homeostasis

• What is homeostasis?

  Maintaining stable internal environment
• Why is homeostasis important?

  It keeps internal environment constant for metabolic reactions
• How does homeostasis help organisms?

  It helps organisms adapt to external changes
• What are the control mechanisms of homeostasis?

  1. Receptors: Detect stimuli and send signals to CNS
  2. Co-ordinator: Interprets information and sends instructions
  3. Effectors: Muscles or glands that act on signals
• What role do receptors play in homeostasis?

  They detect stimuli and send signals to CNS
• What is the function of the co-ordinator in homeostasis?

  Receives and interprets information from receptors
• What are effectors in the context of homeostasis?

  Muscles or glands that respond to signals
• What is negative feedback in homeostasis?

  Receptors detect a change and trigger a response
• How does negative feedback work with blood glucose?

  Signals trigger effectors to reverse the change
• What are examples of negative feedback mechanisms?

  • Maintaining pH
  • Maintaining temperature
  • Water regulation
• What is positive feedback in homeostasis?

  An initial change is enhanced by effectors
• What is an example of positive feedback?

  Blood clotting after a vessel injury
• What is the role of hormones in coordination?

  They are chemical messengers binding to receptors
• What are the steps in hormone coordination?

  1. Hormones produced by endocrine glands
  2. Glands release hormones into bloodstream
  3. Blood carries hormones to target cells
  4. Cells respond to hormones
• Compare the endocrine and nervous systems.

  • Signals: Hormones vs. Nerve impulses
  • Transmission: By blood vs. By neurones
  • Speed: Slow vs. Very rapid
  • Spread: Widespread vs. Localised
  • Duration: Long vs. Short
• What type of gland is the pancreas?

  Exocrine and endocrine gland
• What do alpha cells in the pancreas secrete?

  Glucagon
• What do beta cells in the pancreas secrete?

  Insulin
• What happens when glucose levels increase?

  Alpha cells reduce glucagon and increase insulin
• How does insulin affect muscle and fat cells?

  It makes their membranes more permeable to glucose
• What is glycogenesis?

  Conversion of glucose to glycogen for storage
• What happens when glucose levels decrease?

  Beta cells reduce insulin and alpha cells increase glucagon
• What is glycogenolysis?

  Conversion of glycogen to glucose in the liver
• What does "hypo" mean in medical terms?

  Below normal
• What does "hyper" mean in medical terms?

  Above normal
• What is Type 1 diabetes?

  Insulin-dependent diabetes with no insulin production
• What are symptoms of Type 1 diabetes?

  Thirst, high glucose in urine, blurred vision
• What are the controls for Type 1 diabetes?

  • Injections of insulin
  • Pancreas transplants
  • Balanced diet with insulin dosage
  • Biosensor monitors levels
  • Exercise helps regulate blood glucose
• What is Type 2 diabetes?

  Insulin-independent diabetes with receptor insensitivity
• Who is most likely to develop Type 2 diabetes?

  People over 40 with poor diet or obesity
• What are controls for Type 2 diabetes?

  Regulating diet and matching exercise
• How is insulin genetically engineered?

  1. Harvest bacteria and break open to release insulin
  2. Insert gene for human insulin into bacteria
  3. Put genetically engineered bacteria into fermentation vessels
  4. Allow bacteria to grow
  5. Clean vessels and add nutrient solution
  6. Purify and package insulin
• What is the second messenger model in relation to adrenaline?

  It amplifies the signal from adrenaline
• What happens when adrenaline binds to liver cell receptors?

  It activates a G protein and adenyl cyclase
• What does cAMP do in the second messenger model?

  It activates protein kinases via phosphorylation
• What is the result of protein kinase activation?

  It catalyzes the breakdown of glycogen to glucose
• How does glucose move out of liver cells?

  By facilitated diffusion through channel proteins
• What is the effect of adrenaline on blood glucose concentration?

  It increases glucose concentration for respiration