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Biological influences
Factors that affect thought, feelings and
behaviour
Psychology Unit 3
Factors that affect thought, feelings and
behaviour
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Genetics
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Heredity (nature) – involves the passing of
characteristics from biological parents to
offspring via genes at conception
Influences many characteristics such as blood
type, eye & hair colour, likelihood of developing
certain diseases …
Also influences the developmental rate of our
brain and nervous system, brain chemistry and
production of hormones
All of these factors influence our behaviour
Genetics terms
Heredity
 Biological characteristics passed on from parents to
offspring through DNA
Zygote
 Fertilised ovum: the result of the union of a sperm and
egg cell
Chromosomes
 46 chromosomes in the human body: the full
complement of DNA
Genes
 The basic hereditary unit of DNA
Genetic terms
Mitosis
 Cell division
 Results in the exact replication of a cell, the 2 daughter
cells each containing the same DNA
Meiosis
 The production of gametes ie. sperm and egg cells
 Each gamete contains 23 chromosomes, half the amount
in other cells.
 The process produces unique gametes through crossing
over and random variation
Hormones
Hormones are chemical messengers secreted by
endocrine glands.
 They travel through the bloodstream and affect other
organs (including brain)
 When they act on the brain they regulate, influence and
affect many different parts of the body, our emotions
and even our behaviour
Example: our interest in food, the female ovarian and
menstrual cycle, our moods, our growth rate, our
metabolism
 Hormones are slow-acting, compared to the nervous
system

Specific endocrine glands
Pituitary gland
 regulates many other glands in the body – the ‘master gland’
 produces growth hormone, involved in puberty
Adrenal glands
 produce adrenaline and noradrenaline – fight or flight
response
 results in increased heart rate, blood pressure and breathing
rate.
 also act as neurotransmitters
 also known as epinephrine and norepinephrine
Thyroid gland
 produces thyroxin
 regulates metabolism
Psychoactive drugs
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Drugs
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Psychoactive drugs are chemical
substances that affect the nervous
system and brain activity
They alter thoughts, feelings,
perceptions and behaviours
They generally target specific
neurotransmitters
They may be recreational or
prescription drugs
Neurotransmitters: a review
Classification of recreational drugs
Page 176 of textbook
Depressants
 ‘Downers’
 Calm the activity of the nervous system and slow body
functions
Stimulants
 ‘Uppers’
 Excite the nervous system and arouse body functions
Hallucinogens
 Change our perceptions and give us sensory images without
input from the senses
Classify these recreational drugs
Drug
alcohol
amphetamines
caffeine
cocaine
ecstasy
heroin
ice (methamphetamine)
LSD
marijuana
nicotine
Stimulant, depressant,
hallucinogen
Effect
Scenario: group work
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WA Health Dept. Records show that the numbers of
young people 14-17 years old taken to emergency
departments in the metro area after taking drugs
or alcohol has increased significantly fro 2008 to
2013. The number of 14 year olds has increase by
21%, the number of 15 year olds by 39%, 16 year
olds by 26% and 17 year olds be 21%
Questions: group work
1.
2.
What could be a possible hypothesis to explain the
observed increase in the number of young people
being taken to hospital emergency departments as a
result of their intake of drugs or alcohol?
Describe how each of the following drugs might affect
the person’s body chemistry and therefore change
their behaviour, in the short term as well as the long
term
 Marijuana
 Ecstacy
 Methamphetamine (ice)
Prescription drugs: Anti-depressants
Two main categories of anti-depressants:
 Increase the amount of norepinephrine
(noradrenaline) and serotonin released at the
synapse.
 Inhibit the enzyme that breaks down the
neurotransmitters or block the re-absorption of the
neurotransmitters into the pre-synaptic knob.
Prescription drugs: antipsychotics
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Work to damp down responses to irrelevant stimuli
that cause hallucinations, delusions and the
disordered thoughts of schizophrenics
Most attempt to block synaptic receptors in the
brain’s dopamine pathways