Module 5.1.4- Hormonal communication

• Endocrine system


  Endocrine glands secrete hormones into the bloodstream that regulate processes such as growth, reproduction, and nutrient use (metabolism) by body cells.
• Exocrine glands


  Secretes chemicals (e.g. pancreatic juice) through ducts into organs, or to the surface of the body
• What is a target cell


  A target cell is a cell that possesses specific receptors for a particular hormone. Thus, a hormone affects only its specific target cell.
• Steroid hormone mechanism


  Steroid hormones are lipid-soluble

  1. Hormone passes through lipid membrane

  2. Then binds to steroid hormone receptors in the cytoplasm/nucleus

  3. This forms a hormone-receptor complex

  4. This attaches to DNA to be transcribed

  5. The polypeptide is then synthesised by ribosomes and mRNA.

  
• Non steroid hormone mechanism


  1. hormone binds to receptor on cell membrane (cant pass through the membrane)

  2. G protein is activated

  3. hormone-receptor complex (G protein) activates adenylate cyclase in the membrane

  4. adenylate cyclase catalyzes the formations of cAMP (the second messenger)

  5. cAMP activates protein kinases that lead to cellular changes and hormonal effects
• hormonal vs neuronal communication

  Hormonal- slower, less specific, longer lasting, widespread effect, hormones used, transmission by blood, effect may be permanent and irreversible

  Neuronal- faster, more specific, short lasting, localised, nerve impulses used, transmission by neurones, effect may be temporary and reversible
• Adrenal gland structure- 3 components


  Capsule (outer layer)

  Adrenal cortex

  Medulla

  
• What are the 3 types of hormones produced by the Adrenal Cortex


  Glucocorticoids Mineralocorticoids Androgens (releases sex hormones)
• Glucocorticoids (Adrenal cortex)


  Include cortisol - Regulating metabolism (converting into energy)- Regulate blood pressure and cardiovascular function in response to stress

  Include corticosterone- regulate immune response and inflammatory response
• Mineralocorticoids


  Include aldosterone - helps control blood pressure by maintaining salt and water concentrations in body and body fluids.
• Name the 2 types of hormones produced by the Adrenal Medulla

  Adrenaline - increases heart rate and raises blood glucose concentration levels Noradrenaline- works with adrenaline. - widens pupils - widening of air passages in the lungs- vasoconstriction -> higher blood pressure
• Function of pancreas

  produces enzymes that digest fats, proteins, carbohydrates and nucleic acid. Insulin and Glucagon is produced
• histology of pancreas


  Consists of pancreatic islets or islets of Langerhans & clusters of cells (Acini) (Enzyme-producing exocrine cells)

  1) Acini

  2) Islets of Langerhans

  3) Pancreatic Duct

  
• What do Islets of Langerhans contain

  Alpha cells- produce and release Glucagon Beta cells- produce and release Insulin

  
• Glycogenolysis


  process in which glycogen stored in the liver and muscle cells is broken down into glucose
• Gluconeogenesis


  production of glucose from non-carbohydrate sources
• Lipogensis


  the process of converting protein into fatty acids
• Glycogenesis


  formation of glycogen from glucose
• 3 ways to increase blood glucose concentration

  - Diet- Glycogenolysis- Gluconeogenesis
• 2 ways to decrease blood glucose concentration

  - Respiration- Glycogenesis
• Nearly all cells have insulin receptors. What happens when insulin binds to its glycoprotein receptors.


  - causes a change in the tertiary structure of glucose transport protein channels- more glucose as a result enters the cell - also activates enzymes to convert glucose into glycogen and fat
• How does insulin decrease blood glucose concentration


  - increasing rate of absorption of glucose by cells- increasing respiratory rate of cells- increasing rate of glycogenesis - increasing the rate of glucose to fat conversion- inhibiting release of glucagon from alpha cells of the Islets of Langerhans
• What cells have glucagon receptors

  Only liver and fat cells
• How does glucagon increase blood glucose levels?

  - glycogenolysis- increasing gluconeogenesis- reducing amount of glucose absorbed by liver cells
• What type of system is controlling blood glucose concentration

  Negative feedback.These levels fluctuate

  
• Control of insulin secretion (1)


  1) At normal BG levels, Potassium channels are open and Calcium channels are closed. Cell is at a potential of -70mV. K+ ions diffuse out.

  2) When BG levels rise, glucose enters cell using glucose transporters. This results in the production of ATP within the cell.

  
• Control of insulin secretion (2)


  3) ATP binds to potassium channels causing them to close reducing the potential difference of the cell to -30mV.

  4) Depolarisation occurs causing voltage-gated Calcium channels to open

  5) Calcium ions enter the cell and cause secretory vesicles to release insulin as they leave by exocytosis.

  
• Type 1 diabetes and causes


  Beta cells unable to produce insulinDiabetes of a form that usually develops during childhood or adolescence

  causes- autoimmune response
• Type 2 diabetes and causes


  body cells lose sensitivity to insulin.

  often because glycoprotein insulin receptors do not work properly.

  causes: obesity, physical inactivity, overeating
• Type 1 diabetes treatment


  -Insulin injections

  -Glucose monitoring meter

  -Track food choices and activity

  -Match insulin to achieve desired blood glucose levels
• Type 2 diabetes treatment


  - Carbohydrate controlled diet

  - Exercise regime

  - Rarely use drugs to e.g. stimulate insulin production, slow down glucose absorption etc.
• Advantages of genetically modified insulin


  - produced in pure form (no allergic reaction)

  - produced in higher quantities

  - cheaper production costs

  - overcome religious and ethical concerns for using animal products in humans
• Advantages of using stem cells to produce insulin


  - donor availability would not be an issue

  - reduced likelihood of rejection problems

  - people do not need to inject insulin into themselves
• Disadvantages of using stem cells to produce insulin


  - may induce the formation of tumours as a result of unlimited cell growth

  - stem cell research is a costly process