Endocrine system

• Homeostasis


  Maintenance of a constant internal environment despite changes in the external environment
• Steady state


  A condition where the body's internal environment are balanced
• Homeorhesis


  Maintaining a steady path or trajectory as the body develops or as the environment changes
• The ultimate aim of all these processes is to keep certain aspects of the body's functions, like temperature or blood sugar levels, as close to a constant value as possible
• Homeostatic systems


  • Thermoregulatory
  • Respiratory
  • Excretory
  • Digestive/appetite
  • Reproductive
  • Endocrine
  • Immune
  • Circulatory
• Internal components of homeostasis


  • Concentration of oxygen and carbon dioxide
  • pH of the internal environment
  • Concentration of nutrients and waste products
  • Concentration of salts and electrolyte
  • Volume and pressure of extracellular fluid
  • Body temperature
• Receptor


  Part that detects changes or variations in the body's internal environment, such as temperature, pH levels, or nutrient concentrations
• Integrating center


  Assesses the information received and decides what action needs to be taken to restore balance. It acts as the control center of the system.
• Effector


  Carries out the necessary actions to correct the imbalance. This could involve processes like releasing hormones, adjusting organ function, or stimulating muscle movement.
• Autoregulation (local control, intrinsic)


  Cells, tissues, or organs adjust themselves in response to internal signals
• Types of extrinsic control


  • Nervous control
  • Endocrine control
• Nervous control


  Signals from the brain or spinal cord cause quick, short-term responses
• Endocrine control


  Glands produce hormones that cause slower but longer-lasting changes
• Nervous system


  • Network of billions of nerve cells
  • Highly organized fashion
  • Rapid control center of the body
  • Integrating center for homeostasis, movement, and almost all other body functions
• Gap junctions


  Tiny channels that allow molecules to pass directly from one cell to another, enabling quick and direct communication between them
• Chemical messengers


  Molecules released by cells that can affect other cells that have specific receptors for them
• Communication via chemical messengers


  1. Secretory cell releases chemical messenger into ECF (extracellular fluid)

  2. Messenger binds to specific receptors on the "target" cell

  3. Binding of messenger to receptor triggers a response in the target cell
• Types of chemical messengers


  • Classic Endocrine
  • Paracrines
  • Autocrines
  • Cytokines
  • Neurotransmitters
  • Neurohormones
• Negative feedback loop


  The body works to counteract any changes from its set point or ideal conditions
• Negative feedback loop


  1. Initial Disturbance

  2. Detection

  3. Response

  4. Reversal of Disturbance

  5. Return to Homeostasis
• Positive feedback


  The response amplifies or enhances the original stimulus, rather than counteracting it
• Positive feedback loop


  1. Initial Stimulus

  2. Enhancement of Stimulus

  3. Further Enhancement

  4. Continued Amplification

  5. Resolution
• Pancreas


  Exocrine gland that secretes pancreatic juice, and endocrine gland that secretes insulin and glucagon to control blood glucose levels
• Insulin


  Secreted by the pancreas to decrease blood glucose concentration
• Glucagon


  Secreted by the pancreas to increase blood glucose concentration
• Effects of insulin


  Increases permeability of cell surface membrane to glucose, stimulates conversion of glucose to glycogen, increases glucose oxidation
• Lack of insulin secretion


  Glucose cannot be stored or utilized by tissue cells, blood glucose concentration rises, diabetes mellitus develops
• Over-secretion of insulin


  Abnormal decrease in blood glucose concentration, can lead to shock, coma and death
• Diabetes


  Condition where there is a problem with insulin, leading to hyperglycemia and other metabolic disturbances
• Effects of diabetes


  1. Glucose not taken up into cells

  2. Glucose excreted into the urine

  3. Fat and protein stores mobilized as alternative energy source

  4. Increased fat metabolism results in formation of ketone bodies

  5. Ketone bodies can lead to ketoacidosis

  6. Protein stores depleted (muscle wasting)

  7. Electrolyte imbalance

  8. Excessive water loss and dehydration