How is the nervous system organised and what does each part do?
The structure and function of the nervous system: the central and peripheral nervous systems, the autonomic nervous system, and the fight or flight response.
A focused answer to AQA GCSE Psychology 3.7, covering the structure and function of the nervous system, including the central and peripheral nervous systems, the autonomic nervous system, and the fight or flight response.
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What this dot point is asking
AQA wants you to describe how the nervous system is organised into the central and peripheral nervous systems, explain the autonomic nervous system and its two branches, and describe the fight or flight response. In Paper 2 this is examined with both short outline questions and longer description items, and fight or flight is a frequent target, so learn the sequence of bodily changes.
The two main divisions
The CNS processes information and coordinates responses, acting as the control centre. The PNS carries sensory information into the CNS and carries instructions out to muscles and glands. The PNS is itself divided into the somatic nervous system (controlling voluntary movement of skeletal muscle) and the autonomic nervous system (controlling automatic, involuntary functions).
The autonomic nervous system
Fight or flight
The fight or flight response is the body's automatic reaction to a threat. When danger is detected, the sympathetic branch is activated and the adrenal glands release the hormone adrenaline. Heart rate and breathing speed up to supply oxygen to the muscles, blood is diverted to the muscles, the pupils dilate and digestion slows. The body is prepared to either confront the danger (fight) or escape it (flight). Once the threat passes, the parasympathetic branch calms the body down. This response was adaptive for our ancestors facing physical danger, but it can be triggered by modern stressors such as exams, which is why this topic links to stress and psychological problems.
Try this
Q1. Name the two parts of the central nervous system. [2 marks]
- Cue. The brain and the spinal cord.
Q2. Describe the role of the sympathetic branch in fight or flight. [3 marks]
- Cue. It arouses the body, triggering adrenaline release, raising heart rate and breathing to prepare for action.
Q3. Identify the branch of the autonomic nervous system that returns the body to rest. [1 mark]
- Cue. The parasympathetic branch.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20194 marksDescribe the fight or flight response. (Paper 2, Section C)Show worked answer →
A 4-mark Describe item rewards a sequenced physiological account.
When a threat is perceived, the brain (hypothalamus) activates the sympathetic branch of the autonomic nervous system. The adrenal glands release the hormone adrenaline into the bloodstream. This produces bodily changes that prepare the person to confront the danger (fight) or escape it (flight): heart rate and breathing speed up to deliver more oxygen to the muscles, the pupils dilate, and digestion is slowed. Once the threat passes, the parasympathetic branch returns the body to its resting state.
Markers reward the trigger (threat, sympathetic activation), the chemical (adrenaline), at least two bodily changes (raised heart rate and breathing), and the return to calm via the parasympathetic branch.
AQA 20224 marksExplain the difference between the central nervous system and the peripheral nervous system. (Paper 2, Section C)Show worked answer →
A 4-mark Explain item rewards a clear distinction with developed detail on each system.
The central nervous system (CNS) is made up of the brain and the spinal cord; it processes information and coordinates the body's responses, acting as the control centre. The peripheral nervous system (PNS) is all the nerves outside the CNS; its job is to carry messages between the CNS and the rest of the body, taking sensory information in and carrying motor instructions out.
Markers reward the components of each (brain and spinal cord versus all other nerves) and the contrasting roles (processing and control versus relaying messages to and from the body).
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Sources & how we know this
- AQA GCSE Psychology (8182) specification — AQA (2017)