Psychology second chapter

8/7/2019 Psychology second chapter

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Psychology: An IntroductionCharles A. Morris & Albert A. Maisto

2005 Prentice Hall

The Biological Basis of

Behavior

Chapter 2


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2005 Prentice Hall

Neurons: The Messengers

About 100 billion neurons (nerve cells) inthe human brain

Neurons have many of the same featuresas other cells

Nucleus

Cytoplasm

Cell membrane What makes neurons unique is their shape

and function


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Structure of Neurons

Dendrites

Carry information to the cell

body from other neurons

Cell Body (Soma) Contains nucleus

Axon

Carries information to the

next cell

Myelin Sheath Insulates the axon and

speeds up the neural

impulse


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Types of Neurons

Sensory neurons

Carry information from sensory systems to the brain

Also referred to as afferent

Motor neurons

Carry information from the brain to muscles and

glands

Also referred to as efferent

Interneurons

Carry information between other neurons


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Glial Cells

Cells that insulate and support neurons

Create the myelin sheath

Remove waste products Provide nourishment

Prevent harmful substances from entering

the brain


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The Neural Impulse


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The Neural Impulse

Ions

Charged molecules

Resting Potential

When more negative

ions are inside the

neuron than outside

Charge is

approximately -70mV

Neuron is not

transmitting

information


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The Neural Impulse

Polarization

When the electrical charge of a cell moves

away from zero

Depolarization

When the electrical charge of a cell moves

toward zero


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The Neural Impulse

Action Potential

Sudden, massive

change in charge in

the neuron Occurs when

depolarization reaches

the threshold of

excitation

Ions flow across cell

membrane


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The Neural Impulse

Graded Potentials

Subthreshold depolarization

Many subthreshold depolarizations are addedtogether to produce an action potential (a

process known as summation)


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The Neural Impulse

All-or-None Law

A neuron either fires or it does not

When it does fire, it will always produce animpulse of the same strength

Intensity of a stimulus is coded by the

frequency of action potentials


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The Neural Impulse

Absolute refractory period

Period immediately after an

action potential when

another action potential

cannot occur

Relative refractory period

Period following absolute

refractory period when a

neuron will only respond to

a stronger than normalimpulse


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The Synapse

Synaptic space (synaptic cleft)

Tiny gap between neurons

Terminal button Enlarged area at the end of an axon

The synapse

Composed of the terminal button of oneneuron, the synaptic space, and the dendrites

or cell body of the receiving neuron


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Transmission Between Neurons

Synaptic vesicles Sacs in terminal button

that release chemicalsinto synaptic space

Neurotransmitters Chemicals released by

synaptic vesicles

Receptor sites Location on receptor

neuron for specificneurotransmitter


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Some Well-Known

Neurotransmitters Acetylcholine (ACh)

Released at the neuromuscular junction

Plays an important role in arousal and attention

Loss of ACh producing cells is linked to AlzheimersDisease

Dopamine

Affects neurons associated with voluntary movement

Plays a role in learning, memory, and emotions

Loss of dopamine-producing cells causes symptoms

of Parkinsons Disease


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Some Well-Known

Neurotransmitters Serotonin

Found throughout the brain

Appears to sets an emotional tone Low serotonin levels are implicated in

depression

Endorphins

Reduce pain by inhibiting or turning down

neurons that transmit pain information


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Psychopharmacology

Most psychoactive drugs (and toxins) work

by blocking or enhancing synaptic

transmission

Botulism

Blocks release of ACh at the neuromuscular

junction, causing paralysis

Botox is botulism toxin used to prevent facial

muscles from making wrinkles


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Psychopharmacology

Curare

Can stun or kill prey quickly

Blocks ACh receptors causing paralysis

Antipsychotic medications

Block dopamine receptors

Reduces schizophrenic hallucinations

Caffeine Increases the release of excitatory neurotransmitters

by blocking the inhibitory neurotransmitteradenosine


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Psychopharmacology

Cocaine

Prevents reabsorption of dopamine

Leads to heightened arousal of entire nervoussystem


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Neural Plasticity

The brain can be changed, both

structurally and chemically, by experience

Rat studies show that an enrichedenvironment leads to larger neurons with

more connections

Has also been shown in humans

Recent research has uncovered evidence

of neurogenesis, or the production of new

brain cells, in human brains


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Nervous System Organization

Central nervoussystem (CNS) Consists of the brain

and spinal cord Peripheral nervous

system Connects the CNS to

the rest of the body Somatic nervous

system

Autonomic nervoussystem


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Central Nervous System

Central Nervous System

Brain Spinal Cord


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The Brain The Central Core

Medulla

Controls breathing,

heart rate, and blood

pressure Pons

Maintains the sleep-

wake cycle

Cerebellum Coordinates bodys

movements


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Thalamus

Relays information from

sensory receptors to the

brain

Hypothalamus

Influences motivated

behavior

Regulates hunger, thirst,

body temperature, and

sexual drive.

Directly involved in

emotional behavior


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Reticular formation

Network of neurons found throughout the

brain

Serves to alert and arouse higher brain in

response to incoming information


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The Brain The Limbic System

Ring of structures located

between the central core

and the cerebral

hemispheres

Important to learning and

emotional behavior

Hippocampus essential in

formation of new memories

Amygdala, together withthe hippocampus, is

important for regulating

emotions


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The Cerebral Cortex

Occipital lobe

Receives and processes

visual information

Temporal lobe

Complex visual tasks such

as face recognition

Receives and processed

auditory information

Involved in balance, some

emotions and motivations

Some language processing


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The Cerebral Cortex

Parietal lobe

Receives sensory

information from body

Involved in spatial abilities

Frontal lobe

Coordinated information

from other lobes

Controls voluntary

movement, attention,

setting goals, and

expression of appropriate

emotions


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Hemispheric Specialization

Corpus Callosum

Fibers that connect the

two hemispheres

Allow closecommunication

between left and right

hemishphere

Each hemisphereappears to specialize

in certain functions


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Split-Brain Research

Much information about functions of each

hemisphere has come from studying split-

brain patients


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Tools for Studying the

Nervous System


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Microelectrode Techniques

Very small electrodes inserted into

individual neurons

Used to study activity of a single neuron


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Structural Imaging

Computerized Axial Tomography (CT-

scan)

Uses X-rays to create a 3-dimensional image

of the brain

Magnetic Resonance Imaging (MRI)

Uses a magnetic field and radio waves to

produce images


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Functional Imaging

EEG imaging

electrical activity on the scalp from millions of

neurons is used to produce a continuous

picture of activity in the brain

Magentoencephalography (MEG) and

Magnetic source imaging (MSI)

Can localize activity more precisely than EEG


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Functional Imaging

Positron Emission Tomography (PET) and

Single Photon Emission Computed

Tomography (SPECT)

Use radioactive glucose to determine location

of greatest brain activity

Functional Magnetic Resonance Imaging

(fMRI) Shows function and structure by measuring

movement of blood molecules within the brain


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The Spinal Cord


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The Spinal Cord

Complex cable of nerves that connects

brain to rest of the body

Carries motor impulses from the brain tointernal organs and muscles

Carries sensory information from

extremities and internal organs to the brain


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The Spinal Cord

The spinal cord controls some protective

reflex movements without any input from

the brain


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The Peripheral Nervous System

Peripheral Nervous System

Somatic Nervous System Autonomic Nervous System

Sympathetic Division Parasympathetic Division


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The Somatic Nervous System

Consists of neurons that communicate

between the body and the brain

Afferent neurons Neurons that carry messages from sense

organs to spinal cord

Efferent neurons

Neurons that carry messages from the spinal

cord or brain to muscles and glands


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Psychology: An Introduction

Charles A. Morris & Albert A. Maisto 2005 Prentice Hall

The Autonomic Nervous System

Sympathetic division

Most active when you

are angry, afraid, or

aroused Fight-or-flight

response

Increases heart rate

and breathing

Stops digestion


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The Autonomic Nervous System

Parasympathetic

division

Calms body

Produces effectsopposite to those of

the sympathetic

division

Reduces heart rateand breathing

Restores digestion


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The Endocrine System


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Helps coordinate and integrate complex

psychological reactions

Endocrine glands secrete hormones intothe bloodstream

Hormones serve to organize the nervous

system and body

Hormones also activate behavior, such as

sexual behavior


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Thyroid gland Secretes hormones

(primarily thyroxin) thatcontrol metabolism

Parathyroid glands Control levels of

calcium andphosphate which in

turn controls levels ofexcitability


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Pineal gland Secretes melatonin

which regulates thesleep-wake cycle

Pancreas Regulates blood-sugar

levels

Secretes insulin and

glucagon


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Pituitary gland

Referred to as the

master gland

because it regulatesmany other glands

Gonads

Ovaries and testes

secrete estrogens andandrogens

Adrenal glands

Secretes hormones in

reaction to stress


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Genes, Evolution, and

Behavior


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Genetics

Heredity - transmission of trait from one

generation to next

Chromosomes Pairs of thread like bodies that contain genes

Deoxyribonucleic acid (DNA)

Organic molecule arranged in a double-helix

Contains the code of life


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Behavior Genetics

Study of behavior from a genetic

perspective

Animal behavior genetic studies include: Strain studies

Selection studies


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Human Behavior Genetics

Family studies

Assume that close family members share

more of a trait than non-relatives

Used to assess the heritability of

psychological disorders or traits

Twin studies

Used to determine how heritable a trait ordisorder may be

Identical twins would have highest heritability


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Human Behavior Genetics

Adoption studies

Used to assess the influence of environment

Molecular genetics Direct study of the genetic code


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Evolutionary Psychology

Natural selection

Survival of the fittest

Evolutionary psychology looks at theadaptive or survival value of behaviors


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Charles A Morris & Albert A Maisto

Social Implications

Study of biological origins of behavior

could lead to genocide and eugenics

aimed at eliminating certain types of

people

Could also be used to create new

categories of people, such as people bred

to be good soldiers or manual laborers

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Psychology second chapter