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examBoard: AQA
examType: GCSE
lessonTitle: Review and Practice - Nervous System
Your nervous system is like your body's electrical wiring system. It helps you sense the world around you, process information and respond to your environment. Without it, you couldn't feel, think, or move!
Key Definitions:
Your nervous system has two main parts: the central nervous system and the peripheral nervous system. Let's look at each of them.
The CNS consists of your brain and spinal cord. It's the command centre that processes information and coordinates activity across your body.
The PNS includes all the nerves outside the CNS. It connects the CNS to the rest of your body.
Neurons are the building blocks of your nervous system. There are three main types:
Carry information from your senses to your CNS. For example, when you touch something hot, sensory neurons send this information to your brain.
Carry commands from your CNS to your muscles and glands. For example, when your brain decides to move your hand, motor neurons carry this message.
Connect sensory and motor neurons within the CNS. They help process information and decide on appropriate responses.
All neurons have a similar basic structure, although they can vary in size and shape:
If all the neurons in your brain were laid end to end, they would stretch for about 1,000 kilometres! And a single neuron can connect with up to 10,000 other neurons, creating a complex network of communication pathways.
Neurons talk to each other using both electrical and chemical signals. This process happens in a few steps:
When a neuron is stimulated, it creates an electrical signal called an action potential. This signal travels along the axon like a wave. The myelin sheath helps this signal move faster by allowing it to jump from one gap in the sheath to the next.
Neurons don't actually touch each other. There's a tiny gap between them called a synapse. When a nerve impulse reaches the end of an axon, it can't just jump across this gap.
When a nerve impulse reaches the end of an axon:
Dopamine is an important neurotransmitter that helps control the brain's reward and pleasure centres. It also helps regulate movement and emotional responses. Parkinson's disease occurs when the brain cells that produce dopamine die or become impaired. This leads to tremors, stiffness and difficulty with balance and coordination. Understanding how neurotransmitters work has helped scientists develop treatments for conditions like Parkinson's disease.
Reflexes are automatic, rapid responses to stimuli. They help protect your body from harm. A reflex arc is the neural pathway that controls a reflex. It works like this:
This happens without involving your brain, which is why reflexes are so fast!
Part of the peripheral nervous system, the autonomic nervous system controls your involuntary functions like heart rate, digestion and breathing. It has two main divisions:
This is your "fight or flight" system. It prepares your body for action by:
This is your "rest and digest" system. It helps your body conserve energy by:
When the nervous system doesn't function properly, various disorders can occur:
Remember to use specific terminology in your answers. For example, don't just say "the message travels along the nerve" - instead, say "the action potential travels along the axon of the neuron." Being precise shows your understanding of the concepts!
The nervous system is your body's communication network. It consists of the central nervous system (brain and spinal cord) and the peripheral nervous system (all other nerves). Neurons are the basic units of this system and they communicate through electrical signals and chemical messengers called neurotransmitters. Understanding how the nervous system works helps us comprehend how we sense, think, move and respond to our environment.
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