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The Biological Basis of Behavior

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Neurons: The Messengers

Neurons vary in size and shape

All are specialized to receive and transmit information

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Myelinated neuron (Fig. 2-1)

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Three Types of Neurons

Sensory (afferent) neurons: Carry messages from sense organs to the spinal

cord or brain

Motor (efferent) neurons: Carry messages from the spinal cord or brain to

the muscles and glands

Interneurons (association neurons): Carry messages from one neuron to another

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Glial CellsThe nervous system also contains glial cells, or glia, which:

Hold neurons in place, provide nourishment, and remove waste

Prevent harmful substances from passing from the bloodstream into the brain

Form the myelin sheath

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The Neural Impulse (Fig. 2-2)

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The Synapse

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Major NeurotransmittersAcetylcholine

Dopamine

Serotonin

Norepinephrine

Endorphins

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Neural PlasticityThe brain has the ability to be changed by experience.

Rosenzweig (1984)

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The Central Nervous SystemThe nervous system has two parts:

The central nervous system (CNS)• the brain and spinal cord

The peripheral nervous system (PNS)• linking all of the body's parts to the CNS

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The Brain

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Four Lobes of Cerebral Cortex

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The Limbic SystemThe structures listed below are often considered to constitute the limbic system. This system is involved in olfaction, emotions, learning, and memory. The limbic system was introduced as a concept by Paul MacLean in 1952 and was long considered the seat of the emotions. Though some of the structures included in this system are in fact involved in some emotional responses, we now know that it does not correspond exactly to any of the multiple emotional systems in the brain.

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Hemispheric SpecializationCerebrum has two separate cerebral hemispheres

Connected by the corpus callosum

Split-brain research

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Two Cerebral Hemispheres

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Processing of speech and language

Language

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Tools for Studying the BrainMicroelectrode techniques

Macroelectrode techniques

Structural imaging

Computerized Axial Tomography scanning (CT)

Nuclear Magnetic Resonance Imaging (MRI)

Functional imaging

Electroencephalograph (EEG)

Magnetoencephalography (MEG)

Magnetic Source Imaging (MSI)

Positron Emission Tomography (PET) scanning

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The Spinal Cord

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Peripheral Nervous SystemThe peripheral nervous system (PNS) contains two types of neurons:

afferent neurons

efferent neurons

The PNS is divided into two subsystems

Somatic nervous system

Autonomic nervous system

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Autonomic Nervous System

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The Endocrine SystemEndocrine Glands:

Tissues that produce and release hormones

Hormones:

Chemical substances released by glands that help regulate bodily activities

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Endocrine GlandsPituitary gland

Pineal gland

Thyroid gland

Parathyroids

Pancreas

Adrenal glands

Adrenal cortex

Adrenal medulla

Gonads

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Genes, Evolution, and BehaviorBehavioral Genetics

What is the relationship between heredity and behavior?

Evolutionary Psychology

What are the origins of behavior, and what adaptive value do they provide?

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GeneticsGenes

Chromosomes

Deoxyribonucleic acid (DNA)

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Patterns of InheritanceDominant genes, recessive genes

Polygenic inheritance

Genotypes and phenotypes

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Behavior GeneticsA variety of methods are used to study the contribution of genesAnimal behavior genetics

• Strain studies• Selection studies

Human behavior genetics• Family studies• Twin studies• Adoption studies

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Average Risk of Schizophrenia Among Biological Relatives ofPeople with SchizophreniaAverage risk of schizophrenia among

biological relatives (Fig. 2-19)

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Social ImplicationsNew challenges have arisen as a result of our better understanding of genes.

Modern prenatal screening

Over-simplified reporting of genetic technologies in mass media

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Evolutionary PsychologyExamining adaptive value of behaviors from an evolutionary perspective

Common applicationsLanguageMate selection

Criticisms