How do nerve cells work, and why is it important for psychologists

23 Mar 2015

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The biology of psychology, explains a lot about human behaviour. 'Everything psychological is stimulated biologically'. An interesting fact about the information systems of humans and animals is that they are very similar. Due to this similarity, it allows biological psychologists to study the simplest animals, to then go on to understand how our neural systems work. Though our brains are much more complex, than say a rat's, the same basic principles apply. (Myers, 2010)

Our body's neural information system is build completely made of neurons or nerve cells and they are responsible for our thoughts, feelings and many other aspects of human behaviour. These nerve cells conduct electricity and communicate with each other by sending chemical messages through the synaptic gap between them. There are three types of neurons in our body: sensory neurons, motor neurons and interneurons.

"Sensory neurons carry messages from the body's tissues and sensory organs...for processing. The brain and the spinal cord send instructions...via the motors neurons. Between the sensory input and motor output, information is processed in the brain's internal communication system via its interneurons." (Myers, 2010, p.49)

These three neurons effectively run the body, with numbers reaching their millions for the sensory and motor neurons and billions for interneurons. The neuron makes decisions based on the hundreds of signals it receives from many other neurons; these signals being either excitatory or inhibitory. The excitatory signals must exceed a threshold before an action potential is sent out. If the levels of stimulation go above the threshold, it doesn't cause the neuron's impulse intensity to increase; all it does is increase the number of neurons to react, if the stimulus is very strong.

The starting point of information transformation in neurons begins from the signals (impulses) sent from one neuron to the next. Neural impulses are met between neurons at a point called the synapse. Once the dendrites receive their signal, the soma then passes the neural impulses (action potential) along the axon leading to the terminal branches of the axon. At this point, neurotransmitters then create the 'pathway', by binding to the receptor sites of the receiving neuron, for the signals to get across the synaptic gap to reach the dendrites of the next neuron. The excess neurotransmitters that do not pass through to the next neuron are the reabsorbed by the sending neuron; this process is called reuptake. This whole process is repeated between each and every neuron in order for the body to function correctly. (Coon and Mitterer, 2007).

With this knowledge, biological psychologists can understand the normal processes of healthy transmission and be able to pinpoint when there is a problem with them. Psychology has found that neurotransmitters can affect our mental health. The biological explanation for depression links to the neurotransmitter, serotonin. An undersupply of this neurotransmitter can contribute to anxiety, sleep problems and irritability, which are all classified as symptoms of depression (Myers, 2010). It is inconclusive as to what may have caused the change of serotonin levels or depression, was it one or the other? It is still no clear, however, but there are some very effective treatments for depression: SSRIs (Selective Serotonin Reuptake inhibitors) or SNRI (serotonin-norepinephrine reuptake inhibitor). These work by restoring the proper levels of the serotonin and or norepinephrine neurotransmitters, which then reduce such symptoms (Cardwell and Flanagan, 2009). These do not, however, cure depression, as scientists claim there may be some other underlying factors behind the illness. Another neurotransmitter linked with illness is dopamine. Excess dopamine receptor activity is linked schizophrenia. This causes the neurons that use dopamine to fire too often and transmit too many messages. This message 'over load' may produce many of the symptoms of schizophrenia, such as hallucinating, showing little or out of context emotion and holding false and unusual beliefs. Evidence for this comes from that fact that amphetamines increase the amounts of dopamine. So, patient who had no history of mental illnesses, were given large doses, and produced symptoms similar to paranoid schizophrenia. And participants who were already diagnosed with schizophrenia were given a smaller dosage, and they had gotten worse. Treatments prescribed to clients suffering with schizophrenia are anti-psychotics. They work by blocking dopamine receptors, so preventing dopamine-receiving neurons from firing. Like depression, the treatment (anti-psychotics) do not cure schizophrenia, they just control the illness. A second explanation was found, which suggested that it is not excessive dopamine but that fact that there are more dopamine receptors that causes schizophrenia. More receptors lead to more firing and an over production of messages. Autopsies have found that there are generally a large number of dopamine receptors (Owen et al., 1987) and there was an increase in the amount of dopamine in the left amygdale (Falkai et al. 1988).

Without the knowledge of how nerve cells, neurons and neurotransmitters work, and how they affect us as humans, psychologists wouldn't be able to understand, explain or describe how we function. As mentioned earlier, everything psychological is stimulated biologically, so it allows psychologists to understand mental illnesses such as depression and schizophrenia or have the ability to treat them. It is however, required to consider other important biological factors, such as genes, which can play a part in how an individual's biological make up is made up. For example, Harrington et al. (1993) found that having a first degree relative with depression can increase your risk of becoming depressed. With these other considerations in play, there are many ways for psychologists to understand human behaviour, but knowing how nerve cells work is a necessary foundation.

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