Chapter 2 The Biological Basis of Behavior Prentice

Chapter 2 The Biological Basis of Behavior ©Prentice Hall 2003 2 -1

Neurons: The Messengers • The brain of an average human being contains as many as 100 billion nerve cells or neurons. ©Prentice Hall 2003 2 -2

Neurons: The Messengers • Neurons receive messages from other neurons through short fibers, called dendrites. ©Prentice Hall 2003 2 -3

Neurons: The Messengers • A group of axons bundled together forms a nerve or tract. • Some axons are covered with a myelin sheath, made up of glial cells; this increases neuron efficiency and provides insulation. ©Prentice Hall 2003 2 -4

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Three Types of Neurons • Sensory (afferent) neurons: – Carry messages from sense organs to the spinal cord or brain • Interneurons (association neurons): – Carry messages from one neuron to another • Motor (efferent) neurons: – Carry messages from the spinal cord or brain to the muscles and glands ©Prentice Hall 2003 2 -7

Glial Cells • Glial cells form the myelin sheath that insulates and protects neurons. ©Prentice Hall 2003 2 -8

The Neural Impulse ©Prentice Hall 2003 2 -9

The Neuron At Rest • Resting potential: the state of a neuron when not engaged in an action potential – greater positive ions outside the cell membrane and greater negative ions inside the cell • Polarization: inside of neuron is negatively charged relative to the outside ©Prentice Hall 2003 2 -10

The Action Potential • Neural impulse (action potential): – the firing of a nerve cell • Graded potential: – a shift in the electrical charge in a tiny area of a neuron • Threshold of excitation: – the level an impulse must exceed to cause a neuron to fire ©Prentice Hall 2003 2 -11

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The Action Potential • Neurons either fire, or they don’t. • This is called the all-or-none law. • A neuron is more likely to fire more often when stimulated by a strong signal resulting in a rapid neural firing that communicates a message. ©Prentice Hall 2003 2 -13

$The Action Potential • Absolute refractory period: – a period after firing when a$

The Action Potential • Absolute refractory period: – a period after firing when a neuron will not fire again no matter how strong the incoming message • Relative refractory period: – a period after firing when a neuron will fire again only if the incoming message is much stronger than usual ©Prentice Hall 2003 2 -14

The Synapse ©Prentice Hall 2003 2 -15

• Neurotransmitter molecules, released by synaptic vesicles, cross the tiny synaptic space (or cleft) between an axon terminal (or terminal button) of a sending neuron and a dendrite of a receiving neuron. • Here they latch on to receptor sites, much as keys fit into locks, and pass on their excitatory or inhibitory messages. ©Prentice Hall 2003 2 -16

Neurotransmitters and Their Effects • Acetylcholine (ACh): – plays a role in arousal, attention, memory, and motivation • Dopamine: – plays a role in motor disorders, such as parkinson’s disease • Serotonin: – affects emotions, arousal, and sleep ©Prentice Hall 2003 2 -17

Neurotransmitters And Their Effects • Norepinephrine: – Influences wakefulness and arousal, as well as learning, memory, and emotional mood • Endorphins: – Reduce pain by inhibiting the neurons that transmit pain messages to the brain ©Prentice Hall 2003 2 -18

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Drugs and Behavior • Certain drugs produce psychological effects by increasing or decreasing the amount of neurotransmitters at synapses. • Other drugs work on receptor sites, blocking the receptors or interfering with the removal or reabsorption of neurotransmitters. ©Prentice Hall 2003 2 -20

Drugs and Behavior • Drugs and toxins block or enhance the action of neurotransmitters – – – Botulism Curare Chlorprozamine or clozapine Caffeine Cocaine ©Prentice Hall 2003 2 -21

Botulism • A microorganism produces a toxin that causes botulism. • This toxin prevents the release of ACh, which can lead to paralysis and possibly rapid death. ©Prentice Hall 2003 2 -22

Curare • Used by South American native people to tip arrows. • Stuns or kills prey • Blocks the Ach receptors. ©Prentice Hall 2003 2 -23

Chlorprozamine or Clozapine • Trade name Thorazine • Prevents dopamine from binding to receptor sites. • This reduction reduces schizophrenic hallucinations. ©Prentice Hall 2003 2 -24

Caffeine • Caffeine increases the release of excitatory neurotransmitters by blocking the transmitter (adenosine) that inhibits excitatory neurotransmitters. ©Prentice Hall 2003 2 -25

Cocaine • Prevents dopamine from being reabsorbed • Leads to excess amounts of accumulated dopamine • Results in heightened arousal of the entire nervous system. ©Prentice Hall 2003 2 -26

Neural Plasticity and Neurogenesis ©Prentice Hall 2003 2 -27

Brain Growth and Experience • Rosenzweig (1984) demonstrated the importance of experience to neural development. ©Prentice Hall 2003 2 -28

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The Central Nervous System ©Prentice Hall 2003 2 -30

The Central Nervous System • The nervous system is organized into two parts: – The central nervous system (CNS), which consists of the brain and spinal cord. – The peripheral nervous system (PNS), is made up of nerves that radiate throughout the body, linking all of the body's parts to the CNS. ©Prentice Hall 2003 2 -31

The Brain • Physically, the brain has three more or less distinct areas: – The central core, – The limbic system, – The cerebrum. ©Prentice Hall 2003 2 -32

The Spinal Cord • The spinal cord is our communications superhighway. • There are two major pathways in the spinal cord: – The motor neurons – The sensory neurons ©Prentice Hall 2003 2 -33

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Peripheral Nervous System • The peripheral nervous system (PNS) contains two types of neurons: – afferent neurons, which carry sensory messages to the central nervous system, – efferent neurons, which carry messages from the CNS. ©Prentice Hall 2003 2 -35

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Peripheral Nervous System • Neurons involved in making voluntary movements of the skeletal muscles belong to a part of the PNS called the somatic nervous system. • Neurons involved in governing the actions of internal organs belong to a part of the PNS called the autonomic nervous system. ©Prentice Hall 2003 2 -37

Peripheral Nervous System • The autonomic nervous system is divided into two parts: – the sympathetic division, which acts primarily to arouse the body when it is faced with threat, and – the parasympathetic division, which acts to calm the body down, restoring it to normal levels of arousal. ©Prentice Hall 2003 2 -38

Sympathetic Nervous System • • • Dilates pupils No effect on tear glands Weak stimulation of salivary flow Accelerates heart, constricts arterioles Dilates bronchi Inhibits stomach motility and secretions ©Prentice Hall 2003 2 -39

Parasympathetic Nervous System • • • Constricts pupils Stimulates tear glands Strong stimulation of salivary flow Inhibits heart, dilates arterioles Constricts bronchi Stimulates stomach motility & secretion ©Prentice Hall 2003 2 -40

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Hindbrain • Medulla: – Controls breathing, heart rate, blood pressure • Pons: – Regulation of sleep/wake cycle • Cerebellum: – Involved in balance and coordination of movement ©Prentice Hall 2003 2 -42

Midbrain • The relay point for hearing and vision. • One of the places pain is registered. ©Prentice Hall 2003 2 -43

Forebrain Structures • Thalamus • Hypothalamus • Cerebral cortex ©Prentice Hall 2003 2 -44

Forebrain Structures • Thalamus: – Sensory switchboard • Hypothalamus: – Governs motivational (hunger, thirst, sex, sleep, and temperature control) and emotional responses • Limbic system: – Linked primarily to memory, emotions, drives ©Prentice Hall 2003 2 -45

Structures in the Cerebral Cortex • Frontal lobes – Primary motor cortex • Parietal lobes – Primary somatosensory cortex • Temporal lobes • Occipital lobes ©Prentice Hall 2003 2 -46

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Frontal Lobes • Voluntary movement • Attention • Goal-directed behavior ©Prentice Hall 2003 2 -48

Parietal Lobes • Sensations of touch and bodily position • Primary somatosensory cortex: – Registers and processes body sensations • Primary motor cortex: – Controls voluntary muscle movement ©Prentice Hall 2003 2 -49

Temporal Lobe • Processes information concerning hearing, smell, balance and equilibrium ©Prentice Hall 2003 2 -50

Occipital Lobes • Processes information for the sense of vision. ©Prentice Hall 2003 2 -51

Reticular Formation • A network of neurons in the hindbrain, midbrain, and part of the forebrain. • The primary function of this network is to alert and arouse the higher parts of the brain. ©Prentice Hall 2003 2 -52

The Limbic System • System of loosely connected structures located between the central core and the cerebral hemispheres. • Appears to play a central role in times of stress. ©Prentice Hall 2003 2 -53

The Limbic System • Hippocampus: – Aids in the processing of memory for storage • Amygdala: – Involved in fear and aggression • Hypothalamus: – Bodily maintenance functions and pleasurable rewards ©Prentice Hall 2003 2 -54

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Hemispheric Specialization • The cerebrum consists of two separate cerebral hemispheres. • The primary connection between the left and right hemispheres is the corpus callosum. • The corpus callosum allows for close communication between the two hemispheres. ©Prentice Hall 2003 2 -56

Left Hemisphere • • Right hand touch and movement Speech Language Writing for right handers ©Prentice Hall 2003 2 -57

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Right Hemisphere • • • Left hand touch and movement Spatial construction Face recognition Nonverbal imagery Writing for left handers ©Prentice Hall 2003 2 -59

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Tools for Studying the Nervous System • Microelectrode techniques: – Used to study the functioning of a single neuron • Macroelectrode techniques: – Used to measure cortical activity (e. g. , EEG) ©Prentice Hall 2003 2 -61

Tools for Studying the Nervous System • Structural imaging: – Study the structures of the brain • Functional imaging: – Study the functioning of the nervous system ©Prentice Hall 2003 2 -62

Structural Imaging Techniques • Computerized Axial Tomography (CAT or CT) scanning • Nuclear Magnetic Resonance Imaging (NMR or MRI) ©Prentice Hall 2003 2 -63

Computerized Axial Tomography • An X-ray photography unit passes a radioactive ray through bone and brain tissue to show structures of the brain. ©Prentice Hall 2003 2 -64

Magnetic Resonance Imaging • An MRI uses alterations in the electromagnetic field of the body created by a magnet to measure the movement of nuclei as they return to their original axes. ©Prentice Hall 2003 2 -65

Functional Imaging Techniques • • Electroencephalograph (EEG) Magnetoencephalography (MEG) and Magnetic Source Imaging (MSI) Positron Emission Tomography (PET) scanning ©Prentice Hall 2003 2 -66

MEG and MSI • These imaging techniques measure the strength of the magnetic field produced by electrical activity in order to identify its source. ©Prentice Hall 2003 2 -67

Positron Emission Tomography • PET scans show actual brain activity by measuring radiation in the brain emitted from radioactive water that was injected into the bloodstream. ©Prentice Hall 2003 2 -68

The Endocrine System • Endocrine Glands: – Tissues that produce and release hormones • Hormones: – Chemical substances released by glands that help regulate bodily activities ©Prentice Hall 2003 2 -70

Endocrine Glands • Thyroid gland: – Produces the hormone thyroxin, which regulates the body’s rate of metabolism • Parathyroid glands: – Secrete parathormone, which controls and balances the levels of calcium and phosphate in the blood and tissue fluids ©Prentice Hall 2003 2 -71

Endocrine Glands • Pineal gland: – Regulates one’s activity level over the course of a day • Pituitary gland: – Produces the largest number of the body’s hormones • Posterior pituitary: – Affects thirst, sexual behavior, and perhaps paternal and maternal behavior ©Prentice Hall 2003 2 -72

Endocrine Glands • Anterior pituitary: – Produces hormones that cause other glands to produce hormones; Regulates body growth and also affects motivation and emotion • Gonads: – The reproductive glands (testes and ovaries) ©Prentice Hall 2003 2 -73

Adrenal Glands • Adrenal cortex: – Outer covering of the adrenal glands; Releases hormones important for dealing with stress • Adrenal medulla: – Inner core of the adrenal glands that also releases hormones to deal with stress ©Prentice Hall 2003 2 -74

Pancreas • An organ lying between the stomach and small intestine. • It secretes insulin and glucagon to regulate blood-sugar levels. ©Prentice Hall 2003 2 -75

Genes, Evolution and Behavior • The related fields of behavior genetics and evolutionary psychology explore the influences of heredity on human behavior. • Both are helping to settle the nature/nurture debate over the relative contributions of genes and the environment to human similarities and differences. ©Prentice Hall 2003 2 -77

Genes, Evolution and Behavior • Psychologists use a variety of methods to study the contribution of genes in determining variations in certain traits. – Strain studies approach the problem by observing strains of highly inbred genetically similar animals. – Selection studies try to determine the extent to which an animal's traits can be passed on from one generation to another. ©Prentice Hall 2003 2 -78

Genes, Evolution and Behavior • Family studies, twin studies, and adoption studies tackle heritability by looking for similarities in traits as a function of biological closeness. • Molecular genetics focuses on mapping the genes on the chromosomes. ©Prentice Hall 2003 2 -79

Terminology of Genetics • Traits: – Characteristics on which organisms differ • Heredity: – Transmission of traits from one generation to the next • Genes: – Elements that control the transmission of traits; They are found on the chromosomes ©Prentice Hall 2003 2 -80

Terminology of Genetics • Chromosomes: – Pairs of threadlike bodies within the cell nucleus that contain the genes • Deoxyribonucleic acid (DNA): – The main ingredient of chromosomes and genes that forms the code for all genetic information ©Prentice Hall 2003 2 -81

Two Types of Genes • Dominant: – Member of a gene pair that controls the appearance of a certain trait • Recessive: – Member of a gene pair that can control the appearance of a certain trait only if it is paired with another recessive gene ©Prentice Hall 2003 2 -82

Animal Behavior Genetics • Strain studies: – Studies of the heritability of behavioral traits using animals that have been inbred to produce strains that are genetically similar to one another. • Selection studies: – Studies that estimate the heritability of a trait by breeding animals with other animals that have the same trait. ©Prentice Hall 2003 2 -84

Human Behavior Genetics • Family studies: – Studies of heritability based on the assumption that if genes influence a certain trait, close relatives should be more similar on that trait than distant relatives. • Twin studies: – Studies of identical and fraternal twins to determine the relative influence of heredity and environment. ©Prentice Hall 2003 2 -85

Types of Twins • Identical: – Twins developed from a single fertilized ovum. • Fraternal: – Twins developed from two separate fertilized ova. ©Prentice Hall 2003 2 -86

Adoption Studies • Research carried out on children who were adopted at birth by parents not related to them. • The goal of this type of research is to determine the relative influence of heredity and environment on human behavior. ©Prentice Hall 2003 2 -87

Evolutionary Psychology • Evolutionary psychology analyzes human behavioral tendencies by examining their adaptive value from an evolutionary perspective. • It has proved useful in helping to explain some of the commonalities in human behavior that occur across cultures. ©Prentice Hall 2003 2 -89

Ethical Issues • Manipulating human genes in an effort to change how people develop is a new technology that makes many people uneasy. • These concerns may be exaggerated because genes are not all-powerful. • Heredity and environment play a part in shaping most significant human behaviors and traits. ©Prentice Hall 2003 2 -90