How Neurons Communicate

The objective of this assignment is to provide detailed explanation of the way in which neurons communicate with each other. It explores the link between this specific communication and the behaviour exhibited by humans to consider whether human behaviour can be explained purely by biology.

The nervous system consists of numerous cells named neurons. Neurons are located within the Central Nervous System constituting of the brain and spinal cord, and also within in the Peripheral Nervous System (outside the Central Nervous System). Neurons are cells that process and transmit information. Different combinations of neurons compose neural systems that perform individual functions. A neuron comprises of a cell body (containing the nucleus) and an extension termed a process.

A simple reflex action can describe how neurons operate; across the cell wall is a slight electrical voltage. If a sharp object contacts the skin of the finger, the neurons located at the skin of the finger (within the Peripheral Nervous System), which are sensitive to events such as touch and tissue damage (detectors/sensory neurons) are stimulated by the noxious stimulus and a change occurs in the polarity of the cell body from a resting potential to positive, termed an action potential.

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Initiation of an action potential causes rapid conduction of electrical impulses along the neuron toward the next neuron or cell and instigates action potentials in a sequence of neurons until it reaches the motor neurons which trigger the muscles to effect an action ( moving the finger away from the sharp object). This series of action potentials convey information according to the frequency of action potentials in a neuron. The message arrives at the spinal cord and communicates the information to the brain.

Neurons do not connect physically. There are minute gaps between neurons and cells this gap is termed a synapse. When the action potential reaches the presynaptic terminal (the end of the first neuron), chemicals termed neurotransmitters, are swiftly discharged across the synapse to the postsynaptic neuron (receiving neuron) thus altering the electrical property of the postsynaptic neuron. Communication within a cell is electrical yet between neurons the reaction is a chemical one. There are one of two effects that a neurotransmitter can have; excitory, whereby the postsynaptic neuron is commanded to conduct an action potential and inhibitory where the postsynaptic neuron is commanded not to conduct an action potential. The synapse is the juncture whereupon another cell is prompted by the neuron, and communication either continues or concludes. The neurotransmitter, comparable with a lock and key, must fit the receptor of the postsynaptic neuron, otherwise it has no effect. Neurons are categorised by the neurotransmitter they store and release, such as dopamine, serotonin and noradrenalin. Once attached to a receptor, the neurotransmitter is rapidly released then extracted from the synapse and either destroyed by enzymes (inactivation) or taken back into the pre-synaptic neuron and destroyed or reprocessed (re-uptake).

Drawing on this information, it is now explored how far behaviour can be reduced to biological phenomena. These two means of communication through the nervous system, electrical and chemical are significant as "changes in activity of the synapses can cause changes in neural systems, which in turn affects behaviour, cognition and mood (Toates 2007) and underlie the following examples.

Depression is a state of low mood, theories suggest "that there are abnormalities in neurotransmission within certain key neural systems such as the dopaminergic, serotonergic and noradrenergic in the neurotransmitter" (Toates 2007). If neurons emit insufficient chemicals, communication of nerve messages is disrupted and subsequently, appropriate stimulation may not be given to the required part of the brain. Biological methods to alleviate depression chemically influence activity at the synapses.

The function of prescribed mood altering drugs can be very different, for example, Prozac, a selective serotonin reuptake inhibitor, prescribed for 'depression and obsessional neurosis'(Toates 2007), blocks the re-uptake of serotonin. However, Isocarboxazid, a Monoamine Oxidase Inhibitor, inhibits the enzymes that break down the neurotransmitter during inactivation. Notwithstanding their different actions, both drugs increase the neurotransmitters available at the synapse either to exite or inhibit the intended nerve cell. This chemical manipulation can improve symptoms of depression, therefore "points to the involvement of certain types of neurotransmitter in depression."(Toates 2007). To reduce the cause of depression solely to a biological level relying on the basic chemical functions within the brain would suggest it would be possible to predict and alter behaviour. This would be unethical and ignores contributing factors such as environment, experiences, influence and behaviour of friends and the media, which need to be addressed on a psychological level alongside biological chemical manipulation.

Another example of behavioural effects when the synapses of the brain are manipulated with a drug is the fluctuations in mood associated with the use of cocaine. Comparable to Prozac cocaine inhibits the reuptake of serotonin; however, the neurotransmitter involved is dopamine. Elevated mood is induced via the increased quantities of dopamine at the synapse described as 'euphoria' or 'high' (Toates 2007). Due to the rapid effects of cocaine the body cannot maintain the production of dopamine at the speed at which it is released from the neurons. Negative mood is then triggered due to this dopamine depletion, described as a 'downer' or a 'crash' or 'dysphoria' (Toates 2007). It is conceivable that experience of this sudden dysphoria precipitates a desire for more cocaine and could be a biological influence to the behaviour of cocaine addiction.

Although understanding how neurons communicate with each other contributes to our understanding of behaviour at the level of biology, behaviour cannot be reduced to biological explanations. There are other physiological components such as disease, trauma, hormones and genes which are outside the scope of this assignment. However, having this knowledge assists in forming a broader picture involving influences that are outside the body such as environments. This can be demonstrated using the placebo effect, whereby a person feels the effects of an inert substance due to their belief it will work. Thus illustrating the power of expectation, for which there is no physiological explanation.

In conclusion, the communication of neurons within the nervous system assists our understanding of behaviour however, is not the only contributing factor. Reducing explanations of behaviour to a biological level suggests that we are all robots. Within psychology, biology is studied alongside as a contributing perspective to understanding the whole person. Depression illustrates the necessity to incorporate both the biological perspective to target the abnormality in the nervous systems with drugs, whilst concurrently tackling external factors such as environment with psychoanalytic interventions.

(Word count 1,084)

Toates F. (2007). Biological Processes and Psychological explanations. In Miell, A. Pheonix, & K. Thomas (Eds), Mapping Psychology (pp 227-265). Milton Keynes: Open University Press

http://www.netdoctor.co.uk/diseases/depression/monoamineoxidaseinhibitors_000101.htm. Accessed 09.01.2011

Part II

Question 1.

Q1, (a) The two variables on the scatterplot are Exam Mark and Hours spent practising.

Q1, (b), (iii) Neither.

Q1,(c), (iii) Medium.

Q1, (d), (iv) There are many determinants of piano exam marks.

Q1, (e), Variable 1 is Time spent Practising and Variable 2 is Rebecca's rating of musical ability.

Q1,(f), (i) Musical ability has a coefficient of 0.520 indicating a strong positive relationship. This is therefore a stronger relationship than the 0.357 medium relationship with time spent practising. Therefore, yes this would be a valid conclusion.

Q1,(f), (ii) The pupils rating of enjoyment has a coefficient of 0.772 indicating a strong (almost very strong) positive relationship. This is therefore a stronger relationship than the 0.357 medium relationship with time spent practising and also stronger that the strong positive relationship between musical ability. Therefore, yes this would be a valid conclusion, however this would be the most valid conclusion out of the three presented so far.

Q1,(f), (ii) If Rebecca was to remove pupil three's mark then the correlation coefficient would become around 0.5 as it would remove the main mark that was pulling the correlation down. Removing the mark that disagrees the most with the relationship between time spent practising and exam mark, will push the correlation to a strong positive correlation rather than medium correlation.

References:

DSE212 Course Team. (2007). Exploring Psychological Research Methods. Milton Keynes: Open University Press.

Question 2.

Q2, (a),(ii) Whether or not the stooges were present.

Q2, (b), (iii) Whether or not a participant was influenced by the stooges..

Q2,(c), (iv) Between participants because some worked with stooges and some did not.

Q2, (d), (ii) The time for which the original target picture was shown.

(iv) The order in which the 30 sets of pictures were shown

Q2, (e), (ii) Time of day

(iii) The gender of the participants

(vii) Two participants in the experimental group always made quick decisions before any discussions with the stooges so their data was removed before analysis.

Q2,(f), It is important to have both critical and non-critical trials as this experiment requires social pressures to be placed upon participants to establish whether their answers differ from those who do not have social pressure placed upon them. The stooges not being present is the non critical trial and will provide the statistics for which the critical trial (with stooges) can be measured against. Without both there is no ability to draw comparison.

Q2,(g), This is a valid critism. However, the purpose of the experiment is to see what effect, if any, social pressure would have on that 50 per cent, not just facial recognition ability.

Q2, (h),(ii) Quasi-experimental.

Q2,(h), (ii) If Rebecca was to remove pupil three's mark then the correlation coefficient would become around 0.5 as it would remove the main mark that was pulling the correlation down. Removing the mark that disagrees the most with the relationship between time spent practising and exam mark, will push the correlation to a strong positive correlation rather than medium correlation.

Q2,(i), (ii)

References:

DSE212 Course Team. (2007). Exploring Psychological Research Methods. Milton Keynes: Open University Press.

Question 3.

To test this hypothesis, two video tapes would need to be created, one using a Cretan actor and one using a Greek actor telling a mixture of truths and lies.

One group of participants (within participants design) evenly consisting of both cultures would be used. The participants would be asked to watch both videos and would have a pen and paper to mark down the lies.

The dependant variable would be the lies and the independent variable would be the culture. The hypothesis is that ability to detect a lie depends on the culture of both liar and detector. The outcome to prove this hypothesis would be that the Greek participants are able to detect a higher number of the lies told by the Greek actor than the Cretan actor and vice versa for the Cretan participants.

This experiment has a number of confounding variables, (other factors that could have an influence on the results). One confounding variable would be the age of the participants and actors, younger participants may be naïve and not be able to lie or detect lying and an older person may have a lot of experience in lying or detecting lying. Participants and actors would need to be within the same age range ideally between 25 and 35. Another confounding variable could be gender of both participants and actors; a separate experiment between sexes would need to be conducted to counterbalance this. The actor would need to be confident; signs of lying can be misinterpreted if the actor is nervous for example. A counterbalance for this could be using a pupil with a performing arts background. Finally, using a video tape and not actors in person, leaves out body language to a certain extent and also visual signs of deceit such as, sweating on a cool day. Conduct the experiment with actors in the room rather than via video.

(Word Count 314)