Human Phy-2

HUMAN PHYSIOLOGY BME2001 - Week #2 Notes

Course Structure

  • Instructor: Canan Bağcı, PhD, Assistant Professor

  • Outline:

    • Introduction

    • Cells, cellular compartments, tissues, and organs

    • Homeostasis

    • Medical Terminology

    • Cell membrane and substance transport across the cell membrane

Physiology Overview

  • Key Question: How does the body work?

  • Definition: Physiology is the study of body part functions and their interactions from the cellular to the systems level.

    • Integrative science combining anatomy, histology, biophysics, and biochemistry.

  • Importance of understanding the link between structure and function:

    • Historical Example: The heart’s anatomy was understood in the 15th century, but its pumping action wasn’t demonstrated until almost 200 years later.

Levels of Biological Organization

  • Hierarchy of biological organization starts at the atomic level and progresses to the organism:

    • Atom

    • Molecule

    • Macromolecule

    • Organelle

    • Cell

    • Tissue

    • Organ

    • Organ System

    • Organism

Cells

  • Definition: The basic structural and functional unit of an organism.

  • Cell Membrane:

    • Thin, pliable, elastic structure separating intracellular contents from the extracellular environment; composed of:

    • Lipid bilayer – double layer of lipids

    • Proteins

    • Cholesterol

    • Other lipids

    • Carbohydrates

    • Characteristics: Acts as a barrier, impermeable to most water-soluble substances.

  • Key Organelles:

    • Cytoplasm: Gel-like material within the cell.

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

    • Endoplasmic Reticulum (ER): Involved in protein and lipid synthesis.

    • Mitochondria: Sites of ATP production through chemical reactions.

    • Ribosomes: Sites of protein synthesis, found attached to ER or free in cytoplasm.

    • Lysosomes: Act as the cell’s waste disposal system.

  • Cytoskeleton: Composed of protein filaments providing shape, structure, and enabling cell movements such as:

    • Cell migration

    • Cell division

    • Muscle contraction

    • Cilia movement

Cell Types

  • The human body has approximately 200 distinct cell types, each specialized for specific functions.

  • Cell Differentiation: The process where unspecialized cells transform into specialized cells. Despite having the same genes, different cells express different genes, leading to varying structures and functions.

    • Experiment by John B. Gurdon (1962): Demonstrated that a differentiated cell's nucleus can generate a fully functional organism, highlighting that differentiation is not due to gene loss but rather differences in gene expression.

Tissues

  • Definition: Composed of similar cells specialized for specific functions.

  • Four Major Tissue Types:

    • Epithelial Tissue: Covers and protects organ surfaces, forms body cavity linings, and serves as barriers.

    • Connective Tissue: Binds structures, supports organs, serves as frameworks, and aids in tissue repair.

    • Muscle Tissue: Capable of contraction; responsible for body movement.

    • Nervous Tissue: Coordinates body functions and integrates information (e.g., neurons, brain, spinal cord).

Organs

  • Formed by groups of different tissues interacting together, possessing specialized functions.

  • Example: Stomach structure includes:

    • Epithelial tissue covering the inner organ

    • Connective tissue providing support

    • Muscle tissue facilitating contractions and mixing of contents

    • Nervous tissue regulating muscle contractions.

Homeostasis

  • Definition: The ability to maintain relatively stable internal conditions despite continual external changes.

  • Historical Context: The term "homeostasis" was coined by Walter Cannon in 1915:

    • Etymology: From Greek "homeo" (similar) + "stasis" (standing or stable).

  • Homeostasis is essential for cells to live, grow, and perform functions; requires optimal concentrations of:

    • Oxygen

    • Glucose

    • Ions, amino acids, fatty substances

    • Removal of waste products.

Environmental Interaction

  • Organisms have adaptive capacities to slow changes in their environment but can face critical threats during sudden changes.

  • Importance of a stable internal environment supported by:

    • The integumentary system (protection from the external environment)

    • The digestive and respiratory systems (intake of nutrients and oxygen)

    • The urinary system (elimination of metabolic wastes).

Cell Environment

  • Cells are surrounded by an internal sea of extracellular fluid (ECF), which is composed of:

    • Interstitial fluid: Surrounds cells

    • Blood plasma: Liquid component of blood in which blood cells are suspended.

  • Fluid Composition: Approximately 60% of the human body is fluid (mainly water) consisting of ions and other substances.

Homeostatic Control Systems

  • Types of Control Mechanisms:

    1. Local control systems operating within organs

    2. Systems operating throughout the body for interrelations between organs.

  • Homeostasis requires communication, achieved primarily via:

    • Nervous system

    • Endocrine system.

  • Homeostatic Feedback Mechanisms:

    • Negative feedback stabilizes variables by reducing deviation.

    • Positive feedback reinforces changes, resulting in greater deviations until a goal is achieved.

    • Feedforward control anticipates changes to stabilize a system with proactive responses.

Negative Feedback Explained

  • Definition: Any deviation from a normal value is corrected by reducing the deviation.

  • Example: Body Temperature Regulation:

    • Control system target: Body temperature

    • Sensor: Thermoreceptors detect temperature changes

    • Setpoint: 37ºC (normal body temperature)

    • Control center: Hypothalamus processes input

    • Effectors: Sweat glands activate to cool the body.

  • Flow of Negative Feedback:

    • Target → Setpoint → Sensor → Control Center → Effector → Resulting Response

Positive Feedback Examples

  • Positive Feedback: Useful in certain situations but can be destructive.

  • Example of Positive Feedback: Blood clotting process, where the presence of clotting factors accelerates further clotting until bleeding ceases.

Homeostatic Imbalance

  • Large deviations from normal ranges that cannot self-correct lead to health issues requiring medical intervention.

Medical Terminology Basics

  • Structure of Medical Terms:

    • Prefix: Indicates location, direction, size, shape, etc.

    • Root: Relates to body parts.

    • Suffix: Indicates size, shape, or condition (e.g., hypercholesterolemia, erythrocyte).

Common Medical Prefixes and Suffixes

  • Common Prefixes:

    • osteo- (bone)

    • myo/sarco- (muscle)

    • neuro- (nerves)

    • derm- (skin)

    • hepato- (liver)

    • cardio- (heart)

    • gastro- (stomach)

  • Common Suffixes:

    • -itis (inflammation)

    • -opathy (disease)

    • -emia (blood condition)

Anatomical Terminology

  • Purpose: To provide clarity and avoid misunderstandings about body parts and positions.

  • Anatomical Position: Standing erect, face forward, arms at sides with palms facing forward.

  • Relative Position Definitions:

    • Superior: Above another part (e.g., head is superior to neck).

    • Inferior: Below another part (e.g., stomach is inferior to chest).

    • Anterior (Ventral): Toward the front.

    • Posterior (Dorsal): Toward the back.

    • Medial: Toward the midline.

    • Lateral: Away from the midline.

    • Proximal: Closer to the point of attachment.

    • Distal: Farther from the point of attachment.

Body Regions and Sections

  • Body Sections:

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

    • Transverse (Horizontal) Plane: Divides body into superior and inferior portions.

    • Frontal (Coronal) Plane: Divides body into anterior and posterior portions.

  • Common Body Regions:

    • Cephalic (head), Thoracic (chest), Abdominal (abdomen), Pelvic (pelvis), etc.

Cell Membrane Physiology

  • Cell Membrane (Plasma Membrane):

    • Function: Separates intracellular contents from the extracellular environment.

    • Structure: Composed of a lipid bilayer with 55% proteins, 25% phospholipids, 13% cholesterol, 4% other lipids, and 3% carbohydrates.

    • Types of Membrane Lipids:

    • Phospholipids: Most abundant.

    • Sphingolipids: Provide protection and signaling.

    • Cholesterol: Affects fluidity.

  • Fluid Mosaic Model: Describes the cell membrane's structure, allowing flexibility and interaction of membrane components.

Membrane Proteins Functions

  • Functions:

    • Transport: Mediate movement across the membrane.

    • Intercellular Joining: Connects adjacent cells.

    • Enzymatic Activity: Acts as enzymes for biochemical reactions.

    • Cell-cell Recognition: Identifies cells for interactions.

    • Receptor Function: Binds chemical messengers (e.g., hormones).

    • Attachment: Anchors cells to the extracellular matrix and cytoskeleton.

Membrane Transport Mechanisms

  • Passive Transport:

    • Simple Diffusion: Movement from high to low concentration (e.g., O2, CO2).

    • Facilitated Diffusion: Requires carrier proteins for large or polar molecules (e.g., glucose).

  • Active Transport: Moves substances against their concentration gradient, requiring energy.

    • Example: Sodium-potassium pump maintains ion gradients.

  • Endocytosis and Exocytosis: Mechanisms for large substances to enter or exit the cell, respectively.

    • Endocytosis Types:

    • Pinocytosis: Ingestion of liquid.

    • Phagocytosis: Ingestion of large particles.

Conclusion

  • Understanding human physiology is foundational for comprehending the complex interactions within living organisms. This knowledge serves as a basis for medical terminology and the application of physiological concepts in health and disease management.