What is biological psychology?

Biological psychology is a branch of psychology that explores how the structure and function of the brain influence behaviour. This includes examining the roles of hormones, chemicals, and electrical activity within the brain. As a result, biological psychologists aim to pinpoint specific brain areas responsible for controlling different behaviours.

To achieve this, researchers often study individuals who have experienced brain damage. By identifying the damaged region and observing any resulting changes in behaviour, they can link particular brain structures to specific functions.

Biological psychologists also emphasise the significant role of genetics in shaping behaviour. They believe that inherited factors are a major influence.

Investigating genetic influences on behaviour

One key method for exploring genetics involves studying identical twins, who share 100% of their genetic material. Researchers compare traits or behaviours between these twins to assess genetic impact.

This comparison often uses a technique called correlation, which measures the relationship between two variables. For example, if genetic factors strongly influence a trait like aggression, the aggression scores of one twin would likely be similar to those of the other twin.

The central nervous system and its role in behaviour

The central nervous system (CNS) is the core part of the nervous system, consisting of the brain and spinal cord. It acts as the main processing centre for information, coordinating responses to stimuli from the environment.

Connected to the CNS are networks of nerves that extend throughout the body. These nerves transmit signals to and from the CNS, enabling communication with muscles, organs, and senses.

Types of neurones in the nervous system

Neurones are specialised nerve cells that carry electrical impulses, allowing the nervous system to function.

There are two main types involved in connecting the CNS to the body:

• Motor neurones - These carry signals outward from the CNS to muscles and glands, triggering actions like movement or hormone release.
• Sensory neurones - These transmit information inward to the CNS from sensory receptors, such as those detecting touch, pain, or temperature.

The spinal cord as a communication pathway

The spinal cord serves as a vital link between the brain and the body, carrying messages in both directions.

However, for more complex processing or decision-making, the brain takes over. The brain contains billions of neurones that process information internally and then send instructions back through the nervous system to control bodily functions.

The structure of a neurone

Neurones are the building blocks of the nervous system, designed to transmit electrical signals rapidly over long distances. Each neurone has a specific structure that supports this function, allowing information to flow efficiently.

Key components of a neurone

• Cell body - The central part of the neurone, containing the nucleus, which controls the cell's activities and houses genetic material.
• Dendrites - Branch-like extensions from the cell body that receive incoming signals from other neurones.
• Axon - A long, thin fibre extending from the cell body that carries electrical impulses away towards other neurones or body parts.
• Myelin sheath - A fatty insulating layer covering the axon, formed by individual Schwann cells, which speeds up signal transmission by allowing impulses to jump between gaps.
• Nodes of Ranvier - Small gaps between sections of the myelin sheath where the axon is exposed, enabling faster conduction of electrical signals.
• Axon terminals - Branched structures at the end of the axon that connect to other neurones or target cells, releasing chemical messengers.

This structure ensures neurones can communicate effectively, forming networks that underpin all brain activity, including thoughts, memories, and behaviours.

How neurones communicate through synapses

Synapses are the junctions where neurones connect and communicate, allowing the transfer of information across the nervous system. This process is essential for processing thoughts, forming memories, and coordinating responses.

At a synapse, the electrical signal in one neurone is converted into a chemical signal to cross the gap to the next neurone.

The process of neurotransmission

1. An electrical impulse travels down the axon of the presynaptic neurone (the sending neurone) to the axon terminals.
2. This triggers the release of neurotransmitters, which are chemical messengers stored in vesicles within the axon terminals.
3. The neurotransmitters diffuse across the synaptic gap, a tiny space between the two neurones.
4. On reaching the postsynaptic neurone (the receiving neurone), the neurotransmitters bind to receptor sites, which are specialised proteins on the dendrite surface.
5. This binding acts like a key fitting into a lock, as each receptor site is shaped to match only specific neurotransmitters.
6. Once bound, the chemical signal is converted back into an electrical impulse in the postsynaptic neurone, continuing the transmission.

Excitatory and inhibitory synapses

• Excitatory synapses - These encourage the postsynaptic neurone to 'fire', meaning it generates an electrical impulse and releases its own neurotransmitters.
• Inhibitory synapses - These discourage firing, reducing the likelihood of an impulse in the postsynaptic neurone.

Each neurone receives inputs from thousands of synapses. The decision to fire depends on the balance of signals: if excitatory messages significantly outnumber inhibitory ones, the neurone is likely to fire. Conversely, if inhibitory messages dominate, it will not.