Biology, 9th ed, Sylvia Mader Chapter 33 Unit 5 Animal Organization & Homeostasis Dynamic Homeostasis

Unit Main Ideas – Think/Pair/Share What is Homeostasis? How is homeostasis different in single-celled organisms vs. multicellular organisms? What unique challenges to maintaining homeostasis do multicellular organisms have to address?

Homeostasis Introduction Homeostasis is the maintenance of a constant internal environment. Every living thing must maintain homeostasis by regulating body temperature, level of food/water, level of needed gases, etc. Death results when homeostasis is not maintained

Homeostasis in Single vs Multi-Celled Single Celled Organisms must take care of all aspects of homeostasis alone. The organelles within the single cell must regulate water, air, food, pH, and temperature. It has no cells to help, but it also does not have to coordinate anything. Multi-Cellular Organisms are able to maintain homeostasis in teams of specialized cells called tissues. Each cell only has one job (digestion, transport, etc). However, this means they need to be able to coordinate their efforts, so they have to be able to communicate with one another.

Homeostasis in Single vs Multi-Celled Organization helps multi- cellular organisms improve cell efficiency and coordination Cells  Tissues  Organs  Organ systems  Organism

REVIEW: Levels of Organization Tissue - Group of similar cells performing a similar function Organ - Group of tissues performing a specialized function Organ System - Collection of several organs functioning together Organism - A collection of organ systems

Anatomy and Physiology In order to understand how multicellular organisms function, we need to understand how they are put together. Anatomy – The study of the specific parts of a multicellular organism (e.g. What is a Kidney?) Physiology – the study of the function of the specific parts of a multicellular organism (e.g. How does the kidney work?)

Anatomy – Relevant Parts Major Types of Tissue Epithelial tissue covers body surfaces and lines body cavities. (skin) Connective tissue binds and supports body parts. (tendons) Muscular tissue causes motion in body parts. (biceps) Nervous tissue responds to stimuli and transmits impulses for communication/control. (brain)

Epithelial Tissue Epithelial tissue: Forms a continuous layer over body surfaces Lines inner cavities Forms glands Covers abdominal organs

Epithelial Tissue Example Squamous epithelium is composed of flat cells (e.g., air sac linings of lungs, walls of capillaries).

Epithelial Tissue Example Cuboidal epithelium has cube- shaped cells.

Epithelial Tissue Example Columnar epithelium has elongated cells that resemble pillars or columns (e.g., small intestine). Used for absorption

Figure 33.1d

Special Epithelial Tissues Ciliated Epithelia - cells are covered with cilia (e.g., lining of human respiratory tract). Cilia can bend and move material over the surface of the epithelium. Glandular Epithelia - can be unicellular or have multicellular glands. Glands are a single cell or a group of cells that secrete a chemical signal into the body; two types: Exocrine glands secrete their products into ducts or directly into a tube or cavity. Endocrine glands secrete their product directly into the bloodstream.

Connective Tissue Connective tissues bind and connect cells together

Diagram of Fibrous Connective Tissue

Special Connective Tissue Adipose Tissue Fat cells; stores energy, insulates the body, and provides padding Cartilage Classified according to type of collagen and elastic fibers found in the matrix Cartilage cells (chondrocytes), lie in small chambers (lacunae) in the matrix

Connective Tissue Examples

Transports nutrients and oxygen to cells Figure 33.4 Blood - Actually a connective tissue in which cells are embedded in a liquid matrix (plasma) Red blood cells - erythrocytes White blood cells - leukocytes Transports nutrients and oxygen to cells Removes carbon dioxide and other wastes

Muscular Tissue Contractile cells containing actin and myosin filaments (cytoskeleton fibers made to contract and release) used for movement Types Skeletal Muscle Voluntary - Long, striated fibers Smooth Muscle Involuntary - No striations Cardiac Muscle Involuntary, but more similar in structure to skeletal muscle

Muscular Tissue

Nervous Tissue Nervous Tissue is used for fast cell to cell communication Made mostly of cells called neurons that function through electrical impulses

Nervous Tissue Nervous system has three functions Sensory input – receive stimulus Sensory receptors detect changes in the environment Transmit info to the spinal cord Data integration – make a decision Spinal cord and brain integrate information Decision is made regarding appropriate response Motor output – respond to stimulus Response is transmitted to effector (reactionary cells, e.g. muscles) Effector initiates actual response

Neurons and Neuroglia Long axons and dendrites form neuron fibers; bound by connective tissue, they form nerves.

Organ Systems The organ systems of the human body contribute to homeostasis by linking organs that form a specific task The digestive system Takes in and digests food Provides nutrients The respiratory system Adds oxygen to the blood Removes carbon dioxide

Organ Systems The Excretory (Liver and Kidneys) System Store excess glucose as glycogen Later, glycogen is broken down to replace the glucose used The hormone insulin regulates blood sugar Creates bile to digest fat (Kidneys) excrete wastes and salts to regulate water level

Organ Systems The circulatory system The nervous system Communicates and controls body The circulatory system Transports oxygen and nutrients throughout the body

Organ Systems The integumentary system The immune system The skeletal system Provide support and protection The integumentary system Production of hormones and communication signals Provides protection The immune system Protection from disease

Positive and Negative Feedback Regulation Controlling the function of Organ Systems Positive and Negative Feedback Regulation

Negative Feedback Homeostatic Control Partially controlled by hormones (and) Ultimately controlled by the nervous system Negative Feedback is the primary homeostatic mechanism that keeps a variable close to a set value (e.g. constant temperature) Sensor detects change in environment Regulatory Center activates an effector Effector reverses the change Negative = NO CHANGE ALLOWED

Negative Feedback Mechanisms: Simple

Negative Feedback Mechanism Analogy: a thermostat

Same diagram, but now featuring Regulation of Body Temperature

Biology, 9th ed, Sylvia Mader Positive Feedback Chapter 33 Animal Organization & Homeostasis During positive feedback, an event increases the likelihood of another event occurring Childbirth Process Urge to urinate Positive Feedback Does not result in equilibrium; YES TO CHANGE Does not occur as often as negative feedback