أساسيات فيزيولوجيا الكائنات الحية

Introduction to Physiology

• Physiology is a branch of life sciences, including anatomy, histology, cytology, and other biological sciences
• It focuses on the biological processes that enable organisms to perform vital activities and functions
• Examining the entire organism's functions or the functions of organs, tissues, and cells is a key aspect of physiology
• Physiology is a field with a long history, and it's developed alongside human and medical advancements.
• Notable figures include Ibn al-Nafis (discoverer of the minor circulatory system) and al-Razi (who studied environmental effects on health)
• Greek and Roman traditions contributed significantly to the experimental method, which was refined by Arab researchers, influencing the scientific method.

Principles of Physiology

• Substance exchange with the environment:

  • Life organisms differ from their surroundings in the structural and chemical characteristics.
  • Organisms exchange substances with their environment via systems, primarily the lungs, kidneys, digestive tract, and skin.
  • These systems have a large surface area and connection to capillaries. (e.g., small intestine ~10 square meters, lungs ~55 square meters, kidneys ~6 square meters.)

• Metabolism:

  • Organisms use food to generate energy for bodily functions, growth, and life processes.
  • Energy is released through the breakdown of large molecules into smaller ones, which are oxidized through respiration. This yields energy, water, and carbon dioxide. (ex: C6H12O6 + O2 > Energy + CO2 + H2O)
  • Catabolism is the process of breaking down complex molecules into simpler ones and oxidizing them to release energy.
  • Anabolism is the process of constructing complex molecules from simpler components. Metabolism is the combined result of catabolism and anabolism.

Internal Coordination

• Keeping the organism's internal environment stable and coordinated is crucial for survival.
• Smaller organisms directly interact with their surroundings via their cell membranes.
• Larger organisms like humans use complex coordinative mechanisms
  • These include specialized circulatory systems for efficient nutrient and oxygen transport, waste removal, and carbon dioxide release.
  • Endocrine systems comprise various glands that release hormones that are transported via blood to target tissues and organs, causing a slower response compared to the nervous system.

External Coordination

• External environmental changes affect the organism's activity and behaviors.
• Senses and the nervous system help the organism detect and respond to their surroundings.
• Sensory receptors, or recepter, detect stimuli, which are transmitted to the central nervous system.
• Motor nerves trigger responses from organs such as glands and muscles. These responses are either: * Simple reflex responses*, which are quick, automatic actions in response to a stimulus, like touching a hot object. * Complex responses*, relying on brain involvement, encompass sophisticated behaviors, such as foraging, migration, hibernation, and nesting.

Homeostasis

• Homeostasis maintains constant internal conditions.
  • Variables like temperature, pH, bodily fluids, and glucose levels are tightly regulated within narrow parameters.
  • Any deviation from these norms indicates a possible health issue.
• Feedback mechanisms restore balance when alterations occur.
  • Positive feedback mechanisms: are less common and involve accelerating a response, like increasing hormone levels.
  • Negative feedback mechanisms: are more prevalent and bring about physiological responses—e.g., elevated blood sugar triggering insulin release, which converts excess sugar to glycogen, eventually stopping the response.

Cell Membrane and Transport

• Biological membranes are composed of phospholipids, arranged in a bilayer, with cholesterol, and embedded proteins.
  • Polar heads face the exterior of the membrane.
  • Nonpolar tails are in the interior.
• Proteins float in this lipid bilayer, forming channels, and acting as enzymes or carriers for diverse molecules.
• Cell membranes regulate the passage of materials.
• Passive transport involves no energy expenditure, utilizing processes like diffusion, facilitated diffusion, and osmosis.
• Diffusion is the movement of particles from higher to lower concentration.
• Facilitated diffusion requires transport proteins to aid larger or insoluble molecules' passage.
• Osmosis is the movement of water across a semipermeable membrane to equalize concentration. There are three different types of osmotic solutions: *isotonic (equal), hypotonic (lower solute), and hypertonic (higher solute).
• Active transport requires energy (ATP) for movement against a concentration gradient, involved in transferring large or charged particles. This process includes endocytosis (engulfing materials), and exocytosis (releasing substances outside the cell).

Transport Processes Across Cell Membrane

• Filtration is a crucial process involving hydrostatic pressure to drive fluid through membranes, for example, blood filtration in the kidneys.