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Anatomy is the study of the structure of an organism Physiology is the study of the functions an organism performs.

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Presentation on theme: "Anatomy is the study of the structure of an organism Physiology is the study of the functions an organism performs."— Presentation transcript:

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

5 LE 40-4 Digestive system Circulatory system Excretory system Interstitial fluid Cells Nutrients Heart Animal body Respiratory system Blood CO 2 Food Mouth External environment O2O2 50 µm 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). 10 µm Inside a kidney is a mass of microscopic tubules that exchange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM). 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). Unabsorbed matter (feces) Metabolic waste products (urine) Anus 0.5 cm

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

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

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

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13 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 Bioenergetics

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

16 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 oxygen consumed or carbon dioxide produced Quantifying Energy Use

17 Chapter 40

18 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 Bioenergetic Strategies

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 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 conformer allows its internal condition to vary with certain external changes Regulating and Conforming

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

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 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 Ectotherms and Endotherms

27 LE River otter (endotherm) Largemouth bass (ectotherm) Ambient (environmental) temperature (°C) Body 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 LE Radiation Evaporation Conduction Convection

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 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 Circulatory Adaptations

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

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 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 Feedback Mechanisms in Thermoregulation

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

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

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

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

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

51 Binding of a hormone to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm or a change in gene expression The same hormone may have different effects on target cells that have –Different receptors for the hormone –Different signal transduction pathways –Different proteins for carrying out the response

52 The hormone epinephrine has multiple effects in mediating the body’s response to short-term stress

53 LE 45-4 Different receptors different cell responses Epinephrine  receptor Epinephrine  receptor Epinephrine  receptor Vessel constricts Vessel dilates Intestinal blood vessel Skeletal muscle blood vessel Liver cell Different intracellular proteins different cell responses Glycogen deposits Glycogen breaks down and glucose is released from cell

54 Intracellular Receptors for Lipid-Soluble Hormones Steroids, thyroid hormones, and the hormonal form of vitamin D enter target cells and bind to protein receptors in the cytoplasm or nucleus Protein-receptor complexes then act as transcription factors in the nucleus, regulating transcription of specific genes

55 Paracrine Signaling by Local Regulators In paracrine signaling, nonhormonal chemical signals called local regulators elicit responses in nearby target cells Types of local regulators: –Neurotransmitters –Cytokines and growth factors –Nitric oxide –Prostaglandins

56 Prostaglandins help regulate aggregation of platelets, an early step in formation of blood clots

57 The hypothalamus and the pituitary gland control much of the endocrine system The hypothalamus and pituitary integrate many functions of the vertebrate endocrine system

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60 LE 45-6 Testis (male) Ovary (female) Adrenal glands Pancreas Parathyroid glands Thyroid gland Pituitary gland Pineal gland Hypothalamus

61 Relation Between the Hypothalamus and Pituitary Gland The hypothalamus, a region of the lower brain, contains neurosecretory cells The posterior pituitary, or neurohypophysis, is an extension of the hypothalamus Hormonal secretions from neurosecretory cells are stored in or regulate the pituitary gland

62 LE 45-7 Mammary glands, uterine muscles Hypothalamus Kidney tubules Oxytocin HORMONE TARGET ADH Posterior pituitary Neurosecretory cells of the hypothalamus Axon Anterior pituitary

63 Posterior Pituitary Hormones The two hormones released from the posterior pituitary act directly on nonendocrine tissues Oxytocin induces uterine contractions and milk ejection Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys

64 Anterior Pituitary Hormones The anterior pituitary produces both tropic and nontropic hormones

65 Tropic Hormones The four strictly tropic hormones are –Follicle-stimulating hormone (FSH) –Luteinizing hormone (LH) –Thyroid-stimulating hormone (TSH) –Adrenocorticotropic hormone (ACTH) Each tropic hormone acts on its target endocrine tissue to stimulate release of hormone(s) with direct metabolic or developmental effects

66 Nontropic Hormones Nontropic hormones produced by the anterior pituitary: –Prolactin –Melanocyte-stimulating hormone (MSH)  -endorphin

67 Prolactin stimulates lactation in mammals but has diverse effects in different vertebrates MSH influences skin pigmentation in some vertebrates and fat metabolism in mammals Endorphins inhibit pain Nontropic Hormones

68 Growth Hormone Growth hormone (GH) has tropic and nontropic actions GH promotes growth directly and has diverse metabolic effects GH stimulates production of growth factors

69 The hypothalamus and anterior pituitary control secretion of thyroid hormones through two negative feedback loops

70 Thyroid Hormones The thyroid gland consists of two lobes on the ventral surface of the trachea It produces two iodine-containing hormones: triiodothyronine (T 3 ) and thyroxine (T 4 )

71 Thyroid hormones stimulate metabolism and influence development and maturation Hyperthyroidism, excessive secretion of thyroid hormones, can cause Graves’ disease in humans

72 The thyroid gland also produces calcitonin, which functions in calcium homeostasis

73 Parathyroid Hormone and Calcitonin: Control of Blood Calcium Two antagonistic hormones, parathyroid hormone (PTH) and calcitonin, play the major role in calcium (Ca 2+ ) homeostasis in mammals

74 Calcitonin stimulates Ca 2+ deposition in bones and secretion by kidneys, lowering blood Ca 2+ levels PTH, secreted by the parathyroid glands, has the opposite effects on the bones and kidneys, and therefore raises Ca 2+ levels PTH also has an indirect effect, stimulating the kidneys to activate vitamin D, which promotes intestinal uptake of Ca 2+ from food

75 Insulin and Glucagon: Control of Blood Glucose The pancreas secretes insulin and glucagon, antagonistic hormones that help maintain glucose homeostasis Glucagon is produced by alpha cells Insulin is produced by beta cells

76 LE Beta cells of pancreas release insulin into the blood. Insulin Liver takes up glucose and stores it as glycogen. STIMULUS: Rising blood glucose level (for instance, after eating a carbohydrate- rich meal) Blood glucose level declines to set point; stimulus for insulin release diminishes. Homeostasis: Blood glucose level (about 90 mg/100 mL) STIMULUS: Dropping blood glucose level (for instance, after skipping a meal) Blood glucose level rises to set point; stimulus for glucagon release diminishes. Liver breaks down glycogen and releases glucose into the blood. Body cells take up more glucose. Alpha cells of pancreas release glucagon into the blood. Glucagon

77 Target Tissues for Insulin Insulin reduces blood glucose levels by –Promoting the cellular uptake of glucose –Slowing glycogen breakdown in the liver –Promoting fat storage

78 Glucagon increases blood glucose levels by –Stimulating conversion of glycogen to glucose in the liver –Stimulating breakdown of fat and protein into glucose Target Tissues for Glucagon

79 Diabetes Mellitus Diabetes mellitus is perhaps the best- known endocrine disorder It is caused by a deficiency of insulin or a decreased response to insulin in target tissues It is marked by elevated blood glucose levels

80 Type I diabetes mellitus (insulin- dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells Type II diabetes mellitus (non-insulin- dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors

81 Adrenal Hormones: Response to Stress The adrenal glands are adjacent to the kidneys Each adrenal gland actually consists of two glands: the adrenal medulla adrenal cortex

82 Catecholamines from the Adrenal Medulla The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline) These hormones are members of a class of compounds called catecholamines They are secreted in response to stress- activated impulses from the nervous system They mediate various fight-or-flight responses

83 Stress Hormones from the Adrenal Cortex Hormones from the adrenal cortex also function in response to stress They fall into three classes of steroid hormones: –Glucocorticoids, such as cortisol, i nfluence glucose metabolism and the immune system –Mineralocorticoids, such as aldosterone, a ffect salt and water balance –Sex hormones a re produced in small amounts

84 Gonadal Sex Hormones The gonads, testes and ovaries, produce most of the sex hormones: –androgens –Estrogens –progestins

85 The testes primarily synthesize androgens, mainly testosterone, which stimulate development and maintenance of the male reproductive system Testosterone causes increase in muscle and bone mass and is often taken as a supplement to cause muscle growth, which carries health risks

86 Estrogens, most importantly estradiol, are responsible for maintenance of the female reproductive system and the development of female secondary sex characteristics In mammals, progestins, which include progesterone, are primarily involved in preparing and maintaining the uterus

87 Melatonin and Biorhythms The pineal gland, located in the brain, secretes melatonin Light/dark cycles control release of melatonin Primary functions of melatonin appear to relate to biological rhythms associated with reproduction


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