Introduction to Physiology

• Physiology is the study of how living organisms function
• It explores the mechanical, physical, and biochemical functions of living organisms

Areas of Focus

• Physiology examines a wide range of biological processes
• It deals with how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical or physical functions that exist in a living system
• Includes mechanics, physical and chemical processes

Levels of Study

• Molecular: Examines the interactions of molecules within cells
• Cellular: Focuses on the functions of individual cells, including their organelles and processes
• Tissue: Studies the functions of tissues, which are composed of similar cells performing specific tasks
• Organ: Investigates the functions of organs and how they contribute to overall system function
• Systemic: Explores the integrated functions of organ systems and their interactions within the body
• Organismal: Examines the overall physiology of the entire organism, considering the integration of all systems and functions

Key Concepts in Physiology

• Homeostasis refers to the maintenance of a stable internal environment within an organism
• It is a dynamic process involving constant adjustments to maintain equilibrium
• Feedback loops are crucial for maintaining homeostasis.
  • Negative feedback loops counteract changes to restore the original state.
  • Positive feedback loops amplify changes, leading to a greater deviation from the initial state (less common but important in certain processes like childbirth).
• Structure and Function: The anatomy, or structure, of a body part is closely related to its physiology, or function.
• This relationship is evident at all levels of organization, from molecules to organ systems.
• Communication and Integration: Physiological processes often involve communication between different parts of the body.
• This communication occurs through chemical signals (hormones, neurotransmitters) and electrical signals (nerve impulses).
• Integration of information from multiple sources is essential for coordinated responses.
• Energy and Thermodynamics: Living organisms require energy to perform functions, and energy transformations follow the laws of thermodynamics.
• Metabolism includes all the chemical reactions that occur in the body to acquire and use energy.
• Transport and Exchange: Physiological processes often involve the transport of molecules and ions across cell membranes and within the body.
• Exchange of materials between the body and the external environment is also crucial (e.g., gas exchange in the lungs).
• Control Systems: Physiological functions are regulated by various control systems, including the nervous system and endocrine system.
• These systems monitor internal conditions and initiate responses to maintain homeostasis.

Organ Systems

• Cardiovascular System: Transports blood, oxygen, nutrients, hormones, and waste products throughout the body.
  • Key components include: heart, blood vessels (arteries, veins, capillaries), blood.
  • Functions: oxygen and carbon dioxide transport, nutrient delivery, waste removal, immune function, hormone transport, thermoregulation.
• Respiratory System: Facilitates gas exchange between the body and the external environment.
  • Key components include: lungs, airways (trachea, bronchi, bronchioles), diaphragm.
  • Functions: Oxygen uptake, carbon dioxide removal, regulation of blood pH.
• Digestive System: Breaks down food into smaller molecules that can be absorbed into the body.
  • Key components include: mouth, esophagus, stomach, small intestine, large intestine, liver, pancreas, gallbladder.
  • Functions: Digestion, absorption of nutrients, elimination of waste.
• Urinary System: Filters blood and eliminates waste products in the form of urine.
  • Key components include: kidneys, ureters, bladder, urethra.
  • Functions: Waste removal, regulation of blood volume and composition, blood pressure regulation.
• Nervous System: Controls and coordinates bodily functions through electrical and chemical signals.
  • Key components include: brain, spinal cord, nerves, sensory receptors.
  • Functions: Sensory perception, motor control, cognition, emotion, regulation of other organ systems.
• Endocrine System: Regulates bodily functions through the secretion of hormones.
  • Key components include: glands (pituitary, thyroid, adrenal, pancreas, ovaries, testes).
  • Functions: Regulation of metabolism, growth, reproduction, stress response.
• Musculoskeletal System: Provides support, movement, and protection for the body.
  • Key components include: bones, muscles, joints, ligaments, tendons.
  • Functions: Movement, support, protection of internal organs, calcium storage, blood cell production.
• Immune System: Defends the body against pathogens and other harmful substances.
  • Key components include: white blood cells, lymphatic system, spleen, thymus.
  • Functions: Protection against infection, tissue repair, immune surveillance.
• Reproductive System: Enables reproduction.
  • Key components include: ovaries, uterus, testes, associated structures.
  • Functions: Production of gametes (eggs and sperm), hormone production, support of developing embryo/fetus.
• Integumentary System: Protects the body from the external environment.
  • Key components include: skin, hair, nails, sweat glands, sebaceous glands.
  • Functions: Protection, thermoregulation, sensory perception, vitamin D synthesis.

Cellular Physiology

• Cell Membrane: Separates the intracellular environment from the extracellular environment.
  • Composed of a phospholipid bilayer with embedded proteins.
  • Regulates the movement of substances into and out of the cell.
• Membrane Transport: Processes by which substances cross the cell membrane.
  • Passive transport: does not require energy (e.g., diffusion, osmosis, facilitated diffusion).
  • Active transport: requires energy (e.g., ion pumps, vesicular transport).
• Cellular Communication: Cells communicate with each other through chemical signals.
  • Signal transduction pathways: convert extracellular signals into intracellular responses.
• Membrane Potential: The electrical potential difference across the cell membrane.
  • Key for nerve and muscle function.
• Action Potential: A rapid change in membrane potential that propagates along the membrane of excitable cells (e.g., neurons, muscle cells).

Regulation and Control

• Nervous System: Fast, short-lasting responses via electrical and chemical signals.
  • Neurons transmit signals through action potentials and neurotransmitters.
  • Central nervous system (CNS): brain and spinal cord.
  • Peripheral nervous system (PNS): nerves outside the CNS.
• Endocrine System: Slower, longer-lasting responses via hormones.
  • Hormones are secreted into the bloodstream and travel to target cells.
  • Glands secrete hormones that regulate various functions (e.g., growth, metabolism, reproduction).
• Autonomic Nervous System: Regulates involuntary functions (e.g., heart rate, digestion).
  • Sympathetic nervous system: "fight or flight" response.
  • Parasympathetic nervous system: "rest and digest" response.
• Feedback Mechanisms:
  • Negative feedback: reverses changes to maintain stability.
  • Positive feedback: amplifies changes, leading to a greater response.

Specialized Physiological Processes

• Muscle Physiology: Contraction of muscle cells enables movement.
  • Skeletal muscle, smooth muscle, cardiac muscle.
  • Sliding filament mechanism: interaction of actin and myosin filaments.
• Cardiovascular Physiology: Function of the heart and blood vessels to circulate blood.
  • Cardiac cycle: sequence of events during one heartbeat.
  • Blood pressure: force exerted by blood against the walls of blood vessels.
• Respiratory Physiology: Gas exchange in the lungs between air and blood.
  • Ventilation: movement of air into and out of the lungs.
  • Diffusion: movement of gases across the respiratory membrane.
• Renal Physiology: Function of the kidneys to filter blood and regulate fluid balance.
  • Glomerular filtration, tubular reabsorption, tubular secretion.
• Neurophysiology: Function of the nervous system, including sensory perception, motor control, and higher cognitive functions.
  • Action potentials, synaptic transmission, brain function.
• Endocrine Physiology: Hormone secretion and regulation of various physiological processes.
  • Hormone synthesis, hormone receptors, feedback control of hormone secretion.