Homeostasis and the Nervous System

• Key Point

  Homeostasis is the maintenance of a constant internal environment by compensating for changes
• What are the specialized cells in control systems called?

  Receptors
• What is the role of receptors in control systems?

  They detect stimuli in the environment
• What are the coordination centres in control systems?

  Brain, spinal cord, and pancreas
• What do coordination centres do in control systems?

  They receive and process information from receptors
• What are effectors in control systems?

  Muscles or glands
• What is the function of effectors in control systems?

  They carry out responses to restore optimum levels
• What is the mechanism called that regulates control systems?

  • Negative feedback
  • Compares stimulus to a set point
  • Restores optimum levels
• How does the control centre in the brain respond to high blood sugar levels?

  It releases insulin to lower glucose levels
• What happens when blood sugar levels are too high?

  Receptors detect increase, pancreas releases insulin
• What is the response when blood sugar levels are too low?

  The pancreas releases glucagon to increase glucose
• What is the role of glucagon in blood sugar regulation?

  It breaks down glycogen into glucose
• What happens to stored glycogen when blood sugar is low?

  It is broken down into glucose and released
• Where is glycogen stored in the body?

  In the liver
• What is the primary function of the nervous system?

  To react to surroundings and coordinate behavior
• How does information from receptors reach the central nervous system (CNS)?

  It passes through sensory neurones to the CNS
• What role does the CNS play in the nervous system?

  It coordinates the response of effectors
• What are effectors in the nervous system?

  Muscles or glands that respond to stimuli
• What are the steps involved in a reflex action?

  1. Pain stimulus detected by receptors
  2. Impulses travel along sensory neurone to CNS
  3. Impulse passes through relay neurone
  4. Motor neurone carries impulse to effector
  5. Effector responds, e.g., muscle withdraws limb
• What is the nature of reflex actions?

  They are automatic and rapid
• Why are reflex actions important?

  They protect the body from harm
• Are neurones directly connected to each other?

  No, they are not directly connected
• What happens when an electrical impulse reaches a synapse?

  A chemical is released across the gap
• What is the result of the chemical released at a synapse?

  It generates an electrical impulse in the second neurone
• What is the function of the chemical released at a synapse?

  To facilitate impulse transmission between neurones
• What is the purpose of the experiment described in the study material?

  To investigate the effect of a factor on human reaction time
• What is the sample method for investigating reaction time?

  1. Hold a metre ruler vertically.
  2. Subject places fingers on the 50cm line.
  3. Experimenter drops the ruler.
  4. Subject catches the ruler.
  5. Measure distance from the 50cm line.
  6. Repeat with subjects who have or haven't consumed caffeine.
• What does the experimenter do with the ruler?

  The experimenter holds it vertically and drops it
• Where does the subject place their fingers during the experiment?

  On the 50cm line of the ruler
• What is noted after the ruler is caught?

  The distance the ruler travels from the 50cm line
• How does the experiment vary with different subjects?

  Subjects have either consumed caffeine or not
• What are the considerations, mistakes, and errors in this experiment?

  • Difficult to control variables
  • Large sample size needed for reliability
  • Averages should be taken from results
• What is the independent variable in this experiment?

  Whether the subject has taken caffeine
• What is the dependent variable in this experiment?

  The distance that the ruler travels
• What are the control variables in this experiment?

  • Age of the subjects
  • Sex of the subjects
  • Mass of the subjects
• What are the hazards and risks associated with this experiment?

  There are limited risks with this experiment