The Nervous System

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  • Nervous Sysytem
    • Sense  Organs
      • Detect stimuli
        • Change in the environment
          • e.g. light, pressure, pain, chemical, change in position/temperature
      • All contain receptors
        • Group of cells sensitive to a stimulus
          • Change stimulus energy into electrical impulses
      • Eyes
        • Light receptors
          • Sensitive to light
        • Cells - nucleus, cytoplasm, cell membrane
      • Ears
        • Sound receptors
          • Sensitive to sound
        • Balance receptors
          • Sensitive tochanges in position
      • Nose
        • Smell receptors
          • Sensitive to chemical stimuli
      • Tongue
        • Taste receptors
          • Sensitive to bitter, salt, sweet, sour, savoury (MSG - chemical stimuli
      • Skin
        • Touch receptors
          • Sensitive to touch, pressure, pain, temp
    • Central Nervous System
      • Where all info from SO is sent
        • Neurones transmit info
        • Quickto and from CNS
      • Reflexes and actions are coordinated
        • 'instructions' sent to effectors which respond
      • Consists of Brain + Spinal chord
        • Sensory neurones
          • Nerve cells carry signals from receptors in SO to CNS
        • Relay neurones
          • Nerve cells - impulsw from sensory neurone to motor neurone
        • Motor neurones
          • Nerve cells - signals from CNS to effector (muscles or glands)
        • Effectors
          • Muscles and Glands (respond in different ways)
            • Muscles contract
            • Glands secrete hormones
    • Synapses
      • Connect neurones
      • Transfer nerve signals by chemicals diffusing across the gap
      • Chemicals set off new electrical signal in the new neurone
    • Reflexes
      • Automatic response
        • Prevent injuries
      • Reflex Arc
        • Goes through CNS
        • 1. Neurones in reflex arc    -> spinal chord or unconscious part of brain
          • 2. Stimulus detected - impulse sent along sensory neurone to CNS
            • 3. Impulse reaches synapse (sensory + relay) - trigger chemical release - cause impulse along relay neurone
              • 4. Impulse reach synapse (relay + motor) - trigger chemical release - Chemicals down motor neurone
                • 5. Impulse along motor to effector
                  • 6. Muscle contracts / Gland secretes
                • Motor neurone
                  • Effector
                    • Response
                      • 6. Muscle contracts / Gland secretes
                    • 5. Impulse along motor to effector
            • Stimulus
              • Receptor
                • Sensory neurone
                  • Relay neurone
                    • Motor neurone
                      • Effector
                        • Response
                      • 4. Impulse reach synapse (relay + motor) - trigger chemical release - Chemicals down motor neurone
                      • 3. Impulse reaches synapse (sensory + relay) - trigger chemical release - cause impulse along relay neurone
                      • 2. Stimulus detected - impulse sent along sensory neurone to CNS

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