1.5 Homeostasis

Your body is like a finely tuned machine, constantly adjusting to keep everything running smoothly. This process, called homeostasis, involves intricate feedback systems that monitor and regulate crucial factors like temperature and blood sugar.

When things get out of whack, your body springs into action. Negative feedback loops work to bring things back to normal, while positive feedback loops amplify responses in certain situations. It's all about maintaining that delicate balance.

Homeostasis and Feedback Mechanisms

Maintenance of internal environment

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• Homeostasis maintains stable internal environment despite external changes
• Regulates variables such as body temperature (37°C), blood glucose levels (70-110 mg/dL), and pH (7.35-7.45)
• Homeostatic mechanisms operate within normal range for each variable
  • Upper and lower limits define boundaries of normal range
  • Slight fluctuations within normal range tolerated
• Deviations from normal range trigger compensatory mechanisms
  • Work to restore variable back to normal range
• Homeostatic control systems consist of receptors, control centers, and effectors
  • Receptors detect internal environment changes (thermoreceptors, chemoreceptors)
  • Control centers process receptor information and initiate responses (hypothalamus, medulla oblongata)
  • Effectors execute responses to restore homeostasis (sweat glands, skeletal muscles)

Negative vs positive feedback mechanisms

• Negative feedback mechanisms more common, reduce deviations from normal range
  • Regulation of blood glucose levels
    • Blood glucose rises above normal range, pancreas releases insulin
    • Insulin promotes glucose uptake by cells, reduces blood glucose back to normal
  • Regulation of body temperature
    • Body temperature rises above normal range, sweat glands activated
    • Sweating promotes heat loss through evaporation, cooling body back to normal
• Positive feedback mechanisms less common, amplify deviations from normal range
  • Oxytocin release during childbirth
    • Cervix stretching stimulates oxytocin release from posterior pituitary gland
    • Oxytocin promotes further uterine contractions, leading to more cervix stretching
    • Cycle continues, amplifying contractions until baby delivered
  • Blood clotting cascade
    • Blood vessel injury initiates clotting cascade
    • Each cascade step activates more clotting factors, amplifying response
    • Positive feedback loop continues until clot formed to stop bleeding

Components of feedback loops

• Feedback loop consists of four main components: stimulus, receptor, control center, and effector
• Stimulus: Change in internal or external environment that disrupts homeostasis
  • Increase in body temperature, decrease in blood glucose levels
• Receptor: Specialized structures that detect stimulus
  • Thermoreceptors in hypothalamus, glucose receptors in pancreas
• Control center: Receives and processes receptor information, determines appropriate response
  • Hypothalamus, pancreatic islets
• Effector: Executes control center response to restore homeostasis
  • Sweat glands, skeletal muscles, liver, adipose tissue
• Components work together in sequence:
  1. Receptor detects stimulus
  2. Receptor sends stimulus information to control center
  3. Control center processes information, determines appropriate response
  4. Control center sends signals to effector to execute response
  5. Effector carries out response, helps restore homeostasis
  6. As stimulus corrected, receptor detects change, feedback loop continues monitoring and maintaining homeostasis

Homeostatic regulation concepts

• Set point: Ideal value or range for a physiological variable that the body aims to maintain
• Homeostatic range: Acceptable range of values around the set point within which a variable can fluctuate without triggering a significant regulatory response
• Steady state: Condition where the body maintains a relatively stable internal environment despite ongoing changes
• Dynamic equilibrium: Constant adjustments made by homeostatic mechanisms to maintain stability in the face of continuous internal and external changes
• Osmoregulation: Specific homeostatic process that maintains proper water and solute balance in the body