Understanding Homeostasis in Single and Multi-Cellular Organisms

1. Dynamic Homeostasis

2. 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?

3. 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

4. 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.

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

6. 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

7. 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?)

8. Anatomy – Relevant Parts • Major Types of Tissue • Epithelial tissuecovers body surfaces and lines body cavities. (skin) • Connective tissuebinds and supports body parts. (tendons) • Muscular tissuecauses motion in body parts. (biceps) • Nervous tissueresponds to stimuli and transmits impulses for communication/control.(brain)

9. Epithelial Tissue • Epithelial tissue: • Forms a continuous layer over body surfaces • Lines inner cavities • Forms glands • Coversabdominal organs

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

11. Epithelial Tissue Example Cuboidal epithelium has cube-shaped cells.

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

13. Figure 33.1d

14. 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.

15. Connective Tissue • Connective tissues bind and connect cells together

16. Diagram of Fibrous Connective Tissue

17. 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

18. 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

19. 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

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

21. 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

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

23. 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

24. 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

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

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

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

28. 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

29. Negative Feedback Mechanisms:Simple

30. Negative Feedback Mechanism Analogy: a thermostat

31. Same diagram, but now featuring Regulation of Body Temperature

33. Positive Feedback • 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