Anatomy & Physiology: Levels of Organization

Study Notes

Chemical Level: Atoms and molecules form the foundation. Examples include DNA, proteins, lipids, and carbohydrates.
Cellular Level (Cytology): Cells are formed by the combination of chemicals.
Tissue Level (Histology): Groups of similar cells work together to perform a specific function.
Organ Level: Different tissues are organized to create an organ with a specific function.
Organ System Level: Groups of organs cooperate to achieve a common purpose.
Organismal Level: All organ systems function together to make a complete living being.

The body strives to maintain a stable internal environment.
Homeostasis is the reason the body operates within narrow ranges for temperature and pH.
Disruption of homeostasis can lead to illness, disease, or even death.

Controlled Condition: The variable being regulated.
Receptor: Detects changes in the controlled condition.
Control Center: Processes information from the receptor and dictates the response.
Effector: Carries out the response directed by the control center.

Negative Feedback: The most common type, immediately reverses changes. Examples include blood pressure and temperature regulation.
Positive Feedback: Less common, intensifies or escalates changes. Examples include childbirth and blood clotting.

Circulatory: Transports oxygen and nutrients to body cells.
Digestive: Breaks down food and absorbs nutrients.
Endocrine: Regulates homeostasis using hormones.
Integumentary: Provides protection, sensory input, and temperature regulation.
Lymphatic/Immune: Defends against infection, recycles interstitial fluid, and produces blood cells.
Muscular: Facilitates movement and generates heat.
Nervous: Controls body activities, regulates metabolism, and processes thoughts.
Respiratory: Exchanges gases and regulates pH.
Reproductive: Produces gametes (sperm/eggs).
Skeletal: Provides protection, support, and stores minerals.
Urinary: Eliminates waste, maintains pH, and regulates body fluids.

Frontal (Coronal): Divides the body into anterior and posterior sections.
Transverse (Horizontal): Divides the body into superior and inferior sections.
Sagittal: Divides the body into right and left sections.

Atom: The smallest stable unit of matter, composed of:
- Protons: Found in the nucleus, have a positive charge.
- Neutrons: Found in the nucleus, have no charge (neutral).
- Electrons: Orbit the nucleus, have a negative charge.

Atomic Number: The number of protons in an atom.
Mass Number: The number of protons plus neutrons in an atom.
Element: A substance that cannot be broken down into simpler substances; composed of only one type of atom.
Mineral: An inorganic substance naturally occurring in the earth.
Molecule: Two or more atoms joined together (e.g., H2O, O2).
Compound: Two or more different atoms joined together (e.g., NaCl).
Isotope: Atoms of the same element with the same number of protons but different numbers of neutrons.
Cation: A positively charged ion.
Anion: A negatively charged ion.

Ionic Bond: Formed when one atom donates an electron to another atom, resulting in ions (weaker than covalent but stronger than hydrogen).
Covalent Bond: Formed when atoms share electrons, resulting in molecules (strongest bond, won't dissociate in water).
Hydrogen Bond: A weak attraction between a hydrogen atom and an oxygen or nitrogen atom (helps shape molecules like proteins and DNA).

Chemical Reactions: Processes involving the making or breaking of bonds between atoms. Breaking bonds releases energy, and making bonds requires energy.
Catabolism: Breaking down molecules.
Anabolism: Building up molecules.

Dehydration Synthesis: Removal of water to form a larger molecule.
Hydrolysis: Addition of water to break down a large molecule.
Exchange Reaction: Involves both the breaking and forming of bonds, atoms switch places between molecules.
Reversible Reaction: Can proceed in both directions.