49 Lecture Nervous System

8/12/2019 49 Lecture Nervous System

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LECTURE PRESENTATIONS

For CAMPBELL BIOLOGY, NINTH EDITION

Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

© 2011 Pearson Education, Inc.

Lectures by

Erin Barley

Kathleen Fitzpatrick

Nervous Systems

Chapter 49



Overview: Command and Control Center

• The human brain contains about 100 billionneurons, organized into circuits more complex

than the most powerful supercomputers

• A recent advance in brain exploration involves a

method for expressing combinations of colored

proteins in brain cells, a technique called

“brainbow”

• This may allow researchers to develop detailedmaps of information transfer between regions of

the brain




Figure 49.1



• Each single-celled organism can respond to

stimuli in its environment

•

Animals are multicellular and most groupsrespond to stimuli using systems of neurons


Concept 49.1: Nervous systems consist of

circuits of neurons and supporting cells



• The simplest animals with nervous systems, thecnidarians, have neurons arranged in nerve nets

• A nerve net is a series of interconnected nerve

cells

• More complex animals have nerves




• Nerves are bundles that consist of the axons ofmultiple nerve cells

• Sea stars have a nerve net in each arm

connected by radial nerves to a central nerve

ring






Figure 49.2a

Nerve net

(a) Hydra (cnidarian)

Radialnerve

Nerve

ring

(b) Sea star (echinoderm)





Figure 49.2b

Eyespot

BrainNervecords

Transversenerve

Brain

Ventral

nerve cord

Segmental

ganglia

(c) Planarian (flatworm) (d) Leech (annelid)



• Annelids and arthropods have segmentallyarranged clusters of neurons called ganglia




Figure 49.2c

(e) Insect (arthropod) (f) Chiton (mollusc)

Brain

Ventralnerve cord

Segmentalganglia

Anteriornerve ring

Longitudinalnerve cords

Ganglia



• Nervous system organization usually correlateswith lifestyle

• Sessile molluscs (for example, clams and

chitons) have simple systems, whereas more

complex molluscs (for example, octopuses and

squids) have more sophisticated systems




Figure 49.2d

(h) Salamander (vertebrate)(g) Squid (mollusc)

Brain

Brain

Ganglia

Spinalcord(dorsal

nervecord)

Sensoryganglia



• In vertebrates – The CNS is composed of the brain and spinal

cord

– The peripheral nervous system (PNS) is

composed of nerves and ganglia




Organization of the Vertebrate Nervous

System

• The spinal cord conveys information from and

to the brain

•

The spinal cord also produces reflexesindependently of the brain

• A reflex is the body’s automatic response to a

stimulus

– For example, a doctor uses a mallet to triggera knee-jerk reflex




Quadricepsmuscle

Cell body ofsensory neuron indorsal rootganglion

Graymatter

Whitematter

Hamstringmuscle

Spinal cord(cross section)

Sensory neuron

Motor neuron

Interneuron

Figure 49.3



• Invertebrates usually have a ventral nerve cordwhile vertebrates have a dorsal spinal cord

• The spinal cord and brain develop from the

embryonic nerve cord

• The nerve cord gives rise to the central canal

and ventricles of the brain


Fi 49 4



Figure 49.4Central nervoussystem (CNS)

Brain

Spinal cord

Peripheral nervoussystem (PNS)

Cranial nerves

Ganglia outsideCNS

Spinal nerves

Fi 49 5



Figure 49.5

Gray matter

Whitematter

Ventricles



• The central canal of the spinal cord and theventricles of the brain are hollow and filled with

cerebrospinal fluid

• The cerebrospinal fluid is filtered from blood and

functions to cushion the brain and spinal cord as

well as to provide nutrients and remove wastes




• The brain and spinal cord contain – Gray matter , which consists of neuron cell

bodies, dendrites, and unmyelinated axons

– White matter , which consists of bundles of

myelinated axons




Glia

• Glia have numerous functions to nourish,support, and regulate neurons

– Embryonic radial glia form tracks along which

newly formed neurons migrate

– Astrocytes induce cells lining capillaries in the

CNS to form tight junctions, resulting in a

blood-brain barrier and restricting the entry of

most substances into the brain


Figure 49 6



Figure 49.6CNS PNS

VENTRICLE

Cilia

Neuron Astrocyte

Oligodendrocyte

Capillary Ependymal cell

LM 5 0 m

Schwann cell

Microglial cell

Figure 49 6a



Figure 49.6a

CNS PNS

VENTRICLE

Cilia

Neuron Astrocyte

Oligodendrocyte

Capillary Ependymal cell

Schwann cell

Microglial cell





The Peripheral Nervous System

• The PNS transmits information to and from theCNS and regulates movement and the internalenvironment

• In the PNS, afferent neurons transmit informationto the CNS and efferent neurons transmitinformation away from the CNS




• The PNS has two efferent components: themotor system and the autonomic nervous system

• The motor system carries signals to skeletal

muscles and is voluntary

• The autonomic nervous system regulates

smooth and cardiac muscles and is generally

involuntary


Figure 49.7



Efferent neuronsAfferent neurons

Central NervousSystem

(information processing)

Peripheral NervousSystem

Sensoryreceptors

Internaland external

stimuli

Autonomic

nervous system

Motor

system

Control ofskeletal muscle

Sympatheticdivision

Parasympatheticdivision

Entericdivision

Control of smooth muscles,cardiac muscles, glands

Figure 49.7



• The autonomic nervous system hassympathetic, parasympathetic, and enteric

divisions

• The sympathetic division regulates arousal

and energy generation (“fight-or-flight”

response)

• The parasympathetic division has

antagonistic effects on target organs andpromotes calming and a return to “rest and

digest” functions




• The enteric division controls activity of thedigestive tract, pancreas, and gallbladder


Figure 49.8



Parasympathetic division

Action on target organs:

Constricts pupilof eye

Stimulates salivarygland secretion

Constrictsbronchi in lungs

Slows heart

Stimulates activity

of stomach andintestines

Stimulates activityof pancreas

Stimulatesgallbladder

Promotes emptyingof bladder

Promotes erection

of genitalia

Cervical

Thoracic

Lumbar

Synapse

Sacral

Sympatheticganglia

Sympathetic division


Dilates pupil of eye

Accelerates heart

Inhibits salivary

gland secretion

Relaxes bronchiin lungs

Inhibits activity of

stomach and intestines

Inhibits activityof pancreas

Stimulates glucoserelease from liver;inhibits gallbladder

Stimulatesadrenal medulla

Inhibits emptyingof bladder

Promotes ejaculation

and vaginal contractions

g

Figure 49.8a



g



Constricts pupilof eye

Stimulates salivarygland secretion

Constrictsbronchi in lungs

Slows heart

Stimulates activityof stomach and

intestines

Stimulates activityof pancreas

Stimulatesgallbladder

Cervical

Sympatheticganglia



Dilates pupil of eye

Inhibits salivarygland secretion

Figure 49.8b




Promotes emptyingof bladder

Promotes erectionof genitalia

Thoracic

Lumbar

Synapse

Sacral


Accelerates heart

Relaxes bronchiin lungs

Inhibits activity ofstomach and intestines

Inhibits activity

of pancreas

Stimulates glucoserelease from liver;

inhibits gallbladder

Stimulates

adrenal medulla

Inhibits emptyingof bladder

Promotes ejaculationand vaginal contractions



Concept 49.2: The vertebrate brain is

regionally specialized

• Specific brain structures are particularly

specialized for diverse functions

•

These structures arise during embryonicdevelopment


Figure 49.9a



Embryonic brain regions Brain structures in child and adultFigure 49.9b



Embryonic brain regions Brain structures in child and adult

Forebrain

Midbrain

Hindbrain

Telencephalon

Diencephalon

Mesencephalon

Metencephalon

Myelencephalon

Cerebrum (includes cerebral cortex, whitematter, basal nuclei)

Diencephalon (thalamus, hypothalamus,epithalamus)

Midbrain (part of brainstem)

Pons (part of brainstem), cerebellum

Medulla oblongata (part of brainstem)

Midbrain

Forebrain

Hindbrain

Telencephalon

Diencephalon

Mesencephalon

Metencephalon

Myelencephalon

Spinalcord

Cerebrum Diencephalon

Midbrain

Pons

Medullaoblongata

Cerebellum

Spinal cord

ChildEmbryo at 5 weeksEmbryo at 1 month

Figure 49.9ba



Midbrain

Forebrain

Hindbrain

Telencephalon

Diencephalon

Mesencephalon

Metencephalon

Myelencephalon

Spinalcord

Embryo at 5 weeksEmbryo at 1 month

Figure 49.9bb



Cerebrum Diencephalon

Midbrain

Pons

Medullaoblongata

Cerebellum

Spinal cord

Child

Figure 49.9c



Adult brain viewed from the rear

Cerebellum

Basal nucleiCerebrum

Left cerebralhemisphere

Right cerebralhemisphere

Cerebral cortex

Corpus callosum

Figure 49.9d



Diencephalon

Thalamus

Pineal gland

Hypothalamus

Pituitary gland

Spinal cord

Brainstem

Midbrain

Pons

Medulla

oblongata



Arousal and Sleep • The brainstem and cerebrum control arousal

and sleep

• The core of the brainstem has a diffuse networkof neurons called the reticular formation

• This regulates the amount and type ofinformation that reaches the cerebral cortexand affects alertness

•

The hormone melatonin is released by thepineal gland and plays a role in bird andmammal sleep cycles


Figure 49.10



Eye

Reticular formation

Input from touch,pain, and temperaturereceptors

Input from nervesof ears



•Sleep is essential and may play a role in theconsolidation of learning and memory

• Dolphins sleep with one brain hemisphere at a

time and are therefore able to swim while

“asleep”


Figure 49.11



Low-frequency waves characteristic of sleep

High-frequency waves characteristic of wakefulness

Key

Location Time: 0 hours Time: 1 hour

Lefthemisphere

Righthemisphere



Biological Clock Regulation •

Cycles of sleep and wakefulness are examplesof circadian rhythms, daily cycles of biological

activity

• Mammalian circadian rhythms rely on a

biological clock, molecular mechanism that

directs periodic gene expression

• Biological clocks are typically synchronized to

light and dark cycles




Figure 49.12RESULTS



Wild-type hamster

Wild-type hamster withSCN from hamster

hamster

hamster with SCNfrom wild-type hamster

Beforeprocedures

After surgeryand transplant

C i r c a d i a n c y c l e p e r i o d ( h o u r s )

24

23

22

21

20

19



Emotions

•

Generation and experience of emotions involvemany brain structures including the amygdala,

hippocampus, and parts of the thalamus

• These structures are grouped as the limbic

system

• The limbic system also functions in motivation,

olfaction, behavior, and memory






•

Generation and experience of emotion alsorequire interaction between the limbic systemand sensory areas of the cerebrum

• The structure most important to the storage of

emotion in the memory is the amygdala, a massof nuclei near the base of the cerebrum


Figure 49.14



Nucleus accumbens Amygdala

Happy music Sad music



Figure 49.14b



Amygdala

Sad music



Concept 49.3: The cerebral cortex controls

voluntary movement and cognitive functions

• The cerebrum, the largest structure in the

human brain, is essential for awareness,

language, cognition, memory, and

consciousness

• Four regions, or lobes (frontal, temporal,

occipital, and parietal), are landmarks for

particular functions


Figure 49.15

M t t



Motor cortex(control ofskeletal muscles)

Frontal lobe

Prefrontal cortex(decision making,planning)

Broca’s area(forming speech)

Temporal lobe

Auditory cortex (hearing)

Wernicke’s area(comprehending language)

Somatosensory cortex(sense of touch)

Parietal lobe

Sensory associationcortex (integration ofsensory information)

Visual associationcortex (combiningimages and objectrecognition)

Occipital lobe

Cerebellum

Visual cortex(processing visualstimuli and patternrecognition)



Language and Speech

•

Studies of brain activity have mapped areasresponsible for language and speech

• Broca’s area in the frontal lobe is active when

speech is generated

• Wernicke’s area in the temporal lobe is active

when speech is heard

• These areas belong to a larger network of

regions involved in language


Figure 49.16



Hearingwords

Speakingwords

Seeingwords

Generatingwords

Max

Min



Lateralization of Cortical Function

•

The two hemispheres make distinct contributionsto brain function

• The left hemisphere is more adept at language,

math, logic, and processing of serial sequences

• The right hemisphere is stronger at pattern

recognition, nonverbal thinking, and emotional

processing




•

The differences in hemisphere function arecalled lateralization

• Lateralization is partly linked to handedness

• The two hemispheres work together by

communicating through the fibers of the corpus

callosum




Information Processing

•

The cerebral cortex receives input from sensoryorgans and somatosensory receptors

• Somatosensory receptors provide information

about touch, pain, pressure, temperature, and

the position of muscles and limbs

• The thalamus directs different types of input to

distinct locations




•

Adjacent areas process features in the sensoryinput and integrate information from different

sensory areas

• Integrated sensory information passes to the

prefrontal cortex, which helps plan actions andmovements

• In the somatosensory cortex and motor cortex,

neurons are arranged according to the part ofthe body that generates input or receives

commands


Figure 49.17



Frontal lobe Parietal lobe

Primarymotor cortex

Primarysomatosensorycortex

GenitaliaToes

Abdominalorgans

Tongue

Jaw

Hi p

Kn e e

Tongue

Pharynx

H e a d

N e ck

T r unk

Hi p

L e g

Figure 49.17a



Primarymotor cortex

Toes

Tongue

Jaw

Hi p

Kn e e

Figure 49.17b



Primarysomatosensorycortex

Genitalia

Abdominalorgans

TonguePharynx

H e a d

N e ck

T r unk

Hi p

L e g



Frontal Lobe Function

•

Frontal lobe damage may impair decisionmaking and emotional responses but leave

intellect and memory intact

• The frontal lobes have a substantial effect on

“executive functions”


Figure 49.UN01





Evolution of Cognition in Vertebrates

•

Previous ideas that a highly convolutedneocortex is required for advanced cognition

may be incorrect

• The anatomical basis for sophisticated

information processing in birds (without a highlyconvoluted neocortex) appears to be the

clustering of nuclei in the top or outer portion of

the brain (pallium)


Human brain Cerebrum (includingcerebral cortex)

Figure 49.18



Avian brain

Thalamus

Midbrain

Hindbrain Cerebellum

Avian brain

to scale

Thalamus

Midbrain

Hindbrain

Cerebellum

cerebral cortex)

Cerebrum(including pallium)



Concept 49.4 Changes in synaptic

connections underlie memory and learning

• Two processes dominate embryonic

development of the nervous system

– Neurons compete for growth-supporting factors

in order to survive

– Only half the synapses that form during embryo

development survive into adulthood




Neural Plasticity

•

Neural plasticity describes the ability of thenervous system to be modified after birth

• Changes can strengthen or weaken signaling at

a synapse


Figure 49.19

N1N1



N2

N1

N2

1

(a) Synapses are strengthened or weakened in response toactivity.

(b) If two synapses are often active at the same time, thestrength of the postsynaptic response may increase atboth synapses.



Memory and Learning

•

The formation of memories is an example ofneural plasticity

• Short-term memory is accessed via the

hippocampus

• The hippocampus also plays a role in forming

long-term memory, which is stored in the

cerebral cortex

•

Some consolidation of memory is thought tooccur during sleep




Long-Term Potentiation

•

In the vertebrate brain, a form of learning calledlong-term potentiation (LTP) involves an

increase in the strength of synaptic transmission

• LTP involves glutamate receptors

• If the presynaptic and postsynaptic neurons are

stimulated at the same time, the set of receptors

present on the postsynaptic membranes

changes


Figure 49.20 PRESYNAPTICNEURON

Ca2

Na



GlutamateMg2

NMDA

receptor(closed)

Stored

AMPAreceptor

NMDA receptor (open)

POSTSYNAPTICNEURON

(a) Synapse prior to long-term potentiation (LTP)

(b) Establishing LTP

(c) Synapse exhibiting LTP

Depolarization

Actionpotential

2

1

3

1

2

3

4

Figure 49.20a



PRESYNAPTICNEURON

Glutamate Mg2

Ca2

Na

NMDAreceptor

(closed)

Stored

AMPAreceptor

NMDA receptor (open)

POSTSYNAPTICNEURON

(a) Synapse prior to long-term potentiation (LTP)



Figure 49.20c



(c) Synapse exhibiting LTP

Depolarization

Actionpotential

AMPAreceptor

NMDA receptor

1 3

42

St C ll i th B i



Stem Cells in the Brain

•

The adult human brain contains neural stemcells

• In mice, stem cells in the brain can give rise to

neurons that mature and become incorporated

into the adult nervous system

• Such neurons play an essential role in learning

and memory


Figure 49.21



C t 49 5 N t di d



Concept 49.5: Nervous system disorders can

be explained in molecular terms

• Disorders of the nervous system include

schizophrenia, depression, drug addiction,

Alzheimer ’s disease, and Parkinson’s disease

• Genetic and environmental factors contribute to

diseases of the nervous system


Figure 49.22

Genes shared with relatives ofperson ith schi ophrenia

50



person with schizophrenia

12.5% (3rd-degree relative)

25% (2nd-degree relative)

50% (1st-degree relative)

100%

40

30

20

10

0

Relationship to person with schizophrenia

R i s k o f d e v e

l o p i n g s c h i z o p h r e n i a ( % )

I n d i v i d u a l ,

g e n e r a l

p o p u l a t i o n

F i r s t c o u s i n

U n c l e / a u n t

N e p h e w /

n i e c e

F r a t e r n a l

t w i n

I d e n t i c a l

t w i n

G r a n d c h i l d

H a l f s i b l i n g

P a r e n t

F u l l s i b l i n g

C h i l d

S hi h i



Schizophrenia

•

About 1% of the world’s population suffers fromschizophrenia

• Schizophrenia is characterized by hallucinations,

delusions, and other symptoms

• Available treatments focus on brain pathways

that use dopamine as a neurotransmitter


D i



Depression

•

Two broad forms of depressive illness areknown: major depressive disorder and bipolar

disorder

• In major depressive disorder , patients have a

persistent lack of interest or pleasure in mostactivities

• Bipolar disorder is characterized by manic

(high-mood) and depressive (low-mood) phases• Treatments for these types of depression include

drugs such as Prozac


D Addi ti d th B i ’ R d



Drug Addiction and the Brain’s Reward

System

• The brain’s reward system rewards motivation

with pleasure

• Some drugs are addictive because they

increase activity of the brain’s reward system

• These drugs include cocaine, amphetamine,

heroin, alcohol, and tobacco

• Drug addiction is characterized by compulsiveconsumption and an inability to control intake




•

Addictive drugs enhance the activity of thedopamine pathway

• Drug addiction leads to long-lasting changes in

the reward circuitry that cause craving for the

drug


Figure 49.23 Nicotinestimulatesdopamine

Inhibitory neuron



dopamine-releasingVTA neuron.

Dopamine-releasingVTA neuron

Cerebralneuron ofrewardpathway

Opium and heroindecrease activityof inhibitoryneuron.

Cocaine andamphetaminesblock removalof dopaminefrom synaptic

cleft.

Rewardsystemresponse

Al h i ’ Di



Alzheimer’s Disease

•

Alzheimer ’s disease is a mental deteriorationcharacterized by confusion and memory loss

• Alzheimer ’s disease is caused by the formationof neurofibrillary tangles and amyloid plaques in

the brain• There is no cure for this disease though some

drugs are effective at relieving symptoms




Parkinson’s Disease



Parkinson s Disease

•

Parkinson’s disease is a motor disordercaused by death of dopamine-secreting

neurons in the midbrain

• 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


Figure 49.UN02



Nerve net

Hydra (cnidarian) Salamander (vertebrate)

Sensoryganglia

Spinalcord(dorsal

nervecord)

Brain

Figure 49.UN03



Capillary Neuron Microglial cell

Schwanncells

Oligodendrocyte

Astrocyte

PNSCNS

Cilia

VENTRICLEEpendy-malcell



Figure 49.UN05



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49 Lecture Nervous System