Chapter #31Animal Systems and

HomeostasisStructure and Function

Pg. 636 - 644

• Cells are organized into tissues.

• Tissues are organized into organs.

• Organs are organized into systems.

• Systems form an organism.

Organization in Living Things

• Epithelial

• Connective

• Nervous

• Muscular

Four Tissue Types

Epithelial Tissue

• Epithelial cells form the outer covering, line the internal cavities, and make up the glands.

• Examples: Skin, mucous membranes.

Connective Tissue• Consists of

living cells in a secreted matrix.

• Examples: bone, cartilage, blood.

Muscular Tissue• Specialized

protein fibers allow these cells to contract.

• Examples: skeletal muscle, smooth muscle, cardiac muscle.

Nervous Tissue• Neurons have

the ability to pass an “electrical” signal from one cell to another, or to target cells (muscles, glands, organs).

Tissues Form Organs

• Nerves

• Lymph Glands

• Vessels

• Lungs

• Small Intestine

• Skin

Tissues Form Organs

• The skin is an example of an organ made up of multiple tissues: epithelial, muscular, nervous, and connective tissues.

Organs To Organ Systems

•Nervous System

•Endocrine System

•Musculo-skeletal System

•Circulatory System

•Respiratory System

•Digestive System

•Immune System

Organ Systems to Organisms

•Mammals

•Birds

•Amphibians

•Reptiles

•Fish

•Insects

Homeostasis• Homeostasis is the act of keeping

the internal environment of a living organism within an acceptable range of conditions.

• Homeostasis controls temperature, pH, blood volume, oxygen levels, blood sugar levels, and other conditions.

• Negative feedback maintains homeostasis.

Negative Feedback• Negative feedback

keeps conditions within an ideal range.

• As conditions exceed the limits of the ideal range, chemical signals (hormones) regulate conditions. Most often this is controlled by the hypothalamus in the brain.

Maintaining Temperature

Blood Glucose Regulation

Positive Feedback• Positive feedback

takes a condition out of the normal range, often to some end point.

• During labor, oxytocin increases contractions, which stimulate more oxytocin production, until birth occurs.

Thinking Questions1.Why is positive feedback not a

good way to maintain homeostasis?

2.What are some other examples of positive feedback loops in the human body?

3.Why do young animals often have more body fat than adults? How does this maintain homeostasis?