Nervous system

• 2 main components of CNS

  • Brain
  • Spinal Cord
• Brain


  Located within the skull. Organizer and distributor of information for the body.
• Spinal Cord


  Channel for signals between the brain and the rest of the body, and controls simple musculoskeletal reflexes without input from the brain.
• Three main parts of the Brain

  • 1.
  • 2.
  • 3.
• Brain stem


  1. Keeps the automatic systems of your body working

  2. You don't have to think about breathing, you just do it automatically

  3. You don't have to think about your heart beating because your brain keeps it going automatically
• Peripheral Nervous System


  Responsible for relaying messages between the central nervous system and the rest of the body
• 2 main divisions of PNS

  • 1.
  • 2.
• Two main parts of Somatic Nervous system

  • Spinal Nerves
  • Cranial Nerves
• Spinal Nerves


  Carry motor and sensory signals between the spinal cord and the body
• Cranial Nerves


  Carry information into & out of the brain stem
• 2 Subdivisions of Autonomic Nervous System


  • 1.
  • 2.
• Neuron


  A nerve cell, or a cell whose job it is to carry electrochemical messages throughout the nervous system
• Dendrites


  • Tiny threadlike structures which receive and carry information towards the cell body
  • A cell may have as many as 200 dendrites
  • Can be over one meter long
• Myelin Sheath


  • Covers the axon which speeds up the travel of nerve impulses
  • Produced by Schwann cells
  • Contains periodic gaps called Node of Ranvier
• Axon terminals


  • Featherlike fibers at the far end of the axon which pass on messages to the dendrites of other neurons
• Sensory neurons


  Also called afferent neurons, they are the nerve cells that are activated by sensory input from the environment
• Sensory neurons


  • When you touch a hot surface with your fingertips, the sensory neurons will be the ones firing and sending off signals to the rest of the nervous system about the information they have received
• Interneurons


  • Also called connector neurons or association neurons, they read impulses received from sensory neurons
  • They are found in the spinal cord and in the brain
  • When an interneuron receives an impulse from a sensory neuron, it determines what response should be generated
  • If a response is required, it passes the impulse on to the motor neurons
  • They connect spinal motor and sensory neurons
• Motor Neurons


  • Also called efferent neurons, they transmit impulses from the brain and the spinal cord to the effector cells (cells that actively responds to stimulus and effect change), which may be those of muscles, organs or glands
  • When motor neurons receive a signal from the interneuron, they stimulate the effector cells to generate the reaction for the stimulus
• Motor neurons


  • When one already feels pain from pressing a finger hard on a table, the motor neurons carry impulses to the muscles of the hand to stimulate the muscles to pull the finger away from the table