Hormonal Communication

• Endocrine communication by hormones

  1. Secretion of hormones into the bloodstream by endocrine glands

  2. Hormones travel through the blood to reach target cells or tissues

  3. Hormones bind to specific receptors on the cell surface or within the cell

  4. Binding of hormone molecules to receptors triggers a cellular response
• Endocrine communication by hormones


  • Allows hormones to regulate various physiological processes in the body, such as metabolism, growth, and reproduction
• How hormones travel in the bloodstream and interact with specific receptors on target cells

  1. Hormones are secreted by endocrine glands directly into the bloodstream

  2. Hormones are carried by the blood to target cells or tissues

  3. Target cells possess specific receptors that recognize and bind to the hormones

  4. Binding of a hormone to its receptor initiates a series of intracellular signalling events

  5. Cellular response can include changes in gene expression, activation of enzymes, or alterations in cell membrane permeability
• Pancreas


  Dual-function gland with both endocrine and exocrine functions
• Endocrine portion of the pancreas


  • Composed of specialised clusters of cells called islets of Langerhans
  • Islets contain alpha cells, which secrete glucagon, and beta cells, which produce insulin
• Regulation of blood glucose concentration


  Tightly regulated through the action of hormones, primarily insulin and glucagon, in a negative feedback loop
• Regulation of blood glucose concentration

  1. When blood glucose levels rise, beta cells secrete insulin, which promotes glucose uptake, enhancing glycogen synthesis

  2. When blood glucose levels fall, alpha cells release glucagon, which stimulates glycogen breakdown and promotes gluconeogenesis
• Insulin secretion control


  • Involves the coordinated activity of potassium channels and calcium channels in beta cells
  • Under normal conditions, beta cells maintain a resting membrane potential with open potassium channels
  • When blood glucose rises, glucose enters beta cells, increasing ATP-to-ADP ratio, leading to closure of potassium channels, depolarization, and opening of calcium channels
  • Calcium influx triggers insulin exocytosis and secretion
• Type 1 diabetes mellitus


  Autoimmune condition characterised by destruction of pancreatic beta cells, leading to insulin deficiency, often manifests in childhood or early adulthood, requires lifelong insulin therapy
• Type 2 diabetes mellitus


  Metabolic disorder characterised by insulin resistance and relative insulin deficiency, typically develops later in life, associated with obesity, sedentary lifestyle, and genetic predisposition
• Differences between Type 1 and Type 2 diabetes mellitus

  • Etiology
  • Pathophysiology
  • Clinical manifestations
• Treatments for Type 1 and Type 2 diabetes mellitus

  • Exogenous insulin replacement therapy for Type 1 via injections
  • Lifestyle modifications, oral medications, and injectable therapies for Type 2
• Insulin produced by genetically modified bacteria

  • Structurally identical to human insulin, reducing risk of allergic reactions and immune responses
  • Allows for precise dosage adjustments and consistent supply
  • Cost-effective and scalable production
• Stem cell therapy for diabetes mellitus

  • Potential to regenerate pancreatic beta cells and restore insulin production
  • Challenges include immune rejection, tumorigenicity, and optimization of transplantation protocols
• The Adrenal Cortex?

  The cortex produces steroid hormones: Aldosterone, which regulates levels of salts (sodium and potassium) and water balance in the blood, this has an impact on blood volume and pressure.

  
• Cortisol plays a role in regulating metabolism, suppressing inflammation, and maintaining homeostasis during stressful situations.
• Adrenal Cortex mnemonic

  Go find rex, make good sex

  
• the Pancreas endocrine and exocrine function


  The exocrine pancreas produces enzymes that help to digest food, particularly protein. The endocrine pancreas makes the hormone insulin, which helps to control blood sugar levels

  
• Functions of exocrine and endocrine tissue

  
• Structure of Pancreas (islets of langerhans)

  
• Where are alpha and beta cells located and what are their functions?

  Located in the islets of Langerhans. Alpha cells secrete the hormone glucagon and beta cells secrete the hormone insulin.
• How is blood glucose controlled/maintained?

  The cells in the islets of Langerhans monitor the concentration of glucose in the blood. If the concentration rises or falls away from the acceptable concentration then the alpha and beta cells detect the change and respond by releasing a hormone.
• What are islets of Langerhans?

  Small patches of tissue in the pancreas that have an endocrine function and contain alpha and beta cells.
• Describe the secretion of hormones in the pancreas

  Certain areas of the pancreas called the islets of Langerhans contain different types of cells called alpha cells which manufacture and secrete the hormone glucagon and beta cells which manufacture and secrete insulin. The islets are well supplied with blood capillaries and these hormones are secreted directly into the blood.
• When blood glucose is high (i.e. after eating a meal)


  1. Cells in the pancreas detect high blood glucose

  2. Cells stimulate beta cells in the islets of Langerhans to secrete insulin

  3. Insulin travels in the bloodstream to liver and muscle cells

  4. Insulin binds to insulin receptors on their cell surface membrane

  5. Insulin increases the permeability of the membrane to glucose

  6. More glucose is moved from the bloodstream into cells

  7. Insulin stimulates the conversion of glucose into glycogen (glycogenesis)

  8. Insulin stimulates an increase in the rate of respiration
• When blood glucose is low (i.e. running a marathon)

  1. Cells in the pancreas detect low blood glucose

  2. Cells stimulate alpha cells in the islets of Langerhans to secrete glucagon

  3. Glucagon travels in the bloodstream to liver cells

  4. Glucagon binds to glucagon receptors on their cell surface membrane

  5. Glucagon stimulates the breakdown of glycogen into glucose (glycogenolysis)

  6. Glucagon stimulates a decrease in the rate of respiration

  7. Glucagon triggers the production of glucose from non-carbohydrates, such as lipids and amino acids, in a process called gluconeogenesis
• What are the pancreas exocrine and endocrine functions?

  Exocrine gland: by synthesising and secreting pancreatic juices (lipase, amylase, trypsinogen, NaOH) within acini.

  Endocrine gland: by synthesising and secreting hormones into blood vessels.
• What are islets of Langerhans

  Cells within islets of Langerhans monitor blood glucose concentration

  
• alpha cells


  secrete glucagon which stimulates glycogen → glucose

  
• beta cells


  secrete insulin which stimulates glucose → glycogen

  
• Mechanism for insulin release?

  At rest in β-cells, potassium channels are open, resulting in a negative resting potential.

  When glucose concentration rises, glucose diffuses into the cell and is phosphorylated. It is converted to ATP via respiration causing potassium channels to close and calcium open. The calcium causes vesicle of insulin to be exocytosed
• glycogenesis


  glucose → glycogen

  (insulin binding to receptors on liver cell membranes)
• glycogenolysis


  glycogen → glucose

  (glucagon binding to receptors on liver cell membranes)
• gluconeogenesis


  glucagon → glycerol and amino acids → glucose
• Where is glycogen stored

  Glycogen is stored in the liver cells' cytoplasm
• pancreas histology

  
• pancreas histology

  
• Adrenal medulla



  Produces catecholamines, including adrenaline and noradrenaline, which are involved in the body's fight-or-flight response to stress

  
• Adrenal glands


  Consist of two main regions: the outer adrenal cortex and the inner adrenal medulla

  
• Adrenal cortex




  Composed of three distinct layers: zona glomerulosa, zona fasciculata, and zona reticularis