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Summary Edexcel A Level Psychology Notes - Biological Psychology
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A* notes for the Biological Psychology Module at A Level - the ONLY notes you need for this course!
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1Biological Psychology
- Focus on human biology - functioning of brain
- Focus on CNS (brain and spine)
- Focus on functioning at the synapse where neurotransmitters send messages and where
drugs work
- Focus on brain structures and their function, e.g. amygdala relates to aggression
- About how our genes, hormones and CNS affect our behaviour
3.1 Content
3.1.1 The Central Nervous System (CNS) and Neurotransmitters in Human Behaviour
Central Nervous System
- Brain and spinal cord
- The brain processes all incoming information from the senses and is then responsible for
controlling the behaviour that may result from this information
- The spinal cord connects the brain to other body parts, allowing messages to be passed
around the body
- Coordinates body’s activities
- Central processing and control point for all human behaviour
- Cells in the CNS are known as neurons and these cells communicate with other cells
- Neuron - a cell within the nervous system
- Send tiny electrical messages (nerve impulses) along their length
- Motor neurons receive messages from the CNS and generate movements
- Sensory neurons transmit information about the 5 senses from sense organs to the rest of
the brain
- Inter-neurons take messages between other neurons
Neurons
- Cell body - contains cell nucleus (and mitochondria) - houses genetic material for particular
neuron
- Mitochondria provide the neuron with energy
- Dendrites receive messages from other neurons in order to trigger an action potential
within the cell - come from the nucleus of the cell
,2
- Axon - passes the electrical impulse down to end of neuron to allow it to communicate
with others
- Myelin sheath - outside layers to speed up messages
- Nodes of Ranvier - help the electrical impulse or (action potential) to travel down the axon
- Messages travel down the axon to axon terminal buttons
- At end of axon are axon terminals which pass nerve impulse from the cell body to the parts
of the body that they control or activate
- Vesicles store neurotransmitters ready for the next stage of neural transmission
- Inside terminals, vesicles (tiny sacs) release neurotransmitters into synaptic gaps to
another neuron
- Goes from pre-synaptic to post synaptic
- Synaptic gap - the space between the neurons – have specific receptors for each specific
neurotransmitter, e.g. Dopamine has dopamine receptors
Action Potential
- The actual method by which the nerve impulses pass down the axon of the neuron to
stimulate the release of neurotransmitters
- Tiny electrical impulse triggered by a change in the electrical potential of the neuron itself
- Neurons have a slight negative charge (-70Mv) compared to their outside at resting
membrane potential (the difference in electrical potential on each side of the cell
membrane while the cell is at rest)
- When it receives a message from another neuron, it can slightly depolarize the neuron and
reduce its charge (excitatory postsynaptic potential), or hyperpolarize the neuron and
increase its charge (inhibitory postsynaptic potential)
- When a neuron receives more excitatory messages than inhibitory messages, action
potential is triggered (usually at a charge of -55Mv), sending an impulse along the axon to
the axon transmitters
Synaptic Transmission
- Neurotransmitters - chemical messengers that carry a signal
across a synapse from one neuron to another, E.g. Dopamine
and Serotonin
- The synapse is the gap between the terminal button of one
neuron and the dendrite of another
- Receptors - at the dendrites and receive the neurotransmitter if
there is a fit and if they are not already ‘filled’
- Electrical Impulse - coming from the cell body after it receives
the neurotransmitter from the receptors, is sent down the axon
and the impulse causes the release of the neurotransmitter and
the process continues
- Messages passed in the brain using synaptic transmission
- Action potential starts as small electrical impulses generated at the axon hillcock, but
becomes a chemical message once it reaches the terminal buttons
- Neurotransmitters are stored at the terminal buttons and if the receptors at the dendrites
of a nearby neuron are a fit for the neurotransmitter, the message carries on from the axon
terminal of one neuron
- This occurs across the gap and via the dendrites, to the cell body of another neuron
, 3
- Presynaptic neuron - the neuron that is sending the message
- Postsynaptic neuron - the neuron that is receiving the message
- The neurotransmitters diffuse across the synapse and bind to receptors on the post-
synaptic neuron
- This causes the post-synaptic neuron to transmit a nerve impulse
- Any spare neurotransmitters can be taken up again to be reused (reuptake)
- Preventing reuptake leaves more neurotransmitters there and message continues
- Each neuron is responsible for producing a certain chemical or neurotransmitter
- Receptors on the post-synaptic neuron are designed to bind to a specific neurotransmitter
and once detected will be absorbed
- Any leftover enzymes will be destroyed or reuptaken by the pre-synaptic neuron
Function of Neurotransmitters
- Neurotransmitters - Chemicals that pass messages between neurons. Different
neurotransmitters have different functions.
- Acetylcholine - Stimulates muscle contractions, control and movement
- Necessary for memory, thinking and learning, and attention and alertness
- Emotions – anger and sexuality
- Noradrenaline - Emotion such as mood control
- Sleeping, dreaming, learning and flight/fight response
- Dopamine - Posture, control of movement, reinforcement in learning, dependency
(addictions), hormonal regulation and with feelings of pleasure
- Serotonin - Mood control particularly in the limbic system, pain, sleep, regulating body
temperature and hunger
- Without neurotransmitters, the message stops so reuptake has an important role, which is
to stop the message
- Reuptake happens in the pre-synaptic neuron
Limbic System - A set of structures in the brain associated with drives, emotions and moods
3.1.2 The Effect of Recreational Drugs on the Transmission Process in the CNS
- Recreational drugs are taken for pleasure, which distinguishes them from prescribed drugs
- E.g. heroin, cocaine, nicotine, caffeine, alcohol
- The mode of action of a drug is the way it works at the synapse in the brain
- Known as psychoactive drugs because they alter brain function, which changes our mood,
perception, conscious
- Psychoactive drug - anything that alters a function in the brain by changing mood,
perception or consciousness
- Reward pathway - causes us to experience a pleasant rewarding feeling when activated
unsurprisingly
- This encourages us to repeat the behaviour that activated the pathway as we feel good so
are more likely to do it again
- Reward for specific behaviours has an adaptive function, e.g. the reward after eating high
calorie foods endures we store enough fat on our bodies
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