The Central & the Peripheral Nervous System (AQA GCSE Psychology)
Revision Note
Written by: Claire Neeson
Reviewed by: Lucy Vinson
The central nervous system
The human nervous system is divided into two parts:
The central nervous system (CNS)
The peripheral nervous system (PNS)
These two systems are connected and work together so the whole system functions effectively
The two systems collect information from inside the body and from the environment outside it
They process the information and then dispatch instructions to the rest of the body, facilitating an appropriate response
The CNS is made up of the brain and the spinal cord
The brain is central to maintaining life and has many functions including:
Basic functions such as regulating body temperature, heart rate and breathing
Language (production and understanding)
Coordinating movement
Coding sensory data via the sensory organs (e.g. the skin) and the environment
Problem-solving and planning
The spinal cord ensures that signals from the brain are transmitted to the rest of the body via the PNS
The brain stem connects the brain to the spinal cord
Examiner Tips and Tricks
Remember that the CNS consists of only the brain and the spinal cord but this does not mean that these two structures work in isolation: all parts of the human nervous system ‘talk’ to each other i.e. they are interconnected.
The peripheral nervous system
The PNS transmits messages throughout the whole body from the brain and also relays messages back to the brain
The PNS is divided into two sections:
The somatic nervous system (SNS)
The autonomic nervous system (ANS)
The SNS transmits and receives messages from the senses apart from sight
The retina and optic nerve are connected directly to the brain
The other senses — sound, smell, taste and touch — travel via the SNS to communicate with the brain, for example:
touch information from the skin (e.g. the texture of velvet)
taste information from the tongue (e.g. the flavour of ketchup)
The SNS then directs the muscles to move appropriately
Thus, the SNS controls voluntary movements e.g. throwing a ball (as well as the reflex movement involved in pulling your hand away from a hot surface)
If your eyes registered a car coming toward you, the SNS would tell your muscles to move to get you out of the way
The ANS transmits and receives information from the organs e.g. heart-rate, breathing via the lungs
The ANS is involuntary; it cannot be controlled
Worked Example
Here is an example of a question you might be asked on this topic - for AO2.
AO2: You need to apply your knowledge and understanding, usually referring to the ‘stem’ in order to do so (the stem is the example given before the question)
After each featured question there is a ‘model’ answer i.e. one which would achieve top marks in the exam.
Ross is cooking himself a meal and he is about to touch a really hot plate as he is serving up his dinner.
Question: Using the peripheral nervous system, outline how Ross will likely respond to avoid burning himself. [4]
Model answer:
Ross receives a signal from the skin on his hand - it senses the extreme heat (the skin is the sense organ).
This signal is sent from the senses (skin) via the PNS and then to the CNS.
The PNS sends a signal to the muscles in his hand i.e. 'Remove your hand from this plate now!'
The muscles in his hand go into action and Ross takes his hand off the hot plate.
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