Arousal and anxiety states both influence significantly our behaviour. Arousal, which is the state of ‘general physiological and psychological activation and alertness’ (Hill, 2001, pg256) is increased with greater activity of the sympathetic ANS, the function of which is to prepare the body for action and causes greater attention and mental processing activity. When this is experienced as a negative emotional state then it becomes anxiety.
‘Many of the bodily reactions which result from the ANS are produced by its effect on the endocrine glands.’ (Gross, 1999, pg64). ‘The ANS exerts its effects by direct neural stimulation of body organs and by stimulating the endocrine glands to secrete hormones.’ (Class handout, Satar, 2002). The major endocrine glands are as follows: pituitary gland situated in the brain, the thyroid gland, the parathyroid gland, the adrenal glands, the pancreas, the gonads (ovaries in women and testes in men). These glands are ductless and secrete hormones directly into the bloodstream and have an effect on behaviour because hormones are chemical messengers that affect our physical state. The endocrine system is regulated by the hypothalamus, which exerts its effect on the pituitary gland. Hormones released by the pituitary gland control the secretion of the other endocrine glands.
Biological systems can effect human behaviour, which can be shown through the effects of the intake of drugs. ‘Drugs influence behaviour through their effect on neurotransmitters. The molecules of many commonly used psychoactive drugs are of a very similar shape to those of neurotransmitters and operate in a similar way.’ (Gross, 1999, pg68).
First it is necessary to define the term drugs. ‘Drugs are chemicals which have a biological effect on the body’s tissues.’ (Ridings, 2002, pg13). Drugs can have two effects on the biological system; they are either depressants or stimulants. Here we will look at the effect of depressants, in particular alcohol. Depressants are the drugs that depress the CNS; i.e. they slow down mental processes and behaviour. These include tranquilizers, barbiturates, inhalants and alcohol.
Alcohol causes effects on the brain and behaviour and in low doses it can act as a stimulant. The effects of this are that people become more talkative, more outgoing, and less inhibited. Weiss, Lorang, Bloom and Koob (1993) have found that dopamine levels may be involved in the stimulant effects of low doses of alcohol.
However, in higher doses alcohol acts as a depressant, impairing sensory and motor functions. Visual activity, sensitivity to taste and smell are all reduced, reflexes become slower reducing reaction time, speech and movement become ‘sluggish’. Memory processes are also affected. ‘Attention to stimuli, ability to encode new information, and short term memory are all decreased.’ . (Rosenhan & Seligman, 1995, pg526).
Chin and Goldstein (1977) identified one of the main effects of alcohol is a ‘non-specific interaction with neuronal membranes’. The physical state of the membrane lipids is made more fluid through the alcohol dissolving in the membrane. This in turn leads to a reduction in neuronal activity and is what causes the debilitating effects on the sensory and motor functions.
Alcohol also affects the neurotransmitter systems, particularly norepinephrine, dopamine and seratonin. (biogenic amines) and gamma-aminobutyric acid (GABA), which are related to altering mood and anxiety reduction. ‘Alcohol enhances the inhibitory actions of GABA, which is the most important inhibitory transmitter in the brain.’ (Nestoros, 1980; Suzdak, Schwartz, Akolnick, and Paul, 1986; cited by Rosenhan & Seligman, 1995, pg526).
‘Alcohol acts at the same GABA receptor complex as the benzodiazepine anti-anxiety drugs (Librium, Valium, etc.) and it is believed that this action is responsible for the anxiety-relieving properties of alcohol (Lister and Durcan, 1989; Koob, Mendelson, Schafer, Wall, Britton and Bloom, 1989; cited by (Rosenhan & Seligman, 1995, pg526).
Alcohol is a widely used, socially acceptable drug in the majority of western cultures, yet it is rarely seen as a drug that so powerfully impacts our biological systems causing the widely recognised changes in our behaviour.
Electrical and neuro-chemical activity in the brain is also related to behaviour. Neurones are the cells that process and transmit information and when one fires it sends its electrical impulse which in turn causes chemical changes to take place in the cell, mainly involving sodium and potassium. One neurone can be connected to thousands of other neurones. ‘Each neurone has a threshold of response-the amount of stimulation it needs to receive from other neurones to ‘fire’ its own electrochemical message.’ (Hill, 2001, pg257).
This electrochemical message is transmitted by neurotransmitters (chemicals). Dendrites receive electrochemical impulses from other neurones and the axon ‘transmits electrochemical impulses away from the cell body towards other neurones.’ (Hill, 2001, pg257). The neurotransmitters pass across the synaptic gap and travel to specialised receptor sites on the post-synaptic membrane. Once here the chemicals trigger off an electric impulse, which has an excitatory effect on the next neurone. However, some synaptic connections have an inhibitory effect whereby ‘the neurotransmitters taken up by the target neurone will prevent it from firing.’ (Gregory, 2000). This makes it possible to control a nerve response.’
Some neurones form synapses with glands and muscles. If a motor neurone forms a synapse with muscle fibres it causes those fibres to contract briefly when an axon transmits a message. ‘The strength of the muscular contraction depends on the number of motor neurones whose action potentials are causing the release of neurotransmitters. Whether muscle contraction, or glandular activity is initiated or inhibited or not depends on which neurotransmitters are released.’ (Ridings, 2002, pg4)
An example of how this system affects our actions is when we touch a hot object When we touch a hot object there is an increase in the activity of excitatory neurotransmitters. These neurotransmitters communicate with the motor neurones that control the muscles of the hands causing a reflex reaction.
‘Large numbers of neurotransmitters each have their own excitatory or inhibitory effect on certain neurones and are localized in specific groups of neurones and pathways. Normally a single neuron can be labelled by the transmitter it uses: cholinergic, noradrenergic, dopaminergic and serotenergic neurons use acetlycholine (ACh), noradrenaline, dopamine and serotonin respectively,’ (Gross, 1999, pg67).
Looking at one of these neurotransmitters more closely it is possible to realise the implications of the effects these neurotransmitters. For example ‘ACh is particularly prevalent in an area of the forebrain called the hippocampus, which plays a key role in the formation of new memories (Squire, 1987).’ (Atkinson et al, 1996, pg42). With Alzheimer’s disease it has been shown that the neurones producing ACh tend to degenerate, reducing the production of ACh and therefore causing memory loss. ACh is also released at every synapse where a neurone terminates at a skeletal muscle fibre, affecting muscle contraction. This has meant the certain drugs that affect ACh can produce muscle paralysis.
It is possible to study the brain’s electrical and neuro-chemical activity through non-invasive techniques. Examples of these methods available are:
- Electro-encephalograms (EEG)
- Computerized axial tomography (CAT)
- Positron emission tomography (PET)
- Magnetic resonance imaging (MRI)
‘These techniques provide access to processes associated with mental activity, inside the healthy living brain as they happen.' (Gross, 1999, pg68)
EEGs are used to measure electrical activity in the brain by attaching electrodes to the scalp. 'The electrodes record any changes in the electrical field which are produced by the electrical activity of brain cells.' (Hayes, 1994, pg361). A polygraph is then used to receive the information from the electrodes and records the data via a series of pens onto a roll of paper. The disadvantage of using this method is that only a general view of what activity is taking place can be monitored. However, for detecting problems such as epilepsy or brain seizures, this method is effective.
The CAT scanner uses a computer and x-rays of horizontal sections of the brain to build up a three-dimensional x-ray picture. The resulting picture can help identify areas of damaged tissue.
This method has been made more efficient with the PET scanner ‘which uses the same computer-calculation approach as CAT but uses radiation for the information from which the brain slices are computed.’ (Gross, 1999, pg54). Radioactive glucose (tiny and harmless doses) is injected into the bloodstream where it is taken up by neurones in the brain. The radioactivity emitted by the glucose is then picked up be detectors. The more active parts of the brain take up more glucose and therefore emit more radioactivity which means that areas involving specific functions can be identified, for example problem solving. This method can also be used with radioactive chemicals. These chemicals ‘combine with synaptic receptors; measuring receptor activity can tell something about neurotransmitter function in the brain. An example would be studies of changes in dopamine and serotonin receptor numbers in schizophrenia.’ (Cardwell et al, 2000, pg297).
MRI scanning involves placing the head in a powerful magnetic field where successions of electro-magnetic waves are passed through the brain. The neurones in the brain then produce electo-magnetic waves themselves, which are recorded by computer as a three-dimensional picture. The advantage of this procedure over the CAT scan is that not only is the level detail better, but the patient is not exposed to x-rays.
As technology develops so new techniques arise. Some recent scanning technology is the magnetoenecephalography (MEG) which records the tiny magnetic fields produced by active neurones, single-photon emission computerized tomography (SPECT) which tracks blood flow through the brain and superconducting quantum imaging/interference device (SQUID) which also detects tiny changes in magnetic fields.
In conclusion it is clear from this brief overview that the human body is a complex system whereby physiological and psychological intertwine to produce efficient functioning. As technology develops so we can gain insight into the more intricate functioning of the brain, but it is important to remember that although this can shed light on some aspects of behaviour, the complexities of the mind and social interplay will also play a part.
BIBLIOGRAPHY
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Psychology: The Science of Mind and Behaviour, 3rd Edition by Richard Gross, published by Hodder and Stoughton, London, 1999
- Advanced Psychology Through Diagrams, Grahame Hill, Oxford University Press, 2001
- Foundations of Psychology: An Introductory Text, Nicky Hayes, Routeledge, London, 1994.
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Psychology for A Level, 2nd Edition, Cardwell et al, HarperCollins, London, 2000
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Abnormal Psychology: 3rd Edition, Rosenhan and Seligman,
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Hilgard’s Introduction to Psychology: 12th Edition, Atkinson et al, Harcourt Brace, London, 1996
