Introduction to the Human Body: Study Guide

Ch. 1 The Human Body: An Orientation

Anatomy

Anatomy is the study of the structure of body parts and their relationships to one another. It provides the foundation for understanding physiological processes.

• Gross Anatomy: Study of large, visible structures (e.g., muscles, bones).

• Microscopic Anatomy: Study of structures too small to be seen with the naked eye (e.g., cells, tissues).

• Developmental Anatomy: Study of structural changes throughout the lifespan.

Physiology

Physiology is the study of the function of body parts and how they work to carry out life-sustaining activities.

• Cellular Physiology: Functions of cells.

• Systemic Physiology: Functions of organ systems (e.g., cardiovascular physiology).

Complementarity of Structure and Function

The principle of complementarity states that function always reflects structure; what a structure can do depends on its specific form.

• Example: Bones can support and protect body organs because they contain hard mineral deposits.

Levels of Structural Organization

The human body is organized into a hierarchy of structural levels, each building on the previous one.

• Chemical Level: Atoms combine to form molecules.

• Cellular Level: Cells are made up of molecules and organelles.

• Tissue Level: Tissues consist of similar types of cells.

• Organ Level: Organs are made up of different types of tissues.

• Organ System Level: Organ systems consist of different organs that work together closely.

• Organismal Level: The human organism is made up of many organ systems.

Major Organ Systems

• Integumentary System

• Skeletal System

• Muscular System

• Nervous System

• Endocrine System

• Cardiovascular System

• Lymphatic/Immune System

• Respiratory System

• Digestive System

• Urinary System

• Reproductive System

Necessary Life Functions

All living organisms must perform certain functions to maintain life.

• Maintaining Boundaries: Separation between internal and external environments (e.g., skin).

• Movement: Activities promoted by the muscular system, including movement of substances within the body.

• Responsiveness: Ability to sense and respond to stimuli (e.g., withdrawal reflex).

• Digestion: Breakdown of ingested foodstuffs to simple molecules.

• Metabolism: All chemical reactions that occur within body cells.

• Excretion: Removal of wastes from metabolism and digestion.

• Reproduction: Cellular division for growth or repair; production of offspring.

• Growth: Increase in size of a body part or of the organism.

Interdependence of Body Systems

Body systems work together to maintain the health and function of the organism. No system functions in isolation.

• Example: The respiratory and cardiovascular systems work together to supply oxygen and remove carbon dioxide.

Survival Needs

Several factors are required for survival, and their appropriate amounts are essential for life.

• Nutrients: Chemicals for energy and cell building (e.g., carbohydrates, proteins, fats, vitamins, minerals).

• Oxygen: Essential for energy production (cellular respiration).

• Water: Most abundant chemical in the body; provides environment for chemical reactions.

• Normal Body Temperature: Necessary for proper metabolic reactions (about 37°C or 98.6°F).

• Appropriate Atmospheric Pressure: Required for adequate breathing and gas exchange in the lungs.

Homeostasis

Homeostasis is the maintenance of a relatively stable internal environment despite continuous outside changes. It is a dynamic state of equilibrium.

• Variables: Factors that can change (e.g., blood sugar, body temperature, blood volume).

• Receptor: Monitors the environment and responds to changes (stimuli).

• Control Center: Determines the set point at which the variable is maintained, receives input from receptor, and determines appropriate response.

• Effector: Carries out the control center’s response to the stimulus.

Feedback Mechanisms

• Negative Feedback: Most common; reduces or shuts off the original stimulus (e.g., regulation of body temperature, blood glucose by insulin).

• Positive Feedback: Enhances or exaggerates the original stimulus (e.g., labor contractions by oxytocin, blood clotting).

Homeostatic Imbalance

Disturbance of homeostasis increases risk of disease, contributes to changes associated with aging, and may allow destructive positive feedback mechanisms to take over (e.g., heart failure).

Component	Function	Example
Receptor	Detects change	Thermoreceptors in skin
Control Center	Processes information, determines response	Hypothalamus in brain
Effector	Carries out response	Sweat glands

Example: Negative Feedback Loop (Body Temperature Regulation)

• Stimulus: Increased body temperature (e.g., exercise, hot environment)

• Receptor: Thermoreceptors detect change

• Control Center: Hypothalamus receives input and initiates response

• Effector: Sweat glands increase secretion, body cools down

Equation for Homeostatic Control:

$\text{Stimulus} \rightarrow \text{Receptor} \rightarrow \text{Control Center} \rightarrow \text{Effector} \rightarrow \text{Response}$

Additional info: Homeostasis is a central concept in physiology and underlies the function of all organ systems. Disruption of homeostasis can lead to disease states or dysfunction.