homeostasis

• Homeostasis


  The maintenance of a constant internal environment
• Examples of homeostasis


  • Regulating body temperature
  • Regulating blood glucose level
  • Regulating water content
• Homeostasis


  • Involves the nervous system and the endocrine system
  • Involves receptors, coordination centres, and effectors
• Homeostasis process


  1. Receptors detect a stimulus

  2. Coordination centres in the brain, spinal cord or gland process the information

  3. Effectors produce a response
• Body temperature


  Maintained at around 37°C, the temperature at which enzymes work best
• Control of body temperature is an example of a negative feedback mechanism
• Glucose


  A simple sugar used by cells for respiration
• Insulin


  A hormone that regulates the level of sugar in the blood and can be produced by genetically modified bacteria
• Pancreas


  Large gland located in the abdomen near the stomach which produces digestive enzymes and the hormone insulin
• How insulin regulates blood glucose

  1. If the blood glucose concentration is too high, the pancreas produces the hormone insulin that causes glucose to move from the blood into the cells

  2. In liver and muscle cells, excess glucose is converted to glycogen for storage, and will be used at a later date
• Glycogen


  Animals store glucose as glycogen in their liver and muscle tissues
• Type 1 diabetes


  A disorder in which the pancreas fails to produce enough insulin
• Type 1 diabetes


  • Characterised by uncontrolled high blood glucose levels
  • Can be controlled by injecting insulin
• Type 2 diabetes


  The person's body cells no longer respond to insulin
• Type 2 diabetes


  • More common in older people
  • Now becoming common in young people also
  • Can usually be controlled by a carbohydrate controlled diet and an exercise regime
• After a meal


  Carbohydrate is digested into glucose, which raises the overall blood glucose level
• Rising levels of obesity in the general population

  Increasing levels of type 2 diabetes
• Glucagon


  A hormone produced by the pancreas that promotes the breakdown of glycogen into glucose in the liver
• When blood sugar rises


  Insulin encourages the body's cells to take up glucose
• When blood glucose level is too low


  The liver releases stored glucose into the blood, brought about by glucagon
• Negative feedback


  The change in blood glucose level is brought about by the release of glucagon
• The pituitary gland secretes hormones that regulate growth, metabolism, reproduction, water balance, and blood pressure.
• 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)
• Body regulates


  Ensures everything is kept around the right levels
• Temperature and glucose levels do fluctuate but only within small bounds
• Automatic control systems


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


  Detect a change, such as a rise in temperature
• Coordination centres


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


  Carry out the change, such as muscles contracting or glands releasing hormones
• Nervous system


  Sends fast and precise electrical impulses through nerves
• Endocrine system


  Relies on hormones released into the bloodstream, slower and more generalized than the nervous system
• Negative feedback


  Mechanism where the system decreases or increases a level to return it to normal
• Negative feedback mechanism


  1. Receptors detect change

  2. Coordination centres interpret change

  3. Effectors carry out response to return to normal
• Nerve cell


  Also called a neuron
• Nerve cell


  • 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 cell communication


  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. Electrical 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 to do, sends out orders to the body
• Sensory neurons


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