3.1.1 The central nervous system (CNS) and neurotransmitters in
human behaviour, including the structure and role of the neuron,
the function of neurotransmitters and synaptic transmission.
Central nervous system
● The central nervous system is made up of the brain
and the spinal cord.
● The nerves in our body send information via the spinal
cord to the brain where it then processes this
information and sends a message to the body through
the spinal cord.
● Different areas of the brain are responsible for different functions, for example,
the hippocampus is important for memory.
● Neurons in the brain pass messages along through neurotransmitters and
these are released and cross the synaptic gap to be picked up by receptors
Role of neurons
● Neurons in the brain pass messages along through neurotransmitters.
● Neurotransmitters are released and cross the synaptic gap to be picked up by
receptor sites of other neurons.
How neurotransmitters work
● Each neuron has a cell body
● From the cell body an axon leads down to terminal buttons that hold
neurotransmitters in synaptic vesicles and from the cell body there are also
dendrites on the end of which are receptors
● The dendrites of one neuron are close to the terminal buttons of another
neuron but in between, there is a synaptic gap
● An electrical impulse travels down the axon and releases the neurotransmitter
into the gap
● The receptors on the dendrites of the nearby cell either receive the
neurotransmitter (a chemical) if it ‘fits’, or they don’t if it does not ‘fit’
● If the neurotransmitter is taken up it will trigger an electrical impulse in the cell
body, which then travels down the neuron's axon so that the message
continues
Synaptic transmission
, 1. Information is passed down the axon of the neuron as an electrical impulse
known as an action potential.
2. Once the action potential reaches the end of the axon → crosses the synaptic
cleft.
3. At the axon terminal, there are synaptic vesicles that contain
neurotransmitters which are chemical messengers.
4. When the electrical impulse reaches these synaptic vesicles →
neurotransmitters are released which then carry the signal across the synaptic
gap.
5. They bind to receptors on the postsynaptic cell that then become activated.
6. Once the receptors have been activated, they either produce excitatory or
inhibitory effects on the post-synaptic cell, making the post-synaptic cell more
or less likely to fire.
3.1.2 The effect of recreational drugs on the transmission
process in the central nervous system.
Recreational drugs
● Recreational drugs mimic the structure of a neurotransmitter of the natural
neurotransmitter in the body
○ Work by either increasing or decreasing the neurotransmitters at the
synaptic cleft.
● This means that if the recreational drug increases the level of dopamine
○ User will experience euphoria or intense feelings of pleasure.
Ways that recreational drugs can work
Agonists
● Some drugs (nicotine, cannabis, heroin) imitate natural neurotransmitters,
'fooling' the brain into activating pleasure centres
○ However, they are much more powerful than most naturally-occurring
neurotransmitters.
Antagonists
● Other drugs (amphetamines) massively boost the amount of normal
neurotransmitters, triggering the brain's pleasure centres.
Dopamine & Reward
● DOPAMINE is a neurotransmitter associated with REWARD
○ Creates feelings of pleasure and a desire to repeat whatever activity
you are doing when the dopamine flows.
○ Dopamine is generated naturally in the brain when we do activities like
eating or drinking.
● Dopamine normally produces sensations of satisfaction and contentment, but
a rush of dopamine can produce a more intense sensation of EUPHORIA
(pleasure)
, ○ This can happen naturally (for example, during sex, or when drinking a
glass of cool water when you're very thirsty), but recreational drugs
trigger is euphoric artificially and often more strongly.
Reuptake
● The neurotransmitter that is not used by the receptors is taken up again to be
reused
○ Helps regulate the amount of neurotransmitters in the synapse and the
amount of message there is
Reuptake inhibitor
● Stop this absorbing
○ Means that the neurotransmitter will be left in the gap for the message
to continue for longer
Downregulation - becoming addicted
● Binding over time affects the receptors and causes a decrease in the
dopamine receptors
Desensitisation
● when more of a substance is required to achieve the same
response/stimulation.
○ Because there are not so many receptors on the postsynaptic neuron
→ more dopamine will be required to stimulate the postsynaptic neuron
to a “normal” level.
HEROIN → mode of action
● inhibit dopamine from being released
● When the body's natural opiates activate opiate receptors, the release of
inhibitory neurotransmitters is shut down. Without inhibition, dopamine can be
released
● Heroin mimics natural opiates and binds to opiate receptors → turning off
dopamine inhibition.
○ Dopamine is allowed to flood into the synapse, producing an immediate
feeling of sedation and well-being
● Neurons with opiate receptors are in parts of the brain responsibly of pain
signals, stress, response and emotional attachment
COCAINE → mode of action
● Cocaine blocks the dopamine transporters, leaving dopamine trapped in the
synaptic cleft
● Dopamine binds again and again to the receptors overstimulating the cell
● Cocaine concentrates in the reward pathway and is also active in the part of
the brain controlling voluntary movements → abusers are fidgety and unable
to be still
human behaviour, including the structure and role of the neuron,
the function of neurotransmitters and synaptic transmission.
Central nervous system
● The central nervous system is made up of the brain
and the spinal cord.
● The nerves in our body send information via the spinal
cord to the brain where it then processes this
information and sends a message to the body through
the spinal cord.
● Different areas of the brain are responsible for different functions, for example,
the hippocampus is important for memory.
● Neurons in the brain pass messages along through neurotransmitters and
these are released and cross the synaptic gap to be picked up by receptors
Role of neurons
● Neurons in the brain pass messages along through neurotransmitters.
● Neurotransmitters are released and cross the synaptic gap to be picked up by
receptor sites of other neurons.
How neurotransmitters work
● Each neuron has a cell body
● From the cell body an axon leads down to terminal buttons that hold
neurotransmitters in synaptic vesicles and from the cell body there are also
dendrites on the end of which are receptors
● The dendrites of one neuron are close to the terminal buttons of another
neuron but in between, there is a synaptic gap
● An electrical impulse travels down the axon and releases the neurotransmitter
into the gap
● The receptors on the dendrites of the nearby cell either receive the
neurotransmitter (a chemical) if it ‘fits’, or they don’t if it does not ‘fit’
● If the neurotransmitter is taken up it will trigger an electrical impulse in the cell
body, which then travels down the neuron's axon so that the message
continues
Synaptic transmission
, 1. Information is passed down the axon of the neuron as an electrical impulse
known as an action potential.
2. Once the action potential reaches the end of the axon → crosses the synaptic
cleft.
3. At the axon terminal, there are synaptic vesicles that contain
neurotransmitters which are chemical messengers.
4. When the electrical impulse reaches these synaptic vesicles →
neurotransmitters are released which then carry the signal across the synaptic
gap.
5. They bind to receptors on the postsynaptic cell that then become activated.
6. Once the receptors have been activated, they either produce excitatory or
inhibitory effects on the post-synaptic cell, making the post-synaptic cell more
or less likely to fire.
3.1.2 The effect of recreational drugs on the transmission
process in the central nervous system.
Recreational drugs
● Recreational drugs mimic the structure of a neurotransmitter of the natural
neurotransmitter in the body
○ Work by either increasing or decreasing the neurotransmitters at the
synaptic cleft.
● This means that if the recreational drug increases the level of dopamine
○ User will experience euphoria or intense feelings of pleasure.
Ways that recreational drugs can work
Agonists
● Some drugs (nicotine, cannabis, heroin) imitate natural neurotransmitters,
'fooling' the brain into activating pleasure centres
○ However, they are much more powerful than most naturally-occurring
neurotransmitters.
Antagonists
● Other drugs (amphetamines) massively boost the amount of normal
neurotransmitters, triggering the brain's pleasure centres.
Dopamine & Reward
● DOPAMINE is a neurotransmitter associated with REWARD
○ Creates feelings of pleasure and a desire to repeat whatever activity
you are doing when the dopamine flows.
○ Dopamine is generated naturally in the brain when we do activities like
eating or drinking.
● Dopamine normally produces sensations of satisfaction and contentment, but
a rush of dopamine can produce a more intense sensation of EUPHORIA
(pleasure)
, ○ This can happen naturally (for example, during sex, or when drinking a
glass of cool water when you're very thirsty), but recreational drugs
trigger is euphoric artificially and often more strongly.
Reuptake
● The neurotransmitter that is not used by the receptors is taken up again to be
reused
○ Helps regulate the amount of neurotransmitters in the synapse and the
amount of message there is
Reuptake inhibitor
● Stop this absorbing
○ Means that the neurotransmitter will be left in the gap for the message
to continue for longer
Downregulation - becoming addicted
● Binding over time affects the receptors and causes a decrease in the
dopamine receptors
Desensitisation
● when more of a substance is required to achieve the same
response/stimulation.
○ Because there are not so many receptors on the postsynaptic neuron
→ more dopamine will be required to stimulate the postsynaptic neuron
to a “normal” level.
HEROIN → mode of action
● inhibit dopamine from being released
● When the body's natural opiates activate opiate receptors, the release of
inhibitory neurotransmitters is shut down. Without inhibition, dopamine can be
released
● Heroin mimics natural opiates and binds to opiate receptors → turning off
dopamine inhibition.
○ Dopamine is allowed to flood into the synapse, producing an immediate
feeling of sedation and well-being
● Neurons with opiate receptors are in parts of the brain responsibly of pain
signals, stress, response and emotional attachment
COCAINE → mode of action
● Cocaine blocks the dopamine transporters, leaving dopamine trapped in the
synaptic cleft
● Dopamine binds again and again to the receptors overstimulating the cell
● Cocaine concentrates in the reward pathway and is also active in the part of
the brain controlling voluntary movements → abusers are fidgety and unable
to be still
