Anatomy & Physiology: Foundational Concepts, Chemistry, and Cell Biology Study Notes

Homeostasis and Anatomical Organization

Homeostasis: Negative vs. Positive Feedback

Homeostasis is the maintenance of a stable internal environment in the body. Feedback mechanisms regulate physiological processes to maintain balance.

• Negative Feedback: A process that reverses a change to keep a variable within a normal range. Most homeostatic mechanisms are negative feedback loops.

• Positive Feedback: A process that amplifies a change, moving the system further from its starting state. Less common, but important in processes like blood clotting and childbirth.

• Three Components of Feedback Loop:

  • Receptor: Detects changes in the environment.

  • Control Center: Processes information and determines response.

  • Effector: Carries out the response to restore balance.

Anatomical Position and Body Organization

• Anatomical Position: The standard reference position for the body: standing upright, facing forward, arms at sides, palms facing forward.

• 3 Anatomical Sections/Planes:

  • Sagittal Plane: Divides body into left and right parts.

  • Frontal (Coronal) Plane: Divides body into anterior (front) and posterior (back) parts.

  • Transverse (Horizontal) Plane: Divides body into superior (upper) and inferior (lower) parts.

• Directional Terms: Used to describe locations of structures (e.g., superior, inferior, anterior, posterior, medial, lateral, proximal, distal).

• Body Regions: Specific areas of the body, such as the abdominal, thoracic, and pelvic regions.

• Body Cavities & Their Membranes:

  • Visceral Membrane: Covers organs.

  • Parietal Membrane: Lines cavity walls.

• Abdominal Quadrants & Regions: Used to describe locations of organs and pain.

  • Quadrants: Right Upper, Left Upper, Right Lower, Left Lower.

  • Regions: Epigastric, umbilical, hypogastric, etc.

Chapter 2: Chemistry

pH, Acids, and Bases

pH measures the acidity or alkalinity of a solution, which is crucial for physiological processes.

• pH: Indicates the concentration of hydrogen ions ($[H^+]$) in a solution.

• Acid: Substance that donates hydrogen ions ($H^+$).

• Base: Substance that accepts hydrogen ions or donates hydroxide ions ($OH^-$).

• pH Scale: Ranges from 0 (most acidic) to 14 (most basic), with 7 being neutral.

• Formula: $pH = -\log_{10}[H^+]$

Buffers

• Buffer: A solution that resists changes in pH when acids or bases are added.

• Importance: Maintains stable pH in body fluids, essential for enzyme function and metabolic processes.

• Example: Bicarbonate buffer system in blood.

Solutions, Colloids, and Mixtures

• Solution: Homogeneous mixture of solute dissolved in solvent (e.g., salt water).

• Colloid: Mixture with larger particles that do not settle (e.g., milk).

• Mixture: Combination of substances not chemically bonded (e.g., sand and water).

Atoms, Elements, and Chemical Bonds

• Element: Pure substance consisting of one type of atom.

• Valence Shell Electrons: Electrons in the outermost shell, determine chemical reactivity.

• Oxidation and Reduction:

  • Oxidation: Loss of electrons.

  • Reduction: Gain of electrons.

• Ions: Charged atoms or molecules (cations: positive, anions: negative).

• Electrolyte: Substance that dissociates into ions in solution, conducts electricity.

• Chemical Bonds:

  • Covalent Bond: Atoms share electrons (can be polar or nonpolar).

  • Ionic Bond: Transfer of electrons from one atom to another.

  • Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., in water, DNA).

Free Radicals and Antioxidants

• Free Radical: Atom or molecule with an unpaired electron, highly reactive and can damage cells.

• Antioxidant: Substance that neutralizes free radicals (e.g., vitamin C, vitamin E).

Organic Compounds and Macromolecules

• Organic Compound: Contains carbon and hydrogen, often found in living organisms.

• Major Categories: Carbohydrates, lipids, proteins, nucleic acids.

• Carbohydrates: Sugars and starches; classified as monosaccharides, disaccharides, polysaccharides.

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

• Proteins: Made of amino acids; function as enzymes, hormones, structural components.

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

• Nucleotide: Building block of nucleic acids, composed of a sugar, phosphate group, and nitrogenous base.

Cell Biology

Gradients

• Gradient: Difference in concentration, pressure, or electrical charge between two regions.

• Types of Gradients: Concentration, electrical, pressure, temperature.

• Importance: Drive movement of substances across membranes (e.g., diffusion, osmosis).

Cell Theory and Cell Junctions

• Cell Theory: All living things are composed of cells; cells are the basic unit of life; all cells come from pre-existing cells.

• Cell Junctions: Structures that connect cells to each other (e.g., tight junctions, desmosomes, gap junctions).

Plasma Membrane Structure and Function

• Phospholipid Bilayer: Double layer of phospholipids with hydrophilic heads and hydrophobic tails.

• Membrane Proteins: Integral (transmembrane) and peripheral proteins; functions include transport, signaling, and structural support.

• Ligand-Gated Channels: Open or close in response to binding of a chemical messenger (ligand).

Membrane Transport

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Diffusion: Movement of molecules from high to low concentration.

• Filtration: Movement of water and solutes through a membrane by hydrostatic pressure.

• Active Transport: Movement of substances against a gradient, requires energy (ATP).

• Passive Transport: Movement of substances down a gradient, does not require energy.

• Endocytosis: Uptake of materials into the cell by vesicle formation.

• Exocytosis: Release of materials from the cell by vesicle fusion with the membrane.

• Phagocytosis: "Cell eating"; engulfment of large particles by the cell.

Cellular Organelles and Their Functions

• Smooth Endoplasmic Reticulum (ER): Lipid synthesis, detoxification.

• Rough ER: Protein synthesis (has ribosomes attached).

• Nucleus: Contains genetic material (DNA), controls cell activities.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

• Vesicles: Transport materials within the cell.

• Mitochondria: Site of ATP (energy) production.

• Peroxisome: Breaks down fatty acids and detoxifies harmful substances.

• Ribosomes: Synthesize proteins.

• Cytoskeleton: Provides structural support, aids in cell movement.

Other Cellular Structures

• Microvilli: Increase surface area for absorption.

• Glycocalyx: Carbohydrate-rich coating on cell surface, involved in cell recognition.

• Cilia: Hair-like structures that move substances across cell surface.

• Flagella: Long, whip-like structures for cell movement (e.g., sperm cell).

Cellular Metabolism and Signaling

• Ionotropic vs. Metabotropic Receptors:

  • Ionotropic: Directly open ion channels upon ligand binding.

  • Metabotropic: Activate second messenger pathways to produce cellular effects.

• 2nd Messenger System: Intracellular signaling molecules (e.g., cAMP) that mediate effects of hormones and neurotransmitters.

Genetic Information Flow

• Transcription: Synthesis of mRNA from DNA template.

• Translation: Synthesis of protein from mRNA at the ribosome.

• Codon: Three-nucleotide sequence on mRNA that codes for an amino acid.

• Anticodon: Three-nucleotide sequence on tRNA complementary to mRNA codon.

• mRNA: Messenger RNA, carries genetic code from DNA to ribosome.

• tRNA: Transfer RNA, brings amino acids to ribosome during translation.

• Reading a Codon Table: Used to determine which amino acid corresponds to each mRNA codon.

Table: Types of Chemical Bonds

Bond Type	Description	Example
Covalent	Atoms share electrons	H2O (water)
Ionic	Transfer of electrons from one atom to another	NaCl (table salt)
Hydrogen	Weak attraction between hydrogen and electronegative atom	Between water molecules

Table: Major Organic Macromolecules

Macromolecule	Monomer	Function	Example
Carbohydrate	Monosaccharide	Energy source, structure	Glucose, starch
Lipid	Fatty acid, glycerol	Energy storage, membranes	Triglyceride, phospholipid
Protein	Amino acid	Enzymes, structure, signaling	Hemoglobin, collagen
Nucleic Acid	Nucleotide	Genetic information	DNA, RNA

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