Download Chapter 49 - Nervous Systems

Figure 49.1
CAMPBELL
BIOLOGY
Command and Control Center
Concept 49.1: Nervous systems consist of
circuits of neurons and supporting cells
TENTH
EDITION
Reece • Urry • Cain • Wasserman • Minorsky • Jackson
!  The human brain contains about 100 billion
neurons, organized into circuits more complex
than the most powerful supercomputers
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!  By the time of the Cambrian explosion more than
500 million years ago, specialized systems of
neurons had appeared that enables animals to
sense their environments and respond rapidly
!  Powerful imaging techniques allow researchers to
monitor multiple areas of the brain while the
subject performs various tasks
Nervous Systems
!  A recent advance uses expression of
combinations of colored proteins in brain cells, a
technique called “brainbow”
Lecture Presentation by
Nicole Tunbridge and
Kathleen Fitzpatrick
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Figure 49.2
Figure 49.2a
Figure 49.2a, b
Radial
nerve
Nerve
ring
Eyespot
!  The simplest animals with nervous systems, the
cnidarians, have neurons arranged in nerve nets
Nerve net
!  A nerve net is a series of interconnected nerve
cells
(a) Hydra (cnidarian)
!  More complex animals have nerves, in which the
axons of multiple neurons are bundled together
Brain
Ventral
nerve
cord
!  Nerves channel and organize information flow
through the nervous system
Segmental
ganglia
(e) Insect (arthropod)
Brain
Brain
Nerve
cords
Radial
nerve
Nerve
ring
Ventral
nerve cord
Transverse
nerve
(b) Sea star (echinoderm)
Anterior
nerve ring
Brain
Ganglia
(d) Leech (annelid)
(a) Hydra (cnidarian)
Spinal
cord
(dorsal
nerve
cord)
Eyespot
(g) Squid (mollusc)
Nerve net
Brain
Brain
Nerve
cords
Sensory
ganglia
Longitudinal
nerve cords
(f) Chiton (mollusc)
(b) Sea star (echinoderm)
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(a) Hydra (cnidarian)
Segmental
ganglia
(c) Planarian (flatworm)
(d) Leech (annelid)
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Figure 49.2d, e
!  Annelids and arthropods have segmentally
arranged clusters of neurons called ganglia
Eyespot
Ventral
nerve cord
Transverse
nerve
Segmental
ganglia
(d) Leech (annelid)
(c) Planarian (flatworm)
!  The peripheral nervous system (PNS) consists
of neurons carrying information into and out of the
CNS
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Brain
Brain
Nerve
cords
!  The CNS consists of a brain and longitudinal nerve
cords
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Figure 49.2c
!  The simplest cephalized animals, flatworms, have
a central nervous system (CNS)
(b) Sea star (echinoderm)
Ventral
nerve cord
Transverse
nerve
(h) Salamander
(vertebrate)
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!  Bilaterally symmetrical animals exhibit
cephalization, the clustering of sensory organs at
the front end of the body
Radial
nerve
Nerve
ring
Brain
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Nerve net
Segmental
ganglia
(c) Planarian (flatworm)
Ganglia
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Segmental
ganglia
(e) Insect (arthropod)
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Figure 49.2b
Brain
Ventral
nerve
cord
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Figure 49.2f, g
Brain
Ventral
nerve
cord
Segmental
ganglia
Ganglia
Anterior
nerve ring
!  Nervous system organization usually correlates
with lifestyle
Longitudinal
nerve cords
(e) Insect (arthropod)
!  Sessile molluscs (for example, clams and chitons)
have simple systems, whereas more complex
molluscs (for example, octopuses and squids)
have more sophisticated systems
(f) Chiton (mollusc)
Brain
Brain
Ganglia
(g) Squid (mollusc)
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Spinal
cord
(dorsal
nerve
cord)
!  In vertebrates
Ganglia
Sensory
ganglia
(h) Salamander (vertebrate)
Anterior
nerve ring
!  Region specialization is a hallmark of both
systems
Longitudinal
nerve cords
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!  The peripheral nervous system (PNS) is composed
of nerves and ganglia
Ganglia
(f) Chiton (mollusc)
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!  The CNS is composed of the brain and spinal cord
Brain
(g) Squid (mollusc)
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Figure 49.2h
Figure 49.3
Glia
Capillary
!  Glial cells, or glia have numerous functions to
nourish, support, and regulate neurons
Brain
Spinal
cord
(dorsal
nerve
cord)
Neuron
CNS
PNS
!  Radial glial cells and astrocytes can both act as
stem cells
VENTRICLE
Cilia
!  Embryonic radial glia form tracks along which newly
formed neurons migrate
Sensory
ganglia
!  Researchers are trying to find a way to use neural
stem cells to replace brain tissue that has ceased
to function normally
!  Astrocytes induce cells lining capillaries in the
CNS to form tight junctions, resulting in a bloodbrain barrier and restricting the entry of most
substances into the brain
(h) Salamander (vertebrate)
Ependymal
cells
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Astrocytes
Oligodendrocytes
Microglia
Schwann cells
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Figure 49.4
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Figure 49.5
Organization of the Vertebrate Nervous System
!  The CNS develops from the hollow nerve cord
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!  Gray matter, which consists of neuron cell bodies,
dendrites, and unmyelinated axons
White
matter
!  The canal and ventricles fill with cerebrospinal
fluid, which supplies the CNS with nutrients and
hormones and carries away wastes
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!  The brain and spinal cord contain
Gray matter
!  The cavity of the nerve cord gives rise to the
narrow central canal of the spinal cord and the
ventricles of the brain
!  White matter, which consists of bundles of
myelinated axons
Ventricles
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Figure 49.6
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Figure 49.7
Central
nervous
system
(CNS)
Brain
Spinal
cord
Cell body of
sensory neuron in
dorsal root ganglion
Cranial nerves
Ganglia
outside CNS
!  The spinal cord conveys information to and from
the brain and generates basic patterns of
locomotion
Peripheral
nervous
system
(PNS)
The Peripheral Nervous System
Gray
matter
White
matter
Quadriceps
muscle
Spinal cord
(cross section)
Spinal nerves
!  The spinal cord also produces reflexes
independently of the brain
!  For example, a doctor uses a mallet to trigger a
knee-jerk reflex
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!  In the PNS, afferent neurons transmit information
to the CNS and efferent neurons transmit
information away from the CNS
Hamstring
muscle
!  A reflex is the body’s automatic response to a
stimulus
Key
!  The PNS transmits information to and from the
CNS and regulates movement and the internal
environment
Sensory neuron
Motor neuron
Interneuron
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Figure 49.8
Figure 49.9
CENTRAL NERVOUS
SYSTEM
(information processing)
Parasympathetic division
PERIPHERAL NERVOUS
SYSTEM
Efferent neurons
Afferent neurons
Sensory
receptors
Autonomic
nervous system
Motor
system
Control of
skeletal muscle
Internal
and external
stimuli
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Sympathetic division
Dilates pupil of eye
Constricts pupil of eye
Sympathetic Parasympathetic
division
division
!  The PNS has two efferent components: the motor
system and the autonomic nervous system
!  The autonomic nervous system has sympathetic
and parasympathetic divisions
!  The motor system carries signals to skeletal
muscles and is voluntary
!  The sympathetic division regulates arousal and
energy generation (“fight-or-flight” response)
!  The autonomic nervous system regulates
smooth and cardiac muscles and is generally
involuntary
!  The parasympathetic division has antagonistic
effects on target organs and promotes calming
and a return to “rest and digest” functions
Constricts
bronchi in lungs
Cervical
Sympathetic
ganglia
Accelerates heart
Stimulates activity of
stomach and intestines
Inhibits activity of
stomach and intestines
Thoracic
Inhibits activity
of pancreas
Stimulates glucose
release from liver;
inhibits gallbladder
Stimulates gallbladder
Lumbar
Stimulates
adrenal medulla
Promotes emptying
of bladder
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Relaxes bronchi in lungs
Slows heart
Stimulates activity
of pancreas
Enteric
division
Control of smooth muscles,
cardiac muscles, glands
Inhibits salivary
gland secretion
Stimulates salivary
gland secretion
Promotes erection
of genitalia
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Inhibits emptying
of bladder
Sacral
Synapse
Promotes ejaculation and 32
vaginal contractions
Figure 49.9a
Figure 49.9b
Parasympathetic division
Sympathetic division
Constricts pupil of eye
Dilates pupil
of eye
Stimulates salivary
gland secretion
Inhibits salivary
gland secretion
Constricts
bronchi in lungs
Slows heart
Figure 49.UN01
Parasympathetic
division
Relaxes bronchi in lungs
Sympathetic
ganglia
!  Specific brain structures are particularly
specialized for diverse functions
Accelerates heart
Inhibits activity of
stomach and intestines
Thoracic
Cervical
Concept 49.2: The vertebrate brain is regionally
specialized
Sympathetic division
Sympathetic
ganglia
Stimulates activity of
stomach and intestines
Stimulates gallbladder
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Hindbrain
Olfactory
bulb
Cerebrum
Stimulates
adrenal medulla
Promotes emptying
of bladder
Midbrain
Cerebellum
Stimulates glucose
release from liver;
inhibits gallbladder
Lumbar
Stimulates activity
of pancreas
Forebrain
!  The vertebrate brain has three major regions: the
forebrain, midbrain, and hindbrain
Inhibits activity
of pancreas
Inhibits emptying
of bladder
Promotes erection
of genitalia
Sacral
Promotes ejaculation and
vaginal contractions 34
Synapse
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Figure 49.10
!  The forebrain has activities including processing
of olfactory input, regulation of sleep, learning, and
any complex processing
Lamprey
!  Comparison of vertebrates shows that relative
sizes of particular brain regions vary
!  The midbrain coordinates routing of sensory input
!  These size differences reflect the relative
importance of the particular brain function
!  The hindbrain controls involuntary activities and
coordinates motor activities
!  Evolution has resulted in a close match between
structure and function
ANCESTRAL
VERTEBRATE
Ray-finned
fish
Crocodilian
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Figure 49.11b
Midbrain
Midbrain
Midbrain (part of brainstem)
Metencephalon
Pons (part of brainstem), cerebellum
Myelencephalon
Medulla oblongata (part of brainstem)
Hindbrain
Cerebrum
Mesencephalon
Myelencephalon
Diencephalon
Brain structures in child and adult
Diencephalon
Myelencephalon
Cerebrum (includes cerebral cortex, basal nuclei)
Midbrain
Pons
Medulla
oblongata
Telencephalon
Pons (part of brainstem), cerebellum
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Embryo at 1 month
Arousal and Sleep
Right cerebral
hemisphere
Corpus callosum
!  The brainstem and cerebrum control arousal and
sleep
Brainstem
Cerebrum
Diencephalon
!  The core of the brainstem has a diffuse network of
neurons called the reticular formation
Thalamus
Pineal gland
Hypothalamus
Pituitary gland
Basal nuclei
Midbrain
Pons
Medulla
oblongata
Cerebellum
Spinal cord
Child
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Spinal cord
Cerebellum
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Adult brain viewed from the rear
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Cerebral cortex
Midbrain
Pons
Medulla
oblongata
Embryo at 5 weeks
Figure 49.11d
Left cerebral
hemisphere
Diencephalon
Spinal
cord
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Medulla oblongata (part of brainstem)
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Figure 49.11c
Telencephalon
Midbrain (part of brainstem)
Spinal cord
Child
Forebrain
Diencephalon (thalamus, hypothalamus, epithalamus)
Cerebellum
Spinal
cord
Embryo at 5 weeks
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Figure 49.11bc
Cerebrum
Embryo at 1 month
Myelencephalon
Metencephalon
Hindbrain
Brainstem
Forebrain
Hindbrain
Mesencephalon
Diencephalon
Metencephalon
Midbrain
Hindbrain
Metencephalon
Midbrain
Diencephalon
Diencephalon (thalamus, hypothalamus, epithalamus)
Mesencephalon
Mesencephalon
Telencephalon
Forebrain
Cerebrum (includes cerebral cortex, basal nuclei)
Forebrain
Diencephalon
Figure 49.11bb
Embryonic brain regions
Brain structures in child and adult
Telencephalon
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Figure 49.11ba
Embryonic brain regions
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!  The forebrain divides into the diencephelon, which
forms endocrine tissues in the brain, and the
telencephalon, which becomes the cerebrum
Mammal
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!  The rest of the hindbrain gives rise to the cerebellum
Bird
Forebrain
Midbrain
Hindbrain
Figure 49.11a
!  The midbrain and part of the hindbrain form the
brainstem, which joins with the spinal cord at the
base of the brain
Amphibian
Key
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!  During embryonic development the anterior neural
tube gives rise to the forebrain, midbrain, and
hindbrain
Shark
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!  These neurons control the timing of sleep periods
characterized by rapid eye movements (REMs)
and by vivid dreams
!  Sleep is also regulated by the biological clock and
regions of the forebrain that regulate intensity and
duration
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Figure 49.12
Figure 49.13
Biological Clock Regulation
Key
Low-frequency waves characteristic of sleep
!  Sleep is essential and may play a role in the
consolidation of learning and memory
!  Some animals have evolutionary adaptations
allowing for substantial activity during sleep
Eye
Reticular formation
Location
!  Dolphins sleep with one brain hemisphere at a
time and are therefore able to swim while “asleep”
Input from
nerves of
ears
!  Cycles of sleep and wakefulness are examples of
circadian rhythms, daily cycles of biological activity
High-frequency waves characteristic of wakefulness
!  Such rhythms rely on a biological clock, a
molecular mechanism that directs periodic gene
expression and cellular activity
Time: 1 hour
Time: 0 hours
Left
hemisphere
!  Biological clocks are typically synchronized to light
and dark cycles
Right
hemisphere
Input from touch,
pain, and temperature
receptors
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Figure 49.14
Emotions
Thalamus
Hypothalamus
!  In mammals, circadian rhythms are coordinated by
a group of neurons in the hypothalamus called the
suprachiasmatic nucleus (SCN)
!  Generation and experience of emotions involve
many brain structures, including the amygdala,
hippocampus, and parts of the thalamus
!  The SCN acts as a pacemaker, synchronizing the
biological clock
!  These structures are grouped as the limbic system
!  Generating and experiencing emotion often
require interactions between different parts of the
brain
!  The structure most important to the storage of
emotion in the memory is the amygdala, a mass
of nuclei near the base of the cerebrum
Olfactory
bulb
Amygdala
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Hippocampus
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Figure 49.15
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Figure 49.15a
Figure 49.15b
Functional Imaging of the Brain
!  Brain structures are probed and analyzed with
functional imaging methods
Nucleus accumbens
Amygdala
Nucleus accumbens
Amygdala
!  Positron-emission tomography (PET) enables a
display of metabolic activity through injection of
radioactive glucose
!  Today, many studies rely on functional magnetic
resonance imaging (fMRI), in which brain activity is
detected through changes in local oxygen
concentration
Happy music
Sad music
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Happy music
Sad music
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Figure 49.16
Concept 49.3: The cerebral cortex controls
voluntary movement and cognitive functions
!  The range of applications for fMRI include
monitoring recovery from stroke, mapping
abnormalities in migraine headaches, and
increasing the effectiveness of brain surgery
Motor cortex (control of
skeletal muscles)
!  The cerebrum, the largest structure in the human
brain, is essential for language, cognition,
memory, consciousness, and awareness of our
surroundings
Somatosensory
cortex
(sense of touch)
Frontal lobe
Broca’s area
(forming speech)
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Cerebellum
Wernicke’s area
(comprehending
language)
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!  The thalamus directs different types of input to
distinct locations
Occipital lobe
Auditory cortex
(hearing)
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!  Somatosensory receptors provide information
about touch, pain, pressure, temperature, and the
position of muscles and limbs
Visual
association
cortex (combining
images and object
recognition)
Temporal lobe
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!  The cerebral cortex receives input from sensory
organs and somatosensory receptors
Parietal lobe
Prefrontal cortex
(decision making,
planning)
!  Four regions, or lobes (frontal, temporal, occipital,
and parietal), are landmarks for particular
functions
Information Processing
Sensory association
cortex (integration
of sensory information)
Visual cortex
(processing visual
stimuli and pattern
recognition)
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Figure 49.17
Figure 49.18
Language and Speech
Frontal lobe
er a
rm
Leg
Hip
Trunk
Neck
Head
Toes
Teeth
Gums
Jaw
Tongue
Pharynx
Lips
Jaw
Tongue
Primary
motor
cortex
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Max
!  Studies of brain activity have mapped areas
responsible for language and speech
!  Patients with damage in Broca’s area in the frontal
lobe can understand language but cannot speak
Eye
Face
!  In the somatosensory cortex and motor cortex,
neurons are arranged according to the part of the
body that generates input or receives commands
Upp
!  Integrated sensory information passes to the
prefrontal cortex, which helps plan actions and
movements
Parietal lobe
Knee
Hip
Trunk
lder
Shou w
Elbo
!  Information received at the primary sensory areas
is passed to nearby association areas that process
particular features of the input
Abdominal
organs
Hearing
words
Seeing
words
Speaking
words
Generating
words
!  Damage to Wernicke’s area causes patients to be
unable to understand language, though they can
still speak
Genitalia
Min
Primary
somatosensory
cortex
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Figure 49.UN03
Lateralization of Cortical Function
Frontal Lobe Function
!  The two hemispheres make distinct contributions
to brain function
!  The differences in hemisphere function are called
lateralization
!  The left hemisphere is more adept at language,
math, logic, and processing of serial sequences
!  The two hemispheres work together by
communicating through the fibers of the corpus
callosum
!  The right hemisphere is stronger at facial and
pattern recognition, spatial relations, and
nonverbal thinking
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!  The frontal lobes have a substantial effect on
“executive functions”
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Figure 49.19
Cerebrum
(including pallium)
Evolution of Cognition in Vertebrates
Cerebellum
!  Previous ideas that a highly convoluted neocortex
is required for advanced cognition may be
incorrect
!  The anatomical basis for sophisticated information
processing in birds (without a highly convoluted
neocortex) appears to be the clustering of nuclei in
the top or outer portion of the brain (pallium)
!  Frontal lobe damage may impair decision making
and emotional responses but leave intellect and
memory intact
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Concept 49.4: Changes in synaptic connections
underlie memory and learning
Neuronal Plasticity
!  Two processes dominate embryonic development
of the nervous system
Thalamus
Midbrain
(a) Songbird brain
Cerebrum (including
cerebral cortex)
!  Changes can strengthen or weaken signaling at a
synapse
!  Only half the synapses that form during embryo
development survive into adulthood
!  Autism, a developmental disorder, involves a
disruption in activity-dependent remodeling at
synapses
Midbrain
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(b) Human brain
Cerebellum
!  Neuronal plasticity describes the ability of the
nervous system to be modified after birth
!  Neurons compete for growth-supporting factors in
order to survive
Thalamus
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Memory and Learning
Long-Term Potentiation
!  Children affected with autism display impaired
communication and social interaction, as well as
stereotyped, repetitive behaviors
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Figure 49.20
Figure 49.21
N1
N1
!  The formation of memories is an example of
neuronal plasticity
N2
N2
!  In the vertebrate brain, a form of learning called
long-term potentiation (LTP) involves an
increase in the strength of synaptic transmission
!  Short-term memory is accessed via the
hippocampus
(a) Connections between neurons are strengthened or
weakened in response to activity.
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Glutamate
NMDA receptor
(open)
POSTSYNAPTIC
NEURON
!  LTP involves glutamate receptors
!  The hippocampus also plays a role in forming
long-term memory, which is later stored in the
cerebral cortex
(b) If two synapses are often active at the same time,
the strength of the postsynaptic response may
increase at both synapses.
PRESYNAPTIC
NEURON
Mg2+
Stored
AMPA
receptor
1
NMDA
receptor
(closed)
3
2
(b) Establishing LTP
!  If the presynaptic and postsynaptic neurons are
stimulated at the same time, the set of receptors
present on the postsynaptic membranes changes
3
1
2
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Na+
(a) Synapse prior to long-term potentiation (LTP)
!  Some consolidation of memory is thought to occur
during sleep
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Ca2+
Depolarization
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(c) Synapse exhibiting LTP
4 Action
potential
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Figure 49.21a
Figure 49.21b
PRESYNAPTIC
NEURON
Figure 49.21c
Concept 49.5: Many nervous system disorders
can be explained in molecular terms
Ca2+
Na+
!  Disorders of the nervous system include
schizophrenia, depression, drug addiction,
Alzheimer’s disease, and Parkinson’s disease
Mg2+
Glutamate
NMDA receptor
(open)
1
NMDA
receptor
(closed)
Stored
AMPA
receptor
POSTSYNAPTIC
NEURON
3
!  These are a major public health problem
3
1
2
2
4
!  Genetic and environmental factors contribute to
diseases of the nervous system
Action
potential
!  To distinguish between genetic and environmental
variables, scientists often carry out family studies
Depolarization
(a) Synapse prior to long-term potentiation (LTP)
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(b) Establishing LTP
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(c) Synapse exhibiting LTP
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Schizophrenia
Depression
The Brain’s Reward System and Drug Addiction
Figure 49.22
40
Genes shared with relatives of
person with schizophrenia
12.5% (3rd-degree relative)
25% (2nd-degree relative)
50% (1st-degree relative)
100%
!  About 1% of the world’s population suffers from
schizophrenia
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Identical twin
Child
Fraternal twin
Parent
Full sibling
Grandchild
Half sibling
Uncle/aunt
Nephew/niece
Individual,
general
population
Relationship to person with schizophrenia
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Nicotine
stimulates
dopaminereleasing
VTA neuron.
!  Addictive drugs enhance the activity of the
dopamine pathway
!  Drug addiction leads to long-lasting changes in the
reward circuitry that cause craving for the drug
!  Treatments for these types of depression include
drugs such as Prozac, which increase the activity
of biogenic amines in the brain
!  Drug addiction is characterized by compulsive
consumption and an inability to control intake
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Alzheimer’s Disease
Opium and heroin
decrease activity
of inhibitory
neuron.
Cerebral
neuron of
reward
pathway
Reward
system
response
Neurofibrillary tangle
20 µm
!  Alzheimer’s disease is caused by the formation of
neurofibrillary tangles and amyloid plaques in the
brain
!  There is no cure for this disease though some
drugs are effective at relieving symptoms
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Figure 49.UN04
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Figure 49.UN02
Figure 49.UN05
Parkinson’s Disease
Wild-type hamster
! hamster
Wild-type hamster with
SCN from ! hamster
! hamster with SCN
from wild-type hamster
Circadian cycle period (hours)
Brain
Dopa
decarboxylase
!  It is characterized by muscle tremors, flexed
posture, and a shuffling gait
!  There is no cure, although drugs and various other
approaches are used to manage symptoms
L-dopa
Dopamine
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23
22
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Nerve net
Spinal
cord
(dorsal
nerve
cord)
Sensory
ganglia
21
Hydra (cnidarian)
20
19
93
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Amyloid plaque
!  Alzheimer’s disease is a mental deterioration
characterized by confusion and memory loss
Cocaine and
amphetamines
block removal
of dopamine
from synaptic
cleft.
!  Parkinson’s disease is a motor disorder caused
by death of dopamine-secreting neurons in the
midbrain
88
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Figure 49.24
Inhibitory neuron
!  As researchers expand their understanding of the
brain’s reward system, there is hope that their
insights will lead to better prevention and
treatment of drug addiction
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!  These drugs include cocaine, amphetamine,
heroin, alcohol, and tobacco
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Dopaminereleasing
VTA neuron
89
!  Some drugs are addictive because they increase
activity of the brain’s reward system
!  Bipolar disorder is characterized by manic (highmood) and depressive (low-mood) phases
86
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Figure 49.23
!  The brain’s reward system rewards motivation with
pleasure
!  In major depressive disorder, patients have a
persistent lack of interest or pleasure in most
activities
!  Evidence suggests that schizophrenia affects
neuronal pathways that use dopamine as a
neurotransmitter
10
0
!  Two broad forms of depressive illness are known
!  Schizophrenia is characterized by hallucinations,
delusions, and other symptoms
20
First cousin
Risk of developing schizophrenia (%)
50
Before
procedures
After surgery
and transplant
95
Salamander (vertebrate)
96
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Figure 49.UN06
Figure 49.UN07
CNS
Figure 49.UN08
PNS
VENTRICLE
Ependymal
cell
Cilia
Astrocyte
Oligodendrocyte
Cerebrum
Forebrain
Thalamus
Hypothalamus
Pituitary gland
Midbrain
Schwann
cells
Capillary
Neuron
Pons
Hindbrain
Microglial cell
97
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Medulla
oblongata
Cerebellum
Spinal
cord
98
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99
© 2014 Pearson Education, Inc.