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Chapter 3

Biological Aspects of Psychology

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Biology and BehaviorBiology and Behavior• Cells of the Nervous System

• Neural Transmission

• The Nervous System

• The Peripheral Nervous System: Keeping in Touch with the World

• The Central Nervous System: Making Sense of the World

• Techniques for Studying Human Brain Function and Structure

• The Chemistry of Behavior: Neurotransmitters

• The Endocrine System: Coordinating the Internal World

• Linked Exercises

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Biological PsychologyBiological Psychology

• All behavior and mental processes are based on biology.– But, are also influenced by the environment

• Two primary systems direct the activities of the body.– The nervous system

– The endocrine system

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Three Functionsof the Nervous System

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Cells of the Nervous SystemCells of the Nervous System

What are neurons, What are neurons, and what do they do?and what do they do?

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Cells of the Nervous SystemCells of the Nervous System

• NeuronsNeurons– Have the ability to send and receive signalsHave the ability to send and receive signals– Organized in neural networks

• Glial cells Glial cells – Help neurons communicateHelp neurons communicate– Malfunctions may lead to problemsMalfunctions may lead to problems

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A Typical Neuron

• Cell body– Similar to other cells

• Axon– Sends signals to

other neurons

• Dendrites– Receive signals from

other neurons

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Axons

• Function: – Carry signals away from the cell body.– Myelin sheath helps speed the action potential

• Type of Signal Carried: – The action potential

• An all-or-nothing electrochemical signal• Travels down the axon, releasing

neurotransmitters from vesicles

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Dendrites

• Function: – Detect and carry signals to the cell body.

• Type of Signal Carried: – Excitatory postsynaptic potential: electrochemical

signal which encourages a neuron to fire.or– Inhibitory postsynaptic potential: electrochemical

signal which discourages a neuron from firing.

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The Cell Body of a Neuron

• Outer membrane– passes some

substances, blocks others

• Nucleus– Genetic information

• Mitochondria– convert glucose and

oxygen into energy

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Neural Transmission

How do neurons communicate?

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Video: The Beginning of an Action Potential

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Synapses

• Areas for the transfer of signals between neurons

• Neurotransmitters cross to receptors on other cells

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A Synapse

This photograph shows part of a synaptic gap between two neurons, magnified 50,000 times. The ending of the presynaptic cell’s axon is shaded green, the green ovals are mitochondria, and the red spots are the vesicles.

The synapse itself is the narrow gap between the first cell’s green-shaded axon and the blue-shaded dendrite of the cell below.

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Neurotransmitters

• Chemicals released by one cell that bind to the receptors on another cell

• Tell the next cell to fire or not to fire its own action potential

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Receptors

• Proteins on the cell membrane that receive chemical signals

• Recognize specific neurotransmitters– Allows them to begin postsynaptic potentials in the

dendrite

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Integration of Neural Signals

• Signals arrive from many neighboring cells

– Excitatory signals encourage firing

– Inhibitory signals discourage firing

• Firing depends on which messages predominate

– The all-or-nothing law

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The Nervous System

The nervous system has two major divisions– Central Nervous System (CNS)– Peripheral Nervous System (PNS)

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The Peripheral Nervous The Peripheral Nervous System: Keeping in Touch System: Keeping in Touch

with the Worldwith the World

How do sights and soundsHow do sights and soundsreach my brain?reach my brain?

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Autonomic Nervous SystemAutonomic Nervous System

• Controls activities normally outside of Controls activities normally outside of conscious control.conscious control.

• Two SubsystemsTwo Subsystems– Sympathetic nervous systemSympathetic nervous system

• ““SpendsSpends”” energy energy– Parasympathetic nervous systemParasympathetic nervous system

• ““PreservesPreserves”” energy energy

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Somatic Nervous System

• Sensory neurons (afferent neurons)– Send sensory information to CNS

• Motor neurons (efferent neurons)– Send messages from CNS to muscles

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The Central Nervous System: The Central Nervous System:

Making Sense of the WorldMaking Sense of the World

How is my brain How is my brain ““wiredwired””??

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The Spinal Cord

• Relays signals from the senses to the brain.

• Relays signals from the brain to the muscles.

• Directs reflexes.

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A Reflex Pathway

Tapping your knee at just the right spot stimulates sensory neurons to fire, triggering spinal neurons to fire. This stimulates the firing of motor neurons with axons ending in your thigh muscles, causing you to kick. Information about all this also goes to your cerebral cortex, but the reflex happens without waiting for guidance from the brain.

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Techniques for StudyingHuman Brain Function

and Structure

Taking a Closer Look

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EEGEEG(Electroencephalography)(Electroencephalography)

• Technique:Technique: – Multiple electrodes pasted to outside of headMultiple electrodes pasted to outside of head– Senses electrical fields resulting from neural activitySenses electrical fields resulting from neural activity

• What it shows:What it shows: – General electrical activity of the brainGeneral electrical activity of the brain– Represented as a line on a graph or screenRepresented as a line on a graph or screen

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EEG EEG (cont(cont’’d)d)

• Advantages:Advantages:– Detects very rapid changes in electrical activityDetects very rapid changes in electrical activity– Allows analysis of stages of cognitive activityAllows analysis of stages of cognitive activity– May be combined with magnetoencephalography May be combined with magnetoencephalography

(MEG) to localize activity(MEG) to localize activity

• Disadvantages:Disadvantages:– Poor spatial resolution of the source of activityPoor spatial resolution of the source of activity

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PET (Positron Emission Tomography)and

SPECT (Single-Photon Emission Computerized Tomography)

• Technique– Positrons and photons emitted by radioactive substances

• What they show– Indicate specific changes in neuronal activity

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PET and SPECT (cont’d)

• Advantages– Allow functional and biochemical studies– Provide visual image corresponding to anatomy– Better spatial resolution better than EEG

• Disadvantages– Require exposure to low levels of radioactivity– Inferior spatial resolution to MRI– Cannot follow changes faster than 30 seconds

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MRIMRI(Magnetic Resonance Imaging)(Magnetic Resonance Imaging)

• Technique:Technique: – Expose the brain to a magnetic field and measure Expose the brain to a magnetic field and measure

radio frequency wavesradio frequency waves

• What it shows:What it shows: – High resolution image of brain anatomyHigh resolution image of brain anatomy

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MRI (cont)MRI (cont)

• AdvantagesAdvantages– No radioactivityNo radioactivity– High resolution of anatomical details (<1 mm)High resolution of anatomical details (<1 mm)– High temporal resolution (<1/10 of a second)High temporal resolution (<1/10 of a second)

• Disadvantages– Does not indicate functions as they happen

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Combining a PET Scan andMagnetic Resonance Imaging

Combining these techniques providesthree-dimensional views of living brains

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Functional MRI (fMRI)

• Combines the advantages of PET and MRI

• Detects changes in blood flow and oxygen that reflect ongoing changes in neural activity

• Resulting computer analysis shows areas of the brain that appear activated during a task

• Exciting developments:– Discovery of the mirror neuron mechanism – Investigating the effects of acupuncture

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Video: Mirror Neurons

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Critical Thinking about fMRI

• Indicates location of brain activity, but not cause

• Does not tell us how brain works

• Does not measure brain cell activity directly, but measures change in blood flow and oxygen

• Subject to experimenter bias in interpretation

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TMSTMS(Transcranial Magnetic Stimulation)(Transcranial Magnetic Stimulation)• Technique:Technique:

– Temporarily disrupt activity of a small region of the Temporarily disrupt activity of a small region of the brain with an intense magnetic fieldbrain with an intense magnetic field

• What it shows:What it shows: – Loss of normal function of a particular brain regionLoss of normal function of a particular brain region

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TMS TMS (cont(cont’’d.)d.)

• AdvantagesAdvantages– Shows brain regions needed for given tasksShows brain regions needed for given tasks– May treat depression and migraine headaches

• DisadvantagesDisadvantages– Long-term safety not well establishedLong-term safety not well established

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Video: Brain Organization, Video: Brain Organization, Structure and FunctionStructure and Function

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DTI (Diffusion Tensor Imaging)

• Variant of fMRI

• Traces activity of axon pathways

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Major Structures of the Hindbrain• Medulla oblongata

– Controls vital functions– blood pressure– heart rate– breathing

• Reticular formation– Arousal– Attention

• Cerebellum– Coordinates movement– Timing

• Locus coeruleus– Directs attention

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Major Structures of the Forebrain• Cerebral cortex

– Processes complex information

• Suprachiasmatic nuclei– Maintain circadian

rhythms• Striatum & substantia nigra

– Coordinate smooth movement

• Corpus callosum– Connects left and right

hemispheres• Thalamus

– Relays and processes sensory signals

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Major Structures of the ForebrainThe Limbic System

• Amygdala– Involved in emotion

• Hippocampus– Formation of memories– Affected by Alzheimer’s

disease• Hypothalamus

– Regulates drives• Septum

– Pleasure– Anger suppression

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Anatomical Areasof the Cerebral Cortex

Each hemisphere is into four lobes:• Frontal• Parietal• Occipital• Temporal

Divided by• Gyri (ridges)• Sulci (valleys)

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Functional Areasof the Cerebral Cortex

• Motor cortex• Controls movement

• Sensory cortex• Receives sensory information

• Association cortex• Integrates information

• Wernicke’s area• Language interpretation

• Broca’s area• Language organization• Speech production

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Motor and Somatosensory Cortices• Motor cortex

– Moves parts of the body– Areas controlling movement

of neighboring parts of the body occupy neighboring parts of the motor cortex

• Somatosensory cortex– Receives sensory input from

body parts– Areas receiving input from

neighboring body parts are near one another in the sensory cortex

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Lateral Dominance in Normal Brains

• Hemispheric Differences– Left:

• logical abilities• language abilities

– Right: • spatial abilities• artistic abilities• musical abilities• facial recognition

– Individual variability in the precise nature and degree of lateralization

– Differences should not be exaggerated

• Corpus callosum allows Corpus callosum allows the two hemispheres to the two hemispheres to work closely togetherwork closely together

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Split-Brain StudiesSplit-Brain Studies

• Apparatus for studying split-brain patients – Presents image to selected visual fieldPresents image to selected visual field

• In left visual field:In left visual field:– Can name the objectCan name the object

• In right visual field:In right visual field:– Cannot describe Cannot describe

object in wordsobject in words– Can pick the object Can pick the object

out of a groupout of a group

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Neural PlasticityNeural Plasticity

• CNS can:CNS can:– Strengthen neural connections at synapsesStrengthen neural connections at synapses– Establish new neural connectionsEstablish new neural connections

• Basis for forming new memories and learningBasis for forming new memories and learning

• Limits to plasticity in repairing brain damageLimits to plasticity in repairing brain damage

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Helping the CNS to Heal

• Transplant fetal tissue into the adult’s brain

• Coax brain to make its own new neurons– Problem: Synaptic connections must be reestablished.

• Block the action of the CNS protein, “Nogo”

• “Growth factor” proteins

• Special mental and physical exercise programs

• Neural stem cells in adults’ brains– Special glial cells can form new tissue, including neurons

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Linkages: Human Development and the Changing Brain

• Correlation between changes in neural activity and the behavior of newborns and infants– Newborns:

• High activity in thalamus• Purposeful sweeping movements of arms and legs

– 2-3 months old:• Increased activity in much of the cortex• Loss of reflexes such as grasping

– 8-9 months old:• Increased activity in frontal cortex• Increased cognitive activity

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Linkages: Human Development and the Changing Brain

Childhood and adolescence• 6-7 years old:

– More dendrites than adult brains– Use twice the metabolic fuel of

adult brains

• Adolescence:– Pruning of synapses– Loss of gray matter

• Developmental changes reflect plasticity, not appearance of new cells

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Linkages: Human Developmentand the Changing Brain (cont’d)

• Genes determine basic pattern of growth and major lines of connections.

• Enriched environments encourage neural development

Back to Linked Exercises

Back to TOC

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The Chemistry of Behavior: The Chemistry of Behavior: NeurotransmittersNeurotransmitters

How do biochemicalsHow do biochemicalsaffect my mood?affect my mood?

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The Chemistry of Behavior

• Neurotransmitter systems: groups of neurons that uses the same neurotransmitter to communicate– Play dominant roles in

particular functions.

• Neuromodulators act on receptors at synapses.– Modify or “modulate” a cell’s

response to other neurotransmitters.

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Small Molecule Neurotransmitters

Neurotransmitter Normal Function Disorder Associated with Malfunction

Acetylcholine Memory, movement Alzheimer’s disease

Norepinephrine Mood, sleep, learning Depression

Serotonin Mood, appetite, impulsivity Depression

Dopamine Movement, reward Parkinson’s disease, schizophrenia

GABA Sleep, movement Anxiety, Huntington’s disease, epilepsy

Glutamate Memory Damage after cardiovascular accident

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Other Classes of Neurotransmitters

Neurotransmitter Normal Function Disorder Associated with Malfunction

Peptides

Endorphins Pain control No established disorder

Gases

Nitric oxide Memory No established disorder

Back to TOC

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The Endocrine System: The Endocrine System: Coordinating Coordinating

the Internal Worldthe Internal World

How can my hormonesHow can my hormoneshelp me in a crisis?help me in a crisis?

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The Endocrine System

• Regulates functions– Stress responses– Physical growth

• Communicates by secreting hormones

• Controlled by hypothalamus via pituitary gland

• Negative feedback system

Back to TOC

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Linked Exercises

• Linkages: Human Development and the Changing Brain

• Thinking Critically:Thinking Critically: What Can fMRI Tell Us about Behavior and Mental Processes? What Can fMRI Tell Us about Behavior and Mental Processes?

• Focus on Research Methods: Manipulating Genes in Animal Models of Human Disease

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Thinking Critically:Thinking Critically: What Can fMRI Tell Us about What Can fMRI Tell Us about Behavior and Mental Processes?Behavior and Mental Processes?

• What am I being asked to believe or accept?What am I being asked to believe or accept?– fMRI is a 21fMRI is a 21stst century version of phrenology century version of phrenology

• Is evidence available to support the claim?Is evidence available to support the claim?– Neuron firing rates may cancel each other out on Neuron firing rates may cancel each other out on

scansscans– Problems with interpreting fMRI resultsProblems with interpreting fMRI results– Difference rules are decided by experimentersDifference rules are decided by experimenters– Differences do not necessarily reflect actual thinking Differences do not necessarily reflect actual thinking

differencesdifferences

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Thinking Critically:Thinking Critically: What Can fMRI Tell Us about What Can fMRI Tell Us about Behavior and Mental Processes? Behavior and Mental Processes? (cont(cont’’d.)d.)

• Can that evidence be interpreted another way?Can that evidence be interpreted another way?– Image changes mirror thinking and feeling changesImage changes mirror thinking and feeling changes– fMRI led to discovery of mirror neuron mechanismsfMRI led to discovery of mirror neuron mechanisms

• What evidence would help evaluate the What evidence would help evaluate the alternatives?alternatives?

– Actual relationship between scanned activity and Actual relationship between scanned activity and actual behavior and mental processesactual behavior and mental processes

– Evidence about correlation and causation in fMRI Evidence about correlation and causation in fMRI researchresearch

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Thinking Critically:Thinking Critically: What Can fMRI Tell Us about What Can fMRI Tell Us about Behavior and Mental Processes? Behavior and Mental Processes? (cont(cont’’d.)d.)

• What conclusions are most reasonable?What conclusions are most reasonable?– Unlikely to explain how the brain creates behavior Unlikely to explain how the brain creates behavior

and mental processes.and mental processes.– Careful analysis of fMRICareful analysis of fMRI’’s value is important.s value is important.

Back to Linked Exercises

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Focus on Research Methods: Manipulating Genes in Animal Models of Human Disease

• What was the researchers’ question?– Are the proteins that are found in plaques and tangles

the cause of Alzheimer’s disease?

• How did the researchers answer the question?– Inserted a gene for a mutant

form of beta-amyloid precursorprotein into mice.

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Focus on Research Methods: Manipulating Genes (cont’d)

• What did the researchers find?– Mice showed memory impairments and developed

plaques, no tangles.– Plaques and tangles did appear in transgenic mice

with faulty tau, but cannot be the main cause of Alzheimer’s.

Human brains with Alzheimer’s disease (bottom row) and those without it.

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Focus on Research Methods: Manipulating Genes (cont’d)

• What do the results mean?– Transgenic mice can be used to evaluate the roles of mutations

in proteins in causing Alzheimer’s disease.

• What do we still need to know?– Challenge is to use animal models to develop and test effective

treatments for humans.

Back to Linked ExercisesBack to Techniques for Studying the Brain

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In Class Writing Exercises

• Place one at the start of your presentation. • Have your students write for a minute or two

about the quote on the slide.• This will help them center themselves on the

topic to be covered in class.• You may wish to use their responses to generate

class discussion.

The following slides may be used as advance organizers for the topics in this unit.

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In Class Writing Exercise::

Human action can be modified to some extent, but human nature cannot be changed.

Abraham Lincoln

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In Class Writing Exercise::

Every man must do his own growing no matter how tall his grandfather was.

L.J. Peter

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In Class Writing Exercise::

Brain and brain, what is brain?Brain and brain, what is brain?

——Kara, an EymorgKara, an Eymorg((Star TrekStar Trek: : SpockSpock’’s Brains Brain))

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