49 Senses Text
-
Upload
xosimpledream -
Category
Documents
-
view
217 -
download
0
Transcript of 49 Senses Text
-
8/14/2019 49 Senses Text
1/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 49
Sensory and Motor
Mechanisms
-
8/14/2019 49 Senses Text
2/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overview: Sensing and Acting
Bats use sonar to detect their prey
Moths, a common prey for bats
Can detect the bats sonar and attempt to flee
Figure 49.1
-
8/14/2019 49 Senses Text
3/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Both of these organisms
Have complex sensory systems that facilitatetheir survival
The structures that make up these systems
Have been transformed by evolution intodiverse mechanisms that sense various stimuliand generate the appropriate physicalmovement
-
8/14/2019 49 Senses Text
4/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 49.1: Sensory receptors transduce
stimulus energy and transmit signals to thecentral nervous system
Sensations are action potentials
That reach the brain via sensory neurons
Once the brain is aware of sensations
It interprets them, giving the perception of stimuli
-
8/14/2019 49 Senses Text
5/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Sensations and perceptions
Begin with sensory reception, the detection of stimuli by sensory receptors
Exteroreceptors
Detect stimuli coming from the outside of thebody
Interoreceptors Detect internal stimuli
-
8/14/2019 49 Senses Text
6/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Functions Performed by Sensory Receptors
All stimuli represent forms of energy
Sensation involves converting this energy
Into a change in the membrane potential of sensory receptors
-
8/14/2019 49 Senses Text
7/113Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Sensory receptors perform four functions in this
process Sensory transduction, amplification,
transmission, and integration
-
8/14/2019 49 Senses Text
8/113Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Two types of sensory receptors exhibit these
functions A stretch receptor in a crayfish
Figure 49.2a
(a)Crayfish stretch receptors have dendritesembedded in abdominal muscles. When theabdomen bends, muscles and dendrites
stretch, producing a receptor potential in thestretch receptor. The receptor potential triggersaction potentials in the axon of the stretch
receptor. A stronger stretch producesa larger receptor potential and higher requency of action potentials.
Muscle
Dendrites
Stretchreceptor
Axon M e m
b r a n e
p o
t e n
t i a l ( m
V )
50
70
0
70
0 1 2 3 4 5 6 7Time (sec)
Action potentials
Receptor potential
Weak
muscle stretch
50
70
0
70
0 1 2 3 4 5 6 7Time (sec)
Strong
muscle stretch
-
8/14/2019 49 Senses Text
9/113Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A hair cell found in vertebrates
of action potentials in the sensory neuron.Bending in the other direction has the oppositeeffects. Thus, hair cells respond to the directionof motion as well as to its strength and speed.s
(b) Vertebrate hair cells have specialized ciliaor microvilli (hairs) that bend when sur-rounding fluid moves. Each hair cell releasesan excitatory neurotransmitter at a synapse
with a sensory neuron, which conducts actionpotentials to the CNS. Bending in one directiondepolarizes the hair cell, causing it to releasemore neurotransmitter and increasing frequency
50 70
0
70
0 1 2 3 4 5 6 7Time (sec)
Action potentials
No fluidmovement
50 70
0
70
0 1 2 3 4 5 6 7Time (sec)
Receptor potential
Fluid moving inone direction
50 70
0
70
0 1 2 3 4 5 6 7Time (sec)
Fluid moving inother direction
M e m
b r a n e
p o
t e n
t i a l ( m
V )
M e m
b r a n e
p o
t e n
t i a l ( m
V )
M e m
b r a n e
p o
t e n
t i a l ( m
V )
Hairs of hair cell
Neuro-trans-mitter atsynapse
Axon
Lessneuro-trans-mitter
Moreneuro-trans-mitter
Figure 49.2b
-
8/14/2019 49 Senses Text
10/113Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Sensory Transduction
Sensory transduction is the conversion of
stimulus energy Into a change in the membrane potential of a
sensory receptor
This change in the membrane potential
Is known as a receptor potential
-
8/14/2019 49 Senses Text
11/113Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Many sensory receptors are extremely
sensitive With the ability to detect the smallest physical
unit of stimulus possible
-
8/14/2019 49 Senses Text
12/113Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Amplification
Amplification is the strengthening of stimulus
energy By cells in sensory pathways
-
8/14/2019 49 Senses Text
13/113Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Transmission
After energy in a stimulus has been transduced
into a receptor potential Some sensory cells generate action potentials,
which are transmitted to the CNS
-
8/14/2019 49 Senses Text
14/113Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Sensory cells without axons
Release neurotransmitters at synapses withsensory neurons
-
8/14/2019 49 Senses Text
15/113Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Integration
The integration of sensory information
Begins as soon as the information is received
Occurs at all levels of the nervous system
-
8/14/2019 49 Senses Text
16/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Some receptor potentials
Are integrated through summation
Another type of integration is sensoryadaptation
A decrease in responsiveness duringcontinued stimulation
-
8/14/2019 49 Senses Text
17/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Types of Sensory Receptors
Based on the energy they transduce, sensory
receptors fall into five categories Mechanoreceptors
Chemoreceptors
Electromagnetic receptors
Thermoreceptors
Pain receptors
-
8/14/2019 49 Senses Text
18/113
-
8/14/2019 49 Senses Text
19/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The mammalian sense of touch
Relies on mechanoreceptors that are thedendrites of sensory neurons
Figure 49.3
Heat
Light touch Pain
Cold
Hair
Nerve Connective tissue Hair movement Strong pressure
Dermis
Epidermis
-
8/14/2019 49 Senses Text
20/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Chemoreceptors
Chemoreceptors include
General receptors that transmit informationabout the total solute concentration of asolution
Specific receptors that respond to individualkinds of molecules
-
8/14/2019 49 Senses Text
21/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Two of the most sensitive and specific
chemoreceptors known Are present in the antennae of the male
silkworm moth
Figure 49.4 0 . 1
m m
-
8/14/2019 49 Senses Text
22/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Electromagnetic Receptors
Electromagnetic receptors detect various forms
of electromagnetic energy Such as visible light, electricity, and
magnetism
-
8/14/2019 49 Senses Text
23/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Some snakes have very sensitive infrared
receptors That detect body heat of prey against a colder
background
Figure 49.5a(a) This rattlesnake and other pit vipers have a pair of infrared receptors,
one between each eye and nostril. The organs are sensitive enoughto detect the infrared radiation emitted by a warm mouse a meter away.The snake moves its head from side to side until the radiation is detectedequally by the two receptors, indicating that the mouse is straight ahead.
-
8/14/2019 49 Senses Text
24/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Many mammals appear to use the Earths
magnetic field lines To orient themselves as they migrate
Figure 49.5b
(b) Some migrating animals, such as these beluga whales, apparentlysense Earths magnetic field and use the information, along withother cues, for orientation.
-
8/14/2019 49 Senses Text
25/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Thermoreceptors
Thermoreceptors, which respond to heat or cold
Help regulate body temperature by signalingboth surface and body core temperature
-
8/14/2019 49 Senses Text
26/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Pain Receptors
In humans, pain receptors, also callednociceptors
Are a class of naked dendrites in the epidermis
Respond to excess heat, pressure, or specificclasses of chemicals released from damagedor inflamed tissues
-
8/14/2019 49 Senses Text
27/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 49.2: The mechanoreceptors involvedwith hearing and equilibrium detect settlingparticles or moving fluid
Hearing and the perception of body equilibrium
Are related in most animals
-
8/14/2019 49 Senses Text
28/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Sensing Gravity and Sound in Invertebrates
Most invertebrates have sensory organs calledstatocysts
That contain mechanoreceptors and function intheir sense of equilibrium
Figure 49.6
Ciliatedreceptor cells
CiliaStatolith
Sensory nerve fibers
-
8/14/2019 49 Senses Text
29/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Many arthropods sense sounds with body hairsthat vibrate
Or with localized ears consisting of atympanic membrane and receptor cells
Figure 49.7
1 mm
Tympanicmembrane
-
8/14/2019 49 Senses Text
30/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Hearing and Equilibrium in Mammals
In most terrestrial vertebrates
The sensory organs for hearing andequilibrium are closely associated in the ear
-
8/14/2019 49 Senses Text
31/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Exploring the structure of the human ear
Figure 49.8
Pinna
Auditorycanal
Eustachiantube
Tympanicmembrane
Stapes
Incus
Malleus
Skullbones
Semicircular canals
Auditory nerve,to brain
Cochlea
Tympanicmembrane
Ovalwindow
Eustachiantube
Roundwindow
Vestibular canal
Tympanic canal
Auditory nerve
BoneCochlear duct
Hair cells Tectorialmembrane
Basilar membrane
To auditorynerve
Axons of sensory neurons
1 Overview of ear structure 2 The middle ear and inner ear
4 The organ of Corti 3 The cochleaOrgan of Corti
Outer ear Middle
ear Inner ear
-
8/14/2019 49 Senses Text
32/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Hearing
Vibrating objects create percussion waves inthe air
That cause the tympanic membrane to vibrate
The three bones of the middle ear
Transmit the vibrations to the oval window onthe cochlea
-
8/14/2019 49 Senses Text
33/113
-
8/14/2019 49 Senses Text
34/113
-
8/14/2019 49 Senses Text
35/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The cochlea can distinguish pitch
Because the basilar membrane is not uniformalong its length
Cochlea(uncoiled)
Basilar membrane
Apex(wide and flexible)
Base(narrow and stiff)
500 Hz(low pitch)1 kHz
2 kHz
4 kHz
8 kHz
16 kHz(high pitch)
Frequency producing maximumvibration
Figure 49.10
-
8/14/2019 49 Senses Text
36/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Each region of the basilar membrane vibratesmost vigorously
At a particular frequency and leads toexcitation of a specific auditory area of thecerebral cortex
E ilib i
-
8/14/2019 49 Senses Text
37/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Equilibrium
Several of the organs of the inner ear
Detect body position and balance
-
8/14/2019 49 Senses Text
38/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The utricle, saccule, and semicircular canals inthe inner ear
Function in balance and equilibrium
Figure 49.11
The semicircular canals, arranged in threespatial planes, detect angular movementsof the head.
Body movement
Nervefibers
Each canal has at its base aswelling called an ampulla,containing a cluster of hair cells.
When the head changes its rateof rotation, inertia preventsendolymph in the semicircular canals from moving with the head,so the endolymph presses against
the cupula, bending the hairs.
The utricle and saccule tell the brain whichway is up and inform it of the bodysposition or linear acceleration.
The hairs of the hair cellsproject into a gelatinous capcalled the cupula.
Bending of the hairs increases thefrequency of action potentials insensory neurons in directproportion to the amount of
rotational acceleration.
Vestibule
Utricle
Saccule
Vestibular nerve
Flowof endolymph
Flowof endolymph
CupulaHairs
Hair cell
H i g d E ilib i i Oth V t b t
-
8/14/2019 49 Senses Text
39/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Hearing and Equilibrium in Other Vertebrates
Like other vertebrates, fishes and amphibians
Also have inner ears located near the brain
-
8/14/2019 49 Senses Text
40/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Most fishes and aquatic amphibians
Also have a lateral line system along bothsides of their body
-
8/14/2019 49 Senses Text
41/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The lateral line system containsmechanoreceptors
With hair cells that respond to water movement
Figure 49.12 Nerve fiber
Supporting cell
Cupula
Sensoryhairs
Hair cell
Segmental muscles of body wall Lateral nerve
Scale EpidermisLateral line canal
Neuromast
Opening of lateralline canal
Lateralline
-
8/14/2019 49 Senses Text
42/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 49.3: The senses of taste and smellare closely related in most animals
The perceptions of gustation (taste) andolfaction (smell)
Are both dependent on chemoreceptors thatdetect specific chemicals in the environment
-
8/14/2019 49 Senses Text
43/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The taste receptors of insects are locatedwithin sensory hairs called sensilla
Which are located on the feet and inmouthparts
-
8/14/2019 49 Senses Text
44/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 49.13
EXPERIMENT Insects taste using gustatory sensilla (hairs) on their feet andmouthparts. Each sensillum contains four chemoreceptors with dendrites thatextend to a pore at the tip of the sensillum. To study the sensitivity of eachchemoreceptor, researchers immobilized a blowfly ( Phormia regina ) by attachingit to a rod with wax. They then inserted the tip of a microelectrode into onesensillum to record action potentials in the chemoreceptors, while they used apipette to touch the pore with various test substances.
N u m
b e r o
f a c t
i o n p o
t e n
t i a l s
i n f i r s t s e c o n d
o f r e s p o n s e
CONCLUSION Any natural food probably stimulates multiple chemoreceptors. Byintegrating sensations, the insects brain can apparently distinguish a very largenumber of tastes.
To brain
Chemo-receptors
Pore at tip
Pipette containingtest substance
To voltagerecorder
Sensillum
Microelectrode
50
30
10
00.5 M NaCl
Meat 0.5 M Sucrose
Honey
Stimulus
Chemoreceptors
RESULTS Each chemoreceptor is especially sensitive to a particular class of substance, but this specificity is relative; each cell can respond tosome extent to a broad range of different chemical stimuli.
Taste in Humans
-
8/14/2019 49 Senses Text
45/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Taste in Humans
The receptor cells for taste in humans
Are modified epithelial cells organized intotaste buds
Five taste perceptions involve several signaltransduction mechanisms
Sweet, sour, salty, bitter, and umami (elicitedby glutamate)
-
8/14/2019 49 Senses Text
46/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Taste pore Sugar molecule
Sensoryreceptor cells
Sensoryneuron
Taste bud
Tongue
G protein Adenylyl cyclase
Ca 2+
ATP
cAMP
Proteinkinase A
Sugar
Sugar receptor
SENSORYRECEPTORCELL Synaptic
vesicle
K+
Neurotransmitter
Sensory neuron
Transduction in taste receptors
Occurs by several mechanisms
Figure 49.14
4 The decrease in the membranes permeability toK+ depolarizes the membrane.
5 Depolarization opens voltage-gated calcium ion(Ca 2+) channels, and Ca 2+ diffuses into the receptor cell.
6 The increased Ca 2+ concentration causessynaptic vesicles to release neurotransmitter.
3 Activated protein kinase A closes K + channels inthe membrane.
2 Binding initiates a signal transduction pathwayinvolving cyclic AMP and protein kinase A.
1 A sugar molecule binds
to a receptor protein onthe sensory receptor cell.
Smell in Humans
-
8/14/2019 49 Senses Text
47/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Smell in Humans
Olfactory receptor cells
Are neurons that line the upper portion of thenasal cavity
-
8/14/2019 49 Senses Text
48/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
When odorant molecules bind to specificreceptors
A signal transduction pathway is triggered,sending action potentials to the brain
Brain
Nasal cavity
Odorant
Odorantreceptors
Plasmamembrane
Odorant
Cilia
Chemoreceptor
Epithelial cell
Bone
Olfactory bulb
Action potentials
MucusFigure 49.15
-
8/14/2019 49 Senses Text
49/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 49.4: Similar mechanisms underlievision throughout the animal kingdom
Many types of light detectors
Have evolved in the animal kingdom and maybe homologous
Vision in Invertebrates
-
8/14/2019 49 Senses Text
50/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Vision in Invertebrates
Most invertebrates
Have some sort of light-detecting organ
-
8/14/2019 49 Senses Text
51/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Light
Light shining fromthe front is detected
Photoreceptor
Visual pigment
Ocellus
Nerve tobrain
Screeningpigment
Light shining frombehind is blockedby the screening pigment
One of the simplest is the eye cup of planarians
Which provides information about lightintensity and direction but does not formimages
Figure 49.16
-
8/14/2019 49 Senses Text
52/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Two major types of image-forming eyes haveevolved in invertebrates
The compound eye and the single-lens eye
-
8/14/2019 49 Senses Text
53/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Compound eyes are found in insects andcrustaceans
And consist of up to several thousand lightdetectors called ommatidia
Figure 49.17ab
Cornea
Crystallinecone
Rhabdom
Photoreceptor Axons
Ommatidium
Lens
2 m m
(a) The faceted eyes on thehead of a fly,
photographed witha stereomicroscope.
(b) The cornea and crystalline cone of each ommatidium function asa lens that focuses light on therhabdom, a stack of pigmented
plates inside a circle of photoreceptors. The rhabdomtraps light and guides it tophotoreceptors. The imageformed by a compound eye is amosaic of dots produced by differentintensities of light entering themany ommatidia from different angles.
-
8/14/2019 49 Senses Text
54/113
-
8/14/2019 49 Senses Text
55/113
Structure of the Eye
-
8/14/2019 49 Senses Text
56/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Structure of the Eye
The main parts of the vertebrate eye are
The sclera, which includes the cornea
The choroid, a pigmented layer
The conjunctiva, that covers the outer surfaceof the sclera
-
8/14/2019 49 Senses Text
57/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The iris, which regulates the pupil
The retina, which contains photoreceptors The lens, which focuses light on the retina
-
8/14/2019 49 Senses Text
58/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The structure of the vertebrate eye
Figure 49.18
Ciliary body
Iris
Suspensoryligament
Cornea
Pupil
Aqueoushumor
Lens
Vitreous humor
Optic disk(blind spot)
Central artery andvein of the retina
Opticnerve
Fovea (center of visual field)
Retina
ChoroidSclera
-
8/14/2019 49 Senses Text
59/113
-
8/14/2019 49 Senses Text
60/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The human retina contains two types of photoreceptors
Rods are sensitive to light but do notdistinguish colors
Cones distinguish colors but are not assensitive
Sensory Transduction in the Eye
-
8/14/2019 49 Senses Text
61/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
y y
Each rod or cone in the vertebrate retina
Contains visual pigments that consist of a light-absorbing molecule called retinal bonded to aprotein called opsin
-
8/14/2019 49 Senses Text
62/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Rods contain the pigment rhodopsin
Which changes shape when it absorbs light
Figure 49.20a, b
Rod
Outer segment
Cell body
Synapticterminal
Disks
Insideof disk
(a) Rods contain the visual pigment rhodopsin, which is embedded ina stack of membranous disks in the rods outer segment.Rhodopsin consists of the light-absorbing molecule retinalbonded to opsin, a protein. Opsin has seven helices that spanthe disk membrane.
(b) Retinal exists as two isomers. Absorption of light convertsthe cis isomer to the trans isomer, whichcauses opsin to change its conformation (shape).After a few minutes, retinal detaches from opsin.In the dark, enzymes convert retinal back to its cisform, which recombines with opsin to form rhodopsin.
Retinal
OpsinRhodopsin
Cytosol
HC
CH2C
CH2C C
HCH 3
CH 3H
CC
CH 3 H CH 3
CC
CC
CC
C
H
H
H
H
OH
H3C
HC
CH2C
CH
2C C
HCH 3
CH 3H
CC
CH 3 H CH 3
C C C C
HH
CH 3
H
C C CHO
CH 3
trans isomer
cis isomer
EnzymesLight
Processing Visual Information
-
8/14/2019 49 Senses Text
63/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
g
The processing of visual information
Begins in the retina itself
-
8/14/2019 49 Senses Text
64/113
-
8/14/2019 49 Senses Text
65/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
In the dark, both rods and cones
Release the neurotransmitter glutamate intothe synapses with neurons called bipolar cells,which are either hyperpolarized or depolarized
-
8/14/2019 49 Senses Text
66/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
In the light, rods and cones hyperpolarize
Shutting off their release of glutamate
The bipolar cells
Are then either depolarized or hyperpolarized
Figure 49.22
Dark Responses
Rhodopsin inactive
Na + channels open
Rod depolarized
Glutamatereleased
Bipolar cell either depolarized or hyperpolarized,depending onglutamate receptors
Light Responses
Rhodopsin active
Na + channels closed
Rod hyperpolarized
No glutamatereleased
Bipolar cell either hyperpolarized or depolarized,depending onglutamate receptors
-
8/14/2019 49 Senses Text
67/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Three other types of neurons contribute toinformation processing in the retina
Ganglion cells, horizontal cells, and amacrinecells
Figure 49.23Opticnervefibers
Ganglioncell
Bipolar cell
Horizontalcell
Amacrinecell
Pigmentedepithelium
NeuronsCone Rod
Photoreceptors
Retina
Retina
Optic nerve
Tobrain
-
8/14/2019 49 Senses Text
68/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Signals from rods and cones
Travel from bipolar cells to ganglion cells
The axons of ganglion cells are part of the opticnerve
That transmit information to the brain
Figure 49.24
Leftvisualfield
Rightvisualfield
Lefteye
Righteye
Optic nerve
Optic chiasm
Lateralgeniculatenucleus
Primaryvisual cortex
-
8/14/2019 49 Senses Text
69/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Most ganglion cell axons lead to the lateralgeniculate nuclei of the thalamus
Which relays information to the primary visualcortex
Several integrating centers in the cerebralcortex
Are active in creating visual perceptions
-
8/14/2019 49 Senses Text
70/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 49.5: Animal skeletons function insupport, protection, and movement
The various types of animal movements
All result from muscles working against some
type of skeleton
-
8/14/2019 49 Senses Text
71/113
Hydrostatic Skeletons
-
8/14/2019 49 Senses Text
72/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A hydrostatic skeleton
Consists of fluid held under pressure in aclosed body compartment
This is the main type of skeleton
In most cnidarians, flatworms, nematodes, andannelids
-
8/14/2019 49 Senses Text
73/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Annelids use their hydrostatic skeleton for peristalsis
A type of movement on land produced byrhythmic waves of muscle contractions
Figure 49.25ac
(a) Body segments at the head and just in frontof the rear are short and thick (longitudinalmuscles contracted; circular musclesrelaxed) and anchored to the ground bybristles. The other segments are thin andelongated (circular muscles contracted;longitudinal muscles relaxed.)
(b) The head has moved forward because
circular muscles in the head segments havecontracted. Segments behind the head andat the rear are now thick and anchored, thuspreventing the worm from slipping backward.
(c) The head segments are thick again andanchored in their new positions. The rear segments have released their hold on theground and have been pulled forward.
Longitudinalmuscle relaxed(extended)
Circular musclecontracted
Circular musclerelaxed
Longitudinalmusclecontracted
HeadBristles
Exoskeletons
-
8/14/2019 49 Senses Text
74/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
An exoskeleton is a hard encasement
Deposited on the surface of an animal
Exoskeletons
Are found in most molluscs and arthropods
Endoskeletons
-
8/14/2019 49 Senses Text
75/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
An endoskeleton consists of hard supportingelements
Such as bones, buried within the soft tissue of an animal
Endoskeletons Are found in sponges, echinoderms, and
chordates
-
8/14/2019 49 Senses Text
76/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The mammalian skeleton is built from morethan 200 bones
Some fused together and others connected at joints by ligaments that allow freedom of movement
-
8/14/2019 49 Senses Text
77/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The human skeleton
Figure 49.26
1 Ball-and-socket joints, where the humerus contactsthe shoulder girdle and where the femur contacts thepelvic girdle, enable us to rotate our arms andlegs and move them in several planes.
2 Hinge joints, such as between the humerus andthe head of the ulna, restrict movement to a singleplane.
3 Pivot joints allow us to rotate our forearm at theelbow and to move our head from side to side.
keyAxial skeletonAppendicular skeleton
Skull
Shoulder girdle
Clavicle
Scapula
Sternum
RibHumerus
Vertebra
Radius
UlnaPelvicgirdle
Carpals
Phalanges
Metacarpals
Femur Patella
Tibia
Fibula
TarsalsMetatarsalsPhalanges
1
Examplesof joints
2
3
Head of humerus
Scapula
Humerus
Ulna
UlnaRadius
Physical Support on Land
-
8/14/2019 49 Senses Text
78/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
In addition to the skeleton
Muscles and tendons help support large landvertebrates
-
8/14/2019 49 Senses Text
79/113
-
8/14/2019 49 Senses Text
80/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Skeletal muscles are attached to the skeletonin antagonistic pairs
With each member of the pair working againsteach other
Figure 49.27
Human Grasshopper
Bicepscontracts
Tricepsrelaxes
Forearmflexes
Bicepsrelaxes
Tricepscontracts
Forearmextends
Extensor musclerelaxes
Flexor musclecontracts
Tibiaflexes
Extensor musclecontracts
Flexor musclerelaxes
Tibiaextends
Vertebrate Skeletal Muscle
-
8/14/2019 49 Senses Text
81/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Vertebrate skeletal muscle
Is characterized by a hierarchy of smaller andsmaller units
Figure 49.28
Muscle
Bundle of muscle fibers
Single muscle fiber (cell)
Plasma membrane
Myofibril
Lightband Dark band
Z line
Sarcomere
TEM 0.5 mI band A band I band
M line
Thickfilaments(myosin)
Thinfilaments(actin)
H zoneSarcomere
Z lineZ line
Nuclei
-
8/14/2019 49 Senses Text
82/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A skeletal muscle consists of a bundle of longfibers
Running parallel to the length of the muscle
A muscle fiber
Is itself a bundle of smaller myofibrils arrangedlongitudinally
-
8/14/2019 49 Senses Text
83/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The myofibrils are composed to two kinds of myofilaments
Thin filaments, consisting of two strands of actin and one strand of regulatory protein
Thick filaments, staggered arrays of myosinmolecules
-
8/14/2019 49 Senses Text
84/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Skeletal muscle is also called striated muscle
Because the regular arrangement of themyofilaments creates a pattern of light anddark bands
-
8/14/2019 49 Senses Text
85/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Each repeating unit is a sarcomere
Bordered by Z lines
The areas that contain the myofilments
Are the I band, A band, and H zone
The Sliding-Filament Model of Muscle Contraction
-
8/14/2019 49 Senses Text
86/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
According to the sliding-filament model of muscle contraction
The filaments slide past each other longitudinally, producing more overlapbetween the thin and thick filaments
-
8/14/2019 49 Senses Text
87/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
As a result of this sliding
The I band and the H zone shrink
Figure 49.29ac
(a) Relaxed muscle fiber. In a relaxed muscle fiber, the I bands
and H zone are relatively wide.
(b) Contracting muscle fiber. During contraction, the thick andthin filaments slide past each other, reducing the width of theI bands and H zone and shortening the sarcomere.
(c) Fully contracted muscle fiber. In a fully contracted musclefiber, the sarcomere is shorter still. The thin filaments overlap,eliminating the H zone. The I bands disappear as the ends of the thick filaments contact the Z lines.
0.5 m
Z HA
Sarcomere
-
8/14/2019 49 Senses Text
88/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The sliding of filaments is based on
The interaction between the actin and myosinmolecules of the thick and thin filaments
The head of a myosin molecule binds to an
actin filament Forming a cross-bridge and pulling the thin
filament toward the center of the sarcomere
-
8/14/2019 49 Senses Text
89/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Myosin-actin interactions underlying musclefiber contraction
Figure 49.30
Thick filament
Thin filaments
Thin filament
ATPATP
ADPADP
ADP
P i P i
P i
Cross-bridge
Myosin head (low-energy configuration)
Myosin head (high-energy configuration)
+
Myosin head (low-
energy configuration)
Thin filament movestoward center of sarcomere.
Thickfilament
ActinCross-bridgebinding site
1 Starting here, the myosin head isbound to ATP and is in its low-energy confinguration.
2 The myosin head hydrolyzesATP to ADP and inorganicphosphate ( I ) and is in itshigh-energy configuration.
P
1 The myosin head binds toactin, forming a cross-bridge.
3
4 Releasing ADP and ( i), myosinrelaxes to its low-energy configuration,sliding the thin filament.
P
5 Binding of a new mole-cule of ATP releases themyosin head from actin,
and a new cycle begins.
The Role of Calcium and Regulatory Proteins
-
8/14/2019 49 Senses Text
90/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A skeletal muscle fiber contracts
Only when stimulated by a motor neuron
-
8/14/2019 49 Senses Text
91/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
When a muscle is at rest
The myosin-binding sites on the thin filamentare blocked by the regulatory proteintropomyosin
Figure 49.31a
ActinTropomyosin Ca 2+-binding sites
Troponin complex
(a) Myosin-binding sites blocked
-
8/14/2019 49 Senses Text
92/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
For a muscle fiber to contract
The myosin-binding sites must be uncovered This occurs when calcium ions (Ca 2+)
Bind to another set of regulatory proteins, thetroponin complex
Figure 49.31b
Ca 2+
Myosin-binding site
(b) Myosin-binding sites exposed
-
8/14/2019 49 Senses Text
93/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The stimulus leading to the contraction of askeletal muscle fiber
Is an action potential in a motor neuron thatmakes a synapse with the muscle fiber
Figure 49.32
Motor neuron axon
Mitochondrion
Synapticterminal
T tubule
Sarcoplasmicreticulum
Myofibril
Plasma membraneof muscle fiber
Sarcomere
Ca 2+ releasedfrom sarcoplasmicreticulum
-
8/14/2019 49 Senses Text
94/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The synaptic terminal of the motor neuron
Releases the neurotransmitter acetylcholine,depolarizing the muscle and causing it toproduce an action potential
-
8/14/2019 49 Senses Text
95/113
-
8/14/2019 49 Senses Text
96/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
ACh
Synapticterminalof motor
neuronSynaptic cleft T TUBULE
PLASMA MEMBRANE
SR
ADP
CYTOSOL
Ca 2+
Ca 2+
P 2
Cytosolic Ca 2+ isremoved by activetransport intoSR after actionpotential ends.
6
Review of contraction in a skeletal muscle fiber
Figure 49.33
Acetylcholine (ACh) released by synaptic terminal diffuses across synapticcleft and binds to receptor proteins on muscle fibers plasma membrane,triggering an action potential in muscle fiber.
1
Action potential is propa-gated along plasmamembrane and downT tubules.
2
Action potentialtriggers Ca 2+release from sarco-plasmic reticulum(SR).
3
Myosin cross-bridges alternately attachto actin and detach, pulling actinfilaments toward center of sarcomere;ATP powers sliding of filaments.
5
Calcium ions bind to troponin;troponin changes shape,removing blocking actionof tropomyosin; myosin-bindingsites exposed.
4
Tropomyosin blockage of myosin-binding sites is restored; contractionends, and muscle fiber relaxes.
7
Neural Control of Muscle Tension
-
8/14/2019 49 Senses Text
97/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Contraction of a whole muscle is graded
Which means that we can voluntarily alter theextent and strength of its contraction
-
8/14/2019 49 Senses Text
98/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
There are two basic mechanisms by which thenervous system produces graded contractionsof whole muscles
By varying the number of fibers that contract
By varying the rate at which muscle fibers arestimulated
-
8/14/2019 49 Senses Text
99/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
In a vertebrate skeletal muscle
Each branched muscle fiber is innervated byonly one motor neuron
Each motor neuron
May synapse with multiple muscle fibers
Figure 49.34
Spinal cord
Nerve
Motor neuroncell body
Motor unit 1
Motor unit 2
Motor neuronaxon
Muscle
Tendon
Synaptic terminals
Muscle fibers
-
8/14/2019 49 Senses Text
100/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A motor unit
Consists of a single motor neuron and all themuscle fibers it controls
Recruitment of multiple motor neurons
Results in stronger contractions
-
8/14/2019 49 Senses Text
101/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A twitch
Results from a single action potential in amotor neuron
More rapidly delivered action potentials
Produce a graded contraction by summation
Figure 49.35
Actionpotential Pair of
actionpotentials
Series of actionpotentials at
high frequency
Time
T e n s i o n
Singletwitch
Summation of two twitches
Tetanus
-
8/14/2019 49 Senses Text
102/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Tetanus is a state of smooth and sustainedcontraction
Produced when motor neurons deliver a volleyof action potentials
Types of Muscle Fibers
-
8/14/2019 49 Senses Text
103/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Skeletal muscle fibers are classified as slowoxidative, fast oxidative, and fast glycolytic
Based on their contraction speed and major pathway for producing ATP
-
8/14/2019 49 Senses Text
104/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Types of skeletal muscles
-
8/14/2019 49 Senses Text
105/113
-
8/14/2019 49 Senses Text
106/113
C 49 7 L i i
-
8/14/2019 49 Senses Text
107/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 49.7: Locomotion requires energy toovercome friction and gravity
Movement is a hallmark of all animals
And usually necessary for finding food or
evading predators
Locomotion
Is active travel from place to place
Swimming
O i f i i
-
8/14/2019 49 Senses Text
108/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overcoming friction
Is a major problem for swimmers Overcoming gravity is less of a problem for
swimmers
Than for animals that move on land or fly
Locomotion on Land
W lki i h i li l d
-
8/14/2019 49 Senses Text
109/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Walking, running, hopping, or crawling on land
Requires an animal to support itself and moveagainst gravity
Di d i f li l d
-
8/14/2019 49 Senses Text
110/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Diverse adaptations for traveling on land
Have evolved in various vertebrates
Figure 49.36
Flying
Fli ht i th t i d l h lift
-
8/14/2019 49 Senses Text
111/113
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Flight requires that wings develop enough lift
To overcome the downward force of gravity
-
8/14/2019 49 Senses Text
112/113
A i l th t i li d f i i g
-
8/14/2019 49 Senses Text
113/113
Animals that are specialized for swimming
Expend less energy per meter traveled thanequivalently sized animals specialized for flying or running