Pharmacology for EMS Week 2: Homeostasis

Pharmacology for EMS - Week 2: Introduction to Homeostasis

• Objectives:

  • Describe homeostasis and transport mechanisms for normal cellular function
  • Discuss properties of hydrophilic and hydrophobic substances
  • Describe protein synthesis and protein roles in the body
  • Describe enzyme role and function
  • Describe and give examples of positive and negative feedback mechanisms

• Homeostasis:

  • Maintaining a stable internal environment despite external stressors
  • A dynamic process, not constant over time (e.g., temperature, pH, glucose levels)
  • Considered individually for each physiological variable
  • Homeostatic failure in one variable can affect others
  • Regulated by control systems (feedback mechanisms, reflexes, hormones, chemical messengers, biological rhythms)
  • Cells have specific requirements or "normal ranges" for glucose, oxygen, salts, pH, waste products, and temperature (e.g., temperature 36.5-37.5°C, pH 7.35-7.45)

• Drug Administration and Homeostasis:

  • Administering drugs implies the body's homeostatic and feedback mechanisms are not functioning correctly
  • Drugs are administered exogenously (from outside the body) to intervene

• Transport:

  • Cells maintain electrical and chemical differences between intracellular and extracellular environments to allow reaction and interaction
  • Maintaining concentration gradients in cells requires a constant battle against diffusion
  • Some molecules easily pass through cell membranes; others need assistance (facilitated diffusion), or active transport against concentration gradients

• Equilibrium:

  • Cells maintain osmolarity and electrochemical equilibrium between the extracellular fluid (ECF) and intracellular fluid (ICF) with no net movement of water or molecules under normal conditions.
  • There is a difference in ion concentration and an electrochemical charge due to active transport into and out of cells

• Diffusion:

  • All molecules are constantly vibrating
  • Higher energy state leads to more movement
  • Diffusion results in even distribution of molecules within a container until concentration is uniform in the container
  • The rate of diffusion is related to concentration differences between compartments

• Diffusion in Living Organisms:

  • Essential for processes like oxygen, carbon dioxide, salt, ion, and glucose diffusion
  • Complicated pathology or drug action often results from altered concentration gradients or impaired diffusion at the molecular level

• Diffusion Across a Semi-Permeable Membrane:

  • Osmosis is water diffusion from low solute concentration to high solute concentration through a semipermeable membrane.
  • Equilibrium occurs when competing forces of concentration (osmotic) gradient and hydrostatic pressure are in balance
  • Electrochemical potential difference also considered for equilibrium

• Transport across cell membranes:
  -Cells maintain concentration gradients despite continuous diffusion

• Enzymes:

  • Proteins that act as catalysts, lowering activation energy for chemical reactions
  • Not consumed by reactions, allowing repeated use with additional substrates
  • Subject to specificity, affinity, competition, and saturation in their binding
  • Accelerate both forward and reverse chemical reactions

• Enzymes and Drug Metabolism:

  • Most drugs are metabolized or modified by enzymes
  • Common mechanisms of drug action include altered enzyme induction/inhibition or kinetics. This will be discussed in greater detail in future lectures

• Proteins:

  • Involved in all physiological processes; Some are enzymes
  • Receptors can be regulated
  • Protein structure is not static, and changes in structure affect protein properties
  • Protein structure can be affected by heat and extremes in pH

• Hydrogen Ions, pH, and Acidity:

  • pH measures acidity/basicity (lower pH means more acidic)
  • Pure water pH = 7.0
  • ICF pH ~ 7.0-7.2 and ECF pH ~ 7.35-7.45
  • Acidity refers to free/unbound hydrogen ion concentration
  • Hydrogen ion concentration is expressed as a negative log Small changes in pH can have a large effect on molecular interactions

• Feedback Mechanisms:

  • Positive feedback leads to accelerating amplification of initial stimulus.
  • Negative feedback leads to the inhibition of further reaction
    • Negative feedback regulates homeostasis
  • Most physiological processes use negative feedback to maintain physiological properties and concentrations within narrow ranges.
  • Drugs can affect the body's natural feedback mechanisms

• Drugs Revision for Week 3:

  • Study ibuprofen, paracetamol, and Entonox with emphasis on dose, presentation, indications, and contraindications