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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Central Nervous System
The central nervous system (CNS) is like the body's command centre. It receives information from all over your body, processes it and then sends out instructions about what to do next. Whether you're catching a ball, solving a maths problem, or pulling your hand away from something hot, your CNS is coordinating everything!
Key Definitions:
The brain is the control centre of the CNS. It weighs about 1.4 kg and contains around 86 billion neurons! It's protected by the skull and three layers of membranes called meninges. The brain has different regions that control different functions:
The spinal cord is a long, thin bundle of nervous tissue that extends from the brain down through the vertebral column. It:
Neurons are specialized cells designed to transmit information as electrical impulses. They're the building blocks of your nervous system and come in different shapes and sizes depending on their job.
A typical neuron has three main parts:
Contains the nucleus and organelles. This is where most of the cell's metabolism happens.
Short branched extensions that receive signals from other neurons and carry them toward the cell body.
A long extension that carries signals away from the cell body to other neurons, muscles, or glands. Many axons are covered in a fatty myelin sheath that speeds up transmission.
Neurons don't physically touch each other. Instead, they communicate across tiny gaps called synapses using chemical messengers.
Nerve impulses are electrical signals that travel along neurons. Here's how they work:
At the synapse, electrical signals are converted to chemical signals and back again:
Reflex actions are rapid, automatic responses to stimuli that don't involve conscious thought. They protect us from harm by creating immediate reactions to dangerous situations.
A reflex arc is the neural pathway that controls a reflex action. It involves:
Example: If you touch something hot, pain receptors in your fingers send signals to your spinal cord. The spinal cord processes this information and immediately sends signals to the muscles in your arm to pull away all before your brain has fully registered what's happening!
When the spinal cord is damaged, communication between the brain and parts of the body below the injury can be disrupted. This can lead to paralysis or loss of sensation. In 2012, a groundbreaking study used electrical stimulation to help four men with complete spinal cord injuries regain some voluntary movement. This research shows that with the right stimulation, some neural pathways might be reactivated even after severe injury.
Different parts of the brain process different types of information. For example, the occipital lobe processes visual information, while the temporal lobe processes sound. The brain can receive and process multiple types of information simultaneously!
Your brain is constantly bombarded with sensory information from your eyes, ears, skin, nose and tongue. It filters this information, focusing on what's important and ignoring what isn't. For example, you might not notice the feeling of your clothes against your skin until you think about it, but you'd immediately notice if someone tapped you on the shoulder.
The motor cortex in your brain controls voluntary movements. When you decide to move, signals travel from the motor cortex down the spinal cord to the relevant muscles. The cerebellum helps coordinate these movements, making them smooth and precise. This is why activities like riding a bike or playing a musical instrument become easier with practice your cerebellum learns the patterns!
The CNS can be affected by various conditions that disrupt its normal function. Understanding these disorders helps scientists develop treatments and preventive measures.
A progressive brain disorder that affects memory and thinking skills. It involves the build-up of abnormal proteins in the brain that disrupt communication between neurons.
An autoimmune disease where the immune system attacks the myelin sheaths around axons, disrupting nerve signals. This can cause a wide range of symptoms including vision problems, muscle weakness and coordination difficulties.
A neurological disorder characterised by recurrent seizures caused by abnormal electrical activity in the brain. Seizures can range from brief lapses of attention to severe convulsions.
Your brain uses about 20% of your body's energy, despite making up only about 2% of your body weight! It's constantly active, even when you're asleep. In fact, some areas of your brain are more active during sleep than when you're awake, helping to consolidate memories and clear out waste products.
Your central nervous system is incredibly important but also vulnerable. Here are some ways to keep it healthy:
Remember, your central nervous system is what makes you you it stores your memories, controls your movements and shapes how you experience the world. Taking care of it is one of the most important things you can do for your health!
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