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Biology in Focus - Chapter 38
- 1. CAMPBELL BIOLOGY IN FOCUS
© 2014 Pearson Education, Inc.
Urry • Cain • Wasserman • Minorsky • Jackson • Reece
Lecture Presentations by
Kathleen Fitzpatrick and Nicole Tunbridge
38
Nervous and
Sensory Systems
- 2. © 2014 Pearson Education, Inc.
Overview: Sense and Sensibility
Gathering, processing, and organizing
information are essential functions of all nervous
systems
- 4. © 2014 Pearson Education, Inc.
The ability to sense and react originated billions of
years ago in prokaryotes
Hydras, jellies, and cnidarians are the simplest
animals with nervous systems
In most cnidarians, interconnected nerve cells form
a nerve net, which controls contraction and
expansion of the gastrovascular cavity
Concept 38.1: Nervous systems consist of circuits
of neurons and supporting cells
- 5. © 2014 Pearson Education, Inc.
Figure 38.2
(a) Hydra (cnidarian)
Spinal
cord
(dorsal
nerve
cord)
Brain
(b) Planarian (flatworm)
(c) Insect (arthropod) (d) Salamander (vertebrate)
Sensory
ganglia
Brain
Nerve
cords
Eyespot
Transverse
nerve
Segmental
ganglia
Brain
Nerve net
Ventral
nerve cord
- 6. © 2014 Pearson Education, Inc.
In more complex animals, the axons of multiple
nerve cells are often bundled together to form
nerves
These fibrous structures channel and organize
information flow through the nervous system
Animals with elongated, bilaterally symmetrical
bodies have even more specialized systems
- 7. © 2014 Pearson Education, Inc.
Cephalization is an evolutionary trend toward a
clustering of sensory neurons and interneurons at
the anterior
Nonsegmented worms have the simplest clearly
defined central nervous system (CNS), consisting
of a small brain and longitudinal nerve cords
- 8. © 2014 Pearson Education, Inc.
Annelids and arthropods have segmentally arranged
clusters of neurons called ganglia
In vertebrates
The CNS is composed of the brain and spinal cord
The peripheral nervous system (PNS) is composed
of nerves and ganglia
- 9. © 2014 Pearson Education, Inc.
Glia
Glia have numerous functions to nourish, support,
and regulate neurons
Embryonic radial glia form tracks along which newly
formed neurons migrate
Astrocytes (star-shaped glial cells) induce cells
lining capillaries in the CNS to form tight junctions,
resulting in a blood-brain barrier
- 10. © 2014 Pearson Education, Inc.
Figure 38.3
Ependymal
cell
Neuron
CNS PNS
Oligodendrocyte
Schwann cell
Microglial cell
VENTRICLE
Cilia
Capillary
Astrocytes
Intermingling of
astrocytes with
neurons (blue)
LM
50µm
- 11. © 2014 Pearson Education, Inc.
Figure 38.3a
Astrocytes
Intermingling of
astrocytes with
neurons (blue)
LM
50µm
- 12. © 2014 Pearson Education, Inc.
Organization of the Vertebrate Nervous System
The spinal cord runs lengthwise inside the vertebral
column (the spine)
The spinal cord conveys information to and from the
brain
It can also act independently of the brain as part of
simple nerve circuits that produce reflexes, the
body’s automatic responses to certain stimuli
- 13. © 2014 Pearson Education, Inc.
Figure 38.4
Spinal cord
Central nervous
system (CNS)
Peripheral nervous
system (PNS)
Cranial
nerves
Spinal
nerves
Ganglia
outside
CNS
Brain
- 14. © 2014 Pearson Education, Inc.
The brain and spinal cord contain
Gray matter, which consists mainly of neuron cell
bodies and glia
White matter, which consists of bundles of
myelinated axons
- 15. © 2014 Pearson Education, Inc.
The CNS contains fluid-filled spaces called ventricles
in the brain and the central canal in the spinal cord
Cerebrospinal fluid is formed in the brain and
circulates through the ventricles and central canal
and drains into the veins
It supplies the CNS with nutrients and hormones and
carries away wastes
- 16. © 2014 Pearson Education, Inc.
The Peripheral Nervous System
The PNS transmits information to and from the CNS
and regulates movement and the internal
environment
In the PNS, afferent neurons transmit information to
the CNS and efferent neurons transmit information
away from the CNS
- 17. © 2014 Pearson Education, Inc.
Figure 38.5
Afferent neurons
Sensory
receptors
Internal
and external
stimuli
Autonomic
nervous system
Motor
system
Control of
skeletal muscle
Sympathetic
division
Enteric
division
Control of smooth muscles,
cardiac muscles, glands
Parasympathetic
division
Efferent neurons
Peripheral Nervous
System
Central Nervous
System
(information processing)
- 18. © 2014 Pearson Education, Inc.
The PNS has two efferent components: the motor
system and the autonomic nervous system
The motor system carries signals to skeletal
muscles and can be voluntary or involuntary
The autonomic nervous system regulates smooth
and cardiac muscles and is generally involuntary
- 19. © 2014 Pearson Education, Inc.
The autonomic nervous system has sympathetic,
parasympathetic, and enteric divisions
The enteric division controls activity of the
digestive tract, pancreas, and gallbladder
- 20. © 2014 Pearson Education, Inc.
The sympathetic division regulates the “fight-or-
flight” response
The parasympathetic division generates opposite
responses in target organs and promotes calming
and a return to “rest and digest” functions
- 21. © 2014 Pearson Education, Inc.
Concept 38.2: The vertebrate brain is
regionally specialized
The human brain contains 100 billion neurons
These cells are organized into circuits that can
perform highly sophisticated information processing,
storage, and retrieval
- 23. © 2014 Pearson Education, Inc.
Figure 38.6b
Medulla
oblongata
Embryonic brain regions Brain structures in child and adult
Forebrain
Hindbrain
Midbrain
Telencephalon
Myelencephalon
Metencephalon
Forebrain
Hindbrain
Midbrain
Diencephalon
Cerebrum (includes cerebral cortex,
white matter, basal nuclei)
Medulla oblongata (part of brainstem)
Pons (part of brainstem), cerebellum
Midbrain (part of brainstem)
Diencephalon (thalamus,
hypothalamus, epithalamus)
Telencephalon
Myelencephalon
Metencephalon
Diencephalon
Mesencephalon
Mesencephalon
Embryo at 1 month Embryo at 5 weeks
Spinal
cord
Child
Diencephalon
Midbrain
Cerebellum
Spinal cord
Pons
Cerebrum
- 24. © 2014 Pearson Education, Inc.
Figure 38.6ba
Embryonic brain regions
Brain structures in child and adult
Forebrain
Hindbrain
Midbrain
Telencephalon
Myelencephalon
Metencephalon
Diencephalon
Cerebrum (includes cerebral cortex, white matter,
basal nuclei)
Medulla oblongata (part of brainstem)
Pons (part of brainstem), cerebellum
Midbrain (part of brainstem)
Diencephalon (thalamus, hypothalamus, epithalamus)
Mesencephalon
- 25. © 2014 Pearson Education, Inc.
Figure 38.6bb
Forebrain
Hindbrain
Midbrain
Telencephalon
Myelencephalon
Metencephalon
Diencephalon
Mesencephalon
Embryo at 1 month Embryo at 5 weeks
Spinal
cord
- 26. © 2014 Pearson Education, Inc.
Figure 38.6bc
Medulla
oblongata
Child
Diencephalon
Midbrain
Cerebellum
Spinal cord
Pons
Cerebrum
- 27. © 2014 Pearson Education, Inc.
Figure 38.6c
Basal
nuclei
Cerebellum
Cerebrum
Corpus
callosum
Cerebral
cortex
Left cerebral
hemisphere
Right cerebral
hemisphere
Adult brain viewed from the rear
- 28. © 2014 Pearson Education, Inc.
Figure 38.6d
Diencephalon
Thalamus
Pineal gland
Hypothalamus
Pituitary gland
Spinal cord
Brainstem
Midbrain
Medulla
oblongata
Pons
- 29. © 2014 Pearson Education, Inc.
Arousal and Sleep
Arousal is a state of awareness of the external world
Sleep is a state in which external stimuli are
received but not consciously perceived
Arousal and sleep are controlled in part by clusters
of neurons in the midbrain and pons
- 30. © 2014 Pearson Education, Inc.
Sleep is an active state for the brain and is regulated
by the biological clock and regions of the forebrain,
which regulate the intensity and duration of sleep
Some animals have evolutionary adaptations that
allow for substantial activity during sleep
For example, in dolphins, only one side of the brain
is asleep at a time
- 31. © 2014 Pearson Education, Inc.
Figure 38.7
Location
Left
hemisphere
Right
hemisphere
Time: 1 hour
Key
Time: 0 hours
Low-frequency waves characteristic of sleep
High-frequency waves characteristic of wakefulness
- 32. © 2014 Pearson Education, Inc.
Biological Clock Regulation
Cycles of sleep and wakefulness are examples of
circadian rhythms, daily cycles of biological activity
Mammalian circadian rhythms rely on a biological
clock, a molecular mechanism that directs periodic
gene expression
Biological clocks are typically synchronized to light
and dark cycles and maintain a roughly 24-hour
cycle
- 33. © 2014 Pearson Education, Inc.
In mammals, circadian rhythms are coordinated by
a group of neurons in the hypothalamus called the
suprachiasmatic nucleus (SCN)
The SCN acts as a pacemaker, synchronizing the
biological clock
- 34. © 2014 Pearson Education, Inc.
Emotions
Generation and experience of emotions involve
many brain structures including the amygdala,
hippocampus, and parts of the thalamus
These structures are grouped as the limbic system
- 35. © 2014 Pearson Education, Inc.
Generation and experience of emotion also require
interaction between the limbic system and sensory
areas of the cerebrum
The brain structure that is most important for
emotional memory is the amygdala
- 36. © 2014 Pearson Education, Inc.
Figure 38.8
Thalamus
Hypothalamus
Amygdala
Olfactory
bulb
Hippocampus
- 37. © 2014 Pearson Education, Inc.
The Brain’s Reward System and Drug Addiction
The brain’s reward system provides motivation for
activities that enhance survival and reproduction
The brain’s reward system is dramatically affected
by drug addiction
Drug addiction is characterized by compulsive
consumption and an inability to control intake
- 38. © 2014 Pearson Education, Inc.
Addictive drugs such as cocaine, amphetamine,
heroin, alcohol, and tobacco enhance the activity of
the dopamine pathway
Drug addiction leads to long-lasting changes in the
reward circuitry that cause craving for the drug
- 39. © 2014 Pearson Education, Inc.
Figure 38.9
Inhibitory neuronNicotine
stimulates
dopamine-
releasing
VTA neuron.
Cerebral
neuron of
reward
pathway
Dopamine-
releasing
VTA neuron
Opium and heroin
decrease activity
of inhibitory
neuron.
Cocaine and
amphetamines
block removal
of dopamine
from synaptic
cleft.
Reward
system
response
- 40. © 2014 Pearson Education, Inc.
Functional Imaging of the Brain
Functional imaging methods are transforming our
understanding of normal and diseased brains
In positron-emission tomography (PET) an injection
of radioactive glucose enables a display of metabolic
activity
- 41. © 2014 Pearson Education, Inc.
In functional magnetic resonance imaging, fMRI, the
subject lies with his or her head in the center of a
large, doughnut-shaped magnet
Brain activity is detected by changes in local oxygen
concentration
Applications of fMRI include monitoring recovery
from stroke, mapping abnormalities in migraine
headaches, and increasing the effectiveness of brain
surgery
- 42. © 2014 Pearson Education, Inc.
Figure 38.10
Nucleus accumbens Amygdala
Happy music Sad music
- 43. © 2014 Pearson Education, Inc.
Figure 38.10a
Nucleus accumbens
Happy music
- 45. © 2014 Pearson Education, Inc.
Concept 38.3: The cerebral cortex controls
voluntary movement and cognitive functions
The cerebrum is essential for language, cognition,
memory, consciousness, and awareness of our
surroundings
The cognitive functions reside mainly in the cortex,
the outer layer
Four regions, or lobes (frontal, temporal, occipital,
and parietal), are landmarks for particular functions
- 46. © 2014 Pearson Education, Inc.
Figure 38.11
Frontal lobe
Temporal lobe
Occipital lobe
Parietal lobe
Cerebellum
Motor cortex (control
of skeletal muscles)
Somatosensory cortex
(sense of touch)
Wernicke’s area
(comprehending language)
Auditory cortex
(hearing)
Broca’s area
(forming speech)
Prefrontal cortex
(decision
making,
planning)
Sensory association
cortex (integration
of sensory
information)
Visual association
cortex (combining
images and object
recognition)
Visual cortex
(processing visual
stimuli and pattern
recognition)
- 47. © 2014 Pearson Education, Inc.
Language and Speech
The mapping of cognitive functions within the cortex
began in the 1800s
Broca’s area, in the left frontal lobe, is active when
speech is generated
Wernicke’s area, in the posterior of the left frontal
lobe, is active when speech is heard
- 48. © 2014 Pearson Education, Inc.
Figure 38.12
Hearing
words
Seeing
words
Speaking
words
Generating
words
Max
Min
- 49. © 2014 Pearson Education, Inc.
Lateralization of Cortical Function
The left side of the cerebrum is dominant regarding
language, math, and logical operations
The right hemisphere is dominant in recognition of
faces and patterns, spatial relations, and nonverbal
thinking
The establishment of differences in hemisphere
function is called lateralization
- 50. © 2014 Pearson Education, Inc.
The two hemispheres exchange information through
the fibers of the corpus callosum
Severing this connection results in a “split brain”
effect, in which the two hemispheres operate
independently
- 51. © 2014 Pearson Education, Inc.
Information Processing
The cerebral cortex receives input from sensory
organs and somatosensory receptors
Somatosensory receptors provide information
about touch, pain, pressure, temperature, and the
position of muscles and limbs
The thalamus directs different types of input to
distinct locations
- 52. © 2014 Pearson Education, Inc.
Frontal Lobe Function
Frontal lobe damage may impair decision making
and emotional responses but leave intellect and
memory intact
The frontal lobes have a substantial effect on
“executive functions”
- 54. © 2014 Pearson Education, Inc.
Evolution of Cognition in Vertebrates
In nearly all vertebrates, the brain has the same
number of divisions
The hypothesis that higher order reasoning requires
a highly convoluted cerebral cortex has been
experimentally refuted
The anatomical basis for sophisticated information
processing in birds (without a highly convoluted
neocortex) appears to be a cluster of nuclei in the
top or outer portion of the brain (pallium)
- 55. © 2014 Pearson Education, Inc.
Figure 38.13
Cerebrum
(including pallium)
Thalamus
Midbrain
Hindbrain
Cerebellum
Cerebrum (including
cerebral cortex)
Thalamus
Midbrain
Hindbrain Cerebellum
(a) Songbird brain
(b) Human brain
- 56. © 2014 Pearson Education, Inc.
Neural Plasticity
Neural plasticity is the capacity of the nervous
system to be modified after birth
Changes can strengthen or weaken signaling at a
synapse
Autism, a developmental disorder, involves a
disruption of activity-dependent remodeling at
synapses
Children with autism display impaired communication
and social interaction, as well as stereotyped and
repetitive behaviors
- 57. © 2014 Pearson Education, Inc.
Figure 38.14
(a) Synapses are strengthened or weakened in response to
activity.
(b) If two synapses are often active at the same time, the strength
of the postsynaptic response may increase at both synapses.
N1
N2
N1
N2
- 58. © 2014 Pearson Education, Inc.
Memory and Learning
Neural plasticity is essential to formation of memories
Short-term memory is accessed via the
hippocampus
The hippocampus also plays a role in forming long-
term memory, which is stored in the cerebral cortex
Some consolidation of memory is thought to occur
during sleep
- 59. © 2014 Pearson Education, Inc.
Concept 38.4: Sensory receptors transduce
stimulus energy and transmit signals to the
central nervous system
Much brain activity begins with sensory input
A sensory receptor detects a stimulus, which alters
the transmission of action potentials to the CNS
The information is decoded in the CNS, resulting in
a sensation
- 60. © 2014 Pearson Education, Inc.
Sensory Reception and Transduction
A sensory pathway begins with sensory reception,
detection of stimuli by sensory receptors
Sensory receptors, which detect stimuli, interact
directly with stimuli, both inside and outside the body
- 61. © 2014 Pearson Education, Inc.
Sensory transduction is the conversion of stimulus
energy into a change in the membrane potential of a
sensory receptor
This change in membrane potential is called a
receptor potential
Receptor potentials are graded; their magnitude
varies with the strength of the stimulus
- 62. © 2014 Pearson Education, Inc.
Figure 38.15
(a) Receptor is afferent neuron.
Afferent
neuron
(b) Receptor regulates afferent neuron.
Sensory
receptor
To CNS
Stimulus
Afferent
neuron
Receptor
protein
To CNS
Sensory
receptor
cell Stimulus
Neurotransmitter
Stimulus
leads to
neuro-
transmitter
release.
- 63. © 2014 Pearson Education, Inc.
Transmission
Sensory information is transmitted as nerve impulses
or action potentials
Neurons that act directly as sensory receptors
produce action potentials and have an axon that
extends into the CNS
Non-neuronal sensory receptors form chemical
synapses with sensory neurons
They typically respond to stimuli by increasing the
rate at which the sensory neurons produce action
potentials
- 64. © 2014 Pearson Education, Inc.
The response of a sensory receptor varies with
intensity of stimuli
If the receptor is a neuron, a larger receptor potential
results in more frequent action potentials
If the receptor is not a neuron, a larger receptor
potential causes more neurotransmitter to be
released
- 65. © 2014 Pearson Education, Inc.
Figure 38.16
Gentle pressure
Sensory
receptor
More pressure
Low frequency of
action potentials
High frequency of
action potentials
- 66. © 2014 Pearson Education, Inc.
Perception
Perception is the brain’s construction of stimuli
Action potentials from sensory receptors travel
along neurons that are dedicated to a particular
stimulus
The brain thus distinguishes stimuli, such as light or
sound, solely by the path along which the action
potentials have arrived
- 67. © 2014 Pearson Education, Inc.
Amplification and Adaptation
Amplification is the strengthening of stimulus energy
by cells in sensory pathways
Sensory adaptation is a decrease in
responsiveness to continued stimulation
- 68. © 2014 Pearson Education, Inc.
Types of Sensory Receptors
Based on energy transduced, sensory receptors fall
into five categories
Mechanoreceptors
Electromagnetic receptors
Thermoreceptors
Pain receptors
Chemoreceptors
- 69. © 2014 Pearson Education, Inc.
Mechanoreceptors
Mechanoreceptors sense physical deformation
caused by stimuli such as pressure, touch, stretch,
motion, and sound
Some animals use mechanoreceptors to get a feel
for their environment
For example, cats and many rodents have sensitive
whiskers that provide detailed information about
nearby objects
- 70. © 2014 Pearson Education, Inc.
Electromagnetic Receptors
Electromagnetic receptors detect electromagnetic
energy such as light, electricity, and magnetism
Some snakes have very sensitive infrared receptors
that detect body heat of prey against a colder
background
Many animals apparently migrate using Earth’s
magnetic field to orient themselves
- 71. © 2014 Pearson Education, Inc.
Figure 38.17
(b) Beluga whales
(a) Rattlesnake
Infrared
receptor
Eye
- 72. © 2014 Pearson Education, Inc.
Figure 38.17a
(a) Rattlesnake
Infrared
receptor
Eye
- 74. © 2014 Pearson Education, Inc.
Thermoreceptors detect heat and cold
In humans, thermoreceptors in the skin and anterior
hypothalamus send information to the body’s
thermostat in the posterior hypothalamus
Thermoreceptors
- 75. © 2014 Pearson Education, Inc.
Pain Receptors
In humans, pain receptors, or nociceptors, detect
stimuli that reflect conditions that could damage
animal tissues
By triggering defensive reactions, such as withdrawal
from danger, pain perception serves an important
function
Chemicals such as prostaglandins worsen pain by
increasing receptor sensitivity to noxious stimuli;
aspirin and ibuprofen reduce pain by inhibiting
synthesis of prostaglandins
- 76. © 2014 Pearson Education, Inc.
Chemoreceptors
General chemoreceptors transmit information about
the total solute concentration of a solution
Specific chemoreceptors respond to individual kinds
of molecules
Olfaction (smell) and gustation (taste) both depend
on chemoreceptors
Smell is the detection of odorants carried in the air,
and taste is detection of tastants present in solution
- 77. © 2014 Pearson Education, Inc.
Humans can distinguish thousands of different odors
Humans and other mammals recognize just five
types of tastants: sweet, sour, salty, bitter, and
umami
Taste receptors are organized into taste buds,
mostly found in projections called papillae
Any region of the tongue can detect any of the five
types of taste
- 78. © 2014 Pearson Education, Inc.
Figure 38.18
Tongue
Taste
buds
Sensory
receptor cells
Key
Sensory
neuron
Taste
pore
Food
molecules
Taste bud
Papillae
Papilla
Umami
Bitter
Sour
Salty
Sweet
- 79. © 2014 Pearson Education, Inc.
Concept 38.5: The mechanoreceptors responsible
for hearing and equilibrium detect moving fluid
or settling particles
Hearing and perception of body equilibrium are
related in most animals
For both senses, settling particles or moving fluid is
detected by mechanoreceptors
- 80. © 2014 Pearson Education, Inc.
Sensing of Gravity and Sound in Invertebrates
Most invertebrates maintain equilibrium using
mechanoreceptors located in organs called
statocysts
Statocysts contain mechanoreceptors that detect the
movement of granules called statoliths
Most insects sense sounds with body hairs that
vibrate or with localized vibration-sensitive organs
consisting of a tympanic membrane stretched over
an internal chamber
- 81. © 2014 Pearson Education, Inc.
Figure 38.19
Statolith
Ciliated
receptor
cells
Sensory
nerve fibers
(axons)
Cilia
- 82. © 2014 Pearson Education, Inc.
Hearing and Equilibrium in Mammals
In most terrestrial vertebrates, sensory organs for
hearing and equilibrium are closely associated in
the ear
- 83. © 2014 Pearson Education, Inc.
Figure 38.20
Outer ear Inner ear
Middle
ear
Malleus
Skull
bone
Incus
Stapes Semicircular
canals
Auditory nerve
to brain
Auditory
canal
Tympanic
membrane
Oval
window
Round
window
Eustachian
tube
Cochlea
Pinna
Auditory
nerve
Cochlear
duct
Organ
of Corti
Vestibular
canal
Tympanic
canal
Bone
To
auditory
nerve
Tectorial
membrane
Basilar
membrane
Axons of
sensory neurons
Hair
cells
Bundled hairs projecting from a hair cell
(SEM)
1µm
- 84. © 2014 Pearson Education, Inc.
Figure 38.20a
Outer ear Inner ear
Middle
ear
Malleus
Skull
bone
Incus
Stapes Semicircular
canals
Auditory nerve
to brain
Auditory
canal
Tympanic
membrane
Oval
window
Round
window
Eustachian
tube
Cochlea
Pinna
- 85. © 2014 Pearson Education, Inc.
Figure 38.20b
Auditory
nerve
Cochlear
duct
Organ
of Corti
Vestibular
canal
Tympanic
canal
Bone
- 86. © 2014 Pearson Education, Inc.
Figure 38.20c
To
auditory
nerve
Tectorial
membrane
Basilar
membrane
Axons of
sensory neurons
Hair
cells
- 87. © 2014 Pearson Education, Inc.
Figure 38.20d
Bundled hairs projecting from a hair cell (SEM)
1µm
- 88. © 2014 Pearson Education, Inc.
Hearing
Vibrating objects create pressure waves in the air,
which are transduced by the ear into nerve impulses,
perceived as sound in the brain
The tympanic membrane vibrates in response to
vibrations in air
The three bones of the middle ear transmit the
vibrations of moving air to the oval window on the
cochlea
- 89. © 2014 Pearson Education, Inc.
The vibrations of the bones in the middle ear create
pressure waves in the fluid in the cochlea that travel
through the vestibular canal
Pressure waves in the canal cause the basilar
membrane to vibrate and attached hair cells to
vibrate
Bending of hair cells causes ion channels in the
hair cells to open or close, resulting in a change in
auditory nerve sensations that the brain interprets
as sound
- 90. © 2014 Pearson Education, Inc.
Figure 38.21
Receptor
potential
More
neuro-
trans-
mitter
Time (sec)
Membrane
potential(mV)
Signal
0 1 2 3 4 5 6 7
(a) Bending of hairs in one direction
−50
−70
0
−70
Receptor
potential
Less
neuro-
trans-
mitter
Time (sec)
Membrane
potential(mV)
Signal
0 1 2 3 4 5 6 7
(b) Bending of hairs in other direction
−50
−70
0
−70
- 91. © 2014 Pearson Education, Inc.
The fluid waves dissipate when they strike the round
window at the end of the vestibular canal
- 92. © 2014 Pearson Education, Inc.
The ear conveys information about
Volume, the amplitude of the sound wave
Pitch, the frequency of the sound wave
The cochlea can distinguish pitch because the
basilar membrane is not uniform along its length
Each region of the basilar membrane is tuned to a
particular vibration frequency
- 93. © 2014 Pearson Education, Inc.
Equilibrium
Several organs of the inner ear detect body
movement, position, and balance
The utricle and saccule contain granules called
otoliths that allow us to perceive position relative to
gravity or linear movement
Three semicircular canals contain fluid and can
detect angular movement in any direction
- 94. © 2014 Pearson Education, Inc.
Figure 38.22
Semicircular
canals
Vestibular
nerve
Vestibule
Saccule
Utricle
Fluid
flow
Nerve
fibers
Hair
cell
Hairs
Cupula
Body movement
PERILYMPH
- 95. © 2014 Pearson Education, Inc.
Concept 38.6: The diverse visual receptors of
animals depend on light-absorbing pigments
The organs used for vision vary considerably among
animals, but the underlying mechanism for capturing
light is the same
- 96. © 2014 Pearson Education, Inc.
Evolution of Visual Perception
Light detectors in animals range from simple
clusters of cells that detect direction and intensity of
light to complex organs that form images
Light detectors all contain photoreceptors, cells
that contain light-absorbing pigment molecules
- 97. © 2014 Pearson Education, Inc.
Light-Detecting Organs
Most invertebrates have a light-detecting organ
One of the simplest light-detecting organs is that of
planarians
A pair of ocelli called eyespots are located near the
head
These allow planarians to move away from light and
seek shaded locations
- 98. © 2014 Pearson Education, Inc.
Figure 38.23
LIGHT
DARK
Ocellus
Ocellus
Visual
pigment
Photoreceptor
Nerve to
brain
Screening
pigment
- 99. © 2014 Pearson Education, Inc.
Insects and crustaceans have compound eyes,
which consist of up to several thousand light
detectors called ommatidia
Compound eyes are very effective at detecting
movement
Compound Eyes
- 101. © 2014 Pearson Education, Inc.
Single-lens eyes are found in some jellies,
polychaetes, spiders, and many molluscs
They work on a camera-like principle: the iris
changes the diameter of the pupil to control how
much light enters
The eyes of all vertebrates have a single lens
Single-Lens Eyes
- 102. © 2014 Pearson Education, Inc.
The Vertebrate Visual System
Vision begins when photons of light enter the eye
and strike the rods and cones
However, it is the brain that “sees”
Animation: Near and Distance Vision
- 103. © 2014 Pearson Education, Inc.
Figure 38.25a
Sclera Choroid
Retina
Fovea
Cornea
Suspensory
ligament
Iris
Optic
nerve
Pupil
Aqueous
humor
Lens
Optic
disk
Vitreous humor
Central
artery and
vein of
the retina
Retina
Optic
nerve
fibers
Rod Cone
Neurons
Photoreceptors
Ganglion
cell
Amacrine
cell
Bipolar
cell
Horizontal
cell Pigmented
epithelium
- 104. © 2014 Pearson Education, Inc.
Figure 38.25aa
Sclera Choroid
Retina
Fovea
Cornea
Suspensory
ligament
Iris
Optic
nerve
Pupil
Aqueous
humor
Lens
Optic
disk
Vitreous humor
Central
artery and
vein of
the retina
- 105. © 2014 Pearson Education, Inc.
Figure 38.25ab
Retina
Optic
nerve
fibers
Rod Cone
Neurons
Photoreceptors
Ganglion
cell
Amacrine
cell
Bipolar
cell
Horizontal
cell Pigmented
epithelium
- 106. © 2014 Pearson Education, Inc.
Figure 38.25b
DisksSynaptic
terminal
Cell
body
Outer
segment
Cone
Cone
Rod
Rod
CYTOSOL
Retinal:
cis isomer
Retinal:
trans isomer
EnzymesLight
Retinal
Opsin
Rhodopsin
INSIDE OF DISK
- 107. © 2014 Pearson Education, Inc.
Figure 38.25ba
DisksSynaptic
terminal
Cell
body
Outer
segment
Cone
Cone
Rod
Rod
- 108. © 2014 Pearson Education, Inc.
Figure 38.25bb
CYTOSOL
Retinal:
cis isomer
Retinal:
trans isomer
EnzymesLight
Retinal
Opsin
Rhodopsin
INSIDE OF DISK
- 109. © 2014 Pearson Education, Inc.
Figure 38.25bc
Retinal:
cis isomer
Retinal:
trans isomer
EnzymesLight
- 111. © 2014 Pearson Education, Inc.
Sensory Transduction in the Eye
Transduction of visual information to the nervous
system begins when light induces the conversion
of cis-retinal to trans-retinal
Trans-retinal activates rhodopsin, which activates
a G protein, eventually leading to hydrolysis of cyclic
GMP
- 112. © 2014 Pearson Education, Inc.
When cyclic GMP breaks down, Na+
channels close
This hyperpolarizes the cell
The signal transduction pathway usually shuts off
again as enzymes convert retinal back to the cis form
- 113. © 2014 Pearson Education, Inc.
Figure 38.26
Active
rhodopsin
Transducin
Light
Inactive
rhodopsin
Phospho-
diesterase
Disk
membrane
Membrane
potential (mV)
Plasma
membrane
Hyper-
polarization
EXTRA-
CELLULAR
FLUID
INSIDE OF DISK
CYTOSOL
Dark Light
Time
GMP
cGMP
Na+
Na+
−40
−70
0
- 114. © 2014 Pearson Education, Inc.
Processing of Visual Information in the Retina
Processing of visual information begins in the retina
In the dark, rods and cones release the
neurotransmitter glutamate into synapses with
neurons called bipolar cells
Bipolar cells are either hyperpolarized or depolarized
in response to glutamate
- 115. © 2014 Pearson Education, Inc.
In the light, rods and cones hyperpolarize, shutting
off release of glutamate
The bipolar cells are then either depolarized or
hyperpolarized
- 116. © 2014 Pearson Education, Inc.
Signals from rods and cones can follow several
pathways in the retina
A single ganglion cell receives information from an
array of rods and cones, each of which responds to
light coming from a particular location
The rods and cones that feed information to one
ganglion cell define a receptive field, the part of the
visual field to which the ganglion cell can respond
A smaller receptive field typically results in a sharper
image
- 117. © 2014 Pearson Education, Inc.
The optic nerves meet at the optic chiasm near the
cerebral cortex
Sensations from the left visual field of both eyes are
transmitted to the right side of the brain
Sensations from the right visual field are transmitted
to the left side of the brain
It is estimated that at least 30% of the cerebral cortex
takes part in formulating what we actually “see”
Processing of Visual Information in the Brain
- 118. © 2014 Pearson Education, Inc.
Color Vision
Among vertebrates, most fish, amphibians, and
reptiles, including birds, have very good color vision
Humans and other primates are among the minority
of mammals with the ability to see color well
Mammals that are nocturnal usually have a high
proportion of rods in the retina
- 119. © 2014 Pearson Education, Inc.
In humans, perception of color is based on three
types of cones, each with a different visual pigment:
red, green, or blue
These pigments are called photopsins and are
formed when retinal binds to three distinct opsin
proteins
- 120. © 2014 Pearson Education, Inc.
Abnormal color vision results from alterations in the
genes for one or more photopsin proteins
The genes for the red and green pigments are
located on the X chromosome
A mutation in one copy of either gene can disrupt
color vision in males
- 121. © 2014 Pearson Education, Inc.
The brain processes visual information and controls
what information is captured
Focusing occurs by changing the shape of the lens
The fovea is the center of the visual field and
contains no rods but a high density of cones
The Visual Field
- 122. © 2014 Pearson Education, Inc.
Figure 38.UN01
Wild-type
hamster
Wild-type
hamster with
SCN from
τ hamster
τ hamster
τ hamster
with SCN
from wild-type
hamster
After surgery
and transplant
Before
procedures
Circadianperiod(hours)
24
23
22
21
20
19
- 123. © 2014 Pearson Education, Inc.
Figure 38.UN03
Cerebral
cortex
Forebrain
Hindbrain
Midbrain
Thalamus
Pituitary gland
Hypothalamus
Spinal
cord
Cerebellum
Pons
Cerebrum
Medulla
oblongata
Editor's Notes
- Figure 38.1 Of what use is a star-shaped nose?
- Figure 38.2 Nervous system organization
- Figure 38.3 Glia in the vertebrate nervous system
- Figure 38.3a Glia in the vertebrate nervous system (LM)
- Figure 38.4 The vertebrate nervous system
- Figure 38.5 Functional hierarchy of the vertebrate peripheral nervous system
- Figure 38.6a Exploring the organization of the human brain (part 1: MRI)
- Figure 38.6b Exploring the organization of the human brain (part 2: brain development)
- Figure 38.6ba Exploring the organization of the human brain (part 2a: brain development, chart)
- Figure 38.6bb Exploring the organization of the human brain (part 2b: brain development, embryo)
- Figure 38.6bc Exploring the organization of the human brain (part 2c: brain development, child)
- Figure 38.6c Exploring the organization of the human brain (part 3: cerebrum and cerebellum)
- Figure 38.6d Exploring the organization of the human brain (part 4: diencephalon and brainstem)
- Figure 38.7 Dolphins can be asleep and awake at the same time.
- Figure 38.8 The limbic system
- Figure 38.9 Effects of addictive drugs on the reward system of the mammalian brain
- Figure 38.10 Functional brain imaging in the working brain
- Figure 38.10a Functional brain imaging in the working brain (part 1: happy music)
- Figure 38.10b Functional brain imaging in the working brain (part 2: sad music)
- Figure 38.11 The human cerebral cortex
- Figure 38.12 Mapping language areas in the cerebral cortex
- Figure 38.UN02 In-text figure, Phineas Gage, p. 777
- Figure 38.13 Comparison of regions for higher cognition in avian and human brains
- Figure 38.14 Neural plasticity
- Figure 38.15 Neuronal and non-neuronal sensory receptors
- Figure 38.16 Coding of stimulus intensity by a single sensory receptor
- Figure 38.17 Specialized electromagnetic receptors
- Figure 38.17a Specialized electromagnetic receptors (part 1: infrared)
- Figure 38.17b Specialized electromagnetic receptors (part 2: magnetic)
- Figure 38.18 Human taste receptors
- Figure 38.19 The statocyst of an invertebrate
- Figure 38.20 Exploring the structure of the human ear
- Figure 38.20a Exploring the structure of the human ear (part 1: overview)
- Figure 38.20b Exploring the structure of the human ear (part 2: cochlea)
- Figure 38.20c Exploring the structure of the human ear (part 3: organ of Corti)
- Figure 38.20d Exploring the structure of the human ear (part 4: hair cell, SEM )
- Figure 38.21 Sensory reception by hair cells
- Figure 38.22 Organs of equilibrium in the inner ear
- Figure 38.23 Ocelli and orientation behavior of a planarian
- Figure 38.24 Compound eyes
- Figure 38.25a Exploring the structure of the human eye (part 1)
- Figure 38.25aa Exploring the structure of the human eye (part 1a: overview)
- Figure 38.25ab Exploring the structure of the human eye (part 1b: retina)
- Figure 38.25b Exploring the structure of the human eye (part 2)
- Figure 38.25ba Exploring the structure of the human eye (part 2a: photoreceptors)
- Figure 38.25bb Exploring the structure of the human eye (part 2b: rhodopsin)
- Figure 38.25bc Exploring the structure of the human eye (part 2c: retinal isomers)
- Figure 38.25bd Exploring the structure of the human eye (part 2d: photoreceptors, SEM)
- Figure 38.26 Production of the receptor potential in a rod cell
- Figure 38.UN01 Skills exercise: designing an experiment using genetic mutants
- Figure 38.UN03 Summary of key concepts: vertebrate brain regions