Hormones

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Hormone Key Words and Types

Endocrine Gland:- a gland that secretes hormones directly into the blood stream - NO ducts

Exocrine Gland:- A gland that secretes hormones into a duct that carries the molecule to their target cells (e.g. Salivary Gland)

Hormone:- Chemical Messengers. Molecules that are released by endocrine glands directly into the blood where they are carried to target cells

Target Tissue:- have cells that possess a specific receptor on their plasma membranes which is complementary to the hormone molecule

Target Cells:- have a receptor which is complementtary to the hormone so it only triggers the desired internal response in target cells

Protein and Peptide Hormones and derivatives of amino acids (Adrenalin, Insulin and Glucagon). These bind to receptors

Steroid Hormones (Sex Hormones)- THese can pass througgh the plamsa membrane and directly affect the DNA

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Steroid Hormone Action

... THese aren't soluble so travel in blood with protein carriers

  • At the cell, the steroid dissociates from the carier and passes through the phospholipid bilayer
  • In the cytoplasm, they bind with a receptor protein and move into the nucleolus as hormone-receptor complexes.
  • In the nucleolus, they can directly influence the DNA - Hormone response elements
  • The binding of the hormone to the DNA has a direct effect on the level of transcription at the site. mRNA is then produced, which then codes fro the synthesis of specific proteins
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Adrenaline

Functions of the Adrenaline Gland:

Adrenal Medulla:- releases Adrenaline (epinephrine) which has widespread effects as most cells possess the receptors. Adrenaline prepares the body for activity (Fight, Flight or Frolic)

Adrenal Cortex:- uses cholesterol to produce steroid hormones. Mineralocortoids- (Aldosternol) helps to control the concentration of Na+ and K+ ions in the blood. Glucocortoids - (Cortosol) control the metabolism of carbohydrates and proteins in the liver

Action of Adrenaline:

Adrenaline is released by the adrenal glands into the blood. Its target cells have complementary shaped receptors. The receptors are associated with an enzyme called adenyl cyclase. Adrenaline is known as the first messenger. When it binds to the receptors, it activates the enzyme adenyl cyclase. Adenyl cyclase converts ATP to cyclic AMP. cAMP is a secondary messenger as it activates other enzymes within the cell in order to carry out a specific function

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The Pancreas

Exocrine Function:- the secretion of digestive enzymes via the pancreatic duct

Endocrine Function: secrete glucagon and insulin into the blood in order to regualte blood sugar

  • alpha cells: - manufacture and secrete glucagon
  • beta cells:- manufacture and secrete insulin

Too Much Blood Sugar:

Rise in concentration -> detected by beta cells -> beta cells secrete insulin into the blood -> Detected by liver and muscle cells ->cells remove glucose from blood adn convert it into glycogen -> glucose falls in concentration

Too Little Blood Sugar:

Fall in concentration -> detected by alpha cells -> alpha cells secrete glucagon into blood -> detected by the liver -> liver cells convert glycogen into glucose and release it into the blood -> glucose concentration rises

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Insulin Production

Blood glucose is too high:

Insulin released by beta cells in the pancreas and binds to specific target cell receptors. This activats adenyl cyclase which converts ATP into cAMP. cAMP activates various enzymes which:

  • increased number of glucose channels on plasma membranes
  • converts glucose to glycogen - Glycogenesis
  • converts glucose to fats
  • use more glucose for respiration (as a substrate)

Blood glucose too low:

Glucagon is released by alpha cells in the pancreas and binds to specific target cell receptors. THe effects of glucagon:

  • converts glycogen into glucose (Glygenolysis)
  • make glucose from fats and amina acids (Gluconeogenesis)
  • use more fatty acids in respiration (as a substrate)
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Effect of Insulin

1) The cell membrane has potassium and calcium ion channels

2) The potassium ion channels are normally open, so potassium ions flow out. pd = -70mv

3) When blood glucose concentration is high, the glucose moves into the cell

4) Glucose is metabolised to produce ATP

5) The ATP closes the potassium ion channels

6) The accumulation of potassium ions alters the potential across the cell membrane to a less negative pd -30mv

7) The change in potential difference opens the calcium ion channels

8) Calcium ions cuase the vesicles on insulin to fuse with the cell membrance, relseasing insulin by exocytosis

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Types of Diabetes

Type 1 diabetes (insulin-dependent):- starts in childhood. Insulin deificiency means there is not enouggh insulin being made by the pancreas due to a malfunction of the insulin producing cells:

  • caused by an autoimmune response where the immune system attacks the beta cells (may led to viral infection)
  • no longer able to manufacture insulin
  • Treated with injections of insulin

Type 2 diabetes (non-insulin-dependent):- tends to be in over 40s. Insulin resistance occurs when there is plenty of insulin made by the pancreas (functioning normally)  but body cells are resistant to its action which results in high blood sugar:

  • the number of receptors on liver cells may decline
  • responsiveness to insulin decreases
  • Risk Factors:- obesity, high sugar/fat content in diet, Asian/Afro-caribbean ethnicity (are gentically predisposed - in over 25s), family history
  • monitoring diet and reducing carbohydrate intake. there are also drugs to slow down the glucose absorption in the gut
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Advantages of Insulin Production in GM Bacteria

  • Exact copy of human insulin - faster and more effective
  • Less chance of becoming insulin tolerant
  • Less chance of side effects/rejection
  • Lower infection rates
  • Cheaper to manufacture
  • Process adaptable to meet demand
  • No moral objections to insulin being taken

Possible Future Treatments:

Stem cells are unspecialised cells that have the ability to develop into any type of cell. They could cure type 1 diabetes. They would be grown ino new beta cells and implanted into the pancreas of a type 1 diabetic and start to make insulin so the person no longer  needs to inject insulin

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