Chapter 40 Animal form and function

Hierarchical Organization of Body Plans Most animals are composed of specialized cells organized into tissues that have different functions Tissues make up organs, which together make up organ systems Some organs, such as the pancreas, belong to more than one organ system

Figure 40.3 Mouth Gastrovascular cavity Exchange Exchange Exchange Figure 40.3 Direct exchange with the environment 0.1 mm 1 mm (a) An amoeba, a single-celled organism (b) A hydra, an animal with two layers of cells

Figure 40.4 External environment Food CO2 O2 Mouth Animal body Respiratory system 250 µm Lung tissue (SEM) Interstitial fluid Heart Nutrients Cells Circulatory system Figure 40.4 Internal exchange surfaces of complex animals Digestive system Excretory system 100 µm 50 µm Lining of small intestine (SEM) Anus Blood vessels in kidney (SEM) Unabsorbed matter (feces) Metabolic waste products (nitrogenous waste)

Table 40.1 Table 40.1 Organ systems in mammals

Structure and Function in Animal Tissues Different tissues have different structures that are suited to their functions Tissues are classified into four main categories: epithelial, connective, muscle, and nervous

Epithelial Tissue Epithelial tissue covers and lines organs and cavities cells that are closely joined Named by: 1. shape of cells cuboidal (like dice), columnar (like bricks squamous (like floor tiles) 2. number of layers simple-one layer stratified- many layers

Connective Tissue Blood Loose connective tissue Cartilage Figure 40.5b Connective Tissue Blood Loose connective tissue Plasma Collagenous fiber White blood cells 55 µm 120 µm Red blood cells Cartilage Elastic fiber Fibrous connective tissue Chondrocytes 100 µm 30 µm Figure 40.5b Exploring structure and function in animal tissues (part 2: connective) Chondroitin sulfate Bone Adipose tissue Nuclei Central canal Fat droplets 700 µm 150 µm Osteon

Matrix consists of fibers in a liquid, jellylike, or solid foundation Connective Tissue Binds and supports other tissues Few cells scattered throughout an extracellular matrix Connective tissue contains cells, including Fibroblasts that secrete the protein of extracellular fibers Macrophages that are involved in the immune system Matrix consists of fibers in a liquid, jellylike, or solid foundation three types of connective tissue fiber, all made of protein Collagenous fibers provide strength and flexibility Reticular fibers join connective tissue to adjacent tissues Elastic fibers stretch and snap back to their original length

six major types of connective tissue Loose connective tissue binds epithelia to underlying tissues and holds organs in place Fibrous connective tissue is found in tendons, which attach muscles to bones, and ligaments, which connect bones at joints Bone is mineralized and forms the skeleton Adipose tissue stores fat for insulation and fuel Blood is composed of blood cells and cell fragments in blood plasma Cartilage is a strong and flexible support material

Muscle Tissue responsible for body movement cells consist of filaments of the proteins actin and myosin, which slide past each other to shorten the muscle (contract) It is divided in the vertebrate body into three types Skeletal muscle, or striated muscle, is responsible for voluntary movement Smooth muscle is responsible for involuntary body activities Cardiac muscle is responsible for contraction of the heart

Muscle Tissue Skeletal muscle Smooth muscle Cardiac muscle Nuclei Figure 40.5c Muscle Tissue Skeletal muscle Nuclei Muscle fiber Sarcomere 100 µm Smooth muscle Cardiac muscle Figure 40.5c Exploring structure and function in animal tissues (part 3: muscle) Nucleus Muscle fibers 25 µm Nucleus Intercalated disk 25 µm

Sends receives integrates nerve signals Makes up the nervous system Nervous Tissue Sends receives integrates nerve signals Makes up the nervous system Rapid coordination, movement. Nervous tissue contains Neurons, or nerve cells, that transmit nerve impulses Glial cells, or glia, support cells Sensory neurons, motor neurons, interneurons

Nervous Tissue Neurons Glia 15 µm Glia Neuron: Dendrites Cell body Figure 40.5d Nervous Tissue Neurons Glia 15 µm Glia Neuron: Dendrites Cell body Axons of neurons Axon 40 µm Figure 40.5d Exploring structure and function in animal tissues (part 4: nervous) Blood vessel (Fluorescent LM) (Confocal LM)

Coordination and Control The endocrine system transmits chemical signals called hormones to receptive cells throughout the body via blood A hormone may affect one or more regions throughout the body Hormones are relatively slow acting, but can have long-lasting effects The nervous system transmits information between specific locations The information conveyed depends on a signal’s pathway, not the type of signal Nerve signal transmission is very fast

Figure 40.6 Signaling in the endocrine and nervous systems Axons (a) Signaling by hormones (b) Signaling by neurons STIMULUS STIMULUS Endocrine cell Cell body of neuron Nerve impulse Axon Hormone Signal travels everywhere. Signal travels to a specific location. Blood vessel Nerve impulse Figure 40.6 Signaling in the endocrine and nervous systems Axons Response Response

Feedback control maintains the internal environment animals manage their internal environment by either regulating or conforming

(temperature conformer) Ambient (environmental) Figure 40.7 40 River otter (temperature regulator) 30 Body temperature (C) 20 Largemouth bass (temperature conformer) 10 Figure 40.7 The relationship between body and environmental temperatures in an aquatic temperature regulator and an aquatic temperature conformer 10 20 30 40 Ambient (environmental) temperature (C)

Homeostasis Organisms use homeostasis to maintain a “steady state” or internal balance regardless of external environment In humans, body temperature, blood pH, and glucose concentration are each maintained at a constant level

Mechanisms of Homeostasis For a given variable, fluctuations above or below a set point serve as a stimulus; these are detected by a sensor and trigger a response The response returns the variable to the set point Positive and negative feedback

(-) (-) Thermostat turns heater off. Room temperature increases. Figure 40.8 Thermostat turns heater off. Room temperature increases. Room temperature decreases. (-) ROOM TEMPERATURE AT 20C (set point) (-) (Error signal) Figure 40.8 A nonliving example of temperature regulation: control of room temperature Room temperature increases. Room temperature decreases. Thermostat turns heater on. (compensatory response) (Effector)

Animation: Negative Feedback

Animation: Positive Feedback

Feedback Control Circadian rhythms Homeostasis in animals relies largely on negative feedback, which helps to return a variable to a normal range Positive feedback amplifies a stimulus and does not usually contribute to homeostasis in animals Set points and normal ranges can change with age or show cyclic variation In animals and plants, a circadian rhythm governs physiological changes that occur roughly every 24 hours

Melatonin concentration Core body temperature (C) Figure 40.9 Body temperature Melatonin concentration 37.1 60 Melatonin concentration in blood (pg/mL) Core body temperature (C) 36.9 40 36.7 20 36.5 2 PM 6 PM 10 PM 2 AM 6 AM 10 AM Time of day (a) Variation in core body temperature and melatonin concentration in blood Start of melatonin secretion Midnight Lowest heart rate Greatest muscle strength Figure 40.9 Human circadian rhythm Lowest body temperature 6 PM 6 AM Most rapid rise in blood pressure Fastest reaction time Highest risk of cardiac arrest Noon (b) The human circadian clock

Homeostatic processes for thermoregulation Thermoregulation - animals maintain an internal temperature within a tolerable range Endothermic animals generate heat by metabolism; birds and mammals are endotherms Ectothermic animals gain heat from external sources; ectotherms include most invertebrates, fishes, amphibians, and nonavian reptiles Endotherms maintain a stable body temperature even during large fluctuations in temperature ectotherms tolerate greater variation in internal temperature The body temperature of a poikilotherm varies with its environment The body temperature of a homeotherm is relatively constant

Variation in Body Temperature The relationship between heat source and body temperature is not fixed (that is, not all poikilotherms are ectotherms)

Circulatory Adaptations Regulation of blood flow near the body surface significantly affects thermoregulation 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

Adjusting Metabolic Heat Production Thermogenesis is the adjustment of metabolic heat production to maintain body temperature Thermogenesis is increased by muscle activity such as moving or shivering Nonshivering thermogenesis takes place when hormones cause mitochondria to increase their metabolic activity Some ectotherms can also shiver to increase body temperature

Time from onset of warm-up (min) Figure 40.15 PREFLIGHT PREFLIGHT WARM-UP FLIGHT 40 Thorax Thorax 35 Temperature (C) Abdomen 30 Abdomen Figure 40.15 Preflight warm-up in the hawkmoth 25 2 4 Time from onset of warm-up (min)

Acclimatization in Thermoregulation Birds and mammals can vary their insulation to acclimatize to seasonal temperature changes When temperatures are subzero, some ectotherms produce “antifreeze” compounds to prevent ice formation in their cells

Physiological Thermostats and Fever Thermoregulation in mammals is controlled by a region of the brain called the hypothalamus The hypothalamus triggers heat loss or heat generating mechanisms Fever, a response to some infections, reflects an increase in the normal range for the biological thermostat Some ectothermic organisms seek warmer environments to increase their body temperature in response to certain infections

Thermostat in hypothalamus activates cooling mechanisms. Figure 40.17 Thermostat in hypothalamus activates cooling mechanisms. Response: Blood vessels in skin dilate. Response: Sweat Body temperature increases. Body temperature decreases. NORMAL BODY TEMPERATURE (approximately 36–38C) Body temperature increases. Body temperature decreases. Figure 40.17 The thermostatic function of the hypothalamus in human thermoregulation Response: Shivering Response: Blood vessels in skin constrict. Thermostat in hypothalamus activates warming mechanisms.

Quantifying Energy Use Metabolic rate is the amount of energy an animal uses in a unit of time Metabolic rate can be determined by An animal’s heat loss The amount of oxygen consumed or carbon dioxide produced Measuring energy content of food consumed and energy lost in waste products

Figure 40.19 Figure 40.19 Measuring the rate of oxygen consumption by a swimming shark

Minimum Metabolic Rate and Thermoregulation Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest at a “comfortable” temperature Standard metabolic rate (SMR) is the metabolic rate of an ectotherm at rest at a specific temperature Both rates assume a nongrowing, fasting, and nonstressed animal Ectotherms have much lower metabolic rates than endotherms of a comparable size

Influences on Metabolic Rate Metabolic rates are affected by many factors besides whether an animal is an endotherm or ectotherm Some key factors are age, sex, size, activity, temperature, and nutrition

Basal (standard) metabolism Activity Figure 40.UN01 Adélie penguin 4-kg male 340,000 kcal/yr Deer mouse 0.025-kg female 4,000 kcal/yr Ball python 4-kg female 8,000 kcal/yr Figure 40.UN01 Skills exercise: interpreting pie charts Key Basal (standard) metabolism Activity Reproduction Growth Thermoregulation

NORMAL RANGE for internal variable Stimulus: change in Response Figure 40.UN03 NORMAL RANGE for internal variable Response Stimulus: change in internal variable Figure 40.UN03 Summary of key concepts: feedback control Control center Sensor