Chapter 28 Introduction Nervous Systems - BBHCSDstaff.bbhcsd.org/gardnere/files/2013/04/Chapter-28-Student-Notes.pdf · © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko

© 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko

PowerPoint Lectures for

Campbell Biology: Concepts & Connections, Seventh Edition

Reece, Taylor, Simon, and Dickey

Chapter 28Chapter 28 Nervous SystemsIntroduction

Spinal cord injuries disrupt communication between

– the central nervous system (brain and spinal cord) and

– the rest of the body.

© 2012 Pearson Education, Inc.

Over 250,000 Americans are living with spinal cordinjuries.

Spinal cord injuries

– happen more often to men,

– happen mostly to people in their teens and 20s,

– are caused by vehicle accidents, gunshots, and falls, and

– are usually permanent because the spinal cord cannot berepaired.

Introduction


Figure 28.0_1

Chapter 28: Big Ideas

Nervous SystemStructure and Function

The Human BrainAn Overview of AnimalNervous Systems

Nerve Signals andTheir Transmission

Figure 28.0_2

NERVOUS SYSTEMSTRUCTURE

AND FUNCTION


28.1 Nervous systems receive sensory input,interpret it, and send out appropriatecommands

The nervous system

– obtains sensory information, sensory input,

– processes sensory information, integration, and

– sends commands to effector cells (muscles) that carry outappropriate responses, motor output.


Figure 28.1A

Sensory receptor

Effector cells

Sensory input

Motor output

Integration

Brain and spinal cord

Central nervoussystem (CNS)

Peripheral nervoussystem (PNS)

The central nervous system (CNS) consists of the

– brain and

– spinal cord (vertebrates).

The peripheral nervous system (PNS)

– is located outside the CNS and

– consists of

– nerves (bundles of neurons wrapped in connective tissue) and

– ganglia (clusters of neuron cell bodies).



Sensory neurons

– convey signals from sensory receptors

– to the CNS.

Interneurons

– are located entirely in the CNS,

– integrate information, and

– send it to motor neurons.

Motor neurons convey signals to effector cells.



Figure 28.1B

Sensoryreceptor

21

3

4

Sensoryneuron

Brain

Spinalcord

Interneuron

CNSPNS

NerveFlexormuscles

Quadricepsmuscles

Ganglion

Motorneuron

28.2 Neurons are the functional units of nervoussystems

Neurons are

– cells specialized for carrying signals and

– the functional units of the nervous system.

A neuron consists of

– a cell body and

– two types of extensions (fibers) that conduct signals,

– dendrites and

– axons.


Myelin sheaths

– enclose axons,

– form a cellular insulation, and

– speed up signal transmission.

28.2 Neurons are the functional units of nervoussystems


Figure 28.2

Signal direction

Nucleus

Myelinsheath

Schwanncell

Dendrites Cellbody Axon

Nodes ofRanvier

Signalpathway

Node of Ranvier

Synapticterminals

NucleusSchwann

cell

Cell body

Layers ofmyelin

NERVE SIGNALSAND THEIR TRANSMISSION


28.3 Nerve function depends on charge differencesacross neuron membranes

At rest, a neuron’s plasma membrane has potentialenergy—the membrane potential, in which

– just inside the cell is slightly negative and

– just outside the cell is slightly positive.

The resting potential is the voltage across theplasma membrane of a resting neuron.


The resting potential exists because of differences inion concentration of the fluids inside and outside theneuron.

– Inside the neuron

– K+ is high and

– Na+ is low.

– Outside the neuron

– K+ is low and

– Na+ is high.

28.3 Nerve function depends on charge differencesacross neuron membranes


Animation: Resting Potential

Figure 28.3

Neuron Axon

Plasmamembrane

Plasmamembrane

Na

channel

Outside of neuron

K channel

Inside of neuron

Na

Na

Na

Na

Na

KK

K

K

KK

K

K

K

K

K

Na Na

Na

Na

Na

Na Na

Na

Na

Na Na

NaNa

NaK

K

KKK

Na-K

pumpATP

K

28.4 A nerve signal begins as a change in themembrane potential

A stimulus is any factor that causes a nerve signalto be generated. A stimulus

– alters the permeability of a portion of the membrane,

– allows ions to pass through, and

– changes the membrane’s voltage.


A nerve signal, called an action potential, is

– a change in the membrane voltage,

– from the resting potential,

– to a maximum level, and

– back to the resting potential.

28.4 A nerve signal begins as a change in themembrane potential


Animation: Action Potential

Figure 28.4

Na Na

K

Additional Na channelsopen, K channels areclosed; interior of cellbecomes more positive.

Na Na

2

K

A stimulus opens some Na

channels; if threshold is reached,an action potential is triggered.

Na Na

K

1 Resting state: Voltage-gated Na

and K channels are closed;resting potential is maintained byungated channels (not shown).

Sodiumchannel

Potassiumchannel Outside

of neuron

Plasma membrane

Inside of neuron

Actionpotential

Threshold

Resting potential

Time (msec)

Mem

bra

ne

po

ten

tial

(mV

)

50

0

50

100

2

3

1

34

51

Na Na

K

4 Na channels closeand inactivate; K

channels open, andK rushes out;interior of cell is morenegative than outside.

Na Na

K

The K channelsclose relativelyslowly, causing abrief undershoot.

5

1 Return to restingstate.

28.5 The action potential propagates itself alongthe axon

Action potentials are

– self-propagated in a one-way chain reaction along aneuron and

– all-or-none events.


Figure 28.5

Axon

Plasmamembrane

Axonsegment

ActionpotentialNa

Na

Na

Action potential

Na

Na

Action potential

K

K

K

K

Na

1

2

3

The frequency of action potentials (but not theirstrength) changes with the strength of the stimulus.

28.5 The action potential propagates itself alongthe axon


28.6 Neurons communicate at synapses

Synapses are junctions where signals aretransmitted between

– two neurons or

– between neurons and effector cells.


Electrical signals pass between cells at electricalsynapses.

At chemical synapses

– the ending (presynaptic) cell secretes a chemical signal, aneurotransmitter,

– the neurotransmitter crosses the synaptic cleft, and

– the neurotransmitter binds to a specific receptor on thesurface of the receiving (postsynaptic) cell.

28.6 Neurons communicate at synapses


Animation: Synapse

Figure 28.6

Axon ofsendingcell

Synapticterminalof sendingcell

Dendriteof receivingcell

Sending cell

Synapticvesicles

Synapticterminal

Synapticcleft

Vesicle fuseswith plasmamembrane

Actionpotentialarrives

Neurotransmitteris released intosynaptic cleft

Neurotransmitterbinds to receptor

Neurotransmittermolecules

Neurotransmitter brokendown and released

Ion channel closes

Ions

Receptor

Receivingcell

Neurotransmitter

Ion channels

Ion channel opens5 6

4

32

1

28.7 Chemical synapses enable complexinformation to be processed

Some neurotransmitters

– excite a receiving cell, and

– others inhibit a receiving cell’s activity by decreasing itsability to develop action potentials.


A receiving neuron’s membrane may receive signals

– that are both excitatory and inhibitory and

– from many different sending neurons.

The summation of excitation and inhibitiondetermines if a neuron will transmit a nerve signal.

28.7 Chemical synapses enable complexinformation to be processed


Figure 28.7

Dendrites

Myelinsheath

Axon

Synaptic terminals

Inhibitory Excitatory

Receivingcell body

Synapticterminals

28.8 A variety of small molecules function asneurotransmitters

Many small, nitrogen-containing molecules areneurotransmitters.

– Acetylcholine is a neurotransmitter

– in the brain and

– at synapses between motor neurons and muscle cells.

– Biogenic amines

– are important neurotransmitters in the CNS and

– include serotonin and dopamine, which affect sleep, mood, andattention.


– Many neuropeptides

– consist of relatively short chains of amino acids important in theCNS and

– include endorphins, decreasing our perception of pain.

– Nitric oxide

– is a dissolved gas and

– triggers erections during sexual arousal in men.

28.8 A variety of small molecules function asneurotransmitters


28.9 CONNECTION: Many drugs act at chemicalsynapses

Many psychoactive drugs

– act at synapses and

– affect neurotransmitter action.

Caffeine counters the effect of inhibitoryneurotransmitters.

Nicotine acts as a stimulant by binding toacetylcholine receptors.

Alcohol is a depressant.


Figure 28.9

AN OVERVIEWOF ANIMAL

NERVOUS SYSTEMS


28.10 EVOLUTION CONNECTION: Theevolution of animal nervous systems reflectschanges in body symmetry

Radially symmetrical animals have a nervous systemarranged in a weblike system of neurons called anerve net.


Figure 28.10A

Nervenet

Neuron

Hydra (cnidarian)

Most bilaterally symmetrical animals evolved

– cephalization, the concentration of the nervous systemat the head end, and

– centralization, the presence of a central nervous systemdistinct from a peripheral nervous system.

28.10 EVOLUTION CONNECTION: Theevolution of animal nervous systems reflectschanges in body symmetry


Figure 28.10B

Eyespot

Brain

Nervecord

Transversenerve

Flatworm (planarian)

Figure 28.10C

Brain

Ventralnervecord

Segmentalganglion

Leech (annelid)

Figure 28.10D

Brain

Ventralnervecord

Ganglia

Insect (arthropod)

Figure 28.10E

Brain

Giantaxon

Squid (mollusc)

In the vertebrates, the central nervous system (CNS)

– consists of the brain and spinal cord and

– includes spaces filled with cerebrospinal fluid

– forming ventricles of the brain,

– forming the central canal of the spinal cord, and

– surrounding the brain.

The vertebrate peripheral nervous system (PNS)consists of

– cranial nerves,

– spinal nerves, and

– ganglia.

28.11 Vertebrate nervous systems are highlycentralized


Figure 28.11A

Centralnervoussystem(CNS)

Peripheralnervoussystem(PNS)

Spinalcord

Cranialnerves

GangliaoutsideCNS

Spinalnerves

Brain

Figure 28.11B

Brain Cerebrospinal fluid

Meninges

Gray matter

Whitematter

Dorsal rootganglion(part of PNS)

Spinal nerve(part of PNS)Central canal

Spinal cord(cross section)

Ventricles

Central canalof spinal cord

Spinal cord

28.12 The peripheral nervous system ofvertebrates is a functional hierarchy

The PNS can be divided into two functionalcomponents:

1. the motor system, mostly voluntary, and

2. the autonomic nervous system, mostly involuntary.


The motor nervous system

– carries signals to and from skeletal muscles and

– mainly responds to external stimuli.

The autonomic nervous system

– regulates the internal environment and

– controls smooth and cardiac muscle and organs andglands of the digestive, cardiovascular, excretory, andendocrine systems.



Figure 28.12A

Peripheral nervous system(to and from the central

nervous system)

Motor system(voluntary and

involuntary; to and fromskeletal muscles)

Autonomic nervous system(involuntary; smooth and

cardiac muscles, various glands)

Parasympatheticdivision

(“Rest and digest”)

Sympatheticdivision

(“Flight and fight”)

Enteric division(muscles and glands

of the digestive system)


The autonomic nervous system is composed ofthree divisions.

1. The parasympathetic division primes the body foractivities that gain and conserve energy for the body.

2. The sympathetic division prepares the body for intense,energy-consuming activities.

3. The enteric division consists of networks of neurons inthe digestive tract, pancreas, and gallbladder that controlsecretion and peristalsis.


Figure 28.12B

Brain

Parasympathetic division

Eye

Constricts pupil

Lung

Constrictsbronchi

Stimulatessalivasecretion

Stimulatesstomach,pancreas,and intestines

Salivaryglands

Sympathetic division

Dilates pupil

Inhibitssalivasecretion

Relaxesbronchi

AcceleratesheartHeart

Liver

Stomach

Adrenalgland

Stimulatesepinephrineand norepi-nephrine release

Pancreas

Intestines

Bladder

Stimulatesglucose release

Inhibitsstomach,pancreas,and intestines

Inhibitsurination

Slowsheart

Stimulatesurination

Spinalcord

Genitalia

Promoteserection ofgenitalia

Promotes ejacu-lation and vaginalcontractions

Figure 28.12B_1

Parasympathetic division

Eye

Constricts pupil

LungConstrictsbronchi

Stimulatessalivasecretion

Salivaryglands

Dilates pupil

Inhibitssalivasecretion

Relaxesbronchi

AcceleratesheartHeart

Slowsheart

Sympathetic division

Figure 28.12B_2

Parasympathetic division Sympathetic division

Stimulatesstomach,pancreas,and intestines

Liver

Stomach

Adrenalgland

Stimulatesepinephrineand norepi-nephrine release

Pancreas

Intestines

Bladder

Stimulatesglucose release

Inhibitsstomach,pancreas,and intestines

Inhibitsurination

Stimulatesurination

Genitalia

Promoteserection ofgenitalia

Promotes ejacu-lation and vaginalcontractions

28.13 The vertebrate brain develops from threeanterior bulges of the neural tube

The vertebrate brain evolved by the enlargementand subdivision of the

– forebrain,

– midbrain, and

– hindbrain.

In the course of vertebrate evolution, the forebrainand hindbrain gradually became subdivided

– structurally and

– functionally.


Figure 28.13Embryonic

Brain RegionsBrain StructuresPresent in Adult

Forebrain

Midbrain

Hindbrain

Hindbrain

Midbrain

Forebrain

Embryo (1 month old) Fetus (3 months old)

Cerebrum (cerebral hemispheres; includescerebral cortex, white matter, basal ganglia)

Diencephalon (thalamus, hypothalamus,posterior pituitary, pineal gland)

Pons (part of brainstem), cerebellum

Medulla oblongata (part of brainstem)

CerebrumDiencephalon

Midbrain

Pons

Cerebellum

Medullaoblongata

Spinal cord

Midbrain (part of brainstem)

In birds and mammals the cerebrum

– is much larger and

– correlates with their sophisticated behavior.

28.13 The vertebrate brain develops from threeanterior bulges of the neural tube


THE HUMAN BRAIN


28.14 The structure of a living supercomputer:The human brain

The human brain is

– more powerful than the most sophisticated computer and

– composed of three main parts:

1. forebrain,

2. midbrain, and

3. hindbrain.


Figure 28.14A

Cerebral cortex(outer regionof cerebrum)

Cerebrum

Thalamus

Hypothalamus

Pituitary gland

Midbrain

Forebrain

Hindbrain

Pons

Medullaoblongata

Cerebellum

Spinalcord

The midbrain, subdivisions of the hindbrain, thethalamus, and the hypothalamus

– conduct information to and from higher brain centers,

– regulate homeostatic functions,

– keep track of body position, and

– sort sensory information.



Figure 28.14B

Left cerebralhemisphere

Right cerebralhemisphere

Thalamus

Basalnuclei

Medullaoblongata

Corpuscallosum

Cerebrum

Cerebellum

Table 28.14

The cerebrum is

– part of the forebrain and

– the largest and most complex part of the brain.

– Most of the cerebrum’s integrative power resides in thecerebral cortex of the two cerebral hemispheres.



28.15 The cerebral cortex is a mosaic ofspecialized, interactive regions

The cerebral cortex

– is less than 5 mm thick and

– accounts for 80% of the total human brain mass.

Specialized integrative regions of the cerebral cortexinclude

– the somatosensory cortex and

– centers for vision, hearing, taste, and smell.


The motor cortex directs responses.

Association areas

– make up most of the cerebrum and

– are concerned with higher mental activities such asreasoning and language.

In a phenomenon known as lateralization, right andleft cerebral hemispheres tend to specialize indifferent mental tasks.

28.15 The cerebral cortex is a mosaic ofspecialized, interactive regions


Figure 28.15

Frontal lobe Parietal lobe

Occipital lobeTemporal lobe

Frontalassociationarea

Speech

Smell

Speech

Moto

rco

rtex

Hearing

Reading

Vision

Visualassociationarea

Somatosensoryassociationarea

Auditoryassociationarea

So

mat

ose

nso

ryco

rtex

28.16 CONNECTION: Injuries and brainoperations provide insight into brainfunction

Brain injuries and surgeries reveal brain functions.

– After a 13-pound steel rod pierced his skull, PhineasGage appeared to have an intact intellect but hisassociates noted negative changes to his personality.

– Stimulation of the cerebral cortex during surgeries causedpatients to recall sensations and memories.

– Cutting the corpus callosum revealed information aboutbrain lateralization.


Figure 28.16A Figure 28.16B

28.17 CONNECTION: fMRI scans provide insightinto brain structure and function

Functional magnetic resonance imaging (fMRI) is

– a scanning and imaging technology used to study brainfunctions,

– used on conscious patients,

– monitors changes in blood oxygen usage in the brain, and

– correlates to regions of intense brain function.


Figure 28.17

28.18 Several parts of the brain regulate sleep andarousal

Sleep and arousal involve activity by the

– hypothalamus,

– medulla oblongata,

– pons, and

– neurons of the reticular formation.


Sleep

– is essential for survival,

– is an active state, and

– may be involved in consolidating learning and memory.

28.18 Several parts of the brain regulate sleep andarousal


28.19 The limbic system is involved in emotions,memory, and learning

The limbic system is

– a functional group of integrating centers in the

– cerebral cortex,

– thalamus,

– hypothalamus, and

– involved in

– emotions, such as nurturing infants and bonding emotionally toother people,

– memory, and

– learning.


Figure 28.19

Cerebrum

HippocampusAmygdalaOlfactorybulb

Thalamus

Hypothalamus

Prefrontalcortex

Smell

28.20 CONNECTION: Changes in brainphysiology can produce neurologicaldisorders

Many neurological disorders can be linked tochanges in brain physiology, including

– schizophrenia,

– major depression,

– Alzheimer’s disease, and

– Parkinson’s disease.



Schizophrenia is

– a severe mental disturbance and

– characterized by psychotic episodes in which patientslose the ability to distinguish reality.



Depression

– Two broad forms of depressive illness have beenidentified:

1. major depression and

2. bipolar disorder, manic-depressive disorder.

– Treatments may include selective serotonin reuptakeinhibitors (SSRIs), which increase the amount of timeserotonin is available to stimulate certain neurons in thebrain.


Figure 28.20A

Figure 28.20B

140

120

100

80

60

40

095 96

Year

Pre

scri

pti

on

s(m

illio

ns)

20

97 98 99 00 01 02 03 04 05 06 07 08

Alzheimer’s disease is

– characterized by confusion, memory loss, and personalitychanges and

– difficult to diagnose.



Parkinson’s disease is

– a motor disorder and

– characterized by

– difficulty in initiating movements,

– slowness of movement, and

– rigidity.



Figure 28.20C

1. Describe the structural and functional subdivisionsof the nervous system.

2. Describe the three parts of a reflex, distinguishingthe three types of neurons that may be involved inthe reaction.

3. Describe the structures and functions of neuronsand myelin sheaths.

4. Define a resting potential and explain how it iscreated.

You should now be able to


5. Explain how an action potential is produced andthe resting membrane potential restored.

6. Explain how an action potential propagates itselfalong a neuron.

7. Compare the structures, functions, and locations ofelectrical and chemical synapses.

8. Compare excitatory and inhibitoryneurotransmitters.

9. Describe the types and functions ofneurotransmitters known in humans.



10. Explain how drugs can alter chemical synapses.

11. Describe the diversity of animal nervous systemsand provide examples.

12. Describe the general structure of the brain, spinalcord, and associated nerves of vertebrates.

13. Compare the functions of the motor nervoussystem and autonomic nervous system.



14. Compare the structures, functions, andinterrelationships of the parasympathetic,sympathetic, and enteric divisions of theperipheral nervous system.

15. Explain how the vertebrate brain develops from anembryonic tube.

16. Describe the main parts and functions of thehuman brain.

17. Explain how injuries, illness, and surgery provideinsight into the functions of the brain.



18. Explain how fMRI scans help us understand brainfunctions.

19. Explain how the brain regulates sleep andarousal.

20. Describe the structure and functions of the limbicsystem.

21. Describe the causes, symptoms, and treatmentsof schizophrenia, depression, Alzheimer’sdisease, and Parkinson’s disease.



Chapter 28 Introduction Nervous Systems - BBHCSDstaff.bbhcsd.org/gardnere/files/2013/04/Chapter-28-Student-Notes.pdf · © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko

Documents