Course Overview

Introduction to Human Physiology

Human physiology is the study of the functions and mechanisms occurring in the human body. This course provides foundational knowledge for students in health sciences, focusing on how cells, tissues, organs, and organ systems work together to maintain life.

• Instructor: Prof. Dr. Abby McDonald, DC, BScK

• Class Schedule: Wednesdays, 9am-12pm

• Recommended Study Time: Minimum of 3 hours per week

• Textbook: Cindy L. Stanfield, Human Physiology (6th edition preferred)

Organization of the Human Body

Levels of Organization

The human body is organized into hierarchical levels, each with increasing complexity. Understanding these levels is essential for studying physiology.

• Cells: The basic unit of life. Humans have trillions of cells, with over 200 different types grouped into four main categories.

• Tissues: Groups of similar cells performing a specific function. Four primary types:

  • Nervous tissue: Specialized for communication via electrical signals. Neurons transmit information from sensors and allow perception, emotion, memory, and planning.

  • Muscle tissue: Specialized for contraction and movement. Types include skeletal (voluntary movement), cardiac (heart contraction), and smooth (movement in organs).

  • Epithelial tissue: Sheet-like layers covering body surfaces and lining body tubes and organs. Functions as a barrier and transport membrane.

  • Connective tissue: Provides physical support, anchors structures, and includes bone, blood, and fat. Characterized by an extracellular matrix.

• Organs: Structures composed of two or more tissue types working together to perform specific functions.

• Organ Systems: Groups of organs that perform related functions and interact to accomplish a common purpose (e.g., circulatory, nervous, digestive systems).

Fluid Compartments

The body’s fluids are distributed in distinct compartments, each with unique composition and function.

• Intracellular Fluid (ICF): Fluid within cells; makes up about 2/3 of total body water.

• Extracellular Fluid (ECF): Fluid outside cells; includes plasma (fluid portion of blood) and interstitial fluid (surrounds cells).

Homeostasis

Definition and Importance

Homeostasis is the process by which the body maintains a relatively constant internal environment despite external changes. It is essential for survival and the proper functioning of cells, tissues, and organs.

• Regulated variables include temperature, pH, fluid composition, and blood glucose levels.

• Disruption of homeostasis is the basis for disease and death.

Mechanisms of Homeostasis

• Feedback Mechanisms: Systems that detect changes and initiate responses to restore balance.

  • Negative Feedback: The most common mechanism. A change in a regulated variable triggers a response that opposes the initial change, restoring the variable to its set point.

    • Example: Body temperature regulation. If core temperature rises above 37°C, mechanisms such as sweating are activated to cool the body.

  • Positive Feedback: Less common. The response amplifies the initial change. Usually interrupted by a third factor.

    • Example: Blood clotting cascade.

• Components of Feedback Systems:

  • Sensors: Detect changes in the environment (e.g., chemoreceptors for O2 and CO2 in blood).

  • Integrating Center: Compares detected value to set point and initiates response.

  • Effectors: Carry out the response to restore homeostasis (e.g., muscles, glands).

Homeostasis and Disease: Diabetes

Diabetes is a group of diseases characterized by the inability to regulate blood glucose levels, leading to chronic hyperglycemia.

• Diabetes Mellitus: Characterized by high blood glucose and 'sweet urine.'

  • Type 1: Insulin-dependent, juvenile onset, less common (5-10% of cases).

  • Type 2: Adult onset, associated with insulin resistance, more common.

  • Gestational Diabetes: Occurs during pregnancy; may resolve after birth but increases risk of Type 2 diabetes.

• Diabetes Insipidus: Not related to blood glucose regulation but to antidiuretic hormone (ADH) disruption, leading to excessive urination and thirst.

Diagnosis and Treatment of Diabetes

• Fasting Plasma Glucose (FPG) Test and 2-hour Glucose Tolerance Test are used for diagnosis.

• Treatment: Lifestyle changes, monitoring blood glucose and HbA1C, and pharmaceutical intervention.

Basic Chemistry for Physiology

Elements and Atoms

Understanding the chemical basis of life is essential for physiology. The human body is composed primarily of a few key elements.

• Atoms: The smallest units of matter, composed of protons, neutrons, and electrons.

• Major Elements in the Human Body: Oxygen, Carbon, Hydrogen, Nitrogen (make up 99% of body mass).

Chemical Bonds

• Covalent Bonds: Atoms share electrons. Can be:

  • Non-polar: Equal sharing of electrons (e.g., C–C, C–H bonds). Hydrophobic and lipophilic.

  • Polar: Unequal sharing, resulting in partial charges (e.g., H2O).

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating charged ions (e.g., Na+ and Cl− in table salt).

• Hydrogen Bonds: Weak attractions between the partial positive charge of hydrogen in a polar molecule and a partial negative charge of another atom (important in water and biological molecules).

Biological Molecules

Living organisms are primarily composed of four classes of macromolecules:

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

Lipids

• Triglycerides: Energy storage molecules formed by bonding three fatty acids to glycerol. Can be saturated (no double bonds) or unsaturated (one or more double bonds).

• Phospholipids: Composed of two fatty acids and a phosphate group. Amphipathic (hydrophilic head, hydrophobic tails). Form the bulk of cell membranes as bilayers.

• Steroids: Lipids with four carbon rings. Important in cell membranes and as hormones.

Phospholipid Bilayer

• Phospholipids aggregate to form micelles or bilayers, which are the structural basis of cell membranes.

Water

• Water is the most abundant molecule in the body and is essential for life. Its polarity and ability to form hydrogen bonds make it an excellent solvent for biological reactions.

Summary Table: Types of Chemical Bonds

Key Equations

• General formula for glucose:

• Water dissociation:

Additional info: Some content and context were inferred to provide a complete and coherent study guide suitable for General Biology students.