Transducin (activated)Light
Lack o
f Na
+ curren
t hyp
erpo
larizes mem
bran
e
trans
cis
Figure 46-13Visible spectrum
S opsin 420
M opsin 530
L opsin 560
Figure 46-12No color deficiency Red-green color deficiency
The Eye-Brain ConnectionC
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Responses to StimuliTactile Senses
Chemical SensesWave Senses
Vestibular SensesPositional 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
Myofibril
Dark band Light band
Relaxed
Contracted
Muscle tissue
Bundle of muscle fibers (many cells)
Muscles
Muscle fiber (one cell) contains many myofibrils
Figure 46-20
Myofibril
Relaxed
Contracted
Thin filament (actin) Thick filament (myosin)
Z disk
A
A C
C D
DB
B
Figure 46-21
Myosin head
Actin binding site
ATP binding site
Colors indicate protein subunits
Figure 46-22
CHANGES IN THE CONFORMATION OF THE MYOSIN HEAD PRODUCE MOVEMENT.
1. ATP bound to myosin head. Head releases from thin filament.
2. ATP hydrolized. Head pivots, binds to new actin subunit.
3. Pi released. Head pivots, moves filament (power stroke).
4. ADP released. Cycle is ready to repeat.
Myosin head of thick filament
Actin in thin filament
Figure 46-24
HOW DO ACTION POTENTIALS TRIGGER MUSCLE CONTRACTION?
Motor neuron
Muscle cell
Motor neuronAction potential
ACh
ACh receptor
Action potentials
Thick filaments (myosin)
Thin filaments (actin)
Ca2+ ions
1. Action potential arrives; acetylcholine (Ach) is released.
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.
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).
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