Nervous System and Reflex Arc

• What are the two organ systems that help large multicellular organisms communicate internally?

  The nervous system and the endocrine system
• Why do large multicellular organisms need a communication system?


  To coordinate behavior and respond to their surroundings
• What are the main topics to know about the nervous system?

  • Structure of a nerve cell
  • Structure of the whole nervous system
  • How a reflex arc works
• What is another name for a nerve cell?


  Neuron
• What is the primary function of neurons?


  To carry electrical impulses from one point to another
• How are neurons adapted to their function?


  They are long, thin, and have many branch connections
• What is a synapse?


  A connection between two nerve cells
• What happens when an electrical impulse reaches the end of a nerve cell?


  It causes the release of chemicals that diffuse across the synapse
• What do the chemicals released at a synapse do?


  They trigger another electrical impulse in the next nerve cell
• What constitutes the whole nervous system?


  About 100 billion neurons
• What are the two main parts of the central nervous system?


  The brain and the spinal cord
• What is the role of the central nervous system?


  To process sensory information and send out orders
• How does the central nervous system receive information about the body?


  Through sensory neurons that carry information from receptors
• What type of information do sensory neurons carry?


  Information about changes in the body, like temperature or carbon dioxide levels
• What happens after the central nervous system processes information?


  It sends impulses back out to the body via motor neurons
• What are effectors in the nervous system?


  Muscles or glands that respond to impulses
• What is a reflex arc?


  A nerve pathway that underlies unconscious reflexes
• Why are reflexes beneficial?


  They allow for rapid and automatic responses to stimuli
• What is an example of a reflex action?


  Moving your hand away from a hot pan
• What is the role of receptor cells in a reflex action?


  They detect stimuli such as pressure
• What happens to the impulse in the spinal cord during a reflex action?


  It is transferred to a relay neuron
• What does the relay neuron do in a reflex arc?


  It passes the impulse to a motor neuron
• What is the final step in a reflex arc?


  The motor neuron sends an impulse to an effector
• How do synapses function in a reflex arc?


  They convert electrical signals to chemical signals between neurons
• What are the steps involved in a reflex arc?


  1. Stimulus detected by receptor cells
  2. Sensory neuron carries impulse to spinal cord
  3. Relay neuron transfers impulse within spinal cord
  4. Motor neuron carries impulse to effector
  5. Effector (muscle or gland) responds