Introduction to Human Physiology: Organization, Mechanisms, and Homeostasis

Course Overview and Structure

Course Information

This course introduces students to the fundamental principles of human physiology, focusing on the mechanisms that govern normal body function and the maintenance of homeostasis. The course is taught by Dr. Zepeng Yao and supported by teaching assistants. Lectures are scheduled for MWF, period 8 (3:00-3:50 pm) at WEIL 0270.

• Required Textbook: Human Physiology: An Integrated Approach (8th Edition) by Silverthorn (2019), Pearson Education, Inc.

• Online Resources: Mastering A&P for assignments and eTextbook access; iClicker for interactive participation.

Grading Policy

Grades are determined by a combination of homework, quizzes, discussions, and exams. The breakdown is as follows:

Assignment Type	Grade Percentage	Drops Allowed
Homework Questions (via Pearson)	20%	2
Quizzes	15%	2
Peer Discussions	5%	1
Exams	60%	0

Exams are cumulative and held in-person on specified dates. Students are required to complete a syllabus quiz and orientation module.

Introduction to Physiology

What Is Physiology?

Physiology is the study of the normal function of a living organism and its component parts, including all its chemical and physical processes. It seeks to answer both mechanistic ("how?") and teleological ("why?") questions about body function.

• Mechanistic Approach: Explains the processes and steps by which a function occurs.

• Teleological Approach: Explains the purpose or reason for a function.

Example: Regulation of body temperature involves mechanisms such as shivering and vasoconstriction, and serves the purpose of maintaining optimal conditions for cellular function.

Levels of Organization in Physiology

Physiology spans multiple levels of biological organization, from molecules to the entire organism. Understanding these levels is essential for grasping how body systems interact and maintain health.

• Molecular Level: Involves proteins, nucleic acids, and other biomolecules.

• Cellular Level: Focuses on cell structure and function.

• Tissue Level: Groups of similar cells performing specific functions.

• Organ Level: Structures composed of multiple tissue types working together.

• Organ System Level: Groups of organs that perform coordinated functions.

• Organism Level: The complete living being.

Example: The cardiovascular system includes the heart (organ), blood vessels (tissues and organs), and blood (cells and molecules).

Homeostasis: The Foundation of Physiology

Definition and Importance

Homeostasis is the process by which the body maintains a relatively stable internal environment despite changes in the external environment. The term was coined by Walter B. Cannon in 1929.

• Key Concept: Homeostasis involves correcting changes using negative feedback mechanisms.

• Variables Maintained: Temperature, pH, ion concentrations, blood glucose, etc.

Feedback Mechanisms

Feedback loops are essential for maintaining homeostasis. They can be classified as negative or positive feedback.

• Negative Feedback: The response counteracts the initial change, bringing the variable back to its setpoint.

• Positive Feedback: The response reinforces the change, leading to an amplified effect (not typically homeostatic).

Example of Negative Feedback: Regulation of body temperature—when cold, receptors signal the brain, which activates effectors (shivering, vasoconstriction) to increase temperature.

Example of Positive Feedback: Blood clotting, childbirth contractions.

Components of a Feedback Loop

• Variable: The parameter being regulated (e.g., temperature).

• Sensor: Detects changes in the variable.

• Setpoint: The desired value for the variable.

• Effector: Acts to correct deviations from the setpoint.

Homeostatic Reset and Biological Rhythms

Homeostasis can be "reset" to match new conditions, such as during fever or circadian rhythms. Biological rhythms cause setpoints to change regularly (e.g., body temperature varies throughout the day).

• Circadian Rhythms: Daily fluctuations in physiological variables.

• Fever: Temporary elevation of the temperature setpoint as a response to infection.

Course Schedule Overview

Week	Lecture Topic	Chapters/Notes	Assignments
1	Class Introduction to Physiology	1.1, 1.2, 1.4, 1.5	Quiz 1 (syllabus)
2	Molecule Interactions	2.1, 2.2	HW
3	Energy and Cellular Metabolism	4.1, 4.3, 4.4	Quiz 2
4	Membranes and Intracellular Compartments	3.1, 3.2, 3.3	HW
5	Membrane Transport	5.1, 5.2	Quiz 3
6	Tissues of the Human Body	3.4	HW
7	Communication and Signal Pathways	6.1, 6.2, 6.4, 6.5	Quiz 4
8	Review	-	-
9	Exam 1	-	-
10	Endocrine System	7.1, 7.3, 7.5	HW
11	Neurons	8.1, 8.3, 8.5	Quiz 5
12	Electrical Gradients	8.6, 8.7	HW
13	Synapses	8.8, 8.9	Quiz 6
14	Neuronal Networks	9.1, 9.2	HW
15	Autonomic Nervous System	11.1, 11.2	Quiz 7
16	Sensory Receptors and Motor Systems	10.1, 10.2	HW
17	Muscles	12.1-12.4	Quiz 8
18	Exam 2	-	-
19	Muscles (Ch.12)	12.1-12.4	HW

Key Terms and Concepts

• Physiology: Study of normal body function.

• Homeostasis: Maintenance of stable internal conditions.

• Negative Feedback: Mechanism that restores variable to setpoint.

• Positive Feedback: Mechanism that amplifies change.

• Setpoint: Desired value for a regulated variable.

• Effector: Organ or cell that acts to correct deviations.

• Sensor: Detects changes in the regulated variable.

Formulas and Equations

While introductory physiology is largely conceptual, some equations are fundamental:

• General Feedback Equation:

$\text{Response} = \text{Effector Action} \rightarrow \text{Variable} \rightarrow \text{Sensor} \rightarrow \text{Control Center} \rightarrow \text{Effector}$

• Example: Body Temperature Regulation

$\text{Heat Production} - \text{Heat Loss} = \Delta \text{Body Temperature}$

Summary

This guide provides an overview of the foundational concepts in human physiology, including the organization of the body, mechanisms of function, and the principle of homeostasis. Understanding these basics is essential for further study in anatomy and physiology.