Ch 1: Introduction to Anatomy & Physiology

Levels of Organization in the Human Body

The human body is organized into hierarchical levels, each with specific structural and functional characteristics.

• Molecules: Composed of atoms held together by chemical forces.

• Cells: The smallest structural and functional unit of an organism capable of independent functioning.

• Tissues: Aggregates of similar cells performing a specific function.

• Organs: Groups of tissues working together for a common function.

• Organ Systems: Several organs working together in an integrated manner.

Homeostasis and Feedback Mechanisms

Homeostasis is the maintenance of a stable internal environment. The body uses feedback mechanisms to regulate physiological variables.

• Negative Feedback: A process that returns a variable to its set point, counteracting deviations (e.g., blood pressure regulation, blood glucose concentration, respiratory rate, blood pH regulation).

• Positive Feedback: A process that amplifies a change, moving the variable further from its set point (e.g., platelets aggregating in blood clotting, childbirth).

Key Points:

• Negative feedback is self-terminating.

• Positive feedback is less common and not used frequently in the body.

• Positive feedback does not return the variable to the set point.

Components of a Homeostatic Feedback Loop

• Receptor: Detects changes in the environment (stimuli).

• Control Center: Processes information and determines the response.

• Effector: Carries out the response to restore homeostasis.

Body Planes and Directional Terms

Understanding anatomical terminology is essential for describing locations and directions in the body.

• Planes:

  • Right and left half: Sagittal plane

  • Front and back half: Frontal (coronal) plane

  • Top and bottom half: Transverse (horizontal) plane

• Directional Terms: Superior, inferior, anterior, posterior, medial, lateral, proximal, distal, superficial, deep

• Examples:

  • The fingers are distal to the elbow.

  • The stomach is inferior to the heart.

  • The nose is superior to the mouth.

  • The vertebrae are posterior to the heart.

  • The shoulder is proximal to the elbow.

Ch 3: The Cell and Its Organelles

Cell Organelles and Their Functions

Cells contain specialized structures called organelles, each with distinct functions.

Protein Synthesis: Translation

Translation is the process by which ribosomes synthesize proteins using messenger RNA (mRNA) as a template. It occurs in the cytoplasm.

Plasma Membrane Structure

The plasma membrane is a bilayer of phospholipids with embedded proteins and cholesterol.

• Phospholipid heads are hydrophilic and face the outside and inside of the cell.

• Phospholipid tails are hydrophobic and face each other inside the bilayer.

• Proteins serve as channels, receptors, and enzymes.

• Cholesterol stabilizes the membrane at various temperatures.

• Carbohydrates attached to proteins extend into the extracellular fluid as glycoproteins.

Cell Junctions

Membrane Transport Mechanisms

Types of Membrane Transport

Specific Transport Processes

• Simple Diffusion: Movement of small molecules (e.g., O2, CO2) through the phospholipid bilayer from high to low concentration.

• Osmosis: Diffusion of water across a selectively permeable membrane from high to low water concentration.

• Facilitated Diffusion: Movement of molecules via membrane proteins (channels or carriers) down their concentration gradient.

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

• Primary Active Transport: Direct use of ATP to move substances against their concentration gradient (e.g., Na+/K+ pump).

• Secondary Active Transport: Uses the energy from the movement of one substance down its gradient to move another substance against its gradient.

• Pinocytosis: Cell "drinking"; uptake of extracellular fluid and dissolved solutes via vesicles.

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

• Exocytosis: Vesicles fuse with the plasma membrane to release contents outside the cell.

Osmosis and Tonicity

• Hypertonic Solution: Higher solute concentration outside the cell; cell shrinks (crenates).

• Hypotonic Solution: Lower solute concentration outside the cell; cell swells and may burst (lyse).

• Isotonic Solution: Equal solute concentration; no net movement of water; cell remains the same size.

Examples and Applications

• A red blood cell in distilled water (hypotonic) swells.

• A red blood cell in a concentrated salt solution (hypertonic) shrinks.

• In isotonic solutions, water moves in and out at equal rates.

Comparison: Facilitated vs. Simple Diffusion

• Simple Diffusion: No membrane protein required; small, nonpolar molecules.

• Facilitated Diffusion: Requires membrane protein; larger or polar molecules.

Key Equations

• Fick's Law of Diffusion:

• Where J is the rate of diffusion, D is the diffusion coefficient, and \frac{dC}{dx} is the concentration gradient.

Additional info:

• HIV can enter cells via phagocytosis (receptor-mediated endocytosis).

• Filtration differs from other passive transport as it is driven by pressure, not concentration gradients.

• Primary active transport uses ATP directly, while secondary active transport relies on the gradient established by primary active transport.