Chapter 1: Introduction to Anatomy & Physiology (A&P)

Characteristics of Living Things

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

• Cellular Composition: All living things are composed of one or more cells, which are the basic units of life.

• Metabolism: The sum of all chemical reactions in the body, including catabolism (breaking down molecules) and anabolism (building molecules).

• Growth: Increase in size and/or number of cells.

• Response to Stimuli: Ability to detect and respond to changes in the environment.

• Reproduction: Production of new organisms or new cells.

• Homeostasis: Maintenance of a stable internal environment.

Structural Organization: Atom to Organism

The human body is organized in a hierarchy from the simplest to the most complex level:

1. Atoms

2. Molecules

3. Organelles

4. Cells

5. Tissues

6. Organs

7. Organ Systems

8. Organism

Anatomical Position and Directional Terms

Standard anatomical position is standing upright, facing forward, arms at the sides with palms facing forward. Directional terms describe locations of structures relative to other structures or locations in the body.

• Anterior (ventral): Front of the body

• Posterior (dorsal): Back of the body

• Superior (cranial): Toward the head

• Inferior (caudal): Toward the feet

• Medial: Toward the midline

• Lateral: Away from the midline

• Proximal: Closer to the point of attachment

• Distal: Farther from the point of attachment

Body Planes and Cavities

• Planes: Imaginary lines dividing the body into sections (sagittal, frontal/coronal, transverse/horizontal).

• Cavities: Spaces within the body that contain internal organs.

  • Dorsal cavity: Cranial and vertebral cavities

  • Ventral cavity: Thoracic and abdominopelvic cavities

Homeostasis and Feedback Mechanisms

Homeostasis is maintained by feedback loops that regulate internal conditions.

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

• Positive Feedback: Enhances a change, moving the variable further from the set point (e.g., blood clotting, childbirth).

• Components of Feedback Loops: Stimulus, receptor, control center, effector.

Example: In temperature regulation, the skin (receptor) senses a change, the brain (control center) processes the information, and sweat glands (effectors) respond.

Chapter 2: Chemistry of Life

Atoms and Subatomic Particles

All matter is composed of atoms, which consist of subatomic particles:

• Protons: Positively charged, found in the nucleus

• Neutrons: No charge, found in the nucleus

• Electrons: Negatively charged, orbit the nucleus

Atomic number is the number of protons. Mass number is the sum of protons and neutrons.

Electron Shells and Chemical Bonding

• Electrons occupy energy levels called shells.

• The first shell holds up to 2 electrons; the second and third shells hold up to 8 electrons each.

• Atoms are most stable when their outermost shell is full (octet rule).

• Atoms form chemical bonds to achieve stability:

  • Ionic bonds: Transfer of electrons from one atom to another

  • Covalent bonds: Sharing of electrons between atoms

  • Hydrogen bonds: Weak attractions between polar molecules

Major Elements in the Human Body

• Four elements make up about 96% of the human body: Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N).

Types of Chemical Reactions

• Synthesis (Anabolic) Reactions: Build larger molecules from smaller ones (e.g., protein synthesis).

• Decomposition (Catabolic) Reactions: Break down larger molecules into smaller ones (e.g., digestion).

• Exchange Reactions: Involve both synthesis and decomposition.

• Endergonic Reactions: Absorb energy.

• Exergonic Reactions: Release energy.

• Redox Reactions: Involve the transfer of electrons (oxidation and reduction).

Activation Energy and Reaction Rates

• Activation Energy: The minimum energy required to start a chemical reaction.

• Enzymes: Biological catalysts that lower activation energy and speed up reactions.

• Factors Affecting Reaction Rates: Concentration, temperature, presence of catalysts.

Organic Compounds in the Body

The four main classes of organic compounds are:

• Carbohydrates: Sugars and starches; provide energy.

• Lipids: Fats and oils; store energy, form cell membranes.

• Proteins: Made of amino acids; perform structural, enzymatic, and regulatory functions.

• Nucleic Acids: DNA and RNA; store and transmit genetic information.

Polymers and Monomers

• Monomers: Small building blocks (e.g., amino acids, monosaccharides, fatty acids, nucleotides).

• Polymers: Large molecules made by joining monomers (e.g., proteins, polysaccharides, nucleic acids).

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Saturated vs. Unsaturated Fatty Acids

• Saturated Fatty Acids: No double bonds between carbon atoms; solid at room temperature.

• Unsaturated Fatty Acids: One or more double bonds; liquid at room temperature.

Protein Structure

• Proteins have four levels of structure:

  1. Primary: Sequence of amino acids

  2. Secondary: Local folding (alpha helices, beta sheets)

  3. Tertiary: 3D shape of a single polypeptide

  4. Quaternary: Association of multiple polypeptides

ATP and Nucleotides

• ATP (Adenosine Triphosphate): The primary energy carrier in cells.

• Nucleotides: Building blocks of nucleic acids; consist of a sugar, phosphate group, and nitrogenous base.

• ATP is a nucleotide; nucleotides are related as both are involved in energy transfer and genetic information.

Key Definitions Table

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.