This document has all the topics needed to be covered for as level and a level edexcel psychology paper 1, such as the central nervous system (CNS) and neurotransmitters in human behaviour, recreational drugs and evolution. It has both Ao1 and Ao3 points for describe, evaluate and assess questions.
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3.1 Content
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.
What is the CNS made up of?
The CNS consists of the brain and spinal cord.
it is central processing and control point for all human behaviour. The brain
processes all information from the senses and is then responsible for
controlling behaviour that may result from this info.
-the spinal cord connects the brain to the ret of the body and allows messages
to be passed from the body to the brain.
-the cells in the CNS are known as neurons and these cells communicate with
around 100 other cells at a time.
What is the structure of a nerve cell?
the cell body of the neuron contains the cell nucleus, which houses the
genetic material for that particular neuron. The cell body also contains
other materials that allow the cells to function, such as the mitochondria
(provides neuron with energy).
3.1 Content 1
, Attached to the cell body are dendrites that receive messages from other
neurons in order to trigger an action potential (electrical impulse) within
the cell.
Also attached to the cell body is the axon, an extension of the cell body
that passes the electrical impulses towards axon terminal. At the top of
axon, attaching to the axon to cell body is the axon hillock, which is where
nerve impulses is triggered from. around outside of axon is a fatty layer
called the myelin sheath which insulates and speeds up rate of electrical
impulses transmissions within the axon. There are also breaks between
cells along the myelin sheath known as the nodes of Ranvier.
At the very end of the axon are the axon terminals, and on the end of the
terminals are terminal buttons. Action terminals passes electrical impulse
and triggers a release of chemical messengers (neurotransmitters)
How is the new messages carried out within the neuron (action potential)?
(function of neuron)
1. when the neuron is at rest, inside of the neuron has a negative charge (-
ve) compared to the outside of the neuron.
2. when a neuron receives a message from another neuron, this chemical
message can either stimulate an excitatory post-synaptic potential, so the
positive (+ve) ions move inside the neuron. Neuron becomes slightly
depolarised as the inside charge is reduced. OR it can hyperpolarise the
neuron which means charge is increased and stimulates an inhibitory post-
synaptic potential.
3. when a neuron has received enough excitatory message (increased +ve
ions) or a more excitatory message compared to inhibitory message, this
means the neuron is sufficiently strong enough to reach an action potential
trigger. —> this usually happens when neuron’s charge reaches approx.
-55mv.
4. the action potential sends an electrical impulse along the axon of the
neuron towards axon terminal at the end of the neuron. this means
terminal button is triggered—> synaptic transmission.
3.1 Content 2
, describe what happens during synaptic transmission.
1. Action potential starts an electrical impulse which is generated at axon
hillock. Then the electrical impulse is then transmitted through the axon
and reaches the terminal button which converts the electrical impulse
(calcium ions) into a chemical messenger (neurotransmitters)
2. Vesicles containing neurotransmitters substance will then be released and
travel down to outer membrane of terminal button where the membrane
and vesicle fuse. This allows the neurotransmitters to be diffused across
the synapse from the pre-synaptic nerve to the post-synaptic nerve,
where the NT binds to the receptors and absorbed.
3. any NT not absorbed by receptors will be destroyed by enzymes in
synaptic clef/gap or absorbed back into presynaptic terminal.
An electrical impulse travels along the pre-synaptic neuron (1). The impulse
reaches the synaptic vesicles to release a neurotransmitter (1). These
diffuse across the synaptic gap and attach receptors (1).
3.1.2 The effect of recreational drugs on the transmission process in the central
nervous system.
What causes a pleasant/ nice feeling and encourages us to repeat the
behaviour?
3.1 Content 3
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