Your nervous system is basically your body's electrical wiring -... Show more
Biology185 views·Updated May 14, 2026·14 pagesUnderstanding the Nervous System - WJEC A Level Biology 3.8
Caitlin Ellis@caitlinellis0312
1 / 10
1
of 10
Nervous System Structure and Neurone Types
Think of your nervous system as having two main parts: the central nervous system (brain and spinal cord) that processes information, and the peripheral nervous system that carries messages to and from your body. It's like having a control centre connected to a massive communication network.
You've got three key types of neurones working as a team. Sensory neurones carry signals from receptors (like your skin or eyes) to your brain, motor neurones send instructions from your brain to muscles, and relay neurones act as connectors in your spinal cord. Each has the same basic parts: dendrites to receive signals, a cell body, and an axon to send signals on.
The clever bit is that axons are wrapped in a myelin sheath made of Schwann cells, with gaps called nodes of Ranvier. This setup massively speeds up nerve transmission - think of it like insulation on electrical wires.
Key Point: The reflex arc bypasses your brain for super-quick responses, going straight through your spinal cord from sensory to motor neurones via relay neurones.
2
of 10
Simple Nervous Systems - Nerve Nets
Before we had complex brains, simpler organisms developed nerve nets - and they're still around today in creatures like jellyfish. These systems show us how nervous systems evolved and help explain why our setup is so much more sophisticated.
Nerve nets have just one type of neurone that branches in all directions. When stimulated, impulses travel slowly in every direction rather than following specific pathways. The organism can't tell where the stimulus came from because there's no central nervous system to process directional information.
While this sounds basic, nerve nets do have advantages - they regenerate rapidly when damaged and create simple, reliable response patterns. It's like having a basic alarm system rather than a sophisticated security network.
Key Point: The lack of directional control in nerve nets shows why having specialised neurone types and a CNS gives us such precise responses.
3
of 10
Spinal Cord Organisation
Your spinal cord is brilliantly organised to handle reflexes and relay information to your brain. The structure is crucial for understanding how quick responses happen without conscious thought.
The grey matter (unmyelinated) sits in the centre and contains the cell bodies of relay neurones and motor neurones. The white matter (myelinated) surrounds it and carries signals up and down the cord. Sensory neurone cell bodies live in the dorsal root ganglion, just outside the spinal cord.
When you touch something hot, the signal travels along the dorsal root, synapses with relay neurones in the grey matter, then connects to motor neurones that exit via the ventral root. Your hand pulls away before your brain even knows what's happening.
Key Point: The specific positioning of cell bodies in different regions ensures signals flow in the right direction for effective reflexes.
4
of 10
Action Potentials - The Electrical Signal
Action potentials are basically electrical pulses that zoom along neurones, and understanding them is essential for explaining how your nervous system actually works. The process follows a predictable pattern that's the same every time.
Your neurone starts at resting potential with sodium channels closed and potassium channels open. When stimulation reaches the threshold potential , voltage-gated sodium channels snap open, sodium floods in, and the neurone becomes positive . This is depolarisation.
After reaching the action potential, sodium channels close and potassium channels open wide. Potassium rushes out, making the neurone negative again (repolarisation). It actually becomes more negative than resting potential (hyperpolarisation) during the refractory period, which stops signals travelling backwards.
Key Point: The refractory period ensures action potentials only travel in one direction and prevents the neurone from being over-stimulated.
5
of 10
All-or-Nothing Principle
Here's something that might surprise you - action potentials are always exactly the same strength, regardless of how strong the original stimulus was. This is called the all-or-nothing principle, and it's crucial for preventing your brain from being overwhelmed.
If a stimulus doesn't reach the threshold value, absolutely nothing happens - no action potential is generated at all. But once threshold is reached, you get the full action potential every single time. Your nervous system doesn't do "half-measures."
So how does your brain tell the difference between a gentle touch and a painful pinch? It's all about frequency. Stronger stimuli create more action potentials per second, not stronger individual signals. This system acts like a filter, ensuring only significant stimuli get through to your brain.
Key Point: The all-or-nothing principle prevents minor stimuli from overwhelming your nervous system while ensuring important signals always get through clearly.
6
of 10
Speed of Nerve Transmission
Not all nerve impulses travel at the same speed - and understanding what affects transmission speed helps explain why some responses are lightning-fast while others are slower. Three main factors control how quickly signals move.
Temperature affects the kinetic energy of ions, so warmer conditions mean faster ion movement and quicker transmission. This is why you might feel sluggish in cold weather. Axon diameter matters too - thicker axons have less resistance, allowing ions to move more easily.
Myelination is the real game-changer though. Instead of the whole axon depolarising, action potentials jump between nodes of Ranvier. This saltatory conduction can increase transmission speed by up to 50 times compared to unmyelinated neurones.
Key Point: Myelinated neurones with large diameters in warm conditions transmit impulses fastest - which is why your major motor and sensory pathways are heavily myelinated.
7
of 10
8
of 10
9
of 10
10
of 10
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Most popular content: Nervous System
5BiologyNervous System Overview
Explore the key components of the nervous system, including sensory receptors, the reflex arc, synapses, and the human eye. This summary provides a clear understanding of how stimuli are processed and responses are generated, ideal for GCSE students preparing for exams.
103,941134
BiologyNervous System Overview
Explore the structure and function of the nervous system, including the roles of neurons, the central and peripheral nervous systems, and their subdivisions. This summary covers key concepts such as neuron types, signal transmission, and the nervous system's role in communication within the body. Ideal for students studying biology or human anatomy.
93844
BiologyNervous System Signal Flow
Explore the mechanisms of signal transmission in the nervous system, including the roles of receptors, effectors, and neural pathways. This summary covers the autonomic nervous system's sympathetic and parasympathetic divisions, the structure and function of neural pathways, and the brain's role in processing sensory information and initiating responses.
S51073
BiologyUnderstanding the Nervous System
Explore the structure and function of the human nervous system, including the roles of the brain, spinal cord, and the three types of neurons: sensory, relay, and motor. This summary highlights neural transmission and the system's importance in responding to environmental changes and maintaining homeostasis.
112453
BiologyNervous System Overview
Explore the structure and function of the nervous system, including the central and peripheral nervous systems, motor and sensory systems, and key disorders such as Alzheimer's and Parkinson's disease. This summary covers essential concepts like neurons, neurotransmitters, and nerve impulses, providing a comprehensive understanding for students studying human biology.
12851
Most popular content in Biology
9C
BiologyCell Biology and Cell structure
cell structures
92,4940
BiologyAQA Biology: Key Concepts
Explore essential AQA Biology topics including Photosynthesis, Respiration, Homeostasis, Genetics, and Ecology. This comprehensive knowledge organizer covers key concepts such as energy transfer, hormonal control, and genetic variation, providing a solid foundation for your studies. Ideal for exam preparation and understanding biological processes.
108,372296
T
BiologyThe functions of subcellular structures - B1 Biology
Flashcards on the different functions of subcellular structures: cell membrane, nucleus, mitochondria, ribosomes, cytoplasm, permant vacuole, chloroplasts and cell wall.
102,0775
BiologyA-Level Biology Year 1 Overview
Comprehensive summary of AQA A-Level Biology Year 1, covering key topics such as cellular structure, protein synthesis, immune response, gas exchange, and more. Ideal for exam preparation and understanding biological concepts. Includes detailed insights into cellular processes, biological classification, and the circulatory system.
1214,471686
1
Biology1.cells Gcse biology question cards
combined science higher biology
91,8294
BiologyBiology paper 1 Summary
Notes for Biology paper 1 contains the full course for AQA higher combined!
103,973106
T
BiologyTypes of cells
biology
109760
B
BiologyBiology Paper 1 quiz
this is a simple quiz on key knowledge needed for paper 1
102,4045
C
BiologyCells part 1 function of cells.
About cells and function of cells etc.
118051
Most popular content
9
SociologySociology of Education Overview
Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.
12102,1743,037
SociologySociology of Families: Comprehensive Revision
Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.
1273,0542,303
CriminologyCriminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
1253,8751,050
English LiteratureAn Inspector Calls: Character Insights
Explore in-depth analysis and key quotes for characters in J.B. Priestley's 'An Inspector Calls'. This resource covers Gerald Croft, Inspector Goole, Sheila Birling, Mrs. Birling, Eric Birling, and Eva Smith, focusing on themes of class, gender roles, and social responsibility. Ideal for students aiming for Grade 8 and above.
1025,133899
CriminologyWJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
126,887123
CriminologyCriminology Theories Overview
Explore key criminology theories and their implications on crime and deviance. This comprehensive summary covers biological, psychological, and sociological perspectives, including labelling theory, right realism, and the impact of social campaigns on policy development. Ideal for A-Level criminology students seeking to understand the complexities of criminal behaviour and the factors influencing crime prevention strategies.
129,741211
English LiteratureRomeo and Juliet: Key themes
Key Romeo and Juliet themes and analysed quotes
106,573194
English LiteratureMacbeth: Guilt and Ambition
Explore the complex themes of guilt and ambition in Shakespeare's 'Macbeth'. This analysis covers key characters, including Macbeth and Lady Macbeth, their moral dilemmas, and the tragic consequences of their ambition. Ideal for students studying character motivations, thematic elements, and the psychological impact of power. Includes insights on the natural order, manipulation, and the descent into madness.
918,711389
C
BiologyCell Biology and Cell structure
cell structures
92,4940
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user
Biology185 views·Updated May 14, 2026·14 pagesUnderstanding the Nervous System - WJEC A Level Biology 3.8
Caitlin Ellis@caitlinellis0312
Your nervous system is basically your body's electrical wiring - it lets you feel, think, and react to everything around you. Understanding how nerve cells communicate and create responses is crucial for A Level Biology, and once you get the... Show more
1
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Nervous System Structure and Neurone Types
Think of your nervous system as having two main parts: the central nervous system (brain and spinal cord) that processes information, and the peripheral nervous system that carries messages to and from your body. It's like having a control centre connected to a massive communication network.
You've got three key types of neurones working as a team. Sensory neurones carry signals from receptors (like your skin or eyes) to your brain, motor neurones send instructions from your brain to muscles, and relay neurones act as connectors in your spinal cord. Each has the same basic parts: dendrites to receive signals, a cell body, and an axon to send signals on.
The clever bit is that axons are wrapped in a myelin sheath made of Schwann cells, with gaps called nodes of Ranvier. This setup massively speeds up nerve transmission - think of it like insulation on electrical wires.
Key Point: The reflex arc bypasses your brain for super-quick responses, going straight through your spinal cord from sensory to motor neurones via relay neurones.
2
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Simple Nervous Systems - Nerve Nets
Before we had complex brains, simpler organisms developed nerve nets - and they're still around today in creatures like jellyfish. These systems show us how nervous systems evolved and help explain why our setup is so much more sophisticated.
Nerve nets have just one type of neurone that branches in all directions. When stimulated, impulses travel slowly in every direction rather than following specific pathways. The organism can't tell where the stimulus came from because there's no central nervous system to process directional information.
While this sounds basic, nerve nets do have advantages - they regenerate rapidly when damaged and create simple, reliable response patterns. It's like having a basic alarm system rather than a sophisticated security network.
Key Point: The lack of directional control in nerve nets shows why having specialised neurone types and a CNS gives us such precise responses.
3
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Spinal Cord Organisation
Your spinal cord is brilliantly organised to handle reflexes and relay information to your brain. The structure is crucial for understanding how quick responses happen without conscious thought.
The grey matter (unmyelinated) sits in the centre and contains the cell bodies of relay neurones and motor neurones. The white matter (myelinated) surrounds it and carries signals up and down the cord. Sensory neurone cell bodies live in the dorsal root ganglion, just outside the spinal cord.
When you touch something hot, the signal travels along the dorsal root, synapses with relay neurones in the grey matter, then connects to motor neurones that exit via the ventral root. Your hand pulls away before your brain even knows what's happening.
Key Point: The specific positioning of cell bodies in different regions ensures signals flow in the right direction for effective reflexes.
4
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Action Potentials - The Electrical Signal
Action potentials are basically electrical pulses that zoom along neurones, and understanding them is essential for explaining how your nervous system actually works. The process follows a predictable pattern that's the same every time.
Your neurone starts at resting potential with sodium channels closed and potassium channels open. When stimulation reaches the threshold potential , voltage-gated sodium channels snap open, sodium floods in, and the neurone becomes positive . This is depolarisation.
After reaching the action potential, sodium channels close and potassium channels open wide. Potassium rushes out, making the neurone negative again (repolarisation). It actually becomes more negative than resting potential (hyperpolarisation) during the refractory period, which stops signals travelling backwards.
Key Point: The refractory period ensures action potentials only travel in one direction and prevents the neurone from being over-stimulated.
5
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
All-or-Nothing Principle
Here's something that might surprise you - action potentials are always exactly the same strength, regardless of how strong the original stimulus was. This is called the all-or-nothing principle, and it's crucial for preventing your brain from being overwhelmed.
If a stimulus doesn't reach the threshold value, absolutely nothing happens - no action potential is generated at all. But once threshold is reached, you get the full action potential every single time. Your nervous system doesn't do "half-measures."
So how does your brain tell the difference between a gentle touch and a painful pinch? It's all about frequency. Stronger stimuli create more action potentials per second, not stronger individual signals. This system acts like a filter, ensuring only significant stimuli get through to your brain.
Key Point: The all-or-nothing principle prevents minor stimuli from overwhelming your nervous system while ensuring important signals always get through clearly.
6
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Speed of Nerve Transmission
Not all nerve impulses travel at the same speed - and understanding what affects transmission speed helps explain why some responses are lightning-fast while others are slower. Three main factors control how quickly signals move.
Temperature affects the kinetic energy of ions, so warmer conditions mean faster ion movement and quicker transmission. This is why you might feel sluggish in cold weather. Axon diameter matters too - thicker axons have less resistance, allowing ions to move more easily.
Myelination is the real game-changer though. Instead of the whole axon depolarising, action potentials jump between nodes of Ranvier. This saltatory conduction can increase transmission speed by up to 50 times compared to unmyelinated neurones.
Key Point: Myelinated neurones with large diameters in warm conditions transmit impulses fastest - which is why your major motor and sensory pathways are heavily myelinated.
7
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
8
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
9
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
10
of 10Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Most popular content: Nervous System
5BiologyNervous System Overview
Explore the key components of the nervous system, including sensory receptors, the reflex arc, synapses, and the human eye. This summary provides a clear understanding of how stimuli are processed and responses are generated, ideal for GCSE students preparing for exams.
103,941134
BiologyNervous System Overview
Explore the structure and function of the nervous system, including the roles of neurons, the central and peripheral nervous systems, and their subdivisions. This summary covers key concepts such as neuron types, signal transmission, and the nervous system's role in communication within the body. Ideal for students studying biology or human anatomy.
93844
BiologyNervous System Signal Flow
Explore the mechanisms of signal transmission in the nervous system, including the roles of receptors, effectors, and neural pathways. This summary covers the autonomic nervous system's sympathetic and parasympathetic divisions, the structure and function of neural pathways, and the brain's role in processing sensory information and initiating responses.
S51073
BiologyUnderstanding the Nervous System
Explore the structure and function of the human nervous system, including the roles of the brain, spinal cord, and the three types of neurons: sensory, relay, and motor. This summary highlights neural transmission and the system's importance in responding to environmental changes and maintaining homeostasis.
112453
BiologyNervous System Overview
Explore the structure and function of the nervous system, including the central and peripheral nervous systems, motor and sensory systems, and key disorders such as Alzheimer's and Parkinson's disease. This summary covers essential concepts like neurons, neurotransmitters, and nerve impulses, providing a comprehensive understanding for students studying human biology.
12851
Most popular content in Biology
9C
BiologyCell Biology and Cell structure
cell structures
92,4940
BiologyAQA Biology: Key Concepts
Explore essential AQA Biology topics including Photosynthesis, Respiration, Homeostasis, Genetics, and Ecology. This comprehensive knowledge organizer covers key concepts such as energy transfer, hormonal control, and genetic variation, providing a solid foundation for your studies. Ideal for exam preparation and understanding biological processes.
108,372296
T
BiologyThe functions of subcellular structures - B1 Biology
Flashcards on the different functions of subcellular structures: cell membrane, nucleus, mitochondria, ribosomes, cytoplasm, permant vacuole, chloroplasts and cell wall.
102,0775
BiologyA-Level Biology Year 1 Overview
Comprehensive summary of AQA A-Level Biology Year 1, covering key topics such as cellular structure, protein synthesis, immune response, gas exchange, and more. Ideal for exam preparation and understanding biological concepts. Includes detailed insights into cellular processes, biological classification, and the circulatory system.
1214,471686
1
Biology1.cells Gcse biology question cards
combined science higher biology
91,8294
BiologyBiology paper 1 Summary
Notes for Biology paper 1 contains the full course for AQA higher combined!
103,973106
T
BiologyTypes of cells
biology
109760
B
BiologyBiology Paper 1 quiz
this is a simple quiz on key knowledge needed for paper 1
102,4045
C
BiologyCells part 1 function of cells.
About cells and function of cells etc.
118051
Most popular content
9SociologySociology of Education Overview
Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.
12102,1743,037
SociologySociology of Families: Comprehensive Revision
Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.
1273,0542,303
CriminologyCriminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
1253,8751,050
English LiteratureAn Inspector Calls: Character Insights
Explore in-depth analysis and key quotes for characters in J.B. Priestley's 'An Inspector Calls'. This resource covers Gerald Croft, Inspector Goole, Sheila Birling, Mrs. Birling, Eric Birling, and Eva Smith, focusing on themes of class, gender roles, and social responsibility. Ideal for students aiming for Grade 8 and above.
1025,133899
CriminologyWJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
126,887123
CriminologyCriminology Theories Overview
Explore key criminology theories and their implications on crime and deviance. This comprehensive summary covers biological, psychological, and sociological perspectives, including labelling theory, right realism, and the impact of social campaigns on policy development. Ideal for A-Level criminology students seeking to understand the complexities of criminal behaviour and the factors influencing crime prevention strategies.
129,741211
English LiteratureRomeo and Juliet: Key themes
Key Romeo and Juliet themes and analysed quotes
106,573194
English LiteratureMacbeth: Guilt and Ambition
Explore the complex themes of guilt and ambition in Shakespeare's 'Macbeth'. This analysis covers key characters, including Macbeth and Lady Macbeth, their moral dilemmas, and the tragic consequences of their ambition. Ideal for students studying character motivations, thematic elements, and the psychological impact of power. Includes insights on the natural order, manipulation, and the descent into madness.
918,711389
C
BiologyCell Biology and Cell structure
cell structures
92,4940
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user