Chapter 3 The Biological basis of Behavior

Table of Contents Communication in the Nervous System Hardware: –Glia – structural support and insulation –Neurons – communication –Soma – cell body –Dendrites – receive –Axon – transmit away

Table of Contents Myelin sheath – speeds up transmission Terminal Button – end of axon; secretes neurotransmitters Neurotransmitters – chemical messengers Synapse – point at which neurons interconnect

Table of Contents 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

Table of Contents 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

Table of Contents Neural Impluse

Table of Contents Synaptic cleft Presynaptic neuron –Synaptic vesicles –Neurotransmitters Postsynaptic neuron –Receptor sites

Table of Contents 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

Table of Contents Overview of synaptic transmission

Table of Contents 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 Contents Figure 3.6 Organization of the human nervous system

Table of Contents Figure 3.7 – Peripheral Nervous System – Somatic and Autonomic

Table of Contents Cranial Nerves

Table of Contents 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 –

Table of Contents Electroencephalography (EEG)

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PET scan MRI and fMRI scans

Table of Contents Positron Emission Tomography – PET scan

Table of Contents Magnetic Resonance Imaging - MRI

Table of Contents Functional MRI images showing reduced activation of language areas during a linguistic task in patients with schizophrenia

Table of Contents Functional MRI images

Table of Contents 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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The cerebral cortex in humans

Table of Contents Primary motor cortex with homunculus

Table of Contents 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.

Table of Contents 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

Table of Contents 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

Table of Contents The endocrine system

Table of Contents 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.”

Table of Contents 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

Table of Contents 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. 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

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