BIOL 2210 – Chapter 1: Introduction, Homeostasis, Gradient & Flow

Introduction

Key Terminology

• Anatomy

  • Study of body structure and physical relationships among body parts.

  • "To cut apart"; historically based on dissection.

• Gross Anatomy

  • Macroscopic structures visible to the naked eye (e.g., organs, muscles, bones).

  • Sub‐disciplines: surface anatomy, regional anatomy, systemic anatomy, developmental anatomy, comparative anatomy.

• Microscopic Anatomy

  • Structures too small to be seen without magnification.

  • Divided into:

  • Cytology – study of individual cells and their internal structures.

  • Histology – study of tissues (groups of similar cells and extracellular matrix).

• Physiology

  • Study of function; explains "how" and "why" structures work.

  • Sub‐disciplines include human, cell, systemic, pathological, and exercise physiology.

Interrelationships of Organ Systems

• Example 1: Respiratory & Circulatory Systems

  • Lungs (respiratory) supply O2; blood (circulatory) transports O2 to tissues & removes CO_2.

• Example 2: Digestive & Endocrine Systems

  • Digestive tract breaks food into nutrients; pancreas (endocrine function) releases insulin & glucagon to regulate blood glucose.

• Additional overlap examples (useful for exam essays):

  • Musculoskeletal (movement), Nervous + Endocrine (homeostatic regulation), Integumentary + Immune (first‐line defense).

Structural Organization of the Human Body

• Atom

  • Smallest unit of an element retaining its properties (e.g., C, H, O).

• Molecule

  • Two or more atoms bonded (e.g., H2O, CO2).

• Chemical / Macromolecule

  • Large complex molecules (proteins, nucleic acids, polysaccharides, lipids).

• Organelle

  • Specialized intracellular structures (mitochondria, ribosomes) performing specific functions.

• Cell

  • Basic living unit; smallest unit capable of life processes (e.g., neuron, hepatocyte).

• Tissue

  • Groups of similar cells & extracellular matrix performing a common function (epithelial, connective, muscle, nervous).

• Organ

  • Two or more tissue types combined to perform complex functions (heart, skin, stomach).

• Organ System

  • Organs that cooperate for related functions (11 human systems: integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, reproductive).

• Organism

  • Single complete individual (the human body) capable of metabolism, growth, responsiveness, regulation, reproduction.

(Refer to Figure 1.5 in text; diagram typically proceeds left→right from atoms to organism.)

Homeostasis

Definition & Significance

• Homeostasis: The maintenance of a stable internal environment within physiological limits despite external fluctuations. Coined by Walter Cannon. Essential for survival; failure leads to disease or death.

Feedback Mechanisms

Negative Feedback Cycles

• Mechanism: A change is sensed; response reverses or reduces the original stimulus, returning variable toward set point.

• Physiological Example – Thermoregulation

  1. Stimulus: Core temp rises above 37^\circ\text{C}.

  2. Receptor: Thermoreceptors in skin & hypothalamus detect change.

  3. Control Center: Hypothalamus compares value to set point.

  4. Effectors:

  • Sweat glands → sweating increases evaporative heat loss.

  • Skin blood vessels → vasodilation increases heat radiation.

  1. Outcome: Body temperature decreases toward normal.

• Physiological Example – Blood Glucose (not in prompt but good to know)

  • High glucose → pancreas releases insulin → cells absorb glucose → lowers blood glucose.

Positive Feedback Cycles

• Mechanism: Response amplifies original stimulus; produces rapid change until an outside event stops the cycle.

• Physiological Example – Childbirth

  1. Stimulus: Head of fetus pushes on cervix.

  2. Receptors: Stretch receptors in cervix fire nerve impulses.

  3. Control Center: Hypothalamus signals posterior pituitary.

  4. Effector: Release of oxytocin into blood.

  5. Response: Stronger uterine contractions push fetus further → more stretch → more oxytocin → loop continues until delivery (external stop).

• Physiological Example – Blood Clotting (extra): Platelet chemicals recruit more platelets until clot seals vessel.

Key Vocabulary for Essays

• 37^\circ\text{C} normal body temperature

• Vasodilation vs. Vasoconstriction (diameter changes of skin blood vessels regulate heat transfer).

• Shivering (muscle contractions generating heat when body temp falls).

Gradient and Flow

Gradient Concept

• Gradient: A difference in variable (chemical concentration, electrical charge, pressure, or temperature) between two points.

  • Represented as “delta” \Delta value: \Delta C, \Delta P, \Delta T.

  • Forms potential energy that drives movement.

Typical Direction of Flow

• Chemicals, heat, and fluids flow down their gradient (high → low):

  • Chemicals: Diffusion from high to low concentration.

  • Heat: Passes from warmer to cooler regions.

  • Fluids: Move from areas of higher pressure to lower pressure (e.g., blood flow, filtration in kidneys).

• Movement up a gradient requires energy (active transport, pumps).

Reading Assignment: Deeper Insight 1.5

• Located at the end of Chapter 1; explores medical imaging techniques (X‐ray, CT, MRI, sonography).

• Canvas Study Questions likely cover:

  • Advantages / disadvantages of each imaging modality.

  • Radiation exposure levels (quantified in \text{mSv}).

  • Safety considerations, ethical use, cost‐benefit in diagnostics.

• Recommendation: Extract key comparisons into a table; memorize typical uses (e.g., CT = head trauma, MRI = soft tissue, ultrasound = pregnancy).

Connections & Implications

• Integration Theme: Structure (anatomy) informs function (physiology). Example: Thin alveolar walls (anatomy) facilitate gas exchange (physiology).

• Clinical Relevance: Disruption of homeostasis leads to pathophysiology; understanding gradients explains drug diffusion, nerve impulses, kidney filtration.

• Ethical Dimension: Imaging exposes patients to radiation; clinicians must apply ALARA (As Low As Reasonably Achievable) principle.

Suggested Study Strategies

• Create flashcards for each bolded term & feedback example.

• Diagram the hierarchy of structural organization; label with personal examples for memory anchors.

• Practice free‐response explaining thermoregulation and childbirth cycles using proper terminology.

• Solve application problems: e.g., predict outcome if vasoconstriction fails in cold environment.

• Link gradients to daily life (perfume diffusion, water towers, hot coffee cooling).