Responding to Stimuli 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?

Figure 46-00

Responses to StimuliTactile Senses

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sensory

motor

Pictogram of Brain Sensitivity and Responsiveness

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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


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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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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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


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



http://www.tvtome.com/images/shows/4/8/40-11946.jpg



http://www.coreywolfe.com/NOV%202004/mlp.jpg



http://www.astrostreasurechest.net/websmurfclub/images/pinsmurfoncloudrainbow.jpg



http://jojoretrotoybox.homestead.com/files/Rainbow_Brite_Logo_2.jpg



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!


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

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.visionassociates.net/picts/Refractive%20errors.JPG

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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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).

Documents

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