I.Animal Size/Shape and the Environment II. Four tissue categories IV.Feedback Control and temperature regulation V.Metabolic Rate and Energy Use VII. Summary Lecture 12 Outline (Ch. 40)

2 What things to animals do to maintain homeostasis?

3 Overview: Diverse Forms, Common Challenges Anatomy: study of biological form of an organism Physiology: study of biological functions of an organism Communication and integration Support and movement Regulation and maintenance Defense Reproduction and development

Cells must continually be bathed in aqueous medium to exchange gasses, nutrients, wastes – all by diffusion which is only effective over short distances. A.How long does it take a small molecule to travel 1 um? B.How long to travel 1 mm?

5 0.5 cm Nutrients Digestive system Lining of small intestine Mouth Food External environment Animal body CO 2 O2O2 Circulatory system Heart Respiratory system Cells Interstitial fluid Excretory system Anus Unabsorbed matter (feces) Metabolic waste products (nitrogenous waste) Kidney tubules 10 µm 50 µm Lung tissue More complex organisms have highly folded internal surfaces Overview: Diverse Forms, Common Challenges Cells bathed in interstitial fluid

How does the surface area to volume ratio change as a cell increases in size? (let’s say cells are roughly spherical) diameter: SA cell: Volume cell: d = 1 µm d = 10 µm d = 100 µm SA = 4r 2 V = 4/3r 3

7 Exchange 0.15 mm (a) Single cell 1.5 mm (b) Two layers of cells Exchange Mouth Gastrovascular cavity Rate of exchange related to SA Amount of exchange related to V Overview: Diverse Forms, Common Challenges

8 Tissues are classified into four main categories: Tissue Structure and Function Humans: 210 different cell types – can you name them?! ;)

9 Epithelial Tissue Cuboidal epithelium Simple columnar epithelium Pseudostratified ciliated columnar epithelium Stratified squamous epithelium Simple squamous epithelium Note differences in cell shape and type of layering Tissue Structure and Function

10 Apical surface Basal surface Basal lamina 40 µm Tissue Structure and Function Epithelial cells are attached to a basal lamina at their base.

11 Connective Tissue Connective tissue binds / supports other tissues sparsely packed cells scattered in extracellular matrix matrix - fibers in a liquid, jellylike, or solid foundation There are six main types of connective tissue.

12 Connective Tissue Collagenous fiber Loose connective tissue Elastic fiber 120 µm Cartilage Chondrocytes 100 µm Chondroitin sulfate Adipose tissue Fat droplets 150 µm White blood cells 55 µm Plasma Red blood cells Blood Nuclei Fibrous connective tissue 30 µm Osteon Bone Central canal 700 µm Tissue Structure and Function

13 Muscle Tissue Muscle tissue: long cells (muscle fibers) that contract in response to nerve signals Skeletal muscle - striated, voluntary movement Smooth muscle – not striated, involuntary body activities Cardiac muscle – striated, contraction of the heart

14 Muscle Tissue 50 µm Skeletal muscle Multiple nuclei Muscle fiber Sarcomere 100 µm Smooth muscle Cardiac muscle Nucleus Muscle fibers 25 µm Nucleus Intercalated disk Tissue Structure and Function

Glial cells Nervous Tissue 15 µm Dendrites Cell body Axon Neuron Axons Blood vessel 40 µm 15 Tissue Structure and Function Nervous tissue senses stimuli, transmits signals Nervous tissue contains: Neurons transmit nerve impulses Glial cells nourish, insulate, and replenish neurons

16 Self-Check Tissue CategoryTissues/Cells Included; Functions Epithelial Connective Muscle Nervous

17 Response: Heater turned off Stimulus: Control center (thermostat) reads too hot Room temperature decreases Set point: 20ºC Room temperature increases Stimulus: Control center (thermostat) reads too cold Response: Heater turned on Feedback control loops maintain the internal environment in many animals Examples of negative and positive feedback? Which maintains homeostasis? Animals manage their internal environment by regulating or conforming to the external environment

18 regulator: uses internal mechanisms to maintain during external change. Ex: River otter conformer: allows internal variables to change with environment. Ex: Largemouth bass Temperature Regulation

19 Five general adaptations help animals thermoregulate: – Insulation – Circulatory adaptations – Cooling by evaporative heat loss – Behavioral responses – Adjusting metabolic heat production Balancing Heat Loss and Gain Dragonfly “obelisk” posture

20 Temperature Regulation Thermoregulation: process by which animals maintain an internal temperature (a) A walrus, an endotherm (b) A lizard, an ectotherm Endothermic animals generate heat by metabolism (birds and mammals) Ectothermic animals gain heat from external sources (invertebrates, fishes, amphibians, and non- avian reptiles)

We’ve discussed several mechanisms related to homeostasis and in particular temperature regulation. Are all endotherms regulators? Are all ectotherms conformers? Can you think of any examples that do not follow this trend?

22 Metabolic rate is the amount of energy an animal uses in a unit of time Energy Use Measured by amount of oxygen consumed or carbon dioxide produced Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest at a “comfortable” temperature

23 Shrew Harvest mouse Mouse Ground squirrel Rat Cat Dog Sheep Human Horse Elephant Body mass (kg) (log scale) BMR (L O 2 /hr) (log scale) (a) Relationship of BMR to body size 10 –3 10 –2 10 – Energy Use

–1 10 –2 10 – Body mass (kg) (log scale) (b) Relationship of BMR per kilogram of body mass to body size BMR (L O2/hr) (per kg) Shrew Harvest mouse Mouse Rat Ground squirrel Cat Sheep Dog Human Horse Elephant Energy Use Human average daily metabolic rate is only 1.5X BMR!

Which animal would have the highest BMR per unit body weight? 1.human 2.dog 3.mouse 4.whale 5.turtle

26 Energy Budgeting Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity Torpor = physiological state with low activity and metabolism decreased – allows animals to save energy while avoiding difficult and dangerous conditions

In discussing homeostasis, regulation, and hibernation, consider the following: Why would an animal use hibernation? What might be gained by this behavior?

28 Additional metabolism that would be necessary to stay active in winter Actual metabolism Arousals Body temperature Outside temperature Burrow temperature Metabolic rate (kcal per day) Temperature (°C) JuneAugustOctoberDecemberFebruaryApril –15 –10 – Energy Use