F214 Hormones

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  • Hormones
    • An exocrine gland is one that secretes molecules into a duct, which then carries the molecules to where they are used.
    • Hormones are chemicals secreted by endocrine glands. They travel to all cells via the blood but only affect cells in target tissues
      • The adrenal gland produces adrenaline which prepares the body for activity – e.g. increases heart rate, glycogen conversion to glucose, etc.
        • Adrenaline is an example of a first messenger and cyclic AMP is an example of a second messenger
    • The pancreas secretes enzymes into the gut (exocrine gland) and hormones into blood (endocrine gland)
      • Maintenance of Blood Glucose concentration
        • Too High
          • Pancreatic b cells detect high blood glucose – hormone insulin secreted.
            • Insulin stimulates liver cells to take up glucose and convert it to glycogen
              • High glucose causes K+ channels in liver cell membrane to close and Ca2+ channels to open – Ca2+ diffuses in and insulin is secreted
        • Too Low
          • a cells detect low blood glucose – hormone glucagon secreted
            • Glucagon stimulates liver cells to release more glucose into the blood
      • Diabetes
        • Type I diabetes (insulin dependent) – not enough insulin produced
        • Type II (non-insulin-dependent) – liver and muscle cells not responding to insulin
        • Treatment
          • Bacteria can be genetically modified to produce human insulin
          • Pancreatic stem cells could produce new b cells in diabetics.
    • Cardiovascular centre in medulla oblongata of brain sends nerve impulses to Sino Atrial Node (pacemaker) in heart to control heart rate
  • Cardiovascular centre in medulla oblongata of brain sends nerve impulses to Sino Atrial Node (pacemaker) in heart to control heart rate

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