the brain: source of mind and self chapter 4 4 - 1

The Brain: The Brain: Source of Mind and SelfSource of Mind and Self

Chapter 4Chapter 4

4 - 1

The Brain•The most complicated object in the universe

The Brain

• Neurons communicate• Electrically and

chemically

• Trillions of connections between billions of neurons

Brain FactsBrain Facts

• The human brain is about 2% of the total body weight

• The brain of an adult human weighs around 3 pounds (1.5 kg).

• 2% of the body's weight but uses around 20% of its energy.

• The human brain is over three times as big as the brain of other mammals that are of similar body size.

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Brain Myths

• We only use 10% of our brain• We see the world as it is• Memories are like a recording

of events

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Neural CommunicationNeural Communication

• The brain is made up of:The brain is made up of:– Neurons: Neurons: cells that conduct electrochemical signals; cells that conduct electrochemical signals;

basic unit of the nervous systembasic unit of the nervous system

– Glia: Glia: cells that support, nurture, and insulate neurons, cells that support, nurture, and insulate neurons, remove debris when neurons die, enhance the formation remove debris when neurons die, enhance the formation & maintenance of neural connections, and modify neural & maintenance of neural connections, and modify neural functioningfunctioning

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Brain Facts

•100,000,000,000 neurons (100 billion) But the brain has 50x more glial cells: 5,000,000,000,000 glial cells (5 trillion)

Copyright © 2013 Pearson Canada

Structure of the NeuronStructure of the Neuron

• Approximately 100 billion neurons in the brainApproximately 100 billion neurons in the brain• Neurons vary in size and shapeNeurons vary in size and shape

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• DendritesDendrites– Look like tree branchesLook like tree branches– Receives information from other neurons & Receives information from other neurons &

transmits the information to the cell bodytransmits the information to the cell body– Receive messages from as many as 10 000 other Receive messages from as many as 10 000 other

neuronsneurons

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• Cell bodyCell body

– Keeps neuron alive & plays key role in Keeps neuron alive & plays key role in determining whether neuron will “fire” determining whether neuron will “fire”

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• AxonAxon– Extending fibre that conducts impulse away Extending fibre that conducts impulse away

from cell body and transmits to other cellsfrom cell body and transmits to other cells– Branches at end called Branches at end called axon terminalsaxon terminals

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The Myelin SheathThe Myelin Sheath

• Many axons are insulated by surrounding layer Many axons are insulated by surrounding layer of fatty material called of fatty material called myelin sheathmyelin sheath– this is made up of glial cellsthis is made up of glial cells– Purpose to speed conduction of electrical Purpose to speed conduction of electrical

communication & prevent interference from communication & prevent interference from neighbouring signalsneighbouring signals

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The Myelin SheathThe Myelin Sheath

• Multiple Sclerosis Multiple Sclerosis • Damage of the myelin sheaths surrounds Damage of the myelin sheaths surrounds • Mild to severe symptomsMild to severe symptoms• Damage to myelin can lead to slowing or disruption of Damage to myelin can lead to slowing or disruption of

neuronal signaling leading to loss of function neuronal signaling leading to loss of function

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How Neurons CommunicateHow Neurons Communicate

• No direct contact between No direct contact between neuronsneurons

• Communicate through the Communicate through the synapsesynapse

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There are trillions or even quadrillions of synaptic connections.

• Communication occurs through Communication occurs through electrical and chemical signalselectrical and chemical signals– Stimulation causes change in electrical Stimulation causes change in electrical

chargecharge– An explosion of electrical activity can

cause action potential (neuron action potential (neuron firing) firing)

– Synaptic vesicles release chemicals Synaptic vesicles release chemicals called neurotransmitterscalled neurotransmitters

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• Neurotransmitters bind to Neurotransmitters bind to receptors receptors on receiving on receiving neuron and causes changes in the cell membraneneuron and causes changes in the cell membrane

– Excitatory changes – a voltage shift in a Excitatory changes – a voltage shift in a positive directionpositive direction• Increases likelihood of neuron firingIncreases likelihood of neuron firing

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• Neurotransmitters bind to Neurotransmitters bind to receptors receptors on receiving on receiving neuron and causes changes in the cell membraneneuron and causes changes in the cell membrane

– Inhibitory changes – a voltage shift in a Inhibitory changes – a voltage shift in a negative directionnegative direction• Decreases likelihood of neuron firingDecreases likelihood of neuron firing

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Brain Plasticity Brain Plasticity

• The structure and functioning of the brain is The structure and functioning of the brain is constantly changing constantly changing

• Occurs in response to learning, experience or Occurs in response to learning, experience or memory formation or in response to brain damage memory formation or in response to brain damage

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Brain PlasticityBrain Plasticity

– The brain’s ability to change and adapt in response to The brain’s ability to change and adapt in response to experience (e.g., reorganizing or growing new neural experience (e.g., reorganizing or growing new neural connections)connections)

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NeurogenesisNeurogenesis

•Neurogenesis – birth of new neurons•Reynolds and Weiss (1992) – University of Calgary• The inability to generate new neurons is thought to be an important cause of neurological disease and impairment.

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NeurogenesisNeurogenesis

• In most mammals, neurons are added throughout life in two brain regions (the hippocampus and olfactory bulb).

• Neurogenesis may have an affect on stress and depression, learning and memory

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Stem cellsStem cells

• The first stem cell discovery, made by Canadian The first stem cell discovery, made by Canadian scientists (Till & McCulloch, 1961)scientists (Till & McCulloch, 1961)– Immature cells that renew themselves & have the potential Immature cells that renew themselves & have the potential

to develop into mature cellsto develop into mature cells– Stem cells from early embryos can develop into any cell Stem cells from early embryos can develop into any cell

typetype

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Stem-Cell ResearchStem-Cell Research

•Embryonic stem cells can differentiate into any type Embryonic stem cells can differentiate into any type of cell; adult stem cells limitedof cell; adult stem cells limited

– Use is controversial and surrounded by ethical Use is controversial and surrounded by ethical debates regarding extraction*debates regarding extraction*

– Most promising in developing treatments for Most promising in developing treatments for cancer, blood, organ, and brain disorderscancer, blood, organ, and brain disorders

– Canadian researchers have had some success Canadian researchers have had some success with adult stem cells transforming to brain cellswith adult stem cells transforming to brain cells

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Chemical MessengersChemical Messengers

• NeurotransmittersNeurotransmitters

– A chemical substA chemical substance that is released ance that is released by a transmitting neuron at the by a transmitting neuron at the synapse and that alters the activity of synapse and that alters the activity of a receiving neurona receiving neuron

– Each neurotransmitter has different Each neurotransmitter has different effectseffects

• Major neurotransmittersMajor neurotransmitters::

– Serotonin, dopamine, acetylcholine, Serotonin, dopamine, acetylcholine, norepinephrine, GABA, glutamatenorepinephrine, GABA, glutamate

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– Serotonin: Serotonin: sleep, appetite, sensory perception, temperature sleep, appetite, sensory perception, temperature regulation, pain suppression, moodregulation, pain suppression, mood

– Selective Serotonin Reuptake Inhibitor (anti-depressants)Selective Serotonin Reuptake Inhibitor (anti-depressants)– Raising serotonin levels without drugs is good for mental Raising serotonin levels without drugs is good for mental

health and well-being health and well-being – Goes both ways Goes both ways – LightLight– Exercise Exercise – Diet ??Diet ??

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NeurotransmittersNeurotransmitters

Young,S.N. (2007). How to increase serotonin in the human brain without drugs J Psychiatry Neurosci. 32, 394–399.

– Dopamine: Dopamine: voluntary movement, learning, memory, voluntary movement, learning, memory, emotion, pleasure or reward, response to noveltyemotion, pleasure or reward, response to novelty

– Deficient in people with Parkinson’s Disease Deficient in people with Parkinson’s Disease – Perhaps excessive dopamine activity in people with Perhaps excessive dopamine activity in people with

schizophreniaschizophrenia– Micheal J. FoxMicheal J. Fox– https://www.youtube.com/watch?v=ECkPVTZlfP8

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https://www.youtube.com/watch?v=ECkPVTZlfP8

–Acetylcholine: Acetylcholine: muscle action, cognitive functioning, muscle action, cognitive functioning, memory, and emotionmemory, and emotion–Otto Loewi experimentOtto Loewi experiment–Alzheimer’s disease show reduction Alzheimer’s disease show reduction –Curare Curare

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– Norepinephrine: Norepinephrine: increased heart increased heart rate, slowed intestinal activity rate, slowed intestinal activity during stress, learning, memory, during stress, learning, memory, dreaming, waking , emotion (fight dreaming, waking , emotion (fight or flight responses)or flight responses)

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– GABA: GABA: major inhibitory neurotransmittermajor inhibitory neurotransmitter– reduce the activity of the neurons to which it binds– May control the fear or anxiety experienced when May control the fear or anxiety experienced when

neurons are overexcitedneurons are overexcited– Valium binds to same receptors Valium binds to same receptors – close to 40% of the synapses in the human brain work close to 40% of the synapses in the human brain work

with GABA and therefore have GABA receptorswith GABA and therefore have GABA receptors

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– Glutamate: Glutamate: Major excitatory neurotransmitter in brainMajor excitatory neurotransmitter in brain– the most important transmitter for normal brain the most important transmitter for normal brain

functionfunction– over half of all brain synapses release glutamateover half of all brain synapses release glutamate– Vital for learning and memoryVital for learning and memory– Can be toxic Can be toxic

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• EndorphinsEndorphins– Chemical substances in the Chemical substances in the

nervous system that are similar nervous system that are similar in structure and action to in structure and action to opiatesopiates

– Involved in pain reduction and Involved in pain reduction and pleasure,pleasure,

– Partly how placebo medication Partly how placebo medication works works

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• Hormones – Hormones – Chemical Chemical substances, secreted by organs substances, secreted by organs called called endocrine glandsendocrine glands, that , that affect the functioning of other affect the functioning of other organsorgans

• travel in your bloodstream to travel in your bloodstream to tissues or organs. tissues or organs.

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Hormones Hormones

• Can work slowly, over time, and affect many different Can work slowly, over time, and affect many different processes, includingprocesses, including

• Growth and developmentGrowth and development• Metabolism - how your body gets energy from the Metabolism - how your body gets energy from the

foods you eatfoods you eat• Sexual functionSexual function• ReproductionReproduction• MoodMood

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HormonesHormones

Major hormones:Major hormones:• Melatonin – regulate daily biological rhythms, Melatonin – regulate daily biological rhythms,

sleep sleep • Oxytocin – childbirth contractions, milk ejection, Oxytocin – childbirth contractions, milk ejection,

stress stress • Adrenal hormones – emotion, stress, Adrenal hormones – emotion, stress, epinephrineepinephrine• Sex hormones – androgens, progesterone and Sex hormones – androgens, progesterone and

estrogensestrogens

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Mapping the BrainMapping the Brain

• Many ways scientists can study the brain:Many ways scientists can study the brain:– Lesion methodLesion method

• Involves damaging or removing section of Involves damaging or removing section of brain in animals and then observing the brain in animals and then observing the effectseffects

– Electrical & magnetic detectionElectrical & magnetic detection– Brain scansBrain scans– Patients with brain damagePatients with brain damage

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Electrical & Magnetic DetectionElectrical & Magnetic Detection

• Electroencephalography (EEG)Electroencephalography (EEG)

– Recording neural activity detected by Recording neural activity detected by electrodeselectrodes

– Electrical activity recorded in a visual Electrical activity recorded in a visual patter (brain waves) patter (brain waves)

– Limited precision because it is recording Limited precision because it is recording multiple cells multiple cells

– http://www.learner.org/courses/neuroscience/videos/videos.html?dis=U&num=01

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http://www.learner.org/courses/neuroscience/videos/videos.html?dis=U&num=01



Electrical & Magnetic DetectionElectrical & Magnetic Detection

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

– Uses a powerful magnetic field Uses a powerful magnetic field produced by a wire coil placed on produced by a wire coil placed on person’s head to stimulate cellsperson’s head to stimulate cells

– Can cause neurons to fire & Can cause neurons to fire & inactivate othersinactivate others

– Virtual and temporary lesion method Virtual and temporary lesion method – https://www.youtube.com/watch?v=

XJtNPqCj-iA4 - 38

https://www.youtube.com/watch?v=XJtNPqCj-iA

https://www.youtube.com/watch?v=XJtNPqCj-iA

Brain ScansBrain Scans

• MRI (magnetic resonance MRI (magnetic resonance imaging)imaging)

– Method for studying body and Method for studying body and brain tissue, using magnetic brain tissue, using magnetic fields and special radio fields and special radio receiversreceivers

• Performance assessed by Performance assessed by functional MRI or fMRI functional MRI or fMRI

• http://www.learner.org/courses/neuroscience/videos/videos.html?dis=U&num=01

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Thinking Critically about Brain Scans Thinking Critically about Brain Scans

• Images can be manipulatedImages can be manipulated• Data often over simplified Data often over simplified • Tell us Tell us wherewhere things occur in the brain, not things occur in the brain, not whywhy or or

howhow • Variability among brains makes it difficult to rely on Variability among brains makes it difficult to rely on

brain imaging to diagnose mental disorders brain imaging to diagnose mental disorders

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Patients with brain damage

• Studying brain pathology can provide insights into the normal organization of the brain

• Phineas Gage• Henry Molaison

Touring the BrainTouring the Brain

• Localization of function - Specialization of particular Localization of function - Specialization of particular brain areas for particular functionbrain areas for particular function

• Major areas/structures:Major areas/structures:– Brain stem (including the cerebellum, thalamus, Brain stem (including the cerebellum, thalamus,

hypothalamus), the limbic system (amygdala, hypothalamus), the limbic system (amygdala, hippocampus), & the cerebrum/cerebral cortexhippocampus), & the cerebrum/cerebral cortex

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The Brain StemThe Brain Stem

• MedullaMedulla– Responsible for automatic functions Responsible for automatic functions

such as breathing & heart rate (ANS)such as breathing & heart rate (ANS)

• PonsPons– Involved in sleeping, & dreamingInvolved in sleeping, & dreaming

• Reticular activating system (RAS)Reticular activating system (RAS)– Extends from brain stem; stimulates Extends from brain stem; stimulates

the cortex such as awakening from the cortex such as awakening from sleepsleep

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• CerebellumCerebellum– Regulates movement & Regulates movement &

balancebalance– Involved in learning of Involved in learning of

certain kinds of simple skills certain kinds of simple skills & acquired reflexes& acquired reflexes

– Role in complex movements Role in complex movements and some cognitive tasks and some cognitive tasks (e.g., problem solving)(e.g., problem solving)

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• HypothalamusHypothalamus• Involved in emotions & Involved in emotions &

drives vital to survival, drives vital to survival, such as fear, hunger, thirst such as fear, hunger, thirst & reproduction; regulates & reproduction; regulates autonomic nervous systemautonomic nervous system

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• ThalamusThalamus– Brain structure that relays Brain structure that relays

sensory messages to the sensory messages to the cerebral cortexcerebral cortex

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

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The Limbic SystemThe Limbic System

• AmygdalaAmygdala– Involved in arousal and Involved in arousal and

regulation of emotion; initial regulation of emotion; initial emotional response to emotional response to sensory informationsensory information

– Involved in forming and Involved in forming and retrieving emotional retrieving emotional memories memories

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• HippocampusHippocampus– Involved in the storage of new information Involved in the storage of new information

in memoryin memory– Henry Molaison Henry Molaison – Vulnerable to stressVulnerable to stress– Shrunken in people with depression Shrunken in people with depression – Larger in London taxi driversLarger in London taxi drivers– Involved in navigation Involved in navigation – Neurogenesis Neurogenesis

The Limbic SystemThe Limbic System

The CerebrumThe Cerebrum

• CerebrumCerebrum

– Largest brain structureLargest brain structure

– Divided into two Divided into two cerebral cerebral hemisphereshemispheres, connected by , connected by corpus callosumcorpus callosum

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The CerebrumThe Cerebrum

• CerebrumCerebrum

– Hemispheres specialized for Hemispheres specialized for certain tasks certain tasks ((lateralizationlateralization))

– Contains layers of densely Contains layers of densely packed cells called packed cells called cerebral cerebral cortexcortex (divided into (divided into lobeslobes))

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Lobes of the CortexLobes of the Cortex

• Occipital lobesOccipital lobes– Includes visual cortexIncludes visual cortex

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• Parietal lobesParietal lobes– Includes somatosensory Includes somatosensory

cortex (pressure, pain, cortex (pressure, pain, touch, temperature)touch, temperature)

– HomunculusHomunculus– Attention & mental Attention & mental

operationsoperations

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• Temporal lobesTemporal lobes– Includes the auditory cortexIncludes the auditory cortex– Memory, perception, Memory, perception,

emotionemotion

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• Frontal lobesFrontal lobes– Includes the motor cortex & Includes the motor cortex &

language/speech area (left)language/speech area (left)– Emotion, planning, creative Emotion, planning, creative

thinkingthinking

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Prefrontal Cortex Prefrontal Cortex

• Reasoning, decision making, planning, personality Reasoning, decision making, planning, personality • Phineas Gage Phineas Gage

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Nervous System

Central Nervous System

Peripheral Nervous System

Spinal Cord Somatic Nervous System

Autonomic Nervous System

Cranial Nerves

Spinal Nerves Sympathetic

division

Frontal Lobotomy• Early 20th century • psychosurgical procedure in which the

connections the prefrontal cortex and underlying structures are severed

• miracle cure for mental illness• 40,000 patients in the United

States in the 1950s

Alzheimer’s disease and brain changes

•Amyloid precursor proteins

•Beta-amyloid (Aβ) plaques

•Cause or side effect?

Alzheimer’s disease and brain changes

• Tau• Neurofibrillary tangles

Diagnostic Criteria

• Memory deficits.• Abnormal speech, executive function

impairment, unable to recognize people or objects, or impaired motor skills.

• Impairment in performance of daily activities.

• The symptoms have a gradual onset and there is continued cognitive decline.

Alzheimer’s disease: Progression

Confusion and memory problems, decreased ability to concentrate or learn new things


Decline in judgement and reasoning, increased confusion and paranoia


Advanced mental impairments such as the inability to communicate, become fearful or aggressive


Substantial physical decline, impaired reflexes, rigid muscles, inability to walk, talk or eat

Potential Risk Factors

• Age • Traumatic brain injury?• Depression• Vascular disruption• Genetics

Potential Protective Factors

• Education • Career• Aerobic exercise• Socializing• Positive emotions

Brain Controversies…

• Lateralization – different functions or specializations between hemispheres

• Sex differences

Two Hemispheres of the BrainTwo Hemispheres of the Brain

Hemispheres have different Hemispheres have different areas of specialization & control areas of specialization & control opposite sides of the bodyopposite sides of the body

– Communicate through Communicate through corpus corpus callosumcallosum

– Whatever happens in one side is instantly communicated to the other

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LateralizationLateralization

• Both hemispheres play a role in nearly every Both hemispheres play a role in nearly every behavioursbehaviours

• The cerebral lobe is more important for The cerebral lobe is more important for understanding brain function then the understanding brain function then the cerebral hemispherecerebral hemisphere

• Laterality is affected by environmental and Laterality is affected by environmental and genetic factorsgenetic factors

Kolb and Whishaw (2003) 69

Male and Female Brains?Male and Female Brains?

• Are there sex differences in the brain? • There are some anatomical differences BUT

behavioural differences are debatable. • For example, there are differences in

lateralization

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Problems with Gendered Brains?Problems with Gendered Brains?

– the overlap between the sexes is greater than the overlap between the sexes is greater than the differences the differences

– A brain difference does not necessarily explain A brain difference does not necessarily explain behaviour or performance (i.e., organized behaviour or performance (i.e., organized differently yet produce same results)differently yet produce same results)

– Sex differences in the brain could be Sex differences in the brain could be the result the result rather than rather than the cause the cause of behavioural/cultural of behavioural/cultural differencesdifferences

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The Importance of Studying Sex DifferencesThe Importance of Studying Sex Differences

• Stuttering and dyslexia – 4x more likely in boysStuttering and dyslexia – 4x more likely in boys• Attention deficit hyperactivity disorder – 10x more Attention deficit hyperactivity disorder – 10x more

likely in boyslikely in boys• Autism spectrum disorder – 4x more likely in boysAutism spectrum disorder – 4x more likely in boys• Major depressive disorder, anxiety disorders and Major depressive disorder, anxiety disorders and

panic disorders – 2x more likely in womenpanic disorders – 2x more likely in women• Anorexia nervosa – 13x more likely in womenAnorexia nervosa – 13x more likely in women

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End of Chapter 4End of Chapter 4

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the brain: source of mind and self chapter 4 4 - 1

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