The Biological Approach Notes

The biological approach

Define the biological approach

A person’s thoughts feelings and actions are determined by….

• His/her genetic inheritance; we all inherit genes from our parents and these genes determine key features regarding not only appearance and health status but also psychological variables such as intelligence, aggression and ability to relate to others and many human behaviours such as attachment, communication and our ability to remember and learn.

• Hormones and neurotransmitters, which are chemical messengers which tell our body how to react

• The central nervous system, including neuroanatomy and neuronal organisation, nowadays it is understood that our environment/ experiences affect how our brains work and concepts such as neuroplasticity and epigenetics are exiting areas to explore

Terminology

Central nervous system (CNS)

• The central nervous system comprises the spinal cord and the brain.

• The brain is made of nerve cells called neurons

• At the end of the neurons, structures called receptors receive chemical signals (via neurotransmitters)from other neurons

Synapse

• Gap between the axon of one neuron and the dendrite of the next neuron.

Receptor

• A molecular structure or site on the surface or interior of a cell that binds with substances such as hormones, antigens, drugs, or neurotransmitters

Neurone

• A specialized, impulse-conducting cell that is the functional unit of the nervous system, consisting of the cell body and its processes, the axon and dendrites.

Neurotransmitter

• Chemicals produced by neurons that pass on nerve signals across a synapse between two neurons

• Examples: dopamine, serotonin, adrenalin

Genes

• Contains a set of instructions and is a carrier of information

• Each individual has a genotype, which is genetic constitution.

• Each person also has a phenotype, which is what the individual becomes when their genes interact with each other and with the environment

• Genes are inherited, 50% from each biological parent

• Consists of a long strand of DN; a chromosome is another chain of DNA, one of the functions of DNA is to control gene activity

Hormones

• Chemical produced by the endocrine system and released in the bloodstream. Hormones are transported to targets organs which they affect in different ways.

• Examples: testosterone produced by the testis affects the growth of facial hair for example Oestrogen produced by the ovaries affects the growth of breasts

Brain lateralisation

• The brain is organised in highly specialised areas which are located on various sides of the brain. Brain lateralisation is the difference between the right and the left hemisphere of the brain

Content

Briefly describe the role of the central nervous system and neurotransmitters in human behaviour

• The nervous system has 2 main parts, the CNS and PNS

• The CNS consists of the brain and the spinal cord and there are then further subdivisions

• Other parts of the brain include:

  • The thalamus- near the base; passes information on from the senses

  • The cerebellum- stores well learned practical skills

  • The cortex- the most recent development of the brain for humans, which stores information and is involved in problem solving and decision making

Neurotransmitters

• Neurotransmitters are chemical messengers (e.g. dopamine and noradrenaline) that act between neurones in the brain

• This allows the brain to process thoughts and memories

• The nervous system consists of neurones and glia

• Glial cells carry out repairs, act as insulators and remove waste products from the brain; research is still going on into the role of glia

• Neurones are cells that receive and transmit messages, passing them from cell to cell

• At one end, a neurone has dendrites, which are finger-like structures surrounding the nucleus

• From the nucleus there is a long extension called an axon, which reaches to an axon terminal

• The axon terminal of one neurone reaches to the dendrites of another neurone

• Between the terminal and the dendrites there is a gap called the synapse

• The synaptic cleft sits between two neurones

• On one side, at the dendrites, there are receptors of a certain shape prepared to receive the neurotransmitter from the other neurone

• If the neurotransmitter fits it will trigger and electrical impulse in the cell body, which then travels down the neurones axon so the message continues, if not, the message is blocked

• Manufactured drugs work in this way, they mimic natural neurotransmitters, more or less fit certain receptors, and are received like neurotransmitters and the message from them ‘works’. Some drugs block the message.

• They fit the receptor, so the natural neurotransmitters cannot pass the message on because the receptor is not available (competitive inhibition)

Describe the role of genes in behaviour (including the nature/nurture debate).

Examples of the effects of genes on humans

• Human chromosome 4 has a marker known as G8. It is not yet known what G8 contributes, but the gene for Huntington’s disease lies close to it. If a parent and child both have Huntington’s disease, then in 98% of cases they both have the same G8 marker. This suggest the gene for Huntington’s disease travels with the G8 marker

• Some diseases and characteristics are sex linked in that they are controlled by the sex genes. This is why some diseases/ characteristics are more common in one particular sex e.g. colour blindness is most common in men

• if one parent contributes two copies of chromosome 21, then...

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