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Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures forBio logy, Seventh Edit ion
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 48
Nervous Systems
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Overview: Command and Control Center
The human brain
Contains an estimated 100 billion nerve cells,
or neurons
Each neuron
May communicate with thousands of other
neurons
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Functional magnetic resonance imaging
Is a technology that can reconstruct a three-dimensional map of brain activity
Figure 48.1
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The results of brain imaging and other research
methods Reveal that groups of neurons function in
specialized circuits dedicated to different tasks
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Concept 48.1: Nervous systems consist of
circuits of neurons and supporting cells All animals except sponges
Have some type of nervous system
What distinguishes the nervous systems of
different animal groups
Is how the neurons are organized into circuits
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Organization of Nervous Systems
The simplest animals with nervous systems,
the cnidarians Have neurons arranged in nerve nets
Figure 48.2a
Nerve net
(a) Hydra (cnidarian)
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Sea stars have a nerve net in each arm
Connected by radial nerves to a central nervering
Figure 48.2b
Nerve
ring
Radial
nerve
(b) Sea star (echinoderm)
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In relatively simple cephalized animals, such as
flatworms A central nervous system (CNS) is evident
Figure 48.2c
Eyespot
Brain
Nerve
cord
Transverse
nerve
(c) Planarian (flatworm)
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Annelids and arthropods
Have segmentally arranged clusters ofneurons called ganglia
These ganglia connect to the CNS
And make up a peripheral nervous system
(PNS)Brain
Ventral
nerve
cord
Segmental
ganglion
Brain
Ventral
nerve cord
Segmental
ganglia
Figure 48.2d, e (d) Leech (annelid) (e) Insect (arthropod)
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Anterior
nerve ring
Longitudinal
nerve cords
Ganglia
Brain
Ganglia
Figure 48.2f, g (f) Chiton (mollusc) (g) Squid (mollusc)
Nervous systems in molluscs
Correlate with the animals lifestyles
Sessile molluscs have simple systems
While more complex molluscs have moresophisticated systems
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The three stages of information processing
Are illustrated in the knee-jerk reflex
Figure 48.4
Sensory neurons
from the quadricepsalso communicate
with interneurons
in the spinal cord.
The interneurons
inhibit motor neurons
that supply the
hamstring (flexor)muscle. This inhibition
prevents the hamstring
from contracting,
which would resist
the action of
the quadriceps.
The sensory neurons communicate with
motor neuronsthat supply the quadriceps. The
motor neurons convey signals to the quadriceps,
causing it to contract and jerking the lower leg forward.
4
5
6
The reflex is
initiated by tapping
the tendon connected
to the quadriceps
(extensor) muscle.
1
Sensors detect
a sudden stretch in
the quadriceps.
2 Sensory neurons
convey the information
to the spinal cord.
3
Quadriceps
muscle
Hamstring
muscle
Spinal cord(cross section)
Gray matter
White
matter
Cell body of
sensory neuron
in dorsal
root ganglion
Sensory neuron
Motor neuron
Interneuron
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Neuron Structure
Most of a neurons organelles
Are located in the cell body
Figure 48.5
Dendrites
Cell body
Nucleus
Axon hillock
AxonSignal
direction
Synapse
Myelin sheath
Synaptic
terminals
Presynaptic cell Postsynaptic cell
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Most neurons have dendrites
Highly branched extensions that receivesignals from other neurons
The axon is typically a much longer extension
That transmits signals to other cells at
synapses
That may be covered with a myelin sheath
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Neurons have a wide variety of shapes
That reflect their input and output interactions
Figure 48.6ac
Axon
Cell
body
Dendrites
(a) Sensory neuron (b) Interneurons (c) Motor neuron
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Supporting Cells (Glia)
Glia are supporting cells
That are essential for the structural integrity ofthe nervous system and for the normal
functioning of neurons
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In the CNS, astrocytes
Provide structural support for neurons andregulate the extracellular concentrations of
ions and neurotransmitters
Figure 48.7 50m
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Oligodendrocytes (in the CNS) and Schwann
cells (in the PNS)
Are glia that form the myelin sheaths around
the axons of many vertebrate neurons
Myelin sheathNodes of
Ranvier
Schwann
cellSchwann
cell
Nucleus of
Schwann cell
Axon
Layers of myelin
Node of Ranvier
0.1 m
Axon
Figure 48.8
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Concept 48.2: Ion pumps and ion channels
maintain the resting potential of a neuron
Across its plasma membrane, every cell has a
voltage
Called a membrane potential
The inside of a cell is negative
Relative to the outside
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The membrane potential of a cell can be
measured
Figure 48.9
APPLICATION Electrophysiologists use intracellular recording to measure the membrane potential of
neurons and other cells.
TECHNIQUE A microelectrode is made from a glass capillary tube filled with an electrically conductive
salt solution. One end of the tube tapers to an extremely fine tip (diameter < 1 m). While looking through a
microscope, the experimenter uses a micropositioner to insert the tip of the microelectrode into a cell. A
voltage recorder (usually an oscilloscope or a computer-based system) measures the voltage between themicroelectrode tip inside the cell and a reference electrode placed in the solution outside the cell.
Microelectrode
Reference
electrode
Voltage
recorder
70 mV
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In all neurons, the resting potential
Depends on the ionic gradients that existacross the plasma membrane
CYTOSOL EXTRACELLULAR
FLUID
[Na+]
15 mM
[K+]
150 mM
[Cl]
10 mM
[A]
100 mM
[Na+]
150 mM
[K+]
5 mM
[Cl]
120 mM
+
+
+
+
+
Plasma
membrane
Figure 48.10
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The concentration of Na+is higher in the
extracellular fluid than in the cytosol
While the opposite is true for K+
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By modeling a mammalian neuron with an
artificial membrane
We can gain a better understanding of the
resting potential of a neuron
Figure 48.11a, b
Inner
chamberOuter
chamberInner
chamber
Outer
chamber92 mV +62 mV
Artificial
membrane
Potassium
channel
K+
Cl
150 mM
KCL
150 mM
NaCl15 mM
NaCl
5 mM
KCL
Cl
Na+
Sodium
channel
+
+
+
+
+
+
(a) Membrane selectively permeable to K
+
(b) Membrane selectively permeable to Na+
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A neuron that is not transmitting signals
Contains many open K+channels and feweropen Na+channels in its plasma membrane
The diffusion of K+and Na+through these
channels
Leads to a separation of charges across the
membrane, producing the resting potential
G t d I Ch l
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Gated Ion Channels
Gated ion channels open or close
In response to membrane stretch or thebinding of a specific ligand
In response to a change in the membrane
potential
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Concept 48.3: Action potentials are the signals
conducted by axons
If a cell has gated ion channels
Its membrane potential may change in
response to stimuli that open or close thosechannels
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Some stimuli trigger a hyperpolarization
An increase in the magnitude of the membranepotential
Figure 48.12a
+50
0
50
100
Time (msec)0 1 2 3 4 5
Threshold
Resting
potential Hyperpolarizations
Membranepotentia
l(mV)
Stimuli
(a) Graded hyperpolarizations
produced by two stimuli that
increase membrane permeability
to K+.The larger stimulus produces
a larger hyperpolarization.
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Other stimuli trigger a depolarization
A reduction in the magnitude of the membranepotential
Figure 48.12b
+50
0
50
100
Time (msec)
0 1 2 3 4 5
Threshold
Resting
potentialDepolarizations
Membranepotential(mV)
Stimuli
(b) Graded depolarizations produced
by two stimuli that increase
membrane permeability to Na+.
The larger stimulus produces a
larger depolarization.
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P d ti f A ti P t ti l
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Production of Action Potentials
In most neurons, depolarizations
Are graded only up to a certain membranevoltage, called the threshold
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An action potential
Is a brief all-or-none depolarization of aneurons plasma membrane
Is the type of signal that carries information
along axons
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Both voltage-gated Na+channels and voltage-
gated K+channels
Are involved in the production of an action
potential
When a stimulus depolarizes the membrane
Na+channels open, allowing Na+to diffuse into
the cell
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As the action potential subsides
K+channels open, and K+flows out of the cell
A refractory period follows the action potential
During which a second action potential cannotbe initiated
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Figure 48.14
+ + + + + +
+ + + + + +
+ + + + + +
+ + + + + +
+ + + +
+ +
+ +
+ ++ +
+ ++ +
+ + + + + + + +
Na+
Na+
Na+
Action
potential
Action
potential
Action
potentialK+
K+
K+
Axon
An action potential is generated
as Na+flows inward across the
membrane at one location.
1
2 The depolarization of the action
potential spreads to the neighboring
region of the membrane, re-initiating
the action potential there. To the left
of this region, the membrane is
repolarizing as K+flows outward.
3 The depolarization-repolarization process is
repeated in the next region of the
membrane. In this way, local currents
of ions acrossthe plasma membrane
cause the action potential to be propagated
alongthe length of the axon.
K+
At the site where the action potential is
generated, usually the axon hillock
An electrical current depolarizes the
neighboring region of the axon membrane
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Action potentials in myelinated axons
Jump between the nodes of Ranvier in aprocess called saltatory conduction
Cell body
Schwann cell
Myelin
sheath
Axon
Depolarized region(node of Ranvier)
++ +
++ +
++ +
++
Figure 48.15
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In a chemical synapse, a presynaptic neuron
Releases chemical neurotransmitters, whichare stored in the synaptic terminal
Figure 48.16
Postsynaptic
neuron
Synaptic
terminal
of presynaptic
neurons
5m
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When an action potential reaches a terminal
The final result is the release ofneurotransmitters into the synaptic cleft
Figure 48.17
Presynaptic
cell
Postsynaptic cell
Synaptic vesicles
containing
neurotransmitterPresynaptic
membrane
Postsynaptic
membrane
Voltage-gated
Ca2+channel
Synaptic cleft
Ligand-gated
ion channels
Na+K+
Ligand-
gated
ion channel
Postsynaptic
membrane
Neuro-
transmitter
1 Ca2+
2
3
4
5
6
Direct Synaptic Transmission
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Direct Synaptic Transmission
The process of direct synaptic transmission
Involves the binding of neurotransmitters toligand-gated ion channels
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Neurotransmitter binding
Causes the ion channels to open, generating apostsynaptic potential
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Postsynaptic potentials fall into two categories
Excitatory postsynaptic potentials (EPSPs)
Inhibitory postsynaptic potentials (IPSPs)
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After its release, the neurotransmitter
Diffuses out of the synaptic cleft
May be taken up by surrounding cells and
degraded by enzymes
Summation of Postsynaptic Potentials
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Summation of Postsynaptic Potentials Unlike action potentials
Postsynaptic potentials are graded and do notregenerate themselves
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Since most neurons have many synapses on
their dendrites and cell body
A single EPSP is usually too small to trigger an
action potential in a postsynaptic neuron
Figure 48.18a
E1 E1
Restingpotential
Threshold of axon of
postsynaptic neuron
(a) Subthreshold, no
summation
Terminal branch of
presynaptic neuron
Postsynapticneuron E1
0
70
Membranepotential
(mV)
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If two EPSPs are produced in rapid succession
An effect called temporal summation occurs
Figure 48.18b
E1 E1
Action
potential
(b) Temporal summation
E1
Axonhillock
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In spatial summation
EPSPs produced nearly simultaneously bydifferent synapses on the same postsynaptic
neuron add together
Figure 48.18c
E1 + E2
Action
potential
(c) Spatial summation
E1E2
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Through summation
An IPSP can counter the effect of an EPSP
Figure 48.18d
E1 E1 + II
(d) Spatial summation
of EPSP and IPSP
E1
I
Indirect Synaptic Transmission
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y p
In indirect synaptic transmission
A neurotransmitter binds to a receptor that isnot part of an ion channel
This binding activates a signal transduction
pathway
Involving a second messenger in the
postsynaptic cell, producing a slowly
developing but long-lasting effect
Neurotransmitters
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The same neurotransmitter
Can produce different effects in different typesof cells
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Major neurotransmitters
Table 48.1
Acetylcholine
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y Acetylcholine
Is one of the most common neurotransmittersin both vertebrates and invertebrates
Can be inhibitory or excitatory
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Amino Acids and Peptides
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p Various amino acids and peptides
Are active in the brain
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Concept 48.5: The vertebrate nervous system
is regionally specialized
In all vertebrates, the nervous system
Shows a high degree of cephalization and
distinct CNS and PNS components
Figure 48.19
Central nervous
system (CNS)Peripheral nervous
system (PNS)
Brain
Spinal cord
Cranial
nerves
Ganglia
outside
CNS
Spinal
nerves
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The brain provides the integrative power
That underlies the complex behavior ofvertebrates
The spinal cord integrates simple responses to
certain kinds of stimuli
And conveys information to and from the brain
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The central canal of the spinal cord and the
four ventricles of the brain
Are hollow, since they are derived from the
dorsal embryonic nerve cord
Gray matter
White
matter
Ventricles
Figure 48.20
The Peripheral Nervous System
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The PNS transmits information to and from the
CNS
And plays a large role in regulating a
vertebrates movement and internal
environment
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The cranial nerves originate in the brain
And terminate mostly in organs of the headand upper body
The spinal nerves originate in the spinal cord
And extend to parts of the body below the
head
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The PNS can be divided into two functional
components
The somatic nervous system and the
autonomic nervous systemPeripheral
nervous system
Somatic
nervous
system
Autonomic
nervous
system
Sympatheticdivision Parasympatheticdivision Entericdivision
Figure 48.21
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The somatic nervous system
Carries signals to skeletal muscles
The autonomic nervous system
Regulates the internal environment, in aninvoluntary manner
Is divided into the sympathetic,
parasympathetic, and enteric divisions
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The sympathetic and parasympathetic divisions
Have antagonistic effects on target organs
Parasympathetic division Sympathetic division
Action on target organs: Action on target organs:
Location of
preganglionic neurons:
brainstem and sacral
segments of spinal cord
Neurotransmitterreleased by
preganglionic neurons:
acetylcholine
Location of
postganglionic neurons:
in ganglia close to or
within target organs
Neurotransmitter
released by
postganglionic neurons:
acetylcholine
Constricts pupil
of eye
Stimulates salivary
gland secretion
Constrictsbronchi in lungs
Slows heart
Stimulates activity
of stomach and
intestines
Stimulates activity
of pancreas
Stimulates
gallbladder
Promotes emptying
of bladder
Promotes erection
of genitalia
Cervical
Thoracic
Lumbar
Synapse
Sympathetic
ganglia
Dilates pupil
of eye
Inhibits salivary
gland secretion
Relaxes bronchiin lungs
Accelerates heart
Inhibits activity of
stomach and intestines
Inhibits activity
of pancreas
Stimulates glucoserelease from liver;
inhibits gallbladder
Stimulates
adrenal medulla
Inhibits emptying
of bladder
Promotes ejaculation and
vaginal contractionsSacral
Location of
preganglionic neurons:
thoracic and lumbar
segments of spinal cord
Neurotransmitterreleased by
preganglionic neurons:
acetylcholine
Location of
postganglionic neurons:
some in ganglia close to
target organs; others in
a chain of ganglia near
spinal cord
Neurotransmitter
released by
postganglionic neurons:
norepinephrine
Figure 48.22
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The sympathetic division
Correlates with the fight-or-flight response
The parasympathetic division
Promotes a return to self-maintenancefunctions
The enteric division
Controls the activity of the digestive tract,pancreas, and gallbladder
Embryonic Development of the Brain
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In all vertebrates
The brain develops from three embryonicregions: the forebrain, the midbrain, and the
hindbrain
Figure 48.23a
Forebrain
Midbrain
Hindbrain
MidbrainHindbrain
Forebrain
(a) Embryo at one month
Embryonic brain regions
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By the fifth week of human embryonic
development
Five brain regions have formed from the three
embryonic regions
Figure 48.23b
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon
(b) Embryo at five weeks
MesencephalonMetencephalon
Myelencephalon
Spinal cord
Diencephalon
Telencephalon
Embryonic brain regions
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The medulla oblongata
Contains centers that control several visceralfunctions
The pons
Also participates in visceral functions
The midbrain
Contains centers for the receipt and integrationof several types of sensory information
Arousal and Sleep
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A diffuse network of neurons called the
reticular formation
Is present in the core of the brainstem
Figure 48.24
Eye
Reticular formation
Input from touch,
pain, and temperature
receptors
Input from ears
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A part of the reticular formation, the reticular
activating system (RAS)
Regulates sleep and arousal
The Cerebellum
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The cerebellum
Is important for coordination and errorchecking during motor, perceptual, and
cognitive functions
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The cerebellum
Is also involved in learning and rememberingmotor skills
The Diencephalon
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The embryonic diencephalon develops into
three adult brain regions
The epithalamus, thalamus, and hypothalamus
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The epithalamus
Includes the pineal gland and the choroidplexus
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The thalamus
Is the main input center for sensory informationgoing to the cerebrum and the main output
center for motor information leaving the
cerebrum
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The hypothalamus regulates
Homeostasis
Basic survival behaviors such as feeding,
fighting, fleeing, and reproducing
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Biological clocks usually require external cues
To remain synchronized with environmental cycles
Figure 48.25
In the northern flying squirrel (Glaucomys sabrinus), activity normally begins with the onset of darkness and ends
at dawn, which suggests that light is an important external cue for the squirrel. To test this idea, researchers monitored the activity of captive
squirrels for 23 days under two sets of conditions: (a) a regular cycle of 12 hours of light and 12 hours of darkness and (b) constant darkness.
The squirrels were given free access to an exercise wheel and a rest cage. A recorder automatically noted when the wheel was rotating and
when it was still.
EXPERIMENT
Light Dark Light
20
15
10
5
1
(a) 12 hr light-12 hr dark cycle (b) Constant darkness
12 16 20 24 4 8 12 12 16 20 24 4 8 12
Time of day (hr) Time of day (hr)
When the squirrelswere exposed to a regular light/dark
cycle, their wheel-turning activity
(indicated by the dark bars) occurred
at roughly the same time every day.
However, when they were kept in
constant darkness, their activity phase
began about 21 minutes later each day.
RESULTS
The northern flying squirrels internal clock can run in constant darkness, but it does so on
its own cycle, which lasts about 24 hours and 21 minutes. External (light) cues keep the clock running on a 24-hour cycle.
CONCLUSION
Dark
Daysofexperiment
The Cerebrum
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The cerebrum
Develops from the embryonic telencephalon
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The cerebrum has right and left cerebral
hemispheres
That each consist of cerebral cortex overlying
white matter and basal nuclei
Left cerebral
hemisphere
Corpus
callosum
Neocortex
Right cerebral
hemisphere
Basal
nuclei
Figure 48.26
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The basal nuclei
Are important centers for planning and learningmovement sequences
In mammals
The cerebral cortex has a convoluted surface
called the neocortex
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In humans, the largest and most complex part
of the brain
Is the cerebral cortex, where sensory
information is analyzed, motor commands are
issued, and language is generated
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Concept 48.6: The cerebral cortex controls
voluntary movement and cognitive functions
Each side of the cerebral cortex has four lobes
Frontal, parietal, temporal, and occipital
Frontal lobe
Temporal lobe Occipital lobe
Parietal lobe
Frontal
association
area
Speech
Smell
Hearing
Auditory
association
areaVision
Visual
association
area
Somatosensory
association
area
Reading
Speech
Taste
Figure 48.27
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Each of the lobes
Contains primary sensory areas andassociation areas
Information Processing in the Cerebral Cortex
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Specific types of sensory input
Enter the primary sensory areas
Adjacent association areas
Process particular features in the sensory input
and integrate information from different
sensory areas
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In the somatosensory cortex and motor cortex
Neurons are distributed according to the partof the body that generates sensory input or
receives motor input
Figure 48.28
Tongue
JawLips
Primary
motor cortex Abdominal
organs
Pharynx
Tongue
Genitalia
Primary
somatosensory
cortex
Toes
Parietal lobeFrontal lobe
Lateralization of Cortical Function
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During brain development, in a process called
lateralization
Competing functions segregate and displace
each other in the cortex of the left and right
cerebral hemispheres
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Language and Speech
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Studies of brain activity
Have mapped specific areas of the brainresponsible for language and speech
Figure 48.29
Hearing
words
Seeing
words
Speaking
words
Generating
words
Max
Min
f f
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Portions of the frontal lobe, Brocas area and
Wernickes area
Are essential for the generation and
understanding of language
Emotions
Th li bi t
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The limbic system
Is a ring of structures around the brainstem
Figure 48.30
HypothalamusThalamus
Prefrontal cortex
Olfactory
bulb
Amygdala Hippocampus
Thi li bi t i l d th t f th
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This limbic system includes three parts of the
cerebral cortex
The amygdala, hippocampus, and olfactory
bulb
These structures interact with the neocortex tomediate primary emotions
And attach emotional feelings to survival-
related functions
St t f th li bi t f i l
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Structures of the limbic system form in early
development
And provide a foundation for emotional
memory, associating emotions with particular
events or experiences
Memory and Learning
Th f t l l b
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The frontal lobes
Are a site of short-term memory
Interact with the hippocampus and amygdala
to consolidate long-term memory
M d t i ti f
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Many sensory and motor association areas of
the cerebral cortex
Are involved in storing and retrieving words
and images
Cellular Mechanisms of LearningE i t i t b t
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Experiments on invertebrates
Have revealed the cellular basis of some typesof learning
Figure 48.31a, b
(a)Touching the siphon triggers a reflex that
causes the gill to withdraw. If the tail is
shocked just before the siphon is touched,
the withdrawal reflex is stronger. This
strengthening of the reflex is a simple form
of learning called sensitization.
(b) Sensitization involves interneurons that
make synapses on the synaptic terminalsof
the siphon sensory neurons. When the tail
is shocked, the interneurons release
serotonin, which activates a signaltransduction pathway that closes K+
channels in the synaptic terminals of
the siphon sensory neurons. As a result,
action potentials in the siphon sensory
neurons produce a prolonged
depolarization of the terminals. That allows
more Ca2+to diffuse into the terminals,
which causes the terminals to release more
of their excitatory neurotransmitter onto the gill
motor neurons. In response, the motor neurons
generate action potentials at a higher frequency,
producing a more forceful gil l withdrawal.
Siphon
Mantle
Gill
Tail
Head
Gill withdrawal pathway
Touchingthe siphon
Shocking
the tail Tail sensory
neuron
Interneuron
Sensitization pathway
Siphon sensory
neuron
Gill motorneuron
Gill
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Consciousness
M d b i i i t h i
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Modern brain-imaging techniques
Suggest that consciousness may be anemergent property of the brain that is based on
activity in many areas of the cortex
Concept 48 7: CNS injuries and diseases are
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Concept 48.7: CNS injuries and diseases are
the focus of much research
Unlike the PNS, the mammalian CNS
Cannot repair itself when damaged or
assaulted by disease
Current research on nerve cell development
and stem cells
May one day make it possible for physicians to
repair or replace damaged neurons
Nerve Cell Development
Signal molecules direct an axons growth
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Signal molecules direct an axons growth
By binding to receptors on the plasmamembrane of the growth cone
This receptor binding triggers a signal
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This receptor binding triggers a signal
transduction pathway
Which may cause an axon to grow toward or
away from the source of the signal
Figure 48.33a, b
Midline of
spinal cord
Developing axon
of interneuron
Growth
cone
Netrin-1
receptor
Netrin-1
Floor
plate
Cell
adhesionmolecules
SlitreceptorSlit
Developing axon
of motor neuron
Netrin-1
receptor
Slit
receptor
Slit
Netrin-1
1 Growth toward the floor plate.
Cells in the floor plate of the
spinal cord release Netrin-1, which
diffuses away from the floor plate
and binds to receptors on the
growth cone of a developing
interneuron axon. Binding stimulates
axon growth toward the floor plate.
2 Growth across the mid-line.
Once the axon reaches the
floor plate, cell adhesion molecules
on the axon bind to complementary
molecules on floor plate cells,
directing the growth of the axon
across the midline.
3 No turning back.
Now the axon synthesizes
receptors that bind to Slit,
a repulsion protein re-
leased by floor plate cells.
This prevents the axon
from growing back across
the midline.
Netrin-1 and Slit, produced by cells
of the floor plate, bind to receptors
on the axons of motor neurons. In
this case, both proteins act to repel
the axon, directing the motor neuron
to grow away from the spinal cord.
(a) Growth of an interneuron axon toward and across the midline of the spinal cord
(diagrammed here in cross section)
(b) Growth of a motor neuron axon away
from the midline of the spinal cord
The genes and basic events involved in axon
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The genes and basic events involved in axon
guidance
Are similar in invertebrates and vertebrates
Knowledge of these events may be applied one
day
To stimulate axonal regrowth following CNS
damage
Neural Stem Cells
The adult human brain
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The adult human brain
Contains stem cells that can differentiate intomature neurons
Figure 48.34
The induction of stem cell differentiation and
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The induction of stem cell differentiation and
the transplantation of cultured stem cells
Are potential methods for replacing neurons
lost to trauma or disease
Diseases and Disorders of the Nervous System
Mental illnesses and neurological disorders
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Mental illnesses and neurological disorders
Take an enormous toll on society, in both thepatients loss of a productive life and the high
cost of long-term health care
Schizophrenia About 1% of the worlds population
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About 1% of the world s population
Suffers from schizophrenia
Schizophrenia is characterized by
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Schizophrenia is characterized by
Hallucinations, delusions, blunted emotions,and many other symptoms
Available treatments have focused on
Brain pathways that use dopamine as a
neurotransmitter
Depression Two broad forms of depressive illness are
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Two broad forms of depressive illness are
known
Bipolar disorder and major depression
Bipolar disorder is characterized by
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Bipolar disorder is characterized by
Manic (high-mood) and depressive (low-mood)phases
In major depression
Patients have a persistent low mood
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AD is caused by the formation of
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AD is caused by the formation of
Neurofibrillary tangles and senile plaques inthe brain
Figure 48.35
Senile plaque Neurofibrillary tangle20 m
A successful treatment for AD in humans
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A successful treatment for AD in humans
May hinge on early detection of senile plaques
Parkinsons Disease Parkinsons disease is a motor disorder
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Parkinson s disease is a motor disorder
Caused by the death of dopamine-secretingneurons in the substantia nigra
Characterized by difficulty in initiating
movements, slowness of movement, and
rigidity
There is no cure for Parkinsons disease
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There is no cure for Parkinson s disease
Although various approaches are used tomanage the symptoms