1.4 | Core Themes in Anatomy and Physiology

The Cell

Basic unit of life; all living things consist of cells.

Why are cells important

All living things are made of cells; they carry out life processes.

The Internal Environment

Cells live in extracellular fluid; must remain stable for survival.

What is extracellular fluid

Fluid inside the body but outside the cells.

Homeostasis

Maintaining a relatively constant internal environment; essential for life.

Why is homeostasis important

It allows cells and the body to function properly and survive.

Interdependency of Cells

Cells depend on each other to maintain homeostasis; loss of function in one group can harm the organism.

Structure and Function

Anatomical structure determines physiological function; form and function are interrelated.

Gradients and Permeability

Substances move down gradients (pressure, concentration); movement depends on membrane permeability.

What is a gradient

Difference in concentration, pressure, or other factors that drives movement of substances.

Cellular Differentiation

Cells specialize by activating different genes; proteins produced determine their function.

Cell Membrane Mechanisms

Regulate entry and exit of substances; allow cells to respond to signals.

Cell-to-Cell Communication

Cells cooperate by signaling each other via receptors and molecules.

Feedback Loops

Homeostatic mechanisms; negative feedback stabilizes, positive feedback amplifies.

Negative Feedback

Reduces a change to maintain stability.

Positive Feedback

Amplifies a change for processes like childbirth or blood clotting.

Balance

Body replaces lost substances (e.g., amino acids) and eliminates excess (e.g., CO₂).

Energy Processes

All body functions require energy, including heat energy and chemical energy from reactions.

Example of energy use in the body

Muscle contraction, nerve signaling, cellular metabolism.

Homeostasis example

Regulation of body temperature or blood glucose levels.