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Understanding Psychology6th Edition
Charles G. Morris and Albert A. Maisto
PowerPoint Presentation byH. Lynn Bradman
Metropolitan Community College
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Chapter 2
The Biological Basis of Behavior
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Neurons: The Messengers
• The brain of an average human being contains as many as 100 billion nerve cells or neurons.
• Neurons vary in size and shape, but they are all specialized to receive and transmit information.
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Neurons: The Messengers
• Neurons receive messages from other neurons through short fibers, called dendrites.
• A longer fiber, called an axon, carries outgoing messages from the cell.
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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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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
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Glial Cells
• The nervous system also contains a vast number of glial cells or glia.
• Glial cells hold neurons in place, provide nourishment, and remove waste products.
• Glial cells prevent harmful substances from passing from the bloodstream into the brain.
• Glial cells form the myelin sheath that insulates and protects neurons.
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The Neural Impulse
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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
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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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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.
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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
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The Synapse
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• 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.
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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
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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
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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.
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Drugs and Behavior
• Drugs and toxins block or enhance the action of neurotransmitters– Botulism– Curare– Chlorprozamine or clozapine – Caffeine– Cocaine
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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.
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Curare
• Used by South American native people to tip arrows.
• Stuns or kills prey• Blocks the Ach receptors.
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Chlorprozamine or Clozapine
• Trade name Thorazine• Prevents dopamine from binding to
receptor sites.• This reduction reduces schizophrenic
hallucinations.
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Caffeine
• Caffeine increases the release of excitatory neurotransmitters by blocking the transmitter (adenosine) that inhibits excitatory neurotransmitters.
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Cocaine
• Prevents dopamine from being reabsorbed
• Leads to excess amounts of accumulated dopamine
• Results in heightened arousal of the entire nervous system.
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Neural Plasticity and Neurogenesis
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Brain Growth and Experience
• Rosenzweig (1984) demonstrated the importance of experience to neural development.
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The Central Nervous System
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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.
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The Brain
• Physically, the brain has three more or less distinct areas: – The central core, – The limbic system, – The cerebrum.
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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
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Midbrain
• The relay point for hearing and vision.• One of the places pain is registered.• Brain structures found in midbrain:
– superior colliculus– inferior colliculus – substantia nigra
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Forebrain Structures
• Thalamus• Hypothalamus• Cerebral cortex
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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
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Structures in the Cerebral Cortex
• Frontal lobes• Parietal lobes
– Primary somatosensory cortex– Primary motor cortex
• Temporal lobes• Occipital lobes
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Frontal Lobes
• Voluntary movement• Attention• Goal-directed behavior
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Parietal Lobes
• Sensations of touch and bodily position• Primary somatosensory cortex:
– Registers and processes body sensations
• Primary motor cortex: – Controls voluntary muscle movement
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Temporal Lobe
• Processes information concerning hearing, smell, balance and equilibrium
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Occipital Lobes
• Processes information for the sense of vision.
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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.
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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.
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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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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.
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Left Hemisphere
• Right hand touch and movement• Speech• Language• Writing for right handers
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Right Hemisphere
• Left hand touch and movement• Spatial construction• Face recognition• Nonverbal imagery• Writing for left handers
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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)
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Tools for Studying the Nervous System
• Structural imaging: – Study the structures of the brain
• Functional imaging: – Study the functioning of the nervous system
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Structural Imaging Techniques
• Computerized Axial Tomography (CAT or CT) scanning
• Nuclear Magnetic Resonance Imaging (NMR or MRI)
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Computerized Axial Tomography
• An X-ray photography unit passes a radioactive ray through bone and brain tissue to show structures of the brain.
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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.
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Functional Imaging Techniques
• Electroencephalograph (EEG)• Magnetoencephalography (MEG) and• Magnetic Source Imaging (MSI)• Positron Emission Tomography (PET)
scanning
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MEG and MSI
• These imaging techniques measure the strength of the magnetic field produced by electrical activity in order to identify its source.
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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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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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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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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.
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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.
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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
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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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The Endocrine System
• Endocrine Glands: – Tissues that produce and release hormones
• Hormones: – Chemical substances released by glands
that help regulate bodily activities
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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
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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
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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)
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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
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Pancreas
• An organ lying between the stomach and small intestine.
• It secretes insulin and glucagon to regulate blood-sugar levels.
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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.
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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.
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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.
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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
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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
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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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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.
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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.
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Types of Twins
• Identical: – Twins developed from a single fertilized
ovum.
• Fraternal: – Twins developed from two separate
fertilized ova.
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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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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.
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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.