Chapter 1: The Human Body – An Orientation

Levels of Organization

The human body is organized in a hierarchical structure, from the simplest chemical level to the most complex organismal level.

• Atom: The smallest unit of matter (e.g., carbon, hydrogen).

• Molecule: Two or more atoms bonded together (e.g., H2O, CO2).

• Organelle: Specialized structures within cells (e.g., mitochondria, nucleus).

• Cell: The basic unit of life; smallest unit that exhibits all characteristics of life.

• Tissue: Groups of similar cells performing a common function (e.g., muscle tissue).

• Organ: Structures composed of two or more tissue types (e.g., heart, liver).

• Organ System: Groups of organs working together for a common purpose (e.g., digestive system).

• Organism: The complete living being (human).

Organ Systems and Their Functions

There are 11 major organ systems in the human body, each with specific functions:

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

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

• Muscular: Movement, posture, heat production (muscles).

• Nervous: Fast-acting control, response to stimuli (brain, spinal cord, nerves).

• Endocrine: Hormone production, slow-acting control (glands such as thyroid, pancreas).

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

• Lymphatic/Immune: Defense, fluid balance (lymph nodes, spleen).

• Respiratory: Gas exchange (lungs, trachea).

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

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

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

Necessary Life Functions

• Maintaining boundaries (e.g., skin separates internal from external environment)

• Movement (muscular system, movement of substances)

• Responsiveness (ability to sense and respond to stimuli)

• Digestion (breakdown and absorption of nutrients)

• Metabolism (all chemical reactions in the body)

• Excretion (removal of wastes)

• Reproduction (cellular and organismal levels)

• Growth (increase in size and number of cells)

Survival Needs

• Nutrients (for energy and cell building)

• Oxygen (for cellular respiration)

• Water (most abundant substance in the body)

• Normal body temperature (for proper metabolic reactions)

• Appropriate atmospheric pressure (for gas exchange)

Homeostasis

Homeostasis is the maintenance of a stable internal environment despite external changes.

• Feedback Mechanisms: Systems that maintain homeostasis via three components:

  • Receptor: Detects changes (stimuli).

  • Control Center: Determines set point, analyzes input, and determines response.

  • Effector: Carries out the response to restore balance.

• Pathways:

  • Afferent pathway: Carries information from receptor to control center.

  • Efferent pathway: Carries commands from control center to effector.

• Negative Feedback: Most common; response reduces or shuts off the original stimulus (e.g., regulation of body temperature, blood glucose).

• Positive Feedback: Response enhances the original stimulus (e.g., blood clotting, labor contractions).

Anatomical Terminology

• Regional Terms: Specific areas of the body (e.g., brachial = arm, femoral = thigh).

• Directional Terms: Describe positions (e.g., superior/inferior, anterior/posterior, medial/lateral).

• Body Cavities:

  • Dorsal cavity: Contains cranial and vertebral cavities.

  • Ventral cavity: Contains thoracic and abdominopelvic cavities.

• Prefixes, Root Words, Suffixes: Used to construct anatomical terms (e.g., 'hypo-' = below, '-itis' = inflammation).

Chapter 2: Basic Chemistry

Subatomic Particles and Atomic Structure

Atoms are the basic building blocks of matter, composed of subatomic particles:

• Protons: Positively charged, found in the nucleus.

• Neutrons: No charge, found in the nucleus.

• Electrons: Negatively charged, orbit the nucleus.

Atoms combine to form molecules through chemical bonds.

Chemical Bonds

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating charged ions that attract each other (e.g., NaCl).

• Covalent Bonds: Formed when atoms share electrons. Can be:

  • Nonpolar: Electrons shared equally (e.g., O2).

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

• Hydrogen Bonds: Weak attractions between polar molecules, important in water and DNA structure.

Water: Polarity and Importance

• Polarity: Water is a polar molecule, with a partial negative charge near the oxygen and partial positive charges near the hydrogens.

• Unique Properties:

  • High heat capacity (absorbs and releases heat slowly)

  • Excellent solvent (dissolves many substances)

  • Participates in chemical reactions (hydrolysis, dehydration synthesis)

  • Cushioning and protection (e.g., cerebrospinal fluid)

• Importance: Water is essential for transport, temperature regulation, and as a medium for chemical reactions.

Inorganic Compounds

• Water: Most abundant inorganic compound in the body.

• Salts: Ionic compounds that dissociate in water; important for nerve impulses and muscle contraction.

• Acids and Bases: Acids release H+; bases accept H+. Their balance is crucial for physiological processes.

pH Scale and Buffers

• pH Scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (basic), with 7 being neutral.

• Normal Blood pH: 7.35–7.45.

• Buffers: Chemicals that resist changes in pH by absorbing or releasing H+ ions.

Example Buffer System:

• Carbonic acid-bicarbonate buffer in blood:

• Helps maintain blood pH during exercise, alcohol consumption, or vomiting.

Making and Breaking Molecules

• Dehydration Synthesis: Forms new bonds by removing water; builds polymers from monomers.

• Hydrolysis: Breaks bonds by adding water; splits polymers into monomers.

Organic Compounds

• Carbohydrates: Main energy source; monomer = monosaccharide (e.g., glucose); polymer = polysaccharide (e.g., starch, glycogen).

• Lipids: Energy storage, insulation, cell membranes; types include triglycerides, phospholipids, steroids.

• Proteins: Structure, enzymes, transport; monomer = amino acid; polymer = polypeptide/protein.

  • Levels of Protein Structure: Primary, secondary, tertiary, quaternary.

  • Denaturation: Loss of protein shape (and function) due to heat or pH changes.

  • Enzymes: Proteins that speed up chemical reactions by lowering activation energy.

• Nucleic Acids: Store and transmit genetic information; DNA and RNA; monomer = nucleotide.

  • DNA: Contains instructions for protein synthesis.

ATP: The Energy Molecule

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

• Structure: Adenine base, ribose sugar, three phosphate groups.

• Energy Storage: Energy is stored in the high-energy phosphate bonds; released when ATP is hydrolyzed to ADP.

• Phosphorylation: The transfer of a phosphate group to another molecule, activating it.

Table: Comparison of Organic Compounds

Additional info: Some explanations and examples have been expanded for clarity and completeness, such as the detailed functions of organ systems and the properties of water.