Biology Chapter 4

• What is homeostasis?

  Regulation of a constant internal environment
• Why are conditions maintained in homeostasis?

  To ensure optimum conditions for metabolism
• What does homeostasis respond to?

  Internal and external fluctuations
• What does homeostasis regulate in humans?

  Blood glucose, body temperature, CO₂ and water
• How are the levels monitored and regulated in homeostasis?

  Automatic control systems
• What are the two types of automatic control systems?

  Nervous and chemical responses
• What system coordinates nervous responses?

  The nervous system
• What system coordinates chemical responses?

  The endocrine system
• What is information about the environment called?

  A stimulus
• What detects a stimulus?

  A receptor
• What processes the information in homeostasis?

  A central coordination system
• What initiates a response?

  An effector
• What is a synapse?

  The gap where two neurons meet
• Why can't information be passed as an electrical impulse over the synapse?

  There is a gap
• How is a message transmitted across a synapse?

  By chemical neurotransmitters
• What happens when an electrical impulse arrives at the terminal of the first neuron?

  Release of neurotransmitter chemicals
• How do neurotransmitters transmit the signal to the next neuron?

  They bind to receptor sites
• What is special about receptor sites?

  They are specific for each neurotransmitter
• When will a nerve impulse be created in the second neuron?

  When a complimentary chemical binds
• What is a stimulus?

  A change in the environment
• Where is information sent after being received by a receptor?

  Along a sensory neuron to the CNS
• What does CNS stand for?

  Central nervous system
• What is the CNS comprised of?

  Brain and spinal cord
• What happens to the impulse in the CNS?

  Passed through relay neurons and coordinated
• How is a response initiated by the CNS?

  Consciously or subconsciously
• How does the CNS send information about the response?

  Along a motor neuron

  
• What receives the impulse from the motor neuron?

  The effector
• What does the effector do?


  Carries out the response
• What do rod and cone cells respond to?

  Light
• What do cells in the skin respond to?

  Pressure or temperature changes
• What might a muscle do in response?

  Contract to make a movement
• What might a gland do in response?

  Release a chemical
• What kind of response does the nervous system allow?

  A fast, short-lived response
• How is the information passed along in the nervous system?

  As an electrical impulse
• What is the main part of the nerve cell?

  The axon
• What is the axon?

  A long fibre of cytoplasm
• What travels along the axon?

  An electrical impulse
• What does the myelin sheath do?

  Insulates the electrical impulse
• What is the myelin sheath?

  A layer of fatty cells
• What are dendrites?

  Branched endings