The biological Approach

Core assumptions The biological approach suggests that everything psychological is a first biological, so to full understand human behaviour we must look to biological structures and processes within the body, such as: Genetics The central nervous system, which comprises the brain and spinal cord The chemistry of the body

The influence of genes on behaviour Watch this video on the difference between genotypes and phenotypes: https://www.youtube.com/watch?v=gLxi-qbl4J4 Genotype The genotype is an individual’s genetic make-up, which occurs at conception and provides the genetic code for how that individual will develop. It dictates characteristics such as eye and hair colour. Each individual (apart from identical twins) has a genotype which is unique to them.

Phenotype This is the way that genes are expressed through physical, behavioural and psychological characteristics. The expression of a genotype is inevitably influenced by environmental factors. For example, the maximum height of an individual is dictated by the genotype but environmental factors such as nutrition will affect how likely the person is to achieve their potential height. This also relates to psychological characteristics- there may be a genetic predisposition to a behaviour (depression) but it may not express itself due to the environment stopping its development.

Genetic basis of behaviour To study whether behavioural characteristics, such as intelligence or mental disorders are inherited often twin studies are conducted. Monozygotic Twins (Identical) 100% genetically similar Dizygotic Twins (Non-identical) Share 50% of genetics

This is known as the concordance rate. Twin studies are used to determine the likelihood that certain traits have a genetic basis by comparing the extent to which both twins share the same characteristic. This is known as the concordance rate. If MZ twins show a higher likelihood of sharing behaviours/disorders than DZ twins then there is argued to be a genetic component. For example: Disorder Research Concordance rate for MZ twins Concordance rate for DZ twins schizophrenia Gottesman (1991) 48% 17% If you are still unclear- this short video will help explain the information on these slides: https://www.youtube.com/watch?v=Trc2dJgeyvc

Notice that in the previous table the concordance rates for schizophrenia in MZ twins is not 100%. This suggests that although there may be a genetic influence, it is not the sole reason for the disorder occurring. If it was entirely due to genetics you would expect the concordance rates for identical twins to be 100% as they share 100% of their genetics. It seems some behaviours could be a mix of both genetics and environment.

Evolution and behaviour Evolution= the changes in inherited characteristics in a biological population over successive generations. Darwin proposed the theory of natural selection He suggested that any genetically determined behaviour that enhances an individual’s survival (and reproduction) will continue in future generations, i.e. be naturally selected. The selection occurs because the trait gives the possessor certain advantages- it becomes adaptive. The possessor is more likely to survive, reproduce and pass on the adaptive genes. Thus, the trait remains in the gene pool.

Evolution example In simple terms, being aggressive will, at some point in our ancestry, have been advantageous in terms of survival and increased chances of reproduction. This was perhaps due to gaining resources and protection of family. This is turn increased attractiveness to potential mates. This made the likelihood of passing the gene on much greater as there would be more available mates. The genetics could then have been passed on to subsequent generations and the behaviour became more widespread (aggression remains in the gene pool) This video explains more: https://www.youtube.com/watch?v=USR-yHJAEGE&index=2&list=PLcyIoQku6G2nExUPZpqTrOmU716YvBiSz

Biological structures The human body is made up of a number of important systems which work together to help us live. The systems that are particularly useful to explain behaviour and psychology of an individual are: The nervous system (central NS and peripheral NS) The neuron The endocrine system(hormones)

The central nervous system The central NS consists of the brain and the spinal cord. It acts as the centre from which all the physiology of an individual is controlled. The brain is the centre of all conscious awareness. The spinal cord is an extension of the brain. It is responsible for reflex actions e.g. pulling hand away from hot plate. It passes messages to and from the brain and connects nerves to the peripheral NS.

The peripheral nervous system The PNS transmits messages, via millions of neurons (nerve cells), to and from the central nervous system. It is divided into: The autonomic nervous system (ANS) This system governs vital functions in the body such as breathing, heart rate, digestion and stress responses. It is important for survival. The somatic nervous system (SNS) This system controls muscle movement and receives information from sensory receptors.

Sensory neurons carry messages from the PNS to the CNS Sensory neurons carry messages from the PNS to the CNS. They have long dendrites and short axons. Relay neurons (interneuron)- these connect the sensory neurons to the motor or other relay neurons. They have short dendrites and short axons. Motor neurons connect the CNS to effectors such as muscles and glands. They have short dendrites and long axons.

The structure of a neuron The cell body- contains a nucleus, which contains the genetic material of the cell. Branch-like structures called dendrites protrude from the cell body- these carry nerve impulses from other neurons towards the cell body. The axon carries impulses away from the cell body. It is covered in a fatty layer called the myelin sheath that protects the axon and speeds up transmission of the impulse. At the end of the axon are terminal buttons that communicate with the next neuron in the chain across a gap known as the synapse.

Synaptic transmission The process by which neighbouring neurons communicate with each other by sending chemical messages across the gap (the synapse) that separates them. What this video to explain how synaptic transmission occurs in the synapse: https://www.youtube.com/watch?v=WhowH0kb7n0

Neurotransmitters Neurotransmitters are brain chemicals released from synaptic vesicles that relay signals across the synapse from one neuron to another. Neurotransmitters can be broadly divided into those that perform an excitatory functions and those that perform an inhibitory function. For example, serotonin causes inhibition, resulting in the neuron becoming negatively charged and less likely to fire. In contrast, adrenalin (element in the stress response) causes excitation of the post-synaptic neuron by increasing its positive charge and making it more likely to fire.

The endocrine system Works alongside the nervous system Acts more slowly Various glands in the body produce hormones. Hormones are secreted into the bloodstream and affect any cell in the body that has a receptor for that particular hormone. The major endocrine gland is the pituitary gland, located in the brain. It is often called the ‘master gland’ because it controls the release of hormones from all other endocrine glands in the body.