49 Lecture Presentation[1]

8/3/2019 49 Lecture Presentation[1]

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LECTURE PRESENTATIONS

For CAMPBELL BIOLOGY, NINTH EDITIONJane 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


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Overview: Command and Control Center The human brain contains about 100

billion neurons, organized into circuitsmore complex than the most powerfulsupercomputers

A recent advance in brain explorationinvolves a method for expressingcombinations of colored proteins inbrain cells, a technique called

brainbow This may allow researchers to develop

detailed maps of information transferbetween regions of the brain



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Each single-celled organism can respond tostimuli in its environment

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

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

A nerve net is a series of interconnected nervecells

More complex animals have nerves


Concept 49.1: Nervous systems consist of

circuits of neurons and supporting cells


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Nerves are bundles that consist of axons of multiple nervecells

Sea stars have a nerve net in each arm connected by radialnerves to a central nerve ring

Bilaterally symmetrical animals exhibit cephalization, theclustering of sensory organs at the front end of the body

Relatively simple cephalized animals, such as flatworms, have acentral nervous system (CNS)

The CNS consists of a brain and longitudinal nerve cords Annelids & arthropods have segmentally arranged clusters of

neurons called ganglia

Nervous system organization usually correlates with lifestyle

Sessile molluscs (for example, clams and chitons) have simplesystems, whereas more complex molluscs (for example,octopuses and squids) have more sophisticated systems

In vertebrates

The CNS is composed of the brain and spinal cord

Peripheral nervous system(PNS) is composed of nerves & ganglia


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Figure 49.2

Nerve net

(a) Hydra (cnidarian)

Radialnerve

Nervering

(b) Sea star(echinoderm)

Eyespot

Brain

Nerve

cordsTransversenerve

Brain

Ventralnerve cord

Segmentalganglia

(c) Planarian(flatworm)

(d) Leech (annelid)

(h) Salamander(vertebrate)

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

Brain

Brain

Brain

Ventralnerve cord

Segmentalganglia

Anteriornerve ring

Longitudinalnerve cords

Ganglia

Ganglia

Spinalcord(dorsalnervecord)

Sensoryganglia


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Organization of the Vertebrate Nervous

System

The spinal cord conveys information from andto the brain

The spinal cord also produces reflexesindependently of the brain

A reflex is the bodys automatic response to astimulus

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



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Quadricepsmuscle

Cell body ofsensory neuron indorsal rootganglion

Graymatter

Whitematter

Hamstringmuscle

Spinal cord(cross section)

Sensory neuron

Motor neuron

Interneuron

Figure 49.3


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Central nervoussystem (CNS)

Brain

Spinal cord

Peripheral nervoussystem (PNS)

Cranial nerves

Ganglia outsideCNS

Spinal nerves

Invertebratesusually have aventral nervecord while

vertebrates havea dorsal spinalcord

The spinal cord

and braindevelop from theembryonic nervecord

The nerve cordgives rise to thecentral canaland ventricles ofthe brain


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Figure 49.5

Gray matter

Whitematter

Ventricles


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The central canalof the spinal cord and theventriclesof the brain are hollow and filled withcerebrospinal fluid

The cerebrospinal fluid is filtered from blood andfunctions to cushion the brain and spinal cord aswell as to provide nutrients and remove wastes



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The brain and spinal cord containGray matter, whichconsists of neuron cell

bodies, dendrites, and unmyelinated axons

White matter, whichconsists of bundles ofmyelinated axons



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Glia

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

Embryonic radial glia form tracks along whichnewly formed neurons migrate

Astrocytes induce cells lining capilaries in theCNS to form tight junctions, resulting in ablood-brain barrier and restricting the entry ofmost substances into the brain



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Figure 49.6CNS PNS

VENTRICLE

Cilia

Neuron Astrocyte

Oligodendrocyte

Capillary Ependymal cell

LM50m

Schwann cell

Microglial cell


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The Peripheral Nervous System

The PNS transmits information to and from the CNSand regulates movement and the internal environment

In the PNS, afferentneurons transmit information tothe CNS and efferentneurons transmit information

away from the CNS The PNS has two efferent components: the motor

system and the autonomic nervous system

The motor system carries signals to skeletal musclesand is voluntary

The autonomic nervous system regulates smoothand cardiac muscles and is generally involuntary



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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


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The autonomic nervous system hassympathetic, parasympathetic, and entericdivisions

The sympathetic regulates arousal and energygeneration (fight-or-flight response)

The parasympathetic system has antagonisticeffects on target organs and promotes calming

and a return to rest and digest functions The enteric division controls activity of the

digestive tract, pancreas, and gallbladder


Fi


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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

Action on target organs:

Dilates pupil of eye

Accelerates heart

Inhibits salivarygland secretion

Relaxes bronchiin lungs

Inhibits activity ofstomach and intestines

Inhibits activityof pancreas

Stimulates glucoserelease from liver;inhibits gallbladder

Stimulatesadrenal medulla

Inhibits emptyingof bladder

Promotes ejaculation

and vaginal contractions

Figure 49.8


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Concept 49.2: The vertebrate brain is

regionally specialized

Specific brain structures are particularlyspecialized for diverse functions

These structures arise during embryonicdevelopment


Fi 49 9b


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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 49.9b

Fi 49 9


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Figure 49.9c

Adult brain viewed from the rear

Cerebellum

Basal nucleiCerebrum

Left cerebralhemisphere

Right cerebralhemisphere

Cerebral cortex

Corpus callosum

Figure 49 9d


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Figure 49.9d

Diencephalon

Thalamus

Pineal gland

Hypothalamus

Pituitary gland

Spinal cord

Brainstem

Midbrain

Pons

Medulla

oblongata


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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


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Figure 49.10

Eye

Reticular formation

Input from touch,pain, and temperaturereceptors

Input from nervesof ears


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Biological Clock Regulation Cycles of sleep and wakefulness are examples

of circardian rhythms, daily cycles of biologicalactivity

Mammalian circadian rhythms rely on abiological clock, molecular mechanism thatdirects periodic gene expression

Biological clocks are typically synchronized to

light and dark cycles



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In mammals, circadian rhythms are coordinatedby a group of neurons in the hypothalamuscalled the suprachiasmatic nucleus (SCN)

The SCN acts as a pacemaker, synchronizingthe biological clock



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Emotions

Generation and experience of emotions involvesmany brain structures including the amygdala,hippocampus, and parts of the thalamus

These structures are grouped as the limbicsystem

The limbic system also functions in motivation,olfaction, behavior, and memory


Figure 49 13


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Figure 49.13

Hypothalamus

Thalamus

Olfactorybulb

Amygdala Hippocampus


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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


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Figure 49.14

Nucleus accumbens Amygdala

Happy music Sad music


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Concept 49.3: The cerebral cortex controls

voluntary movement and cognitive functions

The cerebrum, the largest structure in thehuman brain, is essential for awareness,language, cognition, memory, andconsciousness

Four regions, or lobes (frontal, temporal,occipital, and parietal) are landmarks for

particular functions


Figure 49.15


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g

Motor cortex(control ofskeletal muscles)

Frontal lobe

Prefrontal cortex(decision making,planning)

Brocas area(forming speech)

Temporal lobe

Auditory cortex (hearing)

Wernickes 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)


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Language and Speech

Studies of brain activity have mapped areasresponsible for language and speech

Brocas area in the frontal lobe is active whenspeech is generated

Wernickes area in the temporal lobe is activewhen speech is heard

These areas belong to a larger network of

regions involved in language


Figure 49.16


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g

Hearingwords

Speakingwords

Seeingwords

Generatingwords

Max

Min


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Lateralization of Cortical Function

The 2 hemispheres make distinct contributions tobrain function

Left hemisphere - more adept at language, math, logic, andprocessing of serial sequences

Right hemisphere is stronger at pattern recognition,nonverbal thinking, and emotional processing

The differences in hemisphere function are calledlateralization

Lateralization is partly linked to handedness

The two hemispheres work together bycommunicating through the fibers of the corpus

callosum 2011 Pearson Education, Inc.


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Information Processing

The cerebral cortex receives input from sensoryorgans and somatosensory receptors

Somatosensory receptors provide informationabout touch, pain, pressure, temperature, andthe position of muscles and limbs

The thalamus directs different types of input todistinct locations



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

Integrated sensory information passes to theprefrontal 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 receivescommands


Figure 49.17


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Frontal lobe Parietal lobe

Primarymotor cortex

Primarysomatosensorycortex

GenitaliaToes

Abdominalorgans

Tongue

Jaw

Hip

Knee

Tongue

Pharynx

Head

Neck

Trunk

Hip

Leg


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Concept 49.4 Changes in synaptic

connections underlie memory and learning

Two processes dominate embryonicdevelopment of the nervous system

Neurons compete for growth-supporting factorsin order to survive

Only half the synapses that form during embryodevelopment survive into adulthood



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Neural Plasticity

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

Changes can strengthen or weaken signaling ata synapse


Figure 49.19


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N2

N1

N2

N1

(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 at

both synapses.


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Memory and Learning

The formation of memories is an example ofneural plasticity

Short-term memory is accessed via thehippocampus

The hippocampus also plays a role in forminglong-term memory, which is stored in thecerebral cortex

Some consolidation of memory is thought tooccur during sleep



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Long-Term Potentiation

In the vertebrate brain, a form of learning calledlong-term potentiation (LTP) involves anincrease in the strength of synaptic transmission

LTP involves glutamate receptors

If the presynaptic and postsynaptic neurons arestimulated at the same time, the set of receptorspresent on the postsynaptic membranes

changes


Figure 49.20PRESYNAPTIC Ca2+


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NEURON

GlutamateMg2+

Na+

NMDA

receptor(closed)

StoredAMPAreceptor

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


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Stem Cells in the Brain

The adult human brain contains neural stemcells

In mice, stem cells in the brain can give rise toneurons that mature and become incorporated

into the adult nervous system

Such neurons play an essential role in learningand memory



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Concept 49.5: Nervous system disorders can

be explained in molecular terms

Disorders of the nervous system includeschizophrenia, depression, drug addiction,Alzheimers disease, and Parkinsons disease

Genetic and environmental factors contribute todiseases of the nervous system


Figure 49.22

50


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Genes shared with relatives ofperson with schizophrenia

12.5% (3rd-degree relative)

25% (2nd-degree relative)

50% (1st-degree relative)100%

50

40

30

20

10

0

Relationship to person with schizophrenia

Riskofdevelopingschizoph

renia(%)

Individual,

general

population

Firstcousin

Uncle/aunt

Nephew/

niece

Fraternal

twin

Identical

twin

Grandchild

Halfsibling

Parent

Fullsibling

Child


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Schizophrenia

About 1% of the worlds population suffers fromschizophrenia

Schizophrenia is characterized by hallucinations,delusions, and other symptoms

Available treatments focus on brain pathwaysthat use dopamine as a neurotransmitter



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Depression

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

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 &


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Drug Addiction &

the Brains Reward System

Some drugs are addictive because they increaseactivity of the brains reward system

cocaine, amphetamine, heroin, alcohol, and tobacco

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

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


Figure 49.23Nicotine Inhibitory neuron


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stimulatesdopamine-releasingVTA neuron.

y

Dopamine-releasingVTA neuron

Cerebralneuron ofrewardpathway

Opium and heroindecrease activityof inhibitory

neuron.Cocaine andamphetaminesblock removalof dopaminefrom synaptic

cleft.

Rewardsystemresponse

Alzheimers Disease


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Amyloid plaque Neurofibrillary tangle 20 m

Alzheimer s Disease Alzheimers disease is a mental deterioration characterized by

confusion and memory loss

Alzheimers disease is caused by the formation of neurofibrillarytangles and amyloid plaques in the brain

There is no cure for this disease though some drugs are effective atrelieving symptoms


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Parkinsons Disease

Parkinsons disease is a motor disordercaused by death of dopamine-secretingneurons in the midbrain

It is characterized by muscle tremors, flexed

posture, and a shuffling gait

There is no cure, although drugs and variousother approaches are used to manage

symptoms

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49 Lecture Presentation[1]