Foreign Perspectives

Chapter 4, on Biological processes and psychological explanation, runs to 60 pages and takes us into the depths of biology so for non-biologists there’s a lot of new terminology introduced very quickly with relatively little depth. As the second option in TMA2 is based on this chapter, the notes on the appropriate sections will probably be more detailed.

I’ve highlighted the key exam topics.

This chapter is very much a whistle-stop tour of how psychology depends on the underlying biology and was formerly covered in somewhat more detail in SD226 Biological Psychology. It’s broken into four basic sections: a brief introduction as to how biology supports psychology, some basic biology, how the nervous system and brain work, and how everything fits together.

We start off with Crick’s (1994) concept of reductionism i.e. that all psychology can ultimately be explained by processes going on within the biology of the brain which the chapter then goes on to knock down. For example, the effects of amphetamine on behaviour can only be understood by considering the position in the social hierarchy of the individual injected (Cacioppo and Berntson, 1992). Similarly, to treat depression one can go down the psychological therapy route or the medicinal route or a combination of the two. Likewise there is the split between the signal that the senses receive and how the brain perceives it: was it just a pattern of dots or was it an exit sign? Finally, the concept of the dualism, the idea that the mind can have an existence independent of the brain.

From here, we dive into some basic biology with quite a lot of terminology introduced along the way. The body is made up of billions of cells which themselves consist of a membrane enclosing a number of organelles e.g. the nucleus, the mitochondria, vesicles, etc. Collectively the cells in the body aim to maintain the levels of a number of key parameters such as temperature and sugar level within acceptable levels (homeostasis) through the regulation of various controls e.g. using sweating to cool down. Cells come in a number of different types but for the purposes of psychology it is the neuron that is the most important as that is the type of cell that transmits information around the body and collectively these form the nervous system. Neurons consist of a cell body which has a number of dendrites and a long tail (process). The brain and spinal cord form the central nervous system with the neurons outside that core forming the peripheral nervous system. Detectors in, for example, the skin relay sensations via the peripheral nervous system to the central nervous system where they are interpreted by the brain whilst motor neurons work in the other direction and cause muscles to move. In addition to neurons, hormones also transmit information and commands around the body by way of the blood and can also affect behaviour. Cells reproduced by replicating the chromosomes within the nucleus, the process of sexual reproduction occuring by the mixing of the chromosomes within the egg and those within the sperm (referred to as the gametes) with the fertilised ovum subsequently reproducing and differentiating billions of times, ultimately forming a new individual. The collection of genes within the original fertilized egg are the genotype with the expression of that genotype within the environment called the phenotype. This is where the nature vs nurture argument originates: even with an identical starting point (e.g. in identical twins), you wouldn’t necessarily get two identical individuals as they would be very unlikely to experience the same environment.

So, how does the nervous system actually work? If you stick a pin in your finger, one or more of the sensory neurons will generate an action potential (i.e. a change in its electrical activity). This electrical activity is transmitted along the neuron (a higher frequency of pulses represents a higher intensity of stimulation) until it reaches the end of the neuron where neurotransmitters in the neuron are passed out of the neuron into the synaptic gap and taken up by receptors in the next neuron in the chain to be passed along by it in turn (the two adjacent neurons are called the synapse, hence the synaptic gap between them). Once sufficient neurotransmitters are taken up by the next neuron in the sequence, this causes excitation; note that inhibition can also occur, depending on the nature of the stimulus. Defects in this transmission process can lead to a range of mental illnesses such as schizophrenia (caused by some sections of the brain being abnormally active). The eye consists of a network of receptor cells called cones (colour sensitive) and rods (sensitive to the light level) which are collectively called the optic nerve (SD329 covers this in lots more detail). A whole range of things can interfere with this information transmission process such as diseases (e.g. Parkinson’s results from a loss of dopamine), prescription medication (e.g. Prozac) and various drugs (e.g. alcohol, heroine, etc.) and these processes can be deliberately modified by reducing the reuptake of the neurotransmitters (e.g. Prozac) but can cause problems (e.g. cocaine by rapidly blocking reuptake means that the production of dopamine can’t keep up which in turn leads to the down).

Moving up from the extreme detail of cells, we look next at how the brain is built and how it functions. It consists of two hemispheres joined by the corpus callosum. The outer creased layer is the cerebral cortex and overall it’s considered to consist of a number of lobes which perform specific activities. Thus, the eyes are wired through the brain to the lateral genuculate nucleus at the back. We know this courtesy of a range of accidents that have happened over the years and, more recently, some techniques that have been developed. Thus, epilepsy which arises from one hemisphere tended to roll over to the other one so Sperry (1969) looked at cutting the connection which in turn permitted a range of quite interesting experiments to be done addressing a single hemisphere. Damage caused by accidents or strokes (brain lesions) also revealed what some sections of the brain got up to (e.g. Phineas Gage lost the sections related to emotional control). Animals have controversially had bits of their brain cut out but these days brain imaging techniques are, of course, preferred. In terms of imaging, there is a wide range of options including positron emission tomography (PET) which looks at the blood flow indicated by the amount of a radioactive tracer injected.

This is all controlled by the somatic nervous system which acts on the skeletal muscles that operate our voluntary behaviour all under control of the motor cortex. The autonomic nervous system runs the involuntary systems (e.g. control of the cardiac muscle in the heart and smooth muscle in the throat etc.). Finally, a couple of areas are largely glossed over including language development and depression.

For the exam, the key topics for this chapter are highlighted above and are:

Neurotransmitter
Phenotype
Genotype
Action potential
Brain lesions