48 Nervous System

8/13/2019 48 Nervous System

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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)


7/123Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

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)



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)



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)



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


acetylcholine

Location of

postganglionic neurons:

in ganglia close to or

within target organs

Neurotransmitter

released by


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


thoracic and lumbar

segments of spinal cord

Neurotransmitterreleased by


acetylcholine

Location of


some in ganglia close to

target organs; others in

a chain of ganglia near

spinal cord

Neurotransmitter

released by


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

Documents

48 Nervous System