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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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