CHP 1

Chapter Overview

Physiology is deeply interconnected with anatomy, the study of body structure.
It involves understanding how different levels of biological organization (cells, tissues, organs) work together to form functional systems that contribute to the overall health and functionality of organisms.

Definition: Physiology studies the normal functioning of living organisms and their parts, incorporating both chemical and physical processes that drive life.
Organization Levels:
- Atoms: The basic building blocks of matter.
- Molecules: Combinations of atoms forming compounds essential for life functions.
- Cells: The smallest unit capable of life processes, which can be independent (single-celled) or part of multicellular organisms.
- Tissues: Groups of similar cells that perform a common function.
- Organs: Structures composed of multiple tissue types working together to perform specific tasks (e.g., heart, lungs).
- Organ systems: Groups of organs that work together to perform complex functions (e.g., circulatory system).
- Organisms: Individual living entities that can be unicellular or multicellular.

Structure and function are tightly interconnected; the shape and arrangement of cells and structures significantly affect their roles.
Organisms require energy for growth, maintenance, reproduction, and response to environmental changes.
Information flow, through mechanisms like nerve impulses and hormonal signals, is critical for coordinating body functions and responses.
Homeostasis is vital for maintaining stable internal conditions necessary for survival despite external changes.

Definition: The maintenance of a stable internal environment (known as extracellular fluid, or ECF) despite fluctuations in external conditions.
Homeostasis is regulated within specific ranges rather than fixed values to ensure flexibility in response to changes in physiology or environment.
A failure in maintaining homeostasis can lead to disease states, which are studied in pathophysiology (e.g., diabetes involves disrupted glucose homeostasis).

ECF consists of plasma and interstitial fluid, which act as a buffer zone between the external environment and intracellular fluid (ICF).
Dynamic steady state: Homeostasis involves continuous material movement between compartments but maintains stable functioning without net changes in concentration.
Equilibrium implies identical composition among compartments, differing from homeostasis which maintains function despite store fluctuations.

Control Mechanisms: Critical for maintaining regulated variables near their setpoints (optimum values). These mechanisms can detect disturbances and implement corrective responses.
Types of control:
- Local: Operates at the tissue or cellular level responding to immediate physiological needs.
- Reflex: Involves long-distance signaling pathways, leading to systemic responses throughout the body.
Feedback Loops:
- Negative feedback: The primary mechanism for stabilizing variables (e.g., regulating body temperature or blood glucose levels).
- Positive feedback: Operates to amplify responses and move variables further away from the setpoint (e.g., during childbirth where oxytocin increases contractions).
- Feedforward control: Anticipates changes in the internal environment, adjusting physiological responses proactively (e.g., salivation in response to food).

Regulated variables such as blood pressure and body temperature exhibit predictable patterns or cycles (biorhythms), contributing to efficient physiological responses.
Circadian rhythms: Biological processes regulated on a roughly 24-hour cycle, affecting numerous functions including sleep-wake cycles, metabolism, and the timing of hormone release.

The importance of integrative science in the field of physiology, recognizing the interconnections between various biological systems.
An understanding of function and mechanisms in bodily systems is crucial for health and disease management.
The relevance of homeostasis and control systems in maintaining physiological balance and responding to environmental changes.