Hormonal communication

• Glycogen 


  The storage form of glucose in animals
• Glucagon


  Hormone released when blood glucose concentration is too low, causes an increase of blood glucose concentration
• Glycogenesis 


  Formation of glycogen from glucose
• Glycogenolysis

  Formation of glucose from glycogen
• endocrine gland = a group of specialised cells that secrete hormones directly into the blood.
• Example of endocrine gland ?

  thyroid gland
• exocrine gland = a group of specialised cells that secrete substances into a duct which transport them to a particular part of the body.
• Example of exocrine gland ?


  salivary glands
• name the two types of hormone ?


  steroid and non-steroid hormones
• What is the main difference between steroid and non-steroid hormones ?


  Steroid hormones are soluble in the phospholipid bilayer so can enter cells while non-steroid are insoluble so act as first messenger binding to receptors on the cell surface membrane.
• what are the structures found in adrenal glands ?


  capsule

  cortex

  medulla

  blood vessels
• Where is adrenaline secreted from ?


  medulla of adrenal glands
• Name 2 hormones released from the adrenal medulla ?


  Adrenaline

  Noradrenaline
• Name 3 non-steroid hormones ?


  Arenaline

  insulin

  Glucagon
• Name 2 steroid hormones ?


  Oestrogen

  testosterone
• Name 2 hormones the adrenal cortex secretes ?


  Glucocorticoids

  Mineralocorticoids
• Give an example of glucocorticoids hormone and its effects ?

  Cortisol, helps regulates carbohydrate metabolism
• Give an example of an mineralocorticoid hormone and its effects ?


  Aldosterone, controls ion reabsorption in the kidney
• name 2 reasons to maintain constant blood glucose concentration ?


  Maintain constant blood water potential

  Maintain constant concentration of respiratory substrate
• what is the pancreas exocrine function ?


  Release of digestive enzymes through ducts
• what digestive enzymes are released from the pancreas ?


  amylase

  protease

  lipase
• what cell type is responsible for release and synthesis of digestive enzymes ?


  Acinar cells
• what is the pancreas endocrine function ?


  release of hormones to control blood glucose concentration
• which cell produces insulin ?


  beta cells
• which cell produces glucagon ?


  alpha cells
• where would you find alpha and beta cells in the pancreas ?


  islet of langerhans
• negative feedback = self regulatory mechanisms return environment to optimum when there is a fluctuation
• Describe the process when blood glucose concentration increase ?

  1. Increase is detected by beta cells in the islets of langerhans
  2. beta cells secrete insulin
  3. Liver becomes more permeable to glucose and enzymes for glycogenesis are activated.
• Describe the process when blood glucose concentration decreases ?


  1. Decrease is detected by alpha cells in the islet of langerhan
  2. Alpha cells secrete glucagon, adrenal gland releases adrenaline
  3. second messenger model occurs to activate enzymes for glycogenolysis.
  4. Glycogenolysis and gluconeogenesis occurs
• how does the islet of langerhans appear under a microscope ?


  Lightly stained, large spherical structures
• How does the pancreatic acini appear under a microscope ?


  Dark stained, small berry-like clusters
• hypoglycaemia = when blood glucose concentration is less than 4 moldm
• hyperglycaemia = blood glusoce concentrstion is more than 6 moldm
• what are the effects of hypoglycaemia ?


  tiredness and irritability

  impairment of brain function
• what are the effects of hyperglycaemia ?


  organ damage
• Use the second messenger model to explain how glucagon works ?

  1. target cell posses specific membrane bound receptor for glucagon
  2. The binding of glucagon to receptor stimulates the g-protein
  3. This activates adenyl cyclase enzyme.
  4. Adenyl cyclase converts ATP into cAMP.
  5. cAMP activates an enzyme kinase pathway which results in glycogenolysis
• How is insulin se creation controlled ?


  Beta cells have K and Na ion channels open normally to maintain -70mV

  As glucose concentration rise, it enter beta cells via facilitated diffusion

  Respiration of glucose produces ATP, causing ATP-gated K+ channels to close

  Lack of K+ leaving cell, cell is depolarised.

  Cell depolarisation results in Ca2+ channels opening

  Diffusion of Ca2+ ions into cell result in secretory vesicles to move towards and fused with cell surface membrane

  Releasing insulin via exocytosis
• How does insulin lead to decrease in blood glucose concentration ?


  Increases cell permeability to glucose

  Increases glucose concentration gradient

  triggers inhibition of enzymes for glycogenolysis
• what are the causes of type 1 diabetes ?


  Inability to produce insulin due to autoimmune disease that attacks beta cells
• what are the causes for type 2 diabetes ?

  Insulin receptors are less responsive due to overexposure from obesity, high sugar diet, lack of exercise