Introduction to Anatomy and Physiology

Characteristics of Living Organisms

Living organisms share several fundamental characteristics that distinguish them from non-living matter.

• Metabolism: The sum of all chemical reactions in the body, including anabolic (building up) and catabolic (breaking down) processes.

• Growth: Increase in size and number of cells.

• Responsiveness: Ability to sense and react to changes in the environment.

• Movement: Motion of the whole body, individual organs, single cells, or structures within cells.

• Reproduction: Formation of new cells for growth, repair, or replacement, and production of a new individual.

• Homeostasis: Maintenance of a stable internal environment.

Body Systems Overview

The human body is organized into 11 major organ systems, each with specific functions:

• Integumentary (skin, hair, nails): Protection, temperature regulation.

• Skeletal (bones, joints): Support, protection, blood cell production.

• Muscular (muscles): Movement, heat production.

• Nervous (brain, spinal cord, nerves): Rapid communication, control.

• Endocrine (glands): Hormone production, regulation.

• Cardiovascular (heart, blood vessels): Transport of nutrients, gases, wastes.

• Lymphatic (lymph nodes, vessels): Immunity, fluid balance.

• Respiratory (lungs, airways): Gas exchange.

• Digestive (stomach, intestines): Breakdown and absorption of nutrients.

• Urinary (kidneys, bladder): Waste elimination, water balance.

• Reproductive (ovaries, testes): Production of offspring.

Directional Terms

Directional terms describe the positions of structures relative to other structures or locations in the body.

• Superior/Inferior: Above/below.

• Anterior (ventral)/Posterior (dorsal): Front/back.

• Medial/Lateral: Toward the midline/away from the midline.

• Proximal/Distal: Closer to/farther from the point of attachment.

• Superficial/Deep: Toward/away from the body surface.

Serous Membranes and Cavities

Serous membranes line body cavities and cover organs, producing serous fluid to reduce friction.

• Visceral layer: Covers the organ.

• Parietal layer: Lines the cavity wall.

• Pleural membrane: Surrounds the lungs.

• Pericardial membrane: Surrounds the heart.

• Serous fluid: Lubricates and reduces friction between layers.

Homeostasis and Feedback Loops

Homeostasis is maintained by feedback mechanisms:

• Negative feedback: Reverses a change to keep a variable within a normal range (e.g., body temperature regulation).

• Positive feedback: Amplifies a change (e.g., blood clotting, childbirth).

• Stimulus: A change in the environment.

• Effector/Response: The organ or cell that acts to restore balance.

The Chemistry of Life

Basic Chemistry Terms

• Atom: The smallest unit of matter.

• Element: A substance made of one type of atom.

• Atomic number: Number of protons in an atom.

• Mass number: Number of protons plus neutrons.

• Isotope: Atoms of the same element with different numbers of neutrons.

• Radioisotopes: Unstable isotopes that emit radiation; used in medical imaging and cancer treatment.

• Valence electrons: Electrons in the outermost shell, involved in bonding.

• Cation: Positively charged ion.

• Anion: Negatively charged ion.

• Hydrophobic: Repels water.

• Hydrophilic: Attracts water.

• Acid: Releases H+ ions in solution.

• Base: Accepts H+ ions or releases OH- ions.

• Buffer: Resists changes in pH.

• Electrolytes: Substances that conduct electricity when dissolved in water.

Subatomic Particles

• Protons: Positive charge, found in nucleus.

• Neutrons: No charge, found in nucleus.

• Electrons: Negative charge, orbit nucleus.

Electron shell capacities:

• 1st shell: 2 electrons

• 2nd shell: 8 electrons

• 3rd shell: 18 electrons

Four major elements in the human body: Oxygen, Carbon, Hydrogen, Nitrogen.

Chemical Bonds

• Ionic bonds: Transfer of electrons between atoms (e.g., NaCl).

• Covalent bonds: Sharing of electrons between atoms.

• Hydrogen bonds: Weak attractions between polar molecules (e.g., water); responsible for surface tension.

• Polar covalent bond: Unequal sharing of electrons (e.g., H2O).

• Nonpolar covalent bond: Equal sharing of electrons (e.g., O2).

Energy in Chemical Reactions

• Endergonic reactions: Absorb energy.

• Exergonic reactions: Release energy.

• To determine reaction type from a graph: If products have more energy than reactants, it's endergonic; if less, exergonic.

Anabolic and Catabolic Reactions

• Anabolic: Build larger molecules from smaller ones (require energy).

• Catabolic: Break down molecules into smaller units (release energy).

Oxidation-Reduction (Redox) Reactions

• Oxidized: Loses electrons.

• Reduced: Gains electrons.

Enzymes and Activation Energy

• Activation energy: Minimum energy required to start a reaction.

• Enzyme: Biological catalyst that lowers activation energy and speeds up reactions.

• Characteristics of enzymes: Specificity, efficiency, can be regulated, not consumed in reaction.

• Factors affecting enzyme rate: Temperature, pH, substrate concentration, inhibitors.

Acids, Bases, and pH

• pH scale: Ranges from 0 (acidic) to 14 (basic), 7 is neutral.

• High H+ concentration = acidic; high OH- concentration = basic.

Macromolecules

There are four major classes of biological macromolecules:

• Fatty acid: Long hydrocarbon chain with carboxyl group.

• Saturated fatty acid: No double bonds; solid at room temperature.

• Unsaturated fatty acid: One or more double bonds; liquid at room temperature.

• Triglyceride: Glycerol + 3 fatty acids; main form of stored fat.

• Phospholipid: Glycerol, 2 fatty acids, phosphate group; major component of cell membranes.

• Sterols (steroids): Four fused carbon rings; e.g., cholesterol.

• Good fats: Omega-3 fatty acids (fish, flaxseed).

• Bad fats: Saturated fats (butter, red meat); increase cardiovascular risk.

• Peptide bonds: Bonds between amino acids in proteins.

• Protein structure: Primary, secondary, tertiary, quaternary levels.

• Denaturation: Loss of protein structure due to heat, pH, chemicals.

• Enzymes: Proteins that catalyze reactions.

• Base pairing (DNA): A-T (2 bonds), G-C (3 bonds).

• Base pairing (RNA): A-U, G-C.

• ATP (Adenosine Triphosphate): Main energy currency of the cell.

• Phosphodiester bonds: Bonds between nucleotides in DNA/RNA.

The Cell

Cell Structure and Organelles

Most animal cells contain three basic components:

• Plasma membrane: Outer boundary, regulates entry/exit.

• Cytoplasm: Fluid and organelles between membrane and nucleus.

• Nucleus: Contains genetic material (DNA).

Plasma Membrane Structure

• Phospholipid bilayer: Main structure; hydrophilic heads, hydrophobic tails.

• Proteins: Transport, receptors, enzymes.

• Cholesterol: Stabilizes membrane fluidity.

• Carbohydrates: Cell recognition.

Fluid mosaic model: Describes the dynamic arrangement of phospholipids and proteins.

Transport Across Membranes

• Passive transport: No energy required; includes diffusion, osmosis, facilitated diffusion.

• Active transport: Requires energy (ATP); includes pumps, endocytosis, exocytosis.

• Simple diffusion: Movement of small, nonpolar molecules (e.g., O2, CO2).

• Facilitated diffusion: Movement via protein channels/carriers (e.g., glucose).

• Osmosis: Diffusion of water across a semipermeable membrane.

• Isotonic: Equal solute concentration; no net water movement.

• Hypotonic: Lower solute outside; water enters cell (cell swells).

• Hypertonic: Higher solute outside; water leaves cell (cell shrinks).

• Exocytosis: Vesicles fuse with membrane to release contents.

• Endocytosis: Cell engulfs material; includes pinocytosis (liquids) and phagocytosis (solids).

Membrane Transport Example: Na+/K+ Pump

• Moves 3 Na+ out and 2 K+ into the cell per ATP used.

Cytoskeleton and Cell Extensions

• Microfilaments: Actin; cell movement, shape.

• Intermediate filaments: Structural support.

• Microtubules: Tubulin; cell division, transport.

• Cell extensions: Cilia (movement), flagella (sperm motility), microvilli (increase surface area).

Genetic Information and Protein Synthesis

• Gene: Segment of DNA coding for a protein.

• Exons: Coding regions of genes.

• Mutations: Changes in DNA sequence.

• Mutagens: Agents causing mutations.

• Promoter: DNA region where transcription starts.

• Apoptosis: Programmed cell death.

Central Dogma of Molecular Biology

• DNA replication → DNA

• DNA transcription → mRNA

• mRNA translation → tRNA → amino acid (protein)

• During RNA processing, introns are removed; mRNA contains only exons.

Protein Pathway in the Cell

• Nucleus (gene) → rER (synthesis/folding) → transport vesicle → Golgi apparatus (modification/packaging) → secretory vesicle → cell membrane (exocytosis)

Additional info: The above notes expand on the study guide points, providing definitions, examples, and context for each major topic in the first three chapters of a typical Anatomy & Physiology course.