Chapter 1: The Human Body – An Orientation

Anatomy vs. Physiology

Anatomy is the study of the structure of body parts and their relationships to one another, while physiology is the study of the function of the body’s structural machinery.

• Anatomy: Focuses on body structures, such as organs, tissues, and cells.

• Physiology: Explains how those structures work and interact to sustain life.

• Example: The heart’s anatomy includes its chambers and valves; its physiology involves how it pumps blood.

Characteristics of Living Matter & Levels of Organization

Living organisms exhibit several key characteristics and are organized in hierarchical levels.

• Characteristics: Organization, metabolism, responsiveness, growth, development, reproduction.

• Levels of Organization:

  1. Chemical (atoms, molecules)

  2. Cellular (cells, organelles)

  3. Tissue (groups of similar cells)

  4. Organ (two or more tissue types)

  5. Organ System (organs working together)

  6. Organismal (the whole organism)

• Principle of Complementarity: Structure and function are interrelated; function always reflects structure.

Components of a Signaling Pathway in Living Systems

Signaling pathways allow cells to communicate and coordinate activities.

• Components: Signal (ligand), receptor, transduction pathway, effector, response.

• Example: Hormone (signal) binds to a receptor, triggering a cascade that leads to a cellular response.

Homeostasis

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

• Regulation: Achieved through feedback mechanisms.

• Significance: Essential for survival; imbalance can lead to disease.

• Example: Body temperature regulation, blood glucose levels.

Negative Feedback

• Definition: A process that reduces or shuts off the original stimulus.

• Example: Regulation of blood pressure, body temperature.

Body Systems: Names, Functions, and Representative Organs

The human body is organized into organ systems, each with specific functions and representative organs.

Body Cavities and Membranes

Body cavities house and protect internal organs; membranes line these cavities and organs.

• Dorsal Cavity: Cranial (brain), vertebral (spinal cord)

• Ventral Cavity: Thoracic (heart, lungs), abdominopelvic (digestive organs, bladder, reproductive organs)

• Serous Membranes: Thin, double-layered membranes (parietal and visceral layers) that reduce friction.

• Examples: Pleura (lungs), pericardium (heart), peritoneum (abdominal organs)

Anatomical and Directional Terminology

Standardized terms describe body positions, directions, and planes.

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

• Body Planes: Sagittal, frontal (coronal), transverse (horizontal).

• Applications: Used to describe locations and relationships of body parts.

Chapter 3: Cells – The Living Units

Cell Anatomy and Physiology

Cells are the basic structural and functional units of life, with specialized structures and functions.

• Compartmentalization: Separation of intracellular (cytoplasm) and extracellular spaces (interstitial fluid).

• Extracellular Fluid: Fluid outside cells; includes interstitial fluid, plasma.

• Intracellular Fluid: Cytoplasm; contains organelles and cytosol.

Cell (Plasma) Membrane

The plasma membrane is a selectively permeable barrier composed of lipids, proteins, and carbohydrates.

• Macromolecules: Phospholipids (form bilayer), cholesterol (stabilizes membrane), proteins (transport, receptors), carbohydrates (cell recognition).

• Functional Classes of Membrane Proteins:

  • Transport proteins (channels, carriers)

  • Receptors for signal transduction

  • Enzymatic activity

  • Cell-cell recognition

  • Attachment to cytoskeleton and extracellular matrix

  • Intercellular joining

DNA: Structure, Location, and Function

• Structure: Double helix composed of nucleotides (A, T, C, G).

• Location: Primarily in the cell nucleus.

• Function: Stores genetic information; directs protein synthesis.

Membrane Function: Selectivity and Regulation

• Purpose: Controls entry and exit of substances; maintains homeostasis.

• Selectivity: Some molecules pass freely; others require transport proteins.

Passive vs. Active Transport

• Passive Transport: No energy required; includes diffusion, facilitated diffusion, osmosis.

• Active Transport: Requires ATP; moves substances against concentration gradient.

• Example: Na+/K+ Pump – moves 3 Na+ out and 2 K+ into the cell per ATP hydrolyzed. Equation:

Vesicular Transport

• Types: Endocytosis (phagocytosis, pinocytosis, receptor-mediated), exocytosis.

• Example: White blood cell engulfing bacteria (phagocytosis).

Resting Membrane Potential

• Definition: The voltage difference across the plasma membrane when the cell is at rest.

• Typical Value: About -70 mV in neurons.

• Maintained by: Na+/K+ pump and differential permeability of the membrane.

Cell Signaling Pathway

• Steps: Signal molecule binds receptor → intracellular signaling cascade → cellular response.

• Example: Hormone binding triggers gene expression changes.

Organelles: Names and General Functions

• Common to All Cells: Plasma membrane, cytoplasm, DNA, ribosomes.

• Differentiation/Specialization: Cells develop unique structures/functions (e.g., muscle vs. nerve cells).

The Cytoskeleton

• Types of Filaments:

  • Microfilaments (actin): cell shape, movement

  • Intermediate filaments: structural support

  • Microtubules: cell shape, organelle movement, spindle fibers

The Cell Cycle

The cell cycle is the series of events that cells go through as they grow and divide.

• Purpose: Growth, repair, reproduction.

• Phases: Interphase (G1, S, G2), Mitotic phase (mitosis and cytokinesis).

Mitosis vs. Meiosis

• Mitosis: Produces two identical diploid cells; for growth and repair.

• Meiosis: Produces four non-identical haploid gametes; for sexual reproduction.

Subphases of Mitosis

• Prophase: Chromosomes condense, spindle forms.

• Metaphase: Chromosomes align at cell equator.

• Anaphase: Sister chromatids separate.

• Telophase: Nuclear envelopes reform, chromosomes decondense.

Chromosome Structure

• Chromosome: DNA molecule with associated proteins.

• Chromatid: One of two identical halves of a duplicated chromosome.

• Centromere: Region where chromatids are joined.

Cell Cycle Regulation and Cancer

• Regulation: Controlled by checkpoints (G1, G2, M) and regulatory proteins (cyclins, CDKs).

• Cancer: Uncontrolled cell division due to loss of regulation.

Protein Synthesis

• Significance of DNA: DNA contains instructions for protein synthesis.

• Replication: DNA makes a copy of itself during S phase.

• Transcription: DNA is transcribed into mRNA in the nucleus.

• Translation: mRNA is translated into protein at the ribosome.

Equation for Transcription:

Equation for Translation: