SNC 2D

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The Nervous System

• SNC 2D

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Nervous System

• The organ system that is made up of
• the brain, spinal cord, and the
• peripheral nerves
• System that senses the environment
• and coordinates appropriate responses

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Central Nervous System

• Consists of the brain and the spinal cord
• Shielded by bones
• Skull protects the brain
• Spine protects the spinal cord
• Cerebrospinal fluid surrounds the brain and
  spinal cord cushions against injury and
  transports chemicals and waste

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Peripheral Nervous System

• Consists of the nerves that connect the body to
  the central nervous system
• Relays information about the internal and
  external environments of the brain
• Subdivided into
• A) nerves that control voluntary muscles
• B) nerves that carry information from sensory
  organs
• C) nerves that regulate involuntary functions

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Nerve Tissue

• Specialized cells that make up nerve tissue are
  called neurons
• Found in brain, spinal cord and nerves
• Approximately 100 billion neurons in human brain
• Neurons conduct electrical signals (nerve
  impulses) from one area of body to another

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Structure
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Sending a Signal

• Nerve cell sends a signal through axon
• Attaches to dendrites of another cell
• Continues until reaches muscle cells
• Signal goes in only one direction

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Myelin Sheath

• Fatty material that surrounds the axon
• Acts like an electrical wire preventing
  electrical impulses from passing to the wrong
  neuron

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Nerves

• Bundles of neurons surrounded
• by connective tissue
• Allow two-way flow of information
• even though each neuron transmits
• information only in one direction

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Sensory Receptors

• Special cells or tissues that receive input from
  our external environment and send signals along
  our peripheral nerves to our central nervous
  system
• Ears, mouth, nose, muscles, and skin
• Other receptors are sensitive to
• pressure, temperature, and pain and
• make us aware of our balance,
• position and motion

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Other functions

• Increase/decrease breathing rate
• Heart beat faster/slower
• Eat/drink/stop
• Perception
• Spinal Cord acts as a short cut for reflexes
• Reflexes do not use brain, occur without
  conscious thought (move hand away from hot
  surface)

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Repair

• Peripheral nervous system can undergo cell
  division to repair severed nerves (few mm
  distance)
• Central nervous system do not regenerate easily

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Diseases and Disorders

• Multiple Sclerosis destroys myelin sheaths so
  that signals are mixed up
• Fall or blow can result in paralysis,
  concussions
• Viruses and bacteria can cause permanent damage
  in brain
• nervous system
• pork tapeworm