Download - Lecture2:Chapter 2 NEW Edited - Dr.Naif AlMutawa

Use with Atkinson & Hilgard’s Introduction to Psychology 15th editionNolen-Hoeksema, Fredrickson, Loftus, Wagenaar ISBN 9781844807284 © 2009 Cengage Learning

Chapter 2

Biological Foundations of Psychology


The Study of the Biological Bases of Psychology

• Pre-adaptation– Describes the process by which an existing system (e.g.

physical disgust/physical pain) is co-opted (“hi-jacked”) in order for new human functions to develop (e.g. moral disgust/response to social exclusion)

• Nervous system– Divided into Central Nervous System (CNS) and

Peripheral Nervous System (PNS)– CNS includes the brain and spinal chord– PNS includes the somatic system and autonomic system


Neurons, the Building Blocks of the Nervous System

• Basic unit of the nervous system = Neuron– Specialized cell that transmits neural impulses or

messages to other neurons, glands and muscles

Figure 2.2 Schematic Diagram of a Neuron. Arrows indicate the direction of the nerve impulse. Some axons are branched; the branches are called collaterals. The axons of many neurons are covered with an insulating myelin sheath that helps increase the speed of the nerve impulse. (Adapted from Human Anatomy by Anthony J. Gaudin and Kenneth C. Jones. Copyright © 1988 by Anthony J. Gaudin and Kenneth C. Jones. Reprinted by permission of the authors.)



• Neurons vary greatly in size and shape• Neurons are classified into three categories

– Sensory neurons – transmit impulses from receptors to CNS

– Motor neurons – carry outgoing signals from CNS to muscles and glands

– Inter-neurons – connect sensory and motor neurons



• Action Potentials– Information travels along neuron in form of neural

impulse called an action potential– Each action potential is the result of movement of

electrically charged particles (ions) in and out of neuron

– Movement of ions controlled by ion channels - when these are closed the neuron is referred to as “resting”

– When a neuron is depolarized above the excitation threshold cell membrane is temporarily unstable, resulting in action potential



• Synaptic transmission and neural coding– All-or-none law – a neuron is either firing action

potential, or not, so how can the nervous system code for/represent complexity of experience?

– Power of nervous system lies in the complexity of the connections between neurons

– Lock-and-key action – the way a neurotransmitter and receptor fit together, which causes a change in permeability of ion channels, either excitatory or inhibitory



• Neurotransmitters– More than 70 identified– Acetylcholine – involved in memory and attention and

transmits signals between nerve and muscle. Prevalent in hippocampus. What problems result?

– Norepinephrine – an increase/decrease in brain correlates with increase or decrease in mood level. Reuptake blocked by cocaine/amphetamines, Lithium speeds it up.

– Dopamine – mediates effects of natural rewards (e.g. food) and effects of drugs of abuse (Schizophrenia)



• ...Neurotransmitters– Serotonin – important role in mood regulation (SSRI).

Also important in sleep and appetite and used for ED.– Glutamate – excitatory in nature – linked with learning

and memory. What area of brain is it mostly found in?– GABA – inhibitory in nature – helps control muscle

movement. Anti anxiety drugs enhance GABA.


The Organization of the Brain



• The hindbrain– Medulla

• Controls breathing & some reflexes which aid upright posture

– Pons• Important in the control of attentiveness/timing of sleep

– Reticular formation• Network of neurons that extend from lower brainstem up to the

thalamus in the forebrain and across other parts, controls arousal, also plays role in ability to focus attention.

– Cerebellum• concerned primarily with control of movement & important for

learning new motor responses



• The midbrain– Superior and inferior colliculus

• Important for transmitting sensory information to brain & in movement control (including eye movement)

– Substantia nigra• Key part of dopamine-containing pathway – deteriorates in

Parkinson’s disease



• The forebrain– Includes cerebrum (split into two hemispheres) and sub-

cortical structures– Thalamus

• Directs incoming information from sense receptors to cerebrum

– Hypothalamus • Regulates eating, drinking & sexual behavior. Exerts control over

ANS & also role in sensation of emotions. Important in homeostatsis.

– Pituitary gland• Part of system of glands called endocrine system involved in

production of hormones



• ...The forebrain– Limbic system

• Provides additional control over some instinctive behaviors regulated by central core

• Hippocampus – special role in recent memory• Amygdala – involved in emotional behavior, e.g. fear

– Cerebral cortex • Receives information from sensory systems; controls motor

responses and contains association areas which are concerned with memory, thought and language



• Mapping the brain– Recent development of sophisticated computer

methods allow detailed images of human brain without damaging or distressing patient

• Methods include computerized axial tomography (CAT or CT), magnetic resonance imaging (MRI), and positron emission tomography (PET)



• Asymmetries in the brain– Language

• Understanding about brain mechanisms for language largely derived from studies of patients with brain damage.

• Aphasia – language deficit caused by brain damage• Broca’s area – involved in speech production• Wernicke’s area – involved in speech comprehension

– Split-brain research • The brain normally acts as integrated whole but for some

epilepsy patients, the corpus callosum surgically severed - these split-brain patients provide important insights into brain function



• ...Asymmetries in the brain– Hemispheric specialization – split-brain research

indicates two hemispheres function differently• Left hemisphere – controls ability to express self through

language and skilled in mathematical abilities• Right hemisphere – comprehends only simple language but

highly developed in spatial and pattern sense• Specialization does not mean two hemispheres work

independently but rather they continually integrate activities


The Autonomic Nervous System

• Autonomic system– System of nerves outside of the brain & spinal chord that

controls the glands and smooth muscles including the heart, blood vessels and stomach lining.

• Autonomic nervous system (ANS)– Activities it controls are autonomous or self-regulating

(e.g. digestion & circulation) – ANS has two divisions – sympathetic & parasympathetic– Sympathetic nervous system – active during excitement– Parasympathetic nervous system – associated with rest


The Endocrine System

• Endocrine system– System of glands which secrete hormones to be

transported through the bloodstream to act in various ways on cells of different types

– The Nervous system controls fast changing activities of the body by directly activating muscles and glands.

– The endocrine system act more slowly indirectly affecting the activities of cell groups in the body by secreting hormones.

– Pituitary gland “master gland” which controls secretion activity of other endocrine glands


The Endocrine System

• Hormones are secreted by endocrine glands into the bloodstream and transported to other parts of the body where they have specific effects.

• Hormones act in various ways on various cells.• Each cell has receptors particular to specific hormones.• Receptors pull those molecules out of the bloodstream

and into the cell. • One of the major endocrine glands is the pituitary gland

that is partly an outgrowth of the brain and lies just belw the hypothalamus.


Evolution, Genes and Behavior

• Evolution of behavior– Natural selection – process described by Charles

Darwin whereby variations on inheritable traits which aid survival are passed on to future generations

– Examination of behavior needs to include ultimate causes of behavior (why behavior evolved through natural selection) and proximate causes (how behavior generated)



• Chromosomes and genes– Genes – segments of deoxyribonucleic acid (DNA)

molecules that form fundamental hereditary unit– Chromosomes – structures which carry genes in the

nucleus of each cell in the body– Chromosomes and genes both exist in pairs– Dominant & recessive genes – each gene in pair can be

dominant or recessive.• Both dominant = dominant gene specifies form of trait developed• One dominant, one recessive = dominant gene determines trait• Both recessive = recessive gene determines trait



...Chromosomes and genes

Sex-linked genes- Normal female has two X chromosomes in pair 23- Normal male has one X and one Y chromosome in pair 23- Men express more recessive traits because gene carried on one of chromosomes in pair 23 will not be countered by dominant gene on other- Genetically determined characteristics linked to twenty-third chromosome pair called sex-linked traits



• Genetic studies of behavior– Some traits determined by single gene but most

characteristics determined by many genes - polygenic– Selective breeding

• Method for studying inheritance of particular traits by mating animals high or low in particular behavioral/physical trait

• Been used to demonstrate inheritance of number of behavioral characteristics

• If selective breeding does not alter a trait then assume that trait is linked primarily to environmental factors



• ...Genetic studies of behavior– Twin studies

• Method used to study relative influences of genetics and environment in behavior

• Identical twins – monozygotic because develop from single fertilised egg therefore share exactly same genes

• Fraternal twins – dizygotic as develop from two fertilised eggs therefore same genetic similarity as other siblings

• Studies indicate some characteristics more similar between identical twins (e.g. intelligence)

• Studies of adopted children indicate genetic influence may become stronger with age



• ...Genetic studies of behavior– Molecular genetics of behavior

• Some researchers suggest certain human traits influenced by specific genes, which are thought to affect particular neurotransmitter receptors

• Such analyses can be misleading and should be treated with caution – further research needed



• ...Genetic studies of behavior– Environmental influences on gene action

• An individual’s inherited potential at birth heavily influenced by environment infant encounters (e.g. diabetes – genetic disposition but obesity important variable)

• Genetics may set limits on individual’s potential, but what happens to that potential depends on the environment in which an individual grows up

Download - Lecture2:Chapter 2 NEW Edited - Dr.Naif AlMutawa

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