The Nervous System for Middle School Science
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The human body is a huge topic! The nervous system is just one of the body's systems that make the human body work. Our nervous system gathers information from our environment (both external and internal) and sends instructions out to the rest of the body.
You can check out the pages of my nervous system unit from Teachers Pay Teachers below. You can also continue on to read more about the nervous system.
The Nervous System
The nervous system is the body’s communication center. It controls everything you do—from moving your muscles to feeling emotions, breathing, and even thinking. It’s made up of special cells called neurons, which carry messages around your body like tiny electrical signals. These messages help different parts of the body talk to each other and respond quickly to what's happening inside and outside of you.
Functions of the Nervous System
The nervous system has three main functions that work together to help your body respond to the world around you: sensory input, processing information, and motor output. Each of these steps is crucial for keeping you safe, helping you think, and allowing your body to function properly.
1. Gathering Information (Sensory Input)
The nervous system constantly gathers information from inside and outside your body using special cells called sensory neurons. These neurons detect changes in your environment—such as light, sound, temperature, and pain—and changes inside your body, like hunger, thirst, or a full stomach. Your sense organs (eyes, ears, skin, nose, and tongue) are filled with sensory neurons that send messages to your brain when they detect something new. For example, when you touch something hot, sensory neurons in your skin immediately send a signal to your brain saying, "This is too hot!"
2. Processing Information (Integration)
Once the brain and spinal cord receive the sensory messages, the central nervous system processes that information. This is when your brain decides what to do with the signals it receives. The brain quickly compares new information with memories and past experiences to make sense of what’s happening. For example, if you hear a loud noise, your brain might decide it’s just thunder—or it might recognize it as something dangerous and tell your body to react. This step happens so fast that you don’t even notice it most of the time.
3. Responding to Information (Motor Output)
After the brain processes the information, it sends out instructions to the rest of the body using motor neurons. These neurons carry signals from the brain and spinal cord to your muscles and organs, telling them what to do. This response is called motor output. It might be something you choose to do, like waving to a friend, or something automatic, like pulling your hand away from a sharp object. Some reactions are also reflexes, which happen so fast that the signal doesn't even need to go all the way to your brain—your spinal cord handles it to protect you.
Overall, the nervous system works like a super-fast messaging and control center. It helps you sense, think, remember, move, and react—all in a matter of seconds. Without it, your body wouldn't be able to function or respond to the world around you.
Parts of the Nervous System
The nervous system is made up of two major parts: the central nervous system (CNS) and the peripheral nervous system (PNS). Each part plays an important role in helping your body sense the world, process information, and respond quickly and correctly.
Central Nervous System (CNS)
The central nervous system is made up of the brain and the spinal cord. It acts like the control center of your body. The CNS takes in information from the senses, processes it, makes decisions, and sends instructions to the rest of your body.
Brain:The brain is the most important and powerful organ in the nervous system. It is protected by the skull and made up of billions of nerve cells. The brain controls your thoughts, emotions, memory, learning, and even the movements of your body. It also controls automatic functions like your heartbeat and breathing.
The brain has different parts, each with a special job:
The cerebrum helps you think, learn, speak, and move your muscles.
The cerebellum controls balance and coordination.
The brainstem controls automatic actions like breathing, heartbeat, and digestion.
Spinal Cord:The spinal cord is a thick bundle of nerves that runs from your brain down your back. It is protected by the bones of the spine (vertebrae). The spinal cord connects the brain to the rest of the body and acts like a highway for messages going to and from the brain. It also controls reflexes, which are fast, automatic actions that protect you from danger (like pulling your hand away from a hot surface).
Peripheral Nervous System (PNS)
The peripheral nervous system includes all the nerves that branch out from the brain and spinal cord and spread throughout your body. These nerves connect the CNS to your arms, legs, organs, and skin, allowing your brain to receive and send messages everywhere.
The PNS is made up of two main types of nerves:
Sensory nerves carry messages to the brain from your senses (like touch, sound, sight, smell, and taste). These help you notice what’s happening around and inside your body.
Motor nerves carry messages from the brain to your muscles and organs. These help you move, breathe, blink, and more.
The PNS also has two important divisions:
The somatic nervous system controls voluntary movements—like walking, jumping, or writing.
The autonomic nervous system controls involuntary actions, like your heartbeat, digestion, and breathing, when you’re not thinking about it. It has two parts:
The sympathetic system, which gets your body ready for action (like in emergencies or stress).
The parasympathetic system, which helps your body rest and relax.
Together, the CNS and PNS form a super-connected network that keeps your body running smoothly. They help you stay aware of your surroundings, make decisions, and take action—whether you're solving a math problem or catching a ball.
Parts of a Neuron
Neurons are special cells in the nervous system that send and receive messages throughout the body. These messages help you think, move, feel, and react. A single neuron has several parts, and each one plays a special role in passing information.
Cell Body (Soma): This is the main part of the neuron that contains the nucleus, which controls the cell’s activities. It keeps the neuron healthy and working properly.
Dendrites: Dendrites are branch-like structures that stick out from the cell body. They receive messages from other neurons and pass them toward the cell body.
Axon: The axon is a long, thin fiber that carries messages away from the cell body and toward other neurons or muscles. Some axons are very short, while others can be over a meter long!
Myelin Sheath: The axon is often covered by a fatty layer called the myelin sheath. This coating acts like insulation around a wire, helping the electrical signals move faster and more efficiently.
Axon Terminals (or Terminal Buttons): At the end of the axon are tiny branches called axon terminals. These send the message to the next cell by releasing chemicals.
How Information Travels Through Neurons
Messages in the nervous system are sent as electrical signals. Here's how the process works:
Message Starts: A message begins in the cell body and moves down the axon like a wave of electricity.
Speed Boost: The myelin sheath helps the message move faster along the axon.
Message Ends: When the signal reaches the axon terminals, it can't jump directly to the next neuron. Instead, it triggers the release of neurotransmitters, which are special chemicals.
Synapse Gap: The message crosses a tiny space between neurons called a synapse with the help of neurotransmitters.
Next Neuron: The next neuron picks up the message with its dendrites, and the process begins again.
Parts of the Brain
The brain is the control center of your body. It’s part of the nervous system and is protected by the skull. The brain controls everything you do—from breathing and blinking to thinking and dreaming. Scientists divide the brain into different parts, and each part has its own important job.
Cerebrum – Thinking and Sensing
Location: The largest part, at the top and front of the brain
Controls: Thinking, memory, emotions, language, and voluntary movements like walking or writing
Fun Fact: The cerebrum is divided into two halves, or hemispheres—left and right. Each side controls the opposite side of your body!
The cerebrum is also divided into lobes:
Frontal lobe: Decision-making, planning, and movement
Parietal lobe: Touch, temperature, and spatial awareness
Occipital lobe: Vision and seeing
Temporal lobe: Hearing and understanding language
Cerebellum – Balance and Coordination
Location: Below the cerebrum, at the back of the brain
Controls: Balance, posture, and muscle coordination
Fun Fact: The cerebellum helps you move smoothly and stay steady. Without it, even simple movements like picking up a pencil would feel clumsy!
Brainstem – Life Support
Location: At the base of the brain, connecting to the spinal cord
Controls: Involuntary actions like breathing, heartbeat, and digestion
Fun Fact: You don’t have to think about breathing or your heart beating—your brainstem does it for you!
The brainstem includes three parts:
Midbrain: Controls eye movement and processes some sounds and sights
Pons: Helps control sleep and connects different parts of the brain
Medulla oblongata: Controls vital body functions like breathing and heartbeat
Limbic System – Emotions and Memory
Location: Deep inside the brain
Controls: Emotions, memory, and motivation
Key Parts:
Amygdala: Helps process emotions like fear and anger
Hippocampus: Important for making and storing memories
All these brain parts work together like a team. For example, when you ride a bike:
The cerebrum helps you decide where to go.
The cerebellum keeps you balanced.
The brainstem keeps you breathing and your heart beating.
The limbic system might make you feel happy or excited.
Your brain is powerful, and even though it weighs only about 3 pounds, it contains billions of nerve cells called neurons that help it send and receive information constantly.
Senses of the Human Body
Your senses help you understand and respond to the world. They send information to your brain about what’s happening both inside and outside your body. Most people are familiar with the five main senses, but humans actually have more than that! These lesser-known senses are just as important for keeping you balanced, aware, and safe.
1. Sight (Vision)
Main organ: Eyes
Your eyes detect light and color using special cells called rods and cones in the retina. These light signals are sent through the optic nerve to the brain, which creates the images you "see." Sight helps you read, watch movies, recognize faces, avoid obstacles, and enjoy nature. Without vision, your brain would be missing a huge source of information.
2. Hearing (Audition)
Main organ: Ears
Sound waves enter your ears and make tiny bones in your middle ear vibrate. These vibrations are turned into electrical signals by the inner ear and sent to your brain. Hearing allows you to enjoy music, follow conversations, listen for warnings like sirens, and learn through spoken language. It also plays a role in balance.
3. Smell (Olfaction)
Main organ: Nose
Inside your nose are smell receptors that detect tiny chemical particles in the air. These signals go to the brain's olfactory bulb, which identifies the smell. Smell is connected to memory and emotion. A single smell, like cookies baking, can remind you of a specific moment or feeling. Smell also helps you detect danger, like smoke or spoiled food.
4. Taste (Gustation)
Main organ: Tongue
Your tongue has taste buds that detect five main tastes: sweet, salty, sour, bitter, and umami (a meaty or savory flavor). Taste works closely with smell to create flavor. When you have a cold and can’t smell well, food may taste bland. Taste helps you choose foods that are good for you and avoid harmful ones.
5. Touch (Tactile Sense)
Main organ: Skin
Your skin is covered with receptors that sense pressure, temperature, texture, and pain. These send messages to the brain to help you react. Touch allows you to feel warmth, comfort, and danger. It's how you know if something is sharp, too hot, or soft like a kitten’s fur. Touch also plays a role in emotional bonding and safety.
Lesser-Known Senses: More Than Just Five
Scientists have discovered that we rely on many more than five senses. While the exact number is debated, experts often estimate that humans have between 9 and over 20 distinct senses. These extra senses help us understand what’s going on inside our bodies and respond to changes in our environment.
Balance (Equilibrioception): This sense helps you stay upright and know which way is up. It comes from the inner ear, where tiny structures sense movement and gravity. You use this sense when you ride a bike, walk on a balance beam, or stand on one foot without falling over.
Body Awareness (Proprioception): Proprioception lets you know where your body parts are, even if you’re not looking at themYou rely on this sense when you touch your nose with your eyes closed or walk without staring at your feet. It helps you move smoothly and coordinate actions.
Temperature (Thermoception): This sense allows you to feel if something is hot or cold. Sensors in your skin and inside your body send these signals to your brain. Thermoception helps you dress for the weather, avoid burns, and stay safe in dangerous temperatures.
Pain (Nociception): Pain is your body’s warning system. When something is wrong, your nerves send pain signals to the brain. This sense helps you avoid injury. For example, if you touch something sharp or step on a tack, pain tells you to stop and protect yourself.
Hunger and Thirst: These internal senses tell you when your body needs energy or water. Your brain monitors your body’s fuel levels and lets you know when it's time to eat or drink, helping you stay healthy and alive.
Your senses work together like a team to help you explore, learn, and survive. They guide your decisions, protect you from harm, and help you enjoy life. From catching a ball to tasting ice cream to sensing a storm coming, your senses give your brain the information it needs to act fast and smart.
Even though the five main senses are the most famous, it’s important to remember that your body uses many different kinds of senses—both inside and out—to keep you aware and in control.
How the Nervous System Interacts with Other Body Systems
The nervous system is like the body’s communication center. It sends and receives messages between the brain and the rest of the body, helping you move, think, feel, and react. But the nervous system doesn’t work alone—it interacts with all other systems in the body to help them do their jobs.
Nervous System and the Circulatory System
The nervous system controls your heart rate and blood pressure. For example, when you're scared or excited, the brain sends signals to the heart to beat faster. It also tells blood vessels to tighten or relax depending on your body’s needs. This helps your body respond to stress, exercise, or rest.
Nervous System and the Respiratory System
Breathing is automatic thanks to the nervous system. The brain tells the lungs and diaphragm when to breathe in and out. When you run or exercise, your brain senses the need for more oxygen and makes you breathe faster.
Nervous System and the Digestive System
When you see or smell food, your brain sends signals to the stomach to get ready to digest. The nervous system also controls how quickly food moves through your digestive tract. It can slow down or speed up digestion based on stress, rest, or activity.
Nervous System and the Muscular and Skeletal Systems
The nervous system works closely with your muscles and bones to help you move. Messages from the brain travel through nerves to muscles, telling them to contract. This lets you walk, jump, write, and even smile. It also helps you stay balanced and react quickly, like catching a ball or stepping away from danger.
Nervous System and the Endocrine System
The endocrine system sends messages using hormones, while the nervous system uses electrical signals. The two systems work together to control things like growth, mood, and energy levels. For example, the brain tells the endocrine glands when to release hormones like adrenaline during a stressful situation.
Nervous System and the Immune System
When you're sick or injured, the nervous system communicates with the immune system to help your body respond. It helps control fever, pain, and inflammation so that your body can fight off germs and start healing.
Every second, your nervous system is working with other systems to keep you safe and healthy. It helps you make fast decisions—like pulling your hand away from a hot stove—and slower ones, like feeling tired when it’s time to sleep.
Flashcards on the Nervous System
Flashcards are the best way to practice remembering new information. You can get digital and printable flashcards at Teachers Pay Teachers, or you can use the flashcards here for free!
The Human Body
Middle School Science
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