Neurotransmission

Neurotransmission… …is one of the most important discoveries that have influenced psychology. The understanding the biology and chemistry work improves the understanding of how humans think and act. Neurotransmission is the method by which messages are sent through the central nervous system.

The brain is made up of how many neurons (or nerve cells)? Neurons receive information from other neurons through their dendrites and transmit the information (by electrical impulse) across the cell body, along the axon, to the terminal buttons at the end. The gap between each neuron is called the synapse. This is where neurons communicate from one to the other. 100 billion!

Neurons are specialised cells transmitting nerve impulses Neurons are specialised cells transmitting nerve impulses. They send electrochemical messages to the brain so that people can respond to stimuli – either from the environment or from internal changes in the body. Direction of impulse Direction of impulse

Neurotransmitters Communication between the neurons is a chemical process – one neuron (presynaptic neuron) sends out chemicals known as neurotransmitters and other neurons (postsynaptic neuron) pick up the chemicals and may and may not pass the message on Neurotransmitters can increase (excitatory) or decrease (inhibitory) the probability that the cell with which it comes in contact will produce an action potential Neurons working with certain neurotransmitters can be found in greater or lesser density in certain parts of the brain Motor cortex: dopamine & acetylcholine The ‘pleasure circuit’ in the limbic system: dopamine Areas responsible for mood: serotonin

In psychology, there are four neurotransmitters that you are more likely to see in research. Dopamine: Controls arousal levels in the brain; vital for physical motivation and associated with addictive behaviours. Serotonin: Controls mood and anxiety levels. High levels of serotonin are associated with optimism. Low levels are associated with irritability. Acetylcholine (ACh): Controls activity in the brain connected with attention, learning and memory Norephinephrine: involved in mental arousal and elevated mood.

The Process of Neurotransmission Three main parts: 1. Neurotransmitters are stored in vesicles inside the terminal button on the axon. Vesicles are transported to the edge of the button and neurotransmitters are released into the synaptic gap

The Process of Neurotransmission 2. In the synapse neurotransmitters can bind with a receptor site on the next neuron if the receptor site is the right type and vacant. Lock and key analogy. If enough NT binds to the receptor site the neuron will ‘fire’. This means it transmits information across the cell body electrically, The information arrives at the end of the axon and the process is repeated.

The Process of Neurotransmission 3. Any unused neurotransmitter is absorbed back into the neuron in came from. This process is called reuptake. It can then be used again. If any neurotransmitter is left in the synapse it will be removed by enzymes.

Common Mistakes The effect of a hormone (melatonin, testosterone, cortisol) is explained rather than a neurotransmitter. The neurotransmitter is not accurately identified or is not mentioned. The description of the study does not have a clearly stated aim, procedure and set of results. The actual effect of the neurotransmitter is not explicitly explained.

Studies Martinez & Kesner (1991) Fisher (2004)