Anatomy is the study of the structure of an organism

1. Trauma Care! • Anatomy is the study of the structure of an organism • Physiology is the study of the functions an organism performs

2. Physical laws and the environment constrain animal size and shape Physical laws and the need to exchange materials with the environment place limits on the range of animal forms

3. Exchange with the Environment • An animal’s size and shape directly affect how it exchanges energy and materials with its surroundings • Exchange occurs as substances dissolved in the aqueous medium diffuse and are transported across the cells’ plasma membranes

4. Mouth LE 40-3 Gastrovascular cavity Diffusion Diffusion Diffusion Two cell layers Single cell

5. External environment CO2 O2 Food LE 40-4 Mouth Animal body Respiratory system Blood 50 µm 0.5 cm A microscopic view of the lung reveals that it is much more spongelike than balloonlike. This construction provides an expansive wet surface for gas exchange with the environment (SEM). Cells Heart Circulatory system 10 µm Nutrients Digestive system Interstitial fluid Excretory system The lining of the small intestine, a digestive organ, is elaborated with fingerlike projections that expand the surface area for nutrient absorption (cross-section, SEM). Inside a kidney is a mass of microscopic tubules that exchange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM). Anus Metabolic waste products (urine) Unabsorbed matter (feces)

6. Animal form and function are correlated at all levels of organization • Most animals are composed of specialized cells organized into tissues that have different functions • Tissues make up organs, which together make up organ systems

7. Tissue Structure & Function • Different tissues have different structures that are suited to their functions • Tissues are classified into four main categories: epithelial, connective, muscle, and nervous

8. Epithelial Tissue • Epithelial tissue covers the outside of the body and lines the organs and cavities within the body • It contains cells that are closely joined

9. Connective Tissue • Connective tissue mainly binds and supports other tissues • It contains sparsely packed cells scattered throughout an extracellular matrix

10. Muscle Tissue • Muscle tissue consists of long cells called muscle fibers, which contract in response to nerve signals • It is divided in the vertebrate body into three types: skeletal, cardiac, and smooth

11. Nervous Tissue • Nervous tissue senses stimuli and transmits signals throughout the animal

12. Organ Systems

13. Bioenergetics • Bioenergetics, the flow of energy through an animal, limits behavior, growth, and reproduction • It determines how much food an animal needs • Studying bioenergetics tells us much about an animal’s adaptations

14. Energy Sources and Allocation • Animals harvest chemical energy from food • Energy-containing molecules from food are usually used to make ATP, which powers cellular work • After the needs of staying alive are met, remaining food molecules can be used in biosynthesis

15. Organic molecules in food External environment LE 40-7 Animal body Digestion and absorption Heat Energy lost in feces Nutrient molecules in body cells Energy lost in urine Cellular respiration Carbon skeletons Heat ATP Biosynthesis: growth, storage, and reproduction Cellular work Heat Heat

16. Quantifying Energy Use • Metabolic rate is the amount of energy an animal uses in a unit of time • One way to measure it is to determine the amount of oxygenconsumed or carbon dioxide produced

17. Thermoregulation Chapter 40

18. Bioenergetic Strategies • An animal’s metabolic rate is closely related to its bioenergetic strategy • Birds and mammals are mainly endothermic: Their bodies are warmed mostly by metabolic heat. • Endotherms typically have higher metabolic rates

19. Amphibians and reptiles other than birds are ectothermic: They gain their heat mostly from external sources • Ectotherms generally have lower metabolic rates

20. Animals regulate their internal environment within relatively narrow limits • The internal environment of vertebrates is called the interstitial fluid and is very different from the external environment • Homeostasis is a balance between external changes and the animal’s internal control mechanisms that oppose the changes

21. Regulating and Conforming • Regulating and conforming are two extremes in how animals cope with environmental fluctuations • A regulator uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation • A conformerallows its internal condition to vary with certain external changes

22. Thermoregulation: Maintaining body temperature within certain boundaries, even when surrounding temperature is very different. Homeostasis:A dynamic state of stability between an animal's internal environment and its external environment

23. Thermoregulators keep core body temperature within certain limits Thermoconformers change body temperature with the temperature outside of its body

24. Mechanisms of Homeostasis • Mechanisms of homeostasis moderate changes in the internal environment • A homeostatic control system has three functional components: • receptor • control center • effector

25. Most homeostatic control systems function by negative feedback, where buildup of the end product shuts the system off • In positive feedback, a change in a variable triggers mechanisms that amplify rather than reverse the change

26. Ectotherms and Endotherms • Ectotherms include most invertebrates, fishes, amphibians, and non-bird reptiles • Endotherms include birds and mammals • In general, ectotherms tolerate greater variation in internal temperature than endotherms

27. 40 River otter (endotherm) LE 40-12 30 Body temperature (°C) 20 Largemouth bass (ectotherm) 10 0 10 20 40 30 Ambient (environmental) temperature (°C)

28. Endothermy is more energetically expensive than ectothermy • Endothermy buffers the animal’s internal temperatures against external fluctuations • Endothermy also enables the animal to maintain a high level of aerobic metabolism

29. Radiation LE 40-13 Evaporation Convection Conduction

30. Insulation • Insulation is a major thermoregulatory adaptation in mammals and birds • Insulation reduces heat flow between an animal and its environment • Examples are skin, feathers, fur, and blubber • In mammals, the integumentary system acts as insulating material

31. Circulatory Adaptations • Many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin • In vasodilation, blood flow in the skin increases, facilitating heat loss • In vasoconstriction, blood flow in the skin decreases, lowering heat loss

32. Many marine mammals and birds have an arrangement of blood vessels called a countercurrent heat exchanger • Countercurrent heat exchangers are important for reducing heat loss

33. Canada goose Pacific bottlenose dolphin LE 40-15 Blood flow Vein Artery Vein Artery 33° 35°C 27° 30° 20° 18° 10° 9°

34. Adjusting Metabolic Heat Production • Some animals can regulate body temperature by adjusting their rate of metabolic heat production • Many species of flying insects use shivering to warm up before taking flight

35. Feedback Mechanisms in Thermoregulation • Mammals regulate body temperature by negative feedback involving several organ systems • In humans, the hypothalamus (a part of the brain) contains nerve cells that function as a thermostat

36. Sweat glands secrete sweat that evaporates, cooling the body. Thermostat in hypothalamus activates cooling mechanisms. LE 40-21 Blood vessels in skin dilate: capillaries fill with warm blood; heat radiates from skin surface. Increased body temperature (such as when exercising or in hot surroundings) Body temperature decreases; thermostat shuts off cooling mechanisms. Homeostasis: Internal body temperature of approximately 36–38°C Body temperature increases; thermostat shuts off warming mechanisms. Decreased body temperature (such as when in cold surroundings) Blood vessels in skin constrict, diverting blood from skin to deeper tissues and reducing heat loss from skin surface. Thermostat in hypothalamus activates warming mechanisms. Skeletal muscles rapidly contract, causing shivering, which generates heat.

37. Torpor and Energy Conservation • Torpor is a physiological state in which activity is low and metabolism decreases • Torpor enables animals to save energy while avoiding difficult and dangerous conditions • Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity

38. Estivation, or summer torpor, enables animals to survive long periods of high temperatures and scarce water supplies • Daily torpor is exhibited by many small mammals and birds and seems adapted to feeding patterns

39. Endocrine Chapter 45

40. Overview: The Body’s Long-Distance Regulators • Animal hormones are chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body • Hormones reach all parts of the body, but only target cells are equipped to respond

41. The endocrine system and the nervous system act individually and together in regulating an animal’s physiology • Animals have two systems of internal communication and regulation: the nervous system and the endocrine system

42. The nervous system conveys high-speed electrical signals along specialized cells called neurons • The endocrine system secretes hormones that coordinate slower but longer-acting responses

43. Control Pathways and Feedback Loops • There are three types of hormonal control pathways: simple endocrine, simple neurohormone, and simple neuroendocrine • A common feature is a feedback loop connecting the response to the initial stimulus • Negative feedback regulates many hormonal pathways involved in homeostasis

44. Example Pathway Low blood glucose Stimulus LE 45-2a Receptor protein Pancreas secretes glucagon ( ) Endocrine cell Blood vessel Target effectors Liver Glycogen breakdown, glucose release into blood Response Simple endocrine pathway

45. Pathway Example Stimulus Suckling LE 45-2b Sensory neuron Hypothalamus/ posterior pituitary Neurosecretory cell Posterior pituitary secretes oxytocin ( ) Blood vessel Target effectors Smooth muscle in breast Milk release Response Simple neurohormone pathway

46. Example Pathway Stimulus Hypothalamic neurohormone released in response to neural and hormonal signals Sensory neuron LE 45-2c Hypothalamus Neurosecretory cell Hypothalamus secretes prolactin- releasing hormone ( ) Blood vessel Anterior pituitary secretes prolactin ( ) Endocrine cell Blood vessel Target effectors Mammary glands Milk production Response Simple neuroendocrine pathway

47. Hormones and other chemical signals bind to target cell receptors, initiating pathways that culminate in specific cell responses • Hormones convey information via the bloodstream to target cells throughout the body • Three major classes of molecules function as hormones in vertebrates: • Proteins and peptides • Amines derived from amino acids • Steroids

48. Signaling by any of these hormones involves three key events: • Reception • Signal transduction • Response

49. Cell-Surface Receptors for Water-Soluble Hormones • The receptors for most water-soluble hormones are embedded in the plasma membrane, projecting outward from the cell surface

50. SECRETORY CELL SECRETORY CELL LE 45-3 Hormone molecule Hormone molecule VIA BLOOD VIA BLOOD Signal receptor TARGET CELL TARGET CELL Signal transduction pathway Signal receptor OR Cytoplasmic response DNA Signal transduction and response mRNA DNA NUCLEUS Nuclear response Synthesis of specific proteins NUCLEUS Receptor in plasma membrane Receptor in cell nucleus