Fundamentals of Human Physiology: Organization, Homeostasis, and Chemistry for Biology

Course Overview

Introduction to Human Physiology

Human physiology is the study of the functions and mechanisms occurring in living organisms, with a focus on the human body. This course covers the foundational principles necessary for understanding 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)

Levels of Organization in the Human Body

Cellular Level

The cell is the basic unit of life. Organisms may be unicellular (e.g., yeast) or multicellular (e.g., humans, with trillions of cells and over 200 cell types).

• Cell Types: Grouped into four major categories:

  • Epithelial cells

  • Connective tissue cells

  • Muscle cells

  • Nervous cells

Tissue Level

Tissues are groups of cells with similar specialization. There are four primary tissue types:

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

• Muscle Tissue: Specialized to exert mechanical force and produce movement. Types include skeletal (voluntary movement), cardiac (pumping blood), and smooth (moving food in the stomach).

• Epithelial Tissue: Sheet-like layers of cells forming barriers and transport membranes. Lines body surfaces, tubes, and organs.

• Connective Tissue: Provides physical support, anchors body structures, and includes an extracellular matrix.

Organ and Organ System Level

Organs are composed of multiple tissue types working together for specific functions. Organ systems are groups of organs that perform related functions and interact to accomplish a common purpose (e.g., circulatory, nervous, digestive systems).

Fluid Compartments of the Body

Body Fluid Organization

The human body contains water distributed in different compartments:

• Intracellular Fluid (ICF): Makes up about 2/3 of body water, found inside cells.

• Extracellular Fluid (ECF): Makes up about 1/3 of body water, found outside cells (includes plasma and interstitial fluid).

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 health and survival; disruption leads to disease and death.

• Regulated Variables: Temperature, pH, fluid composition, etc.

• Integration: Organ systems work together to maintain homeostasis.

Feedback Mechanisms

Homeostasis is maintained through feedback mechanisms:

• Negative Feedback: When a regulated variable decreases, systems respond to increase it, and vice versa. Example: Chemoreceptors monitor O2 and CO2 concentrations in blood; body temperature regulation at 37°C.

• Positive Feedback: The system amplifies the change in the same direction. Example: Blood clotting, childbirth.

Example: Regulating Blood Sugar

Blood glucose regulation is a classic example of homeostasis, involving insulin and glucagon.

• Diabetes Mellitus: Characterized by high blood glucose and 'sweet urine.' Types include Type 1 (insulin-dependent, juvenile onset) and Type 2 (adult onset, insulin resistance).

• Diabetes Insipidus: Involves problems with water regulation due to disrupted anti-diuretic hormone (ADH), not blood glucose.

Diagnostic Criteria for Diabetes

Test	Normal	Pre-diabetes	Diabetes
Fasting Plasma Glucose (FPG)	60-100 mg/dL	100-125 mg/dL	>125 mg/dL
2hr Glucose Tolerance	<139 mg/dL	140-199 mg/dL	>200 mg/dL

Chemistry for Physiology

Atoms and Elements

Atoms are the basic units of matter, composed of protons, neutrons, and electrons. The atomic number is determined by the number of protons. Four elements make up 99% of the human body: hydrogen, carbon, oxygen, and nitrogen.

Chemical Bonds

Atoms combine to form molecules via chemical bonds:

• Covalent Bonds: Electrons are shared between atoms. Can be polar (unequal sharing, partial charges) or non-polar (equal sharing, hydrophobic).

• Ionic Bonds: Electrons are transferred, forming charged ions (cations and anions) held together by electrical forces. Example: Table salt (NaCl).

• Hydrogen Bonds: Weak attractions between partial charges in polar molecules, important for water and biological macromolecules.

Biological Molecules

Organisms are primarily made of four types of macromolecules:

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

Lipids

• Triglycerides: High-energy 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 cell membranes.

• Steroids: Four carbon ring structure, important in cell membranes and as hormones.

Phospholipid Bilayer

Phospholipids aggregate to form micelles or bilayers, which are the bulk of the cytoplasmic membrane and essential for cell compartmentalization.

Summary Table: Types of Chemical Bonds

Bond Type	Description	Example
Covalent (Non-polar)	Equal electron sharing	C-C, CH4
Covalent (Polar)	Unequal electron sharing, partial charges	H2O
Ionic	Electron transfer, charged ions	NaCl
Hydrogen	Weak attraction between polar molecules	Water molecules

Key Equations

• General Homeostasis Equation:

  • $\text{Physiological Response} = \text{Set Point} - \text{Actual Value}$

• Blood Glucose Regulation:

  • $\text{Insulin Release} \propto \text{Increase in Blood Glucose}$

  • $\text{Glucagon Release} \propto \text{Decrease in Blood Glucose}$

Additional info: Some content was inferred and expanded for clarity and completeness, including definitions, examples, and tables based on standard biology curriculum.