1. © Prentice Hall 2003 2-1 Chapter 3A-3C The Biological Basis of Behavior

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

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

4. © Prentice Hall 2003 2-4 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.

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7. © Prentice Hall 2003 2-7 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

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

9. © Prentice Hall 2003 2-9 The Neural Impulse

10. © Prentice Hall 2003 2-10 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

11. © Prentice Hall 2003 2-11 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

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13. © Prentice Hall 2003 2-13 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.

14. © Prentice Hall 2003 2-14 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

15. © Prentice Hall 2003 2-15 The Synapse

16. © Prentice Hall 2003 2-16 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.

17. © Prentice Hall 2003 2-17 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

18. © Prentice Hall 2003 2-18 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 GABA –Inhibitory neurotransmitter Glutamate –Excitatory neurotransmitter; role in memory

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20. © Prentice Hall 2003 2-20 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.

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

22. © Prentice Hall 2003 2-22 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.

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

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

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

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

27. © Prentice Hall 2003 2-27 Neural Plasticity and Neurogenesis

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

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30. © Prentice Hall 2003 2-30 The Central Nervous System

31. © Prentice Hall 2003 2-31 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.

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

33. © Prentice Hall 2003 2-33 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

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35. © Prentice Hall 2003 2-35 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.

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37. © Prentice Hall 2003 2-37 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.

38. © Prentice Hall 2003 2-38 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.

39. © Prentice Hall 2003 2-39 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

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

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

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

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

45. © Prentice Hall 2003 2-45 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

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

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

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

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

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

52. © Prentice Hall 2003 2-52 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.

53. © Prentice Hall 2003 2-53 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.

54. © Prentice Hall 2003 2-54 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

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56. © Prentice Hall 2003 2-56 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.

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

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

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61. © Prentice Hall 2003 2-61 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)

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

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

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

65. © Prentice Hall 2003 2-65 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.

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

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

68. © Prentice Hall 2003 2-68 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.

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

71. © Prentice Hall 2003 2-71 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

72. © Prentice Hall 2003 2-72 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

73. © Prentice Hall 2003 2-73 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)

74. © Prentice Hall 2003 2-74 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

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

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77. © Prentice Hall 2003 2-77 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.

78. © Prentice Hall 2003 2-78 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.

79. © Prentice Hall 2003 2-79 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.

80. © Prentice Hall 2003 2-80 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

81. © Prentice Hall 2003 2-81 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

82. © Prentice Hall 2003 2-82 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

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84. © Prentice Hall 2003 2-84 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.

85. © Prentice Hall 2003 2-85 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.

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

87. © Prentice Hall 2003 2-87 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.

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89. © Prentice Hall 2003 2-89 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.

90. © Prentice Hall 2003 2-90 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.