Copyright © 2007 Pearson Education Canada1 Neurons, Hormones, and the Brain Chapter 4

Copyright © 2007 Pearson Education Canada 1

Neurons, Hormones, Neurons, Hormones, and the Brainand the Brain

Chapter 4Chapter 4


Chapter OutlineChapter Outline

• The Nervous System: A Basic Blueprint The Nervous System: A Basic Blueprint

• Communication in the Nervous SystemCommunication in the Nervous System

• Mapping the BrainMapping the Brain

• A Tour through the BrainA Tour through the Brain

• The Two Hemispheres of the BrainThe Two Hemispheres of the Brain

• Two Stubborn Issues in Brain ResearchTwo Stubborn Issues in Brain Research


The Nervous System: The Nervous System: A basic blueprintA basic blueprint

• The central nervous systemThe central nervous system

• The peripheral nervous systemThe peripheral nervous system– Somatic nervous systemSomatic nervous system– Autonomic nervous systemAutonomic nervous system


Organization of the Nervous SystemOrganization of the Nervous System


The Central Nervous SystemThe Central Nervous System

• BrainBrain• Spinal cordSpinal cord

– A collection of neurons and A collection of neurons and supportive tissue running from supportive tissue running from the base of the brain down the the base of the brain down the centre of the backcentre of the back

– Protected by spinal columnProtected by spinal column


The Peripheral Nervous SystemThe Peripheral Nervous System

• Somatic nervous system:Somatic nervous system: the subdivision of the peripheral the subdivision of the peripheral nervous system that connects to nervous system that connects to sensory and to skeletal musclessensory and to skeletal muscles

• The autonomic nervous system:The autonomic nervous system:the subdivision of the peripheral the subdivision of the peripheral nervous system that that regulates nervous system that that regulates internal organs and glandsinternal organs and glands


The Autonomic Nervous SystemThe Autonomic Nervous System


Communication in the nervous Communication in the nervous systemsystem

• The structure of the neuronThe structure of the neuron

• Neurons in the newsNeurons in the news

• How neurons communicateHow neurons communicate

• Chemical MessengersChemical Messengers


Structure of a NeuronStructure of a Neuron

• Dendrites Dendrites – receive information from other receive information from other

neurons and transmit towards the cell neurons and transmit towards the cell bodybody

• Cell bodyCell body– keeps the neuron alive and keeps the neuron alive and

determines whether it will firedetermines whether it will fire

• AxonAxon– extending fibre that conducts impulses extending fibre that conducts impulses

away from the cell body and transmits away from the cell body and transmits to other cellsto other cells


Types of NeuronsTypes of Neurons


Structure of a NeuronStructure of a Neuron

• Myelin SheathMyelin Sheath– Fatty insulation that may surround the neuron’s Fatty insulation that may surround the neuron’s

axonaxon


Neurons in the NewsNeurons in the News

• NeurogenesisNeurogenesis– The production of new The production of new

neurons from immature neurons from immature stem cellsstem cells

• Stem cellsStem cells– Immature cells that Immature cells that

renew themselves and renew themselves and have the potential to have the potential to develop into mature develop into mature cellscells


Stem-Cell ResearchStem-Cell Research

• Embryonic stem cells appear most promising Embryonic stem cells appear most promising in developing treatments for cancers, organ in developing treatments for cancers, organ and brain diseases (e.g., Alzheimer’s)and brain diseases (e.g., Alzheimer’s)

• Currently have ethical debate over their useCurrently have ethical debate over their use• New techniques try to extract them without New techniques try to extract them without

harming the embryoharming the embryo• McGill team has had some success in McGill team has had some success in

transforming adult cells into brain tissuetransforming adult cells into brain tissue


How Neurons CommunicateHow Neurons Communicate

• Axon terminals Axon terminals release release neurotransmitterneurotransmitter

• Neurotransmitter Neurotransmitter enters the enters the synapsesynapse

• Neurotransmitter Neurotransmitter binds to receptors binds to receptors that it fitsthat it fits


Action PotentialAction Potential• A brief change in electrical voltage that A brief change in electrical voltage that

occurs between the inside and outside of an occurs between the inside and outside of an axon when a neuron is stimulatedaxon when a neuron is stimulated

• This produces an electrical impulseThis produces an electrical impulse


Chemical MessengersChemical Messengers

• NeurotransmittersNeurotransmitters

• HormonesHormones


NeurotransmitterNeurotransmitter

• Chemical substance released by a transmitting Chemical substance released by a transmitting neuron at the synapse and capable of affecting neuron at the synapse and capable of affecting the activity of a receiving neuronthe activity of a receiving neuron


Major NeurotransmittersMajor Neurotransmitters

• SerotoninSerotonin• DopamineDopamine• Acetylcholine (ACh)Acetylcholine (ACh)• NorepinephrineNorepinephrine• Gamma amino butyric acid (GABA)Gamma amino butyric acid (GABA)• GlutamateGlutamate• EndorphinsEndorphins


Opioids and Substance POpioids and Substance P


The Endocrine SystemThe Endocrine System

• Endocrine glands Endocrine glands release hormones release hormones into the bloodstreaminto the bloodstream

• Hormones regulate Hormones regulate growth, metabolism, growth, metabolism, sexual development sexual development and behaviour, and and behaviour, and other functionsother functions


Hormones: Long Distance Hormones: Long Distance MessengersMessengers

• MelatoninMelatonin– Regulates daily biological rhythmsRegulates daily biological rhythms

• Adrenal HormonesAdrenal Hormones– Involved in emotions and stressInvolved in emotions and stress

• Cortisol, epinephrine, and norepinephrineCortisol, epinephrine, and norepinephrine• Sex HormonesSex Hormones

– Regulate development and functioning of Regulate development and functioning of reproductive organsreproductive organs• Androgens, estrogens, and progesteroneAndrogens, estrogens, and progesterone


Mapping the BrainMapping the Brain

• LesioningLesioning– Involves damaging and removing sections Involves damaging and removing sections

of brain in animals, then observing their of brain in animals, then observing their effectseffects

– Some lesions are cased by accidents, Some lesions are cased by accidents, traumas, or disease traumas, or disease


Electroencephalogram (EEG)Electroencephalogram (EEG)• A recording of neural activity detected by A recording of neural activity detected by

electrodeselectrodes


Transcranial magnetic stimulation (TMS)Transcranial magnetic stimulation (TMS)

• Involves delivering a large current Involves delivering a large current through a wire coil on a person’s headthrough a wire coil on a person’s head

• Also used to: Also used to: – produce motor responsesproduce motor responses– temporarily inactivate an area of the braintemporarily inactivate an area of the brain– treat depressiontreat depression


Positron Emission Tomography (PET)Positron Emission Tomography (PET)

• A method for analyzing biochemical activity in A method for analyzing biochemical activity in the brain, using injections of a glucose-like the brain, using injections of a glucose-like substance containing a radioactive elementsubstance containing a radioactive element

• Active areas have increased blood flow

• Sensors detect radioactivity

• Different tasks show distinct activity patterns


Magnetic Resonance Imaging Magnetic Resonance Imaging (MRI)(MRI)

• Method for studying body and Method for studying body and brain tissuebrain tissue

• Magnetic fields align certain Magnetic fields align certain ions and compoundsions and compounds

• When field is removed, these When field is removed, these molecules release energy as molecules release energy as radio wavesradio waves

• Computer calculates tissue Computer calculates tissue density from radio wavesdensity from radio waves

• Provides clear, 3D imagesProvides clear, 3D images


A Tour Through the BrainA Tour Through the Brain

• Brain stemBrain stem• CerebellumCerebellum• ThalamusThalamus• Hypothalamus and the pituitary glandHypothalamus and the pituitary gland• AmygdalaAmygdala• HippocampusHippocampus• Cerebrum and lobes of the cerebral cortexCerebrum and lobes of the cerebral cortex


The Brain StemThe Brain Stem

• Pons Pons – involved in sleeping, involved in sleeping,

waking and dreamingwaking and dreaming• Medulla Medulla

– responsible for certain responsible for certain automatic functions such automatic functions such as breathing and heart as breathing and heart raterate

• Reticular activating system Reticular activating system (or formation)(or formation)– arouses cortex and arouses cortex and

screens incoming screens incoming informationinformation


The CerebellumThe Cerebellum

• Regulates movement and Regulates movement and balancebalance

• Involved in remembering Involved in remembering simple skills and acquired simple skills and acquired reflexesreflexes

• Plays a part in:Plays a part in:– analyzing sensory analyzing sensory

information information – solving problemssolving problems– understanding wordsunderstanding words


The ThalamusThe Thalamus

• Relays sensory Relays sensory messages to the messages to the cerebral cortexcerebral cortex

• Includes all sensory Includes all sensory messages except those messages except those from olfactory bulbfrom olfactory bulb


Hypothalamus and Pituitary GlandHypothalamus and Pituitary Gland

• Involved in emotions and Involved in emotions and drives vital to survival drives vital to survival – fear, hunger, thirst, and fear, hunger, thirst, and

reproductionreproduction• Regulates autonomic Regulates autonomic

nervous systemnervous system• Pituitary glandPituitary gland

– small endocrine gland small endocrine gland which releases which releases hormones and regulates hormones and regulates other endocrine glands other endocrine glands


The AmygdalaThe Amygdala• Responsible for:Responsible for:

– arousalarousal– regulation of emotionregulation of emotion– the initial emotional the initial emotional

response to sensory response to sensory informationinformation

• Plays important role in Plays important role in – mediating anxiety and mediating anxiety and

depressiondepression– emotional memoryemotional memory


The HippocampusThe Hippocampus

• Responsible for:Responsible for:– storage of new storage of new

information in memoryinformation in memory– comparing sensory comparing sensory

information with what information with what the brain expects about the brain expects about the worldthe world

– enabling us to form enabling us to form spatial memories for spatial memories for navigating the navigating the environmentenvironment


The CerebrumThe Cerebrum

• Largest brain structureLargest brain structure• This upper part of the brain is divided into This upper part of the brain is divided into

two cerebral hemispheres that are two cerebral hemispheres that are connected by the connected by the corpus callosumcorpus callosum

• In charge of most sensory, motor and In charge of most sensory, motor and cognitive processescognitive processes

• Surrounded by cerebral cortex, a collection Surrounded by cerebral cortex, a collection of several thin layers of cells (grey matter)of several thin layers of cells (grey matter)


Lobes of the Cerebral CortexLobes of the Cerebral Cortex• Occipital lobes (visual cortex)Occipital lobes (visual cortex)• Parietal lobes (somatosensory cortex)Parietal lobes (somatosensory cortex)• Temporal lobesTemporal lobes

– Memory, perception, emotion and auditory cortexMemory, perception, emotion and auditory cortex– Left lobe, Wernicke’s areaLeft lobe, Wernicke’s area

• Frontal lobesFrontal lobes– Emotion, planning, creative thinking and motor cortexEmotion, planning, creative thinking and motor cortex– Left lobe, Broca’s area Left lobe, Broca’s area


Lobes of the Cerebral CortexLobes of the Cerebral Cortex


Phineas GagePhineas Gage• Gage was a railroad Gage was a railroad

construction foremanconstruction foreman• An 1848 explosion forced a An 1848 explosion forced a

steel tamping rod through steel tamping rod through his headhis head

• Others said he was “…no Others said he was “…no longer Gage…”longer Gage…”

• Lost his job and worked as a Lost his job and worked as a sideshow exhibitsideshow exhibit


The Two hemispheres of the The Two hemispheres of the BrainBrain

• The Split Brain: a house dividedThe Split Brain: a house divided

• The two hemispheres: allies or The two hemispheres: allies or opposites?opposites?


The Corpus CallosumThe Corpus Callosum

• Millions of myelinated Millions of myelinated axons connecting the axons connecting the brain’s hemispheresbrain’s hemispheres

• Provides a pathway for Provides a pathway for communication communication between hemispheresbetween hemispheres

• If surgically severed to If surgically severed to treat epilepsy, treat epilepsy, hemispheres cannot hemispheres cannot communicate directlycommunicate directly


Split-Brain ExperimentSplit-Brain Experiment


Split-Brain ExperimentSplit-Brain Experiment

• Subjects were presented information to one or Subjects were presented information to one or the other side of their brainthe other side of their brain

• Patients identified verbally the pictures to the Patients identified verbally the pictures to the right (i.e., boy)right (i.e., boy)

• When asked to point to the face seen, the When asked to point to the face seen, the patients pointed to the left picturepatients pointed to the left picture


The Two Hemispheres: The Two Hemispheres: Allies or Opposites?Allies or Opposites?

• Research on split-brain patients shows us:Research on split-brain patients shows us:– Nearly all right-handed and the majority of left-Nearly all right-handed and the majority of left-

handed individuals process language mainly in the handed individuals process language mainly in the left hemisphereleft hemisphere

– Many researchers believe in left-hemisphere Many researchers believe in left-hemisphere dominancedominance

– Others insist the right-hemisphere is important for Others insist the right-hemisphere is important for spatial visual problem-solving, comprehending spatial visual problem-solving, comprehending non-verbal sounds, and some language abilitiesnon-verbal sounds, and some language abilities


Two Stubborn issues in Brain Two Stubborn issues in Brain ResearchResearch

• Where is the Self? Where is the Self?

• Are there “his” and “hers” brains? Are there “his” and “hers” brains?


Where is the Self?Where is the Self?• Modern brain scientists explain the mind or soul in Modern brain scientists explain the mind or soul in

physical terms, as a product of the cerebral cortexphysical terms, as a product of the cerebral cortex– The mind is: The mind is:

• a series of independent brain parts dealing with different a series of independent brain parts dealing with different aspects of thoughts (Dennett, 1991)aspects of thoughts (Dennett, 1991)

• a loose confederation of mental systems all working without a loose confederation of mental systems all working without conscious awareness (Gazzaniga, 1998; Roser & Gazzaniga, conscious awareness (Gazzaniga, 1998; Roser & Gazzaniga, 2004)2004)

• Frontal lobes may play a critical roleFrontal lobes may play a critical role• Many still question the relationship between Many still question the relationship between

subjective experience and physical processes of subjective experience and physical processes of the brainthe brain


Are There “His” and “Hers” Brains?Are There “His” and “Hers” Brains?

• After analyzing 49 studies of sex differences in After analyzing 49 studies of sex differences in brain anatomy, researchers found small brain anatomy, researchers found small differences between the two groups and larger differences between the two groups and larger differences within groupsdifferences within groups

• There do appear to be sex differences in There do appear to be sex differences in lateralization of language. Males show left-lateralization of language. Males show left-hemisphere activation only; females, left and hemisphere activation only; females, left and rightright

• There also appear to be differences in amounts There also appear to be differences in amounts of grey matter: females have moreof grey matter: females have more


Gender & Language LateralityGender & Language Laterality


What do “Differences” Mean for What do “Differences” Mean for Behaviour?Behaviour?

• These supposed differences are stereotypesThese supposed differences are stereotypes• A brain difference does not necessarily explain A brain difference does not necessarily explain

behaviour or performancebehaviour or performance• Sex differences in the brain could be the result Sex differences in the brain could be the result

rather than the cause of behavioural differencesrather than the cause of behavioural differences• Use your Use your critical thinkingcritical thinking skills to evaluate all of skills to evaluate all of

the research!the research!

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Copyright © 2007 Pearson Education Canada1 Neurons, Hormones, and the Brain Chapter 4