Health Stats This graph compares bicycle-helmet use and seat-belt use among teens. Why do you think many more teens wear seat belts than bicycle helmets?
Goals/Objectives • Identify parts and functions of the nervous system. • Identify behaviors to keep your nervous system healthy.
Key Terms • Nervous System • Central Nervous System • Peripheral Nervous System
The Nervous System • The body system that carries messages to and from the brain and spinal cord and all other parts of the body is the nervous system. • Composed of 2 divisions: • Central nervous system • Peripheral nervous system
Central Nervous System Peripheral Nervous System The peripheral nervous system is made up of nerves that branch out from the central nervous system to muscles, skin, internal organs, and glands. Sense organs continually send messages, such as odors, sights, or tastes, to your brain. • The central nervous system consists of the brain and spinal cord. • Relays responses to these messages to your muscles and glands as your body responds to changes in your environment.
The Brain • The mass of nerve tissue that acts as the control center of the body is called the brain. • Human brain weighs about 3 lbs. • Can store more information that all the libraries in the world put together • Creates ideas and controls thinking, reasoning, movement, and emotions • The brain has 3 major parts: • The cerebrum • The cerebellum • The brain stem
The Cerebrum • The cerebrum is the largest part of the brain and controls the ability to memorize, think, and learn. • Determines a person’s intelligence and personality • Consists of two halves, called hemispheres • The right hemisphere controls the left side of the body • The left hemisphere controls the right side of the body
The Cerebellum & Brain Stem • The cerebellum is the part of the brain that controls and coordinates muscle activity. • Helps you maintain your balance • You’re ability to catch a ball is a function of your cerebellum. • The brain stem is the part of the brain that controls the functions of the internal organs.
Spinal Cord • The column of nerve cells that extends downward from the brain is the spinal cord. • Carries messages to and from your brain and all parts of your body. • Keeps your brain informed of changes in your body and in your environment • Protected by your vertebrae
Nerve Cells • The nervous system is composed of cells called neurons. • A neuron is a nerve cell that is the structural and functional unit of the nervous system. • A neuron consists of a cell body, and axon, and dendrites.
Parts of a Neuron • A cell body is the main body of the neuron. • An axon is an elongated fiber that carries impulses away from the cell body to the dendrites of another neuron. • Dendrites are branching fibers that receive impulses and carry them to the cell body.
NeuronStructure Dendrite Dendrites carry nerve impulses toward a neuron’s cell body. Synapse The junction between an axon and another cell is a synapse. Chemicals called neurotransmitters pass the impulse from the sending neuron to the receiving cell. CellBody The cell body controls the cell’s basic functions. Axon Impulses travel along axons toward other cells. MyelinSheath Some axons are covered by a myelin sheath that increases the speed of an impulse.
Sensory & Motor Neurons • Sensory and motor neurons work together to help you respond to your environment. • Sensory neurons carry impulses from the sense organs to the spinal cord and brain. • Motor neurons carry responding impulses to muscles and glands from the brain and spinal cord. • Cause responses in muscles and glands
Mixed Messages Notice that the words in the list are written in different colors. This time you should say the color of each word as your partner times you. Do not read the words, rather, identify their colors. Test how well your brain can handle conflicting messages. Material watch or clock with second hand Try This Read the list of words while your partner times how long it takes you.
Mixed Messages Which part of your brain most likely works hardest during this activity? Which task is your brain better at—reading the words or identifying their colors? Once people master basic skills such as tying shoes or reading, they perform them with little thought. How do you think this fact affected your results in this activity? What do you think would happen if you asked a young child who has just learned to read to do this activity? Explain. Think and Discuss Did it take you more time to read the words or say the colors? Describe the experience of saying the colors.
Reflex Action • A reflex action is an involuntary action in which a message is sent to the spinal cord, is interpreted, and is responded to immediately. • Do not take a conscious thought and take only a fraction of a second. • i.e. touching a hot stove and quickly pulling your hand away • Sensory neurons carry the message that you touched something hot to your spinal cord and brain • Your brain interprets the message. • Motor neurons carry the message back to your muscles. • You respond by moving your hand.
Sensory neurons in your hand send impulses to your spinal cord. Neurons in your spinal cord process the information and send commands directly to motor neurons that control muscles in your arm and hand. Your muscles contract and you quickly withdraw your hand. Meanwhile, messages of pain travel to the brain. Shortly after your arm moves, you feel pain. A Reflex Action
FYI – Sensory Signals • Sensory signals are the only signals that travel inward from the peripheral nervous system to the central nervous system, and are sensitive to light, temperature, chemicals, and pressure. • Motor signals travel outward from the central nervous system to the peripheral nervous system.
How to Keep Your Nervous System Healthy • Wear a protective helmet for sports. • Avoid diving into the shallow water or water of unknown depth. • Follow directions for taking any medications that affect the nervous system. • Use a safety belt. • Avoid drinking alcohol and using other drugs that impair the functions of the brain. • Follow directions for using household products that contain chemicals that may affect the nervous system.
Avoiding Head Injuries • A bruiselike injury to the brain is known as a concussion. • A comais a prolonged period of deep unconsciousness. • Head injuries can be avoided. • Wear a helmet when you play contact sports. • Fasten your seat belt. • Before diving into water be sure that it is deep enough and that there are no underwater hazards. • Avoid drugs and alcohol.
Avoiding Nerve Injuries • Individual peripheral nerves also can be injured. • To help prevent carpal tunnel syndrome and similar nerve injuries, it is important to take breaks from repetitive motions and to maintain good posture.
Preventing Infections • Nervous system infections are rare because its tissues are well protected. • Meningitis causes inflammation of the membranes surrounding the brain and spinal cord. • The most serious form of meningitis can be prevented with a vaccine. • A bite from an infected animal can transmit rabies, an infection of the central nervous system. • Avoid contact with animals that act sick or behave strangely.
Living with Epilepsy • Sudden, uncontrolled nerve impulses in the brain can lead to a seizure. • People with a disorder called epilepsy are prone to seizures. • Epileptic seizures include facial twitching, loss of awareness, and muscle spasms.
Preventing Headaches • The most common problem of the nervous system that people experience are headaches. • Proper diet, exercise, and sleep can help prevent headaches. • If you can identify certain foods or odors that trigger headaches, you may be able to avoid those triggers.
Questions • What parts make up your nervous system? • What is the difference between the central nervous system and the peripheral nervous system? • What is the difference between sensory neurons and motor neurons? • What is a reflex action, and how to they help protect the body? • Which part of the brain controls the ability to read? • Why is it so important to protect your nervous system from injury?