Chapter 3 The Biological basis of Behavior. Table of Contents Communication in the Nervous System Hardware: –Glia – structural support and insulation.

Chapter 3

The Biological basis of Behavior

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Communication in the Nervous System

Hardware:– Glia – structural support and insulation– Neurons – communication– Soma – cell body– Dendrites – receive– Axon – transmit away

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Myelin sheath – speeds up transmission

Terminal Button – end of axon; secretes neurotransmitters

Neurotransmitters – chemical messengers

Synapse – point at which neurons interconnect

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The Neural Impulse: Electrochemical Beginnings

Hodgkin & Huxley (1952) - giant squid– Fluids inside and outside neuron – Electrically charged particles (ions)– Neuron at rest – negative charge on inside

compared to outside– -70 millivolts – resting potential

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The Neural Impulse: The Action Potential

Stimulation causes cell membrane to open briefly Positively charged sodium ions flow in Shift in electrical charge travels along neuron The Action Potential All – or – none law

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Synaptic cleft Presynaptic neuron

– Synaptic vesicles– Neurotransmitters

Postsynaptic neuron– Receptor sites

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When a Neurotransmitter Binds: The Postsynaptic Potential

Voltage change at receptor site – postsynaptic potential (PSP)– Not all-or-none– Changes the probability of the postsynaptic neuron firing

Positive voltage shift – excitatory PSP Negative voltage shift – inhibitory PSP

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Signals: From Postsynaptic Potentials to Neural Networks

One neuron, signals from thousands of other neurons Requires integration of signals

– PSPs add up, balance out– Balance between IPSPs and EPSPs

Neural networks– Patterns of neural activity– Interconnected neurons that fire together or sequentially

Synaptic connections– Elimination and creation– Synaptic pruning

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Neurotransmitters

Specific neurotransmitters work at specific synapses– Lock and key mechanism

Agonist – mimics neurotransmitter action Antagonist – opposes action of a neurotransmitter 15 – 20 neurotransmitters known at present Interactions between neurotransmitter circuits Botox – Ach blocker Dopamine – substantia nigra – Parkinson disease

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Organization of the Nervous System

Central nervous system (CNS) – brain and spinal cord– Afferent = toward the CNS/ Efferent = away from the CNS

Peripheral nervous system – nerves that lie outside the central nervous system– Somatic nervous system– voluntary muscles and sensory

receptors– Autonomic nervous system (ANS) – controls automatic,

involuntary functions• Sympathetic – Go (fight-or-flight)• Parasympathetic – Stop

Table of ContentsFigure 3.6 Organization of the human nervous system

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Figure 3.7 – Peripheral Nervous System – Somatic and Autonomic

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Cranial Nerves

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The Cranial Nerves and Their Function

1 – Olfactory - smell S 2 – Optic – vision S 3 – Occulomotor – eye movements, control of pupil and lens, tears MP 4 – Trochlear - eye movements M 5 – Trigeminal – facial sensations, chewing SM 6 – Abducens - eye movements M 7 – Facial – facial muscles, salivary glands, taste SMP 8 – Auditory – acoustic branch: audition S verstibular branch: balance S 9 – Glossopharynegeal – throat muscles, salivary glands, taste SMP 10 – Vagus – parasympathetic control of internal organs, sensation from internal

organs, taste SMP 11 – Spinal accessory – head and neck muscles M 12 – Hypoglossal – tongue and neck muscles M

S, sensory; M, motor; P, parasympatheic function

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Studying the Brain: Research Methods

Electroencephalography (EEG) – Damage studies/lesioning Electrical stimulation (ESB) – Transcranial Magnetic Stimulation (TMS) – Brain imaging –

– computerized tomography – CT – – positron emission tomography - PET – – magnetic resonance imaging – MRI – – functional magnetic resonance imaging – fMRI –

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Electroencephalography (EEG)

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PET scan

MRI and fMRI scans

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Positron Emission Tomography – PET scan

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Magnetic Resonance Imaging - MRI

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Functional MRI images showing reduced activation of language areas during a

linguistic task in patients with schizophrenia

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Functional MRI images

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Brain Regions and Functions

Hindbrain – vital functions – medulla, pons, and cerebellum

Midbrain – sensory functions – dopaminergic projections, reticular activating system

Forebrain – emotion, complex thought – thalamus, hypothalamus, limbic system, cerebrum, cerebral cortex

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The Cerebrum: Two Hemispheres, Four Lobes

Cerebral Hemispheres – two specialized halves connected by the corpus collosum – – Left hemisphere – verbal processing: language, speech, reading,

writing, sequential– Right hemisphere – nonverbal processing: spatial, musical, visual

recognition, parallel Four Lobes: -

– Occipital – vision– Parietal – somatosensory – phantom limb – – Temporal - auditory– Frontal – movement, executive control systems –

Primary functions and associated functions– Language – Broca’s and Wernicke’s areas – loss of language –

aphasia –

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Table of ContentsThe cerebral cortex in humans

Table of ContentsPrimary motor cortex with homunculus

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Mirror Neurons

An area just forward of the primary motor cortex is where “mirror neurons” were first discovered accidentally in the mid-1990s.– May play a role in the acquisition of new motor skills,

• the imitation of others,

• the ability to feel empathy for others,

• and dysfunctions in mirror neuron circuits may underlie the social deficits seen in autistic disorders.

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The Plasticity of the Brain

The brain is more “plastic” or malleable than widely assumed– Aspects of experience can sculpt features of brain

structure– Damage to incoming sensory pathways or tissue can lead

to neural reorganization

Adult brain can generate new neurons – neurogenesis

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Visual input with split-brain – Roger Sperry and others

Split-brain research

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The Endocrine System: Glands and Hormones

Hormones – chemical messengers in the bloodstream– Pulsatile release by endocrine glands– Negative feedback system

Endocrine glands– Pituitary – “master gland,” growth hormone– Thyroid - metabolic rate– Adrenal - salt and carbohydrate metabolism– Pancreas - sugar metabolism– Gonads - sex hormones

Use of steroids

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The endocrine system

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Genes and Behavior: The Interdisciplinary Field of Behavioral Genetics Behavioral genetics = the study of the influence of

genetic factors on behavioral traits Basic terminology: Chromosomes – strands of DNA carrying genetic

information– Human cells contain 46 chromosomes in pairs (sex-cells –

23 single)– Each chromosome – thousands of genes, also in pairs

Dominant, recessive Homozygous, heterozygous Genotype/Phenotype and Polygenic Inheritance

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Research Methods in Behavioral Genetics

Family studies – does it run in the family? Twin studies – compare resemblance of identical

(monozygotic) and fraternal (dizygotic) twins on a trait

Adoption studies – examine resemblance between adopted children and their biological and adoptive parents

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Modern Approaches to the Nature vs. Nurture Debate Molecular Genetics = the study of the

biochemical bases of genetic inheritance– Genetic mapping – locating specific genes - The

Human Genome Project Behavioral Genetics

– The interactionist model– Richard Rose (1995) – “We inherit dispositions, not

destinies.”

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Evolutionary Psychology: Behavior in Terms of Adaptive Significance

Based on Darwin’s ideas of natural selection– Reproductive success key

Adaptations – behavioral as well as physical– Fight-or-flight response– Taste preferences– Parental investment and mating

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Parental Investment and Mating Systems - sociobiology Polygyny – high female, low male – based on a study by

Buss (1994) found in 84 % of human cultures Polyandry – high male, low female – rare but examples have

been found for example in the Pahari of Nepal and India, and Tibet and other limited places in the world. The system in Tibet was based on class and land considerations.

http://www.case.edu/affil/tibet/booksAndPapers/pahari.html Monogamy – shared parental investment but not always

equal. There are few exclusively monogamous species – 15 % of human cultures (Buss, 1994)

Polygynadry – group parental investment and very rare – in chimpanzees mating is promiscuous for males and females

Incest – universal taboo – increased genetic diversity

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– brain asymmetry and speech localization – use of Wadi technique and TMS