B5 - Homeostasis & Response

• Homeostasis


  The regulation of conditions inside the body to maintain a stable internal environment in response to changes in both internal and external conditions
• Cells in the body

  • Need certain conditions to function properly (not too hot/cold, not too acidic/alkaline, good supply of glucose and water)
• How the body regulates conditions

  1. Recognizes when there's a change from optimal conditions

  2. Sends a signal to reverse that change

  3. Levels go back to normal
• Automatic control systems


  • Have 3 main components: receptors, coordination centers, effectors
• Receptors


  Detect a change (e.g. rise in temperature)
• Coordination centers


  Interpret the change and decide what needs to be done
• Effectors


  Carry out the change (e.g. muscles contracting, glands releasing hormones)
• Nervous system


  Sends fast, precise electrical impulses through nerves
• Endocrine system


  Relies on slower, longer-lasting hormones released into the bloodstream
• Negative feedback mechanism


  1. If levels get too high, it decreases them to return to normal

  2. If levels get too low, it increases them to return to normal
• Homeostasis is the overall process of maintaining a stable internal environment through negative feedback loops
• Nerve cell


  Also called a neuron
• Neuron


  • Long
  • Thin
  • Lots of branch connections to either end
  • Adapted to carry electrical impulses from one point to another
• Synapse


  Connection between nerve cells where electrical impulses are converted to chemical signals to pass between cells
• Nerve impulse transmission


  1. Electrical impulse hits end of nerve

  2. Causes release of chemicals

  3. Chemicals diffuse across gap to next nerve cell

  4. Triggers another electrical impulse

  5. Impulse continues along new neuron
• Central nervous system


  Made up of brain and spinal cord<|>Where 'thinking' takes place<|>Takes in sensory information<|>Decides what needs to be done<|>Sends out orders to the rest of the body
• Sensory neurons


  Carry information from receptors all over the body to the central nervous system
• Motor neurons


  Carry impulses from the central nervous system to effectors (muscles or glands)
• Effectors


  Muscles or glands that can be told to contract or release hormones
• Reflex arc


  1. Stimulus detected by receptor cells

  2. Sensory neuron carries impulse to spinal cord

  3. Relay neuron transfers impulse to motor neuron

  4. Motor neuron carries impulse back to effector (muscle) to cause movement
• The benefit of reflexes is that they are rapid and automatic, helping us avoid getting hurt
• Nerve cell


  Also called a neuron
• Neuron


  • Long
  • Thin
  • Lots of branch connections to either end
  • Adapted to carry electrical impulses from one point to another
• Synapse


  Connection between nerve cells where electrical impulses are converted to chemical signals to pass between cells
• Nerve impulse transmission


  1. Electrical impulse hits end of nerve

  2. Causes release of chemicals

  3. Chemicals diffuse across gap to next nerve cell

  4. Triggers another electrical impulse

  5. Impulse continues along new neuron
• Central nervous system


  Made up of brain and spinal cord<|>Where 'thinking' takes place<|>Takes in sensory information<|>Decides what needs to be done<|>Sends out orders to the rest of the body
• Sensory neurons


  Carry information from receptors all over the body to the central nervous system
• Motor neurons


  Carry impulses from the central nervous system to effectors (muscles or glands)
• Effectors


  Muscles or glands that can be told to contract or release hormones
• Reflex arc


  1. Stimulus detected by receptor cells

  2. Sensory neuron carries impulse to spinal cord

  3. Relay neuron transfers impulse to motor neuron

  4. Motor neuron carries impulse back to effector (muscle) to cause movement
• The benefit of reflexes is that they are rapid and automatic, helping us avoid getting hurt