Coordinate

• Receptors


  Structures that can detect stimuli
• Effectors


  Structures that can produce a response to a stimulus
• Response should be coordinated, in animals two communication systems (nervous & hormonal) are involved to bind between receptors and effectors to insure that the right effector did the right response at the right time
• Nerve impulses


  Electrical signals that pass along the nerve cells called neurons, to deliver messages

  
• Neurons


  • They have long, thin fibres of cytoplasm stretching out from the cell body
  • The longest fibre in a neurone is called an axon
  • The shorter fibres are called dendrites
  • The dendrites pick up electrical signals from other neurones lying nearby

  
• Transmission of nerve impulses


  1. Signal passes to the cell body

  2. Then along the axon

  3. Might pass it to another neurone

  
• Central nervous system (CNS)

  Made of neurons, includes two parts; brain protected in the skull & spinal cord protected inside vertebral column
• Functions of CNS


  • Receive messages from receptors
  • Integrate and process information
  • Coordinate responses by sending out signals to effectors
• Nerves are bundles made of many nerve fibers (axons)
• The nervous system is differentiated into two main parts: Central nervous system and Peripheral nervous system
• Impulses


  Carried along neurones

  
• Main parts of the nervous system


  • Central nervous system
  • Peripheral nervous system
• Central nervous system (CNS)


  • Made of neurons, includes brain protected in the skull & spinal cord protected inside vertebral column
• Functions of CNS


  1. Receive messages from the receptors

  2. Coordinate the proper response
• Peripheral nervous system (PNS)


  • Made of receptors and nerves (sensory and motor)

  
• Functions of PNS


  1. Receptors detect the stimuli and convert them to nerve impulses (electrical signals)

  2. Sensory neurones carry impulses from the receptors to CNS

  3. Motor neurones carry impulses from the CNS to effectors

  
• Motor (effector) neurons


  • Has cell body at one end, many short dendrites, with long axon covered with myelin sheath
  • Carry nerve impulses from the CNS to the effectors

  
• Sensory neurons


  • Cell body not at one end, carry impulses from the receptors to CNS

  
• Relay (connector) neurons


  • Inside the CNS
  • Carry impulses from the sensory to motor neurons

  
• Reflex actions


  Automatic and rapid, integrating and coordinating responses to stimuli
• Components of reflex arc


  1. Receptor

  2. Sensory neuron

  3. Relay neuron

  4. Motor neuron

  5. Effector

  
• Reflex arc


  Pathway of nerve impulses in a reflex action
• Differences between voluntary and involuntary actions


  • Voluntary: Under conscious control, Need learning and training, Start in the brain, Slower
  • Involuntary: Not under conscious control, Do not need learning and training, Start at the receptors, Faster
• Voluntary actions


  • Walking, writing, reading, talking
• Involuntary actions


  • Knee jerk, withdrawal reflex, heart beats
• Reflex arc


  Pathway of reflex action
• Components of reflex arc


  • Receptor
  • Sensory neuron
  • Relay neuron
  • Motor neuron
  • Effector

  
• Reflex arc


  Pathway of nerve impulses
• Voluntary and involuntary actions


  • Voluntary
  • Involuntary
• Voluntary actions


  • Walking, writing, reading, talking
• Involuntary actions


  • Knee jerk, withdrawal reflex, heart beats
• Consciousness


  Voluntary actions are under conscious control, involuntary actions are not under conscious control
• Learning and training


  Voluntary actions need learning and training, involuntary actions do not need learning and training
• Pathway


  Voluntary actions start in the brain, involuntary actions start at the receptors
• Speed


  Voluntary actions are slower, involuntary actions are faster
• Synapse


  Junction between two neurons

  
• Structure of synapse


  • Synaptic cleft
  • Synapse
  • Vesicles containing neurotransmitter
  • Receptors on next neuron

  
• How impulses are transmitted at synapse


  1. Arrival of impulse causes vesicles to release neurotransmitter

  2. Neurotransmitter diffuses across synaptic cleft and binds to receptors

  3. This triggers a nerve impulse in the next neuron

  
• Synapse


  Acts as a one-way valve, ensures nerve impulses only travel in one direction
• Many drugs like heroin act on synapse