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Nervous System

Nervous System . Part 1 Biology 12. The Nervous System. An integral part of your body’s communication system. It plays an important role in the smooth functioning of the body. The nervous system is a complex network of cells which are specialized in function. Homeostasis & Nervous System.

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Nervous System

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  1. Nervous System Part 1 Biology 12

  2. The Nervous System • An integral part of your body’s communication system. • It plays an important role in the smooth functioning of the body. • The nervous system is a complex network of cells which are specialized in function.

  3. Homeostasis & Nervous System • The Nervous System allows the body to respond to changes in the internal and external environments. • Communication comes in the form of electrochemical messages relayed to and from the brain, or a series of chemical messengers carried in the blood. • Through a series of adjustments, all systems of the body are regulated to maintain the internal environment within safe limits (homeostasis).

  4. Two divisions... • The nervous system has two main divisions: • Central Nervous System (CNS) • Peripheral Nervous System (PNS)

  5. Central nervous system • Consists of the nerves of the brain and spinal cord. • Brain is known as the “cerebrum” • Acts as a coordinating centre for incoming and outgoing information.

  6. The Cerebrum (brain) • The brain consists of millions of nerve cells that cluster together and interact with each other through the process of neurotransmission. • It controls most of the bodily functions like movements, thoughts, speech, sensations and memory.

  7. The spinal cord • The spinal cord is a continuation of the brain and is surrounded by the vertebral bodies that form the spinal column. • The spinal cord is divided into four main segments; reach transferring signals to different parts of the body.

  8. Video clip • http://www.youtube.com/watch?v=vGxho71tScM&NR=1

  9. Peripheral nervous system • Consists of nerves that carry information between the organs of the body and the central nervous system. • It can be further divided into: • Somatic nervous system • Autonomic nervous system

  10. Nerve cells • Information about your body is continuously relayed to your brain for processing and storage. • The cells that transfer these messages to the brain and around the body are nerve cells.

  11. Cells of the Nervous system • Nerve cells gather & transmits electro-chemical signals. DID YOU KNOW???? • Neurons cannot be repaired • Some last a life time • Approximately 1000 die each day!!!

  12. Nerve vs neurons • A nerve is a bundle of neurons attached by connective tissue

  13. Neuron notables • Average number of neurons in the human brain = 100 billion • Nerve “highway” in the human body contains 100 billion neurons • 1000 impluses/sec

  14. Types of neurons • SENSORY • Carries signals FROM periphery (outside) TO central nervous system for processing • Information FROM environment • NOTE: detect external stimuli (light, sound, touch, heat, smell, & taste) or internal conditions (blood pressure, CO2level & muscle tension)

  15. Types of neurons • MOTOR • Carries signals FROM central nervous system TO body part (e.g. muscles, skin, glands) • Respond to sensory neurons • Responsible for movement

  16. Types of neurons • INTERNEURONS • Connects sensory or motor neurons to central nervous system • Carries messages in-between neurons • Majority of neurons in the brain are interneurons

  17. Parts of a neuron • Cell Body • Contains all organelles, including a nucleus • Dendrites • Projections off cell bodies • Make connections with other cells

  18. Dendrites Cell body Cell body Nucleus Figure 27.3

  19. Parts of a neuron • Axon • Long cable like projection off cell body • Sends messages (nerve impulses) • Myelin Sheath • Fatty protein that covers/insulates most nerves • Increases speed of transmission • Formed by Schwann cells • Nodes of Ranvier • Exposed axon between myelin sheath

  20. Dendrites Cell body Cell body Axon Nucleus Nodes of Ranvier Myelin sheath Figure 27.3

  21. Parts of a neuron • Synaptic knob • End of axon branches • Comes near dendrites of adjacent neurons • Passes messages across synapse (the space between neurons)

  22. Signal direction Dendrites Cell body Cell body Signal pathway Axon Synaptic knobs Supporting cell Nucleus Nodes of Ranvier Myelin sheath Figure 27.3

  23. Direction of message • Moves in only one direction • From dendrite to cell body, axon, then synaptic knob

  24. Signal direction Dendrites Cell body Cell body Signal pathway Axon Synaptic knobs Supporting cell Nucleus Nodes of Ranvier Myelin sheath Figure 27.3

  25. Neurons in Action • The three interconnected functions of the nervous system are carried out by the three types of neurons Sensory input Integration Sensory neuron Sensory receptor Motor neuron Interneuron Motor output Brain and spinal cord Effector Peripheral nervous system (PNS) Central nervous system (CNS) Figure 27.2

  26. Let’s review: video clips • Nervous System explained • Nervous System Rap • How Neurons Work

  27. TASK • Draw a large motor neuron on a white piece of paper. • Label • Cell body • Nucleus • Dendrites • axon • Myelin sheath • Schwann cells • Node of Ranvier • Synaptic knob • Then draw arrows to show the message direction • Identify the motor neuron functions

  28. Motor Neuron Synaptic knob

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