Response and Regulation

• Nervous system


  Controls the activity of the body
• Functions of the nervous system


  1. Detect changes in the environment

  2. Control the actions of the body

  3. Coordinate the responses of the body by linking various actions in specific ways, and making decisions about whether any action is needed and what sort of action to take
• Sense organs


  Groups of special cells called receptor cells, which can detect changes around them, either internally or in the external environment
• Stimuli

  Changes that can be detected by sense organs, including light, sound, chemicals, touch and temperature
• Information processing in the nervous system


  1. Information from sense organs travels to the brain and spinal cord (central nervous system) along nerve cells (neurones)

  2. The brain coordinates the information from the sense organs and takes appropriate action, if necessary
• Impulse


  The information that travels along the nerves as an electrical conduction
• Types of neurones

  • Sensory neurones
  • Motor neurones
• Reaction time

  The time taken between the stimulus and the response
• Reflexes

  • Very rapid response
  • Automatic, involuntary
  • Protective
• Examples of reflexes


  • Knee jerk reflex
  • Breathing
  • Blinking
  • Swallowing
  • Sneezing
  • Coughing
  • Pupil reflex
  • Withdrawal reflex
• Reflex arc

  1. Stimulus

  2. Receptor

  3. Coordinator

  4. Effector

  5. Response
• Reflexes do not involve the brain, they are quick because the impulse only goes through a few synapses
• Homeostasis

  The collection of processes which keep certain conditions in the body at a constant level, maintaining optimal conditions for chemical reactions
• Hormones

  Chemical messengers made in certain organs and travel in the bloodstream, affecting specific parts of the body
• Hormones are mainly used for medium-term and long-term regulation, whereas nerves generally control quicker responses
• Diabetes


  A condition where the body produces little or no insulin, leading to dangerously high blood glucose levels
• Types of diabetes


  • Type 1
  • Type 2
• Type 1 diabetes


  The body stops producing insulin, requiring insulin injections and careful diet management
• Type 2 diabetes


  The body no longer responds properly to insulin, can often be controlled by drugs and diet
• Negative feedback

  A control mechanism where a change in a factor sets off a series of events that bring that factor back to the normal level
• Negative feedback control of blood glucose


  1. High blood glucose

  2. Insulin released

  3. Glucose converted to glycogen and stored

  4. Blood glucose level reduced
• Temperature control


  Maintaining body temperature at around 37°C through various mechanisms
• Temperature regulation by the skin

  1. When hot: Sweat production, blood vessel dilation

  2. When cold: Reduced sweat production, blood vessel constriction, hair erection
• Shivering generates heat in cold conditions
• Lifestyle choices can affect the risk of developing type 2 diabetes
• Drugs can have multiple effects on the body's chemical reactions, with potential short-term benefits but long-term harmful side effects
• Glycogen

  An insoluble carbohydrate stored in the liver
• Insulin


  The hormone that lowers blood glucose levels
• Glucagon


  The hormone that has the opposite action to insulin, raising blood glucose levels
• Sense Organs

  • Eyes sense light
  • Nose senses chemicals (smell)
  • Ears sense sound and balance
  • Tongue senses chemicals (taste)
  • Skin senses changes in temperature, pressure, touch and pain
  • Muscles sense tension