Foundations of Human Physiology

Overview: Anatomy and physiology are interrelated fields.
Human Anatomy: The scientific study of the body’s structures.
- Gross Anatomy: Examination of body structures visible without magnification.
- Microscopic Anatomy: Examination of structures that require magnification to see.
Human Physiology: The study of the functions of the body’s structures, including:
- Chemistry and physics of structures.
- Interactions of structures supporting life functions.
Methodology: Physiology is studied through laboratory experiments, focusing on body structures and chemicals.
Relation of Structure & Function: Understanding body system structures conveys the understanding of their functions.

Hierarchical Organization:
- Chemical Level: Simplest units of matter (atoms and molecules).
- Cellular Level: Cells as the smallest units of life, performing essential physiological functions.
- Tissue Level: Groups of similar cells that perform specific functions.
- Organ Level: Distinct anatomical structures performing specific functions.
- Organ System Level: Groups of organs coordinating to perform major functions or meet physiological needs.
- Organism Level: A living being that can perform all physiological functions independently, maintaining life.

Common Features of Cells:
- Cell (Plasma) Membrane: Barrier regulating entry and exit of substances.
- Nucleus: Control center storing genetic material for protein synthesis.
- Cytosol: Jelly-like fluid medium for biochemical reactions.
Cell Structure:
- All cells possess membranes and organelles critical for function.
- Membrane structure:
- Phospholipid Bilayer: Composed of hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.

Composition: Two layers of phospholipids.
Fluidity: Membrane remains fluid, allowing for dynamic movement of lipids and proteins.
Membrane Protein Functions:
- Allow materials in/out.
- Cell recognition (immune system).
- Receptors binding external molecules (causing cellular responses).
- Stability and contribution to fluidity of the membrane.

Membrane Characteristics: Selectively permeable to substances based on their size and charge.
- Small, Uncharged Substances: Can pass freely (examples: lipids, oxygen, carbon dioxide).
- Water-Soluble Materials: Require assistance to cross due to hydrophobic nature of membrane.

Passive Transport: Movement that does not require energy.
- Simple Diffusion: Small, lipid-soluble molecules moving down concentration gradients (e.g., oxygen, carbon dioxide).
- Facilitated Diffusion: Larger/poorly lipid-soluble molecules move with the aid of channel proteins (e.g., glucose transporters).
Active Transport: Energy (ATP) required to move substances against concentration gradients.
- Sodium-Potassium Pump: Role in maintaining cellular homeostasis (in nervous system function).

Mechanism: Movement of molecules into and out of cells without crossing the membrane directly.
- Endocytosis: Cell ingests material forming a vesicle.
- Phagocytosis: Engulfing large particles (cell eating).
- Pinocytosis: Engulfing small particles or fluids (cell drinking).
- Exocytosis: Export of substances via vesicles.

Definition: Diffusion of water through a semi-permeable membrane.
Importance of Balancing Solute Concentrations: Essential for cell survival and function, water moves down its concentration gradient until equal.
Clinical Significance: Imbalances in solute concentrations can lead to:
- Isotonic Solution: No net water movement (equal concentrations).
- Hypertonic Solution: Higher solutes outside, leading to water exiting the cell (cell shrinks).
- Hypotonic Solution: Lower solutes outside, leading to water entering the cell (cell swells and may burst).

Definition: Membrane-enclosed structures performing distinct functions.
Composition: Make up ~50% of cell volume.
Functions of Organelles:
- Protein synthesis and modification.
- Energy transformation.
- Cleanup processes (e.g., waste management).
Cell-specific organelle variations based on function.

DNA: Blueprint for cellular structure and physiology, containing genes responsible for protein synthesis.
Protein Synthesis:
- Transcription: DNA to mRNA within the nucleus.
- Translation: mRNA to protein in the cytoplasm.
- Importance of Proteins: Building blocks for cellular function, enzymes, and metabolic processes.

Concept: Process by which unspecialized cells become specialized for distinct functions.
Stem Cells: Unique cells capable of differentiating into various cell types.
- Types: Embryonic (pluripotent), fetal (pluripotent), and adult (multipotent) stem cells.
- Applications: Regeneration and repair of cells/tissues.

Overview: Tissues are groups of similar cells.
Categories:
- Epithelial Tissue: Covers surfaces, functions in protection and absorption.
- Connective Tissue: Supports, connects, and protects organs; includes various subtypes.
- Muscle Tissue: Specialized for contraction; types include skeletal, smooth, and cardiac.
- Nervous Tissue: Specialized for signal transmission; neurons and supporting neuroglia cells.

Definition: Maintenance of stable internal conditions essential for survival; regulated by physiological parameters.
Set Point: Range within which physiological values (e.g., temperature, pH, glucose) fluctuate.
Feedback Mechanisms:
- Negative Feedback: Reverses deviations from set points to maintain stability (e.g., temperature regulation).
- Positive Feedback: Intensifies changes (e.g., childbirth) until a specific outcome is achieved.
- Role of the endocrine and nervous systems in communication and regulation of homeostasis.