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Chapter 3

PSYCH101 Chapter Notes - Chapter 3: Cerebral Hemisphere, Basal Ganglia, Acetylcholine

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Neuropsychology Textbook
3. 1 Genetic and Evolutionary Perspectives on Behaviour
The Genetic Code
Genes: guiding process of creating proteins that make up physical structures and regulate
development and physiological processes throughout lifespan
Homozygous: 2 corresponding genes at same location on a pair of chromosomes are the
Heterozygous: 2 different genes at same location on a pair of chromosomes
Dominant vs recessive
DNA: molecule in double-helix shape with 4 nucleotides: adenine, cytosine, guanine, thymine
Genotype: genetic makeup of an organism
Phenotype: physical traits or behavioural characteristics that show genetic variation
Behavioural Genomics: how specific genes are related to behaviour
Typically, combinations of genes influence behaviour
One gene often affects multiple traits
Behavioural Genetics: study of how genes and environment influence behaviour
Monozygotic twins - come from single egg, genetically identical
Dizygotic twins - two separate eggs fertilized by two different sperm cells, 50% in
Heritability: statistic (0-1.0) for degree to which genetic differences between individuals
contribute to individual differences in the behaviour or trait found in a population
Genetic variability
Variability in environment
Epigenetics: changes in gene expression from experience that do not alter genetic code
Diathesis-stress model: correlation between genetic predisposition and life stress
Changes in gene expression do not alter genetic code but can still be hereditary
Natural Selection: favourable traits become increasingly common among individuals of an
interbreeding population
Evolution: change in frequency of genes in interbreeding population over generations
Evolutionary Psychology: attempts to explain human behaviour based on the beneficial
functions in species’ development
Homo habilis (stone tools), homo erectus (fire, upright), homo sapiens
Human brain more powerful than other animals’:
Cerebral cortex has fold and grooves
Large frontal lobes for processing power such as problem solving
Neotony - brain can still develop in size after birth
Hunters vs gathers:
Males perform better in spatial sense (not getting lost while travelling)
Females perform better in spatial location task (remembering where specific
things are)
Intrasexual selection: members of the same sex compete to mate with opposite sex
Intersexual selection: members of opposite sex select mates based on desirable characteristics

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Neuropsychology Textbook
3.2 How the Nervous System Works: Cells and Neurotransmitters
Neural Communication
Neuron: cells in NS for sending and receiving messages throughout body
Cell body: genetic materials, genes synthesize proteins that allow functioning
Dendrites: branches radiating from cell body to transmit messages from other cells
How many (structure) reflects function
Axon Hillock: creates chemical reaction if receives enough stimulation from other
Axon: transports information in the form of electrochemical reactions from the cell
body to the end of the neuron
Neurotransmitters: located in axon terminals, chemicals allowing communication
between neurons
Impulse travelling down axon releases neurotransmitters
Sensory Neurons: receive information to bring to brain
Motor Neurons: carry messages from brain and spinal cord towards muscles
Interneurons: links the above two types of neurons
Neurogenesis: formation of new neurons throughout lifetime from stem cells in some brain
Glial cells: NS cells for mounting immune responses, removing waste, synchronizing activity of
neurons (10:1)
Myelin - fatty sheath insulating individual axons for increased speed and efficiency in
Protects impulse from decay
Multiple Sclerosis - immune system attacks myelin, impairs ability to transmit
information along axons

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Neuropsychology Textbook
Resting and Action potentials in electrical system - neural activities based on changes in
concentrations of ions
Resting Potential - cell inside axon at -70mV, not transmitting messages
Cl- inside, Na+ and K+ outside
Electrostatic gradient: different charges outside and inside cell
Concentration gradient: different concentrations of ions outside and inside cell
Action potential: wave of electrical activity from base of axon and travels down length
Hyperpolarized: when neuron returns into its resting state, sodium ions are pumped out
of cell, making it more negative than resting potential; less likely to fire
Refractory period: neuron cannot fire (2-3
Synapses: small space between nerve cells
All-or-none principle: nerve cells fire at same strength
every time action potential occurs; rate determines
number of cells fired repeatedly for greater stimulus
Presynaptic neuron releases neurotransmitters into a synapse;
then will bind onto postsynaptic neuron which can have one of
two effects:
Excitatory (less negative): increased the probability
that an action potential will occur in a given period of
Inhibitory (more negative): decreased likelihood that
action potential will occur
Excited or inhibited depending on the type of neurotransmitter
Synaptic cleft: the minute space between the axon terminal (terminal button) and the
If a neurotransmitter remained latched onto a receptor for long periods of time, it would
decrease the number of times that the neurons could fire (making brain less powerful)
Neurotransmitters are broken down by enzymes or go through reuptake: a process whereby
neurotransmitter molecules that have been released into the synapse are reabsorbed into the
axon terminals of the presynaptic neuron
Reuptake serves as a sort of natural recycling system for neurotransmitters
Often modified by drugs (e.g. SSRIs)
Types of neurotransmitters
Different neurotransmitters have different effects on our behaviour
Glutamate: most common excitatory neurotransmitter in brains of vertebrates
Helps with ability to form new memories
Abnormal functioning: seizures & epilepsy
GABA (gamma-amino butyric acid): primary inhibitory neurotransmitter of the nervous system,
meaning that it prevents neurons from generating action potentials
Reduces negative charge of neighbouring neurons
Facilitates sleep and reduces arousal of nervous system
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