The Human Body: An Orientation

Topics of Anatomy and Physiology

• Anatomy: The study of the structure of body parts and their relationships to one another.

• Physiology: The study of the function of the body’s structural machinery.

Complementarity of Structure and Function

• Structure determines function; what a structure can do depends on its specific form.

• Example: Bones can support and protect body organs because they contain hard mineral deposits.

Levels of Structural Organization

• Chemical level: Atoms combine to form molecules.

• Cellular level: Cells are made up of molecules.

• Tissue level: Tissues consist of similar types of cells.

• Organ level: Organs are made up of different types of tissues.

• Organ system level: Organ systems consist of different organs that work together closely.

• Organismal level: The human organism is made up of many organ systems.

Necessary Life Functions

• Maintaining boundaries

• Movement

• Responsiveness

• Digestion

• Metabolism

• Excretion

• Reproduction

• Growth

Organ Systems and Functions

• Each organ system has specific functions essential for survival (e.g., the cardiovascular system transports blood, the respiratory system exchanges gases).

Survival Needs

• Nutrients: Provide energy and building blocks for growth and repair.

• Oxygen: Required for metabolic reactions.

• Water: Most abundant chemical in the body; necessary for chemical reactions.

• Normal body temperature: Necessary for chemical reactions to occur at life-sustaining rates.

• Atmospheric pressure: Required for proper breathing and gas exchange in the lungs.

Homeostasis and Feedback Loops

• Homeostasis: The maintenance of a stable internal environment despite continuous external changes.

• Components: Receptor (detects change), Control Center (processes information), Effector (carries out response).

Negative Feedback

• Reduces or shuts off the original stimulus.

• Examples: Body temperature regulation, blood glucose regulation.

Positive Feedback

• Enhances or exaggerates the original stimulus.

• Example: Platelet plug formation during blood clotting.

Chemistry Comes Alive

Matter and Energy

• Matter: Anything that occupies space and has mass.

• Energy: The capacity to do work or put matter into motion.

Potential vs. Kinetic Energy

• Potential energy: Stored energy (e.g., chemical bonds).

• Kinetic energy: Energy in action (e.g., movement of muscles).

Forms of Energy

• Chemical, electrical, mechanical, and radiant energy.

• Energy conversions are inefficient; some energy is lost as heat.

Atomic Structure

• Atoms consist of protons (+, nucleus), neutrons (0, nucleus), and electrons (-, orbitals).

• Atomic number: Number of protons.

• Mass number: Protons + neutrons.

• Atomic weight: Average of mass numbers of all isotopes.

• Isotopes: Atoms with same number of protons but different neutrons (e.g., Carbon-12, Carbon-14).

• Radioisotopes: Unstable isotopes that decay, emitting radiation.

Molecules, Compounds, and Mixtures

• Molecule: Two or more atoms bonded together.

• Compound: Two or more different atoms bonded together.

• Mixtures: Physical combinations of substances (solutions, colloids, suspensions).

• Mixtures can be separated physically; compounds require chemical means.

Chemical Bonding and the Octet Rule

• Electrons in the outer shell (valence electrons) determine chemical behavior.

• Octet rule: Atoms tend to gain, lose, or share electrons to achieve 8 in their valence shell.

• Chemically inert elements: Have full valence shells (e.g., noble gases).

• Chemically reactive elements: Do not have full valence shells.

Types of Chemical Bonds

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

• Covalent bonds: Sharing of electrons (e.g., H2O, CO2).

• Hydrogen bonds: Weak attractions between polar molecules (e.g., between water molecules).

Polar vs. Non-polar Covalent Molecules

• Non-polar: Electrons shared equally (e.g., CO2).

• Polar: Electrons shared unequally (e.g., H2O).

Chemical Reactions

• Synthesis reactions: Atoms/molecules combine (A + B → AB).

• Decomposition reactions: Molecule broken down (AB → A + B).

• Exchange reactions: Bonds made and broken (AB + C → AC + B).

• Redox reactions: Involve electron transfer; oxidation (loss of electrons), reduction (gain of electrons).

• Exergonic reactions: Release energy.

• Endergonic reactions: Absorb energy.

• Many reactions are reversible.

• Factors influencing reaction rate: Temperature, concentration, particle size, catalysts (enzymes).

Inorganic Compounds

• Water: High heat capacity, high heat of vaporization, polar solvent, reactivity, cushioning.

• Salts: Ionic compounds that dissociate in water (e.g., NaCl).

• Acids: Proton donors; release H+ (e.g., HCl).

• Bases: Proton acceptors; release OH- (e.g., NaOH).

pH: Acid-Base Concentration

• pH scale: 0 (acidic) to 14 (basic); 7 is neutral.

• pH and [H+] are inversely related.

• Neutralization: Acid + base → salt + water.

• Strong acids/bases dissociate completely; weak acids/bases dissociate partially.

Organic Compounds

• Carbohydrates: Sugars and starches; energy source.

• Lipids: Fats, oils, steroids; energy storage, cell membranes.

• Proteins: Amino acid polymers; structure, enzymes, transport.

• Protein denaturation: Loss of structure and function due to environmental changes.

• Enzymes: Biological catalysts; lower activation energy.

• DNA: Genetic material; double helix structure.

• ATP: Energy currency of the cell.

Dehydration Synthesis and Hydrolysis

• Dehydration synthesis: Joins molecules by removing water.

• Hydrolysis: Breaks molecules by adding water.

Acid-Base Chemistry

Acid-Base Balance: Acidosis vs. Alkalosis

• Acidosis: Blood pH below 7.35.

• Alkalosis: Blood pH above 7.45.

Bicarbonate Buffer System

• Buffers resist changes in pH.

• Bicarbonate system: Maintains blood pH.

Key Equations:

• When adding strong acid (increasing [H+]):

• When adding strong base (decreasing [H+]):

• Alkaline reserve: The amount of available bicarbonate ions.

Protein Buffer System

• Proteins act as buffers by binding or releasing H+.

Respiratory Regulation of H+

• High [H+] (acidosis): Increased CO2 exhalation (hyperventilation) lowers acidity.

• Low [H+] (alkalosis): Decreased CO2 exhalation (hypoventilation) increases acidity.

Types of Acid-Base Imbalances

Cells: The Living Units

Structure of the Generalized Cell

• All cells have a plasma membrane, cytoplasm, and nucleus.

Plasma Membrane

• Phospholipid bilayer with embedded proteins.

• Functions: Selective barrier, communication, cell recognition.

• Membrane lipids: Phospholipids, cholesterol, glycolipids.

• Membrane proteins: Transport, receptors, enzymes, cell recognition, attachment.

• Glycocalyx: Carbohydrate-rich area for cell recognition and protection.

Cell Junctions

• Tight junctions: Prevent leakage between cells.

• Desmosomes: Anchor cells together.

• Gap junctions: Allow communication between cells.

Membrane Transport

• Passive processes: No energy required (diffusion, osmosis).

• Diffusion: Movement from high to low concentration.

• Osmosis: Diffusion of water across a membrane.

• Isotonic: Same solute concentration as cell.

• Hypertonic: Higher solute concentration than cell (cell shrinks).

• Hypotonic: Lower solute concentration than cell (cell swells).

Active Transport

• Primary active transport: Uses ATP directly (e.g., Na+-K+ pump).

• Secondary active transport: Uses energy from ion gradients (e.g., Na-glucose co-transporter).

Vesicular Transport

• Endocytosis: Bringing substances into the cell (phagocytosis, pinocytosis, receptor-mediated).

• Exocytosis: Expelling substances from the cell.

Resting Membrane Potential (RMP)

• Generated by differences in K+ and Na+ concentrations inside and outside the cell.

• Maintained by active transport (Na+-K+ pump).

Cytoplasmic Organelles

• Mitochondria: ATP production.

• Ribosomes: Protein synthesis.

• Rough ER: Protein synthesis and modification.

• Smooth ER: Lipid synthesis, detoxification.

• Golgi apparatus: Modifies, sorts, and packages proteins/lipids.

• Peroxisomes: Detoxify harmful substances.

• Lysosomes: Digestive enzymes for breakdown of waste.

Cytoskeleton and Cellular Extensions

• Microfilaments, intermediate filaments, microtubules: Provide structure and movement.

• Centrosomes and centrioles: Organize microtubules during cell division.

• Cilia: Move substances across cell surface.

• Flagella: Propel cells (e.g., sperm).

• Microvilli: Increase surface area for absorption.

Nucleus and Genetic Material

• Nucleus: Control center; contains DNA.

• Chromatin: DNA + proteins; condenses to form chromosomes during cell division.

Cell Cycle

• Mitosis: Division of nucleus (prophase, metaphase, anaphase, telophase).

• Cytokinesis: Division of cytoplasm.

DNA Replication and Protein Synthesis

• DNA replication: Copying DNA before cell division.

• Protein synthesis: Transcription (DNA to mRNA), translation (mRNA to protein).

• Types of RNA: mRNA (messenger), tRNA (transfer), rRNA (ribosomal).

• Genetic code: Sequence of three bases (codon) codes for one amino acid.

• Information transfer: DNA → RNA → polypeptide.

Example: During protein synthesis, tRNA brings amino acids to the ribosome, matching the mRNA codon with its anticodon to ensure correct sequence.

Additional info: Where figures or page numbers are referenced, content has been expanded with standard academic explanations for completeness.