Animal Structure and Function: Tissues and Homeostasis

Ch. 40: Introduction to Animal Structure and Function Overview • Functional anatomy • Types of tissues • Epithelial • Connective • Nervous • Muscle • Introduction to Homeostasis • Positive and negative feedback loops • Introduction to Bioenergetics & Thermoregulation

Functional anatomy • Anatomy: study of the structure of an organism • Physiology: study of the functions of an organism • Function relates to form (structure) • Natural selection  best form available to fit function • Tissues: groups of cells with common structure & function • Present in all animals except sponges

Tissues 1) Epithelial • Tightly packed • Covers outside of body, lines organs • Roles: • barrier to injury, microbes, heat loss • Some secrete, absorb • May be ciliated

1) Epithelial (40.5) • Categories: • Simple vs. stratified vs. pseudostratified • Cuboidal, columnar, squamous • Simple squamous= alveoli; blood vessels • diffusion • Stratified squamous=skin • Columnar: secretion & absorption • E.g., Intestine, nasal passages (pseudostratified ciliated columnar) • (Simple) Cuboidal= excretion • E.g., Kidney tubules, glands

Tissues 2) Connective (40.2) • E.g., bone, blood, cartilage, adipose • Role: Bind and support other tissues • Cells distributed in extracellular matrix • Connective (matrix) fiber types: • Collagenous fibers= bundles of collagen molecules • Great tensile strength • Resists stretching • Reticular fibers= thin threads of collagen • Attach connective tissues to adjacent tissues • Elastic fibers= threads of elastin • Tissue quickly returns to original shape

2) Connective • Examples: • Loose connective tissue (Areolar) • Consists of collagenous, reticular, & elastic fibers • Holds organs in place • Attaches epithelia to underlying tissues • Fibrous connective tissue • Densely packed collagenous fibers • Non-elastic • E.g., tendons, ligaments • Cartilage • Collagenous fibers & chondroitin • Secreted by chondrocytes • Strong & flexible • Skeleton of all vertebrate embryos

Tissues 2) Connective • Examples (cont.): • Adipose tissue • Adipose cells: Fat storage • Insulates body, stores fuel molecules • Bone • Mineralized • Osteoblast cells deposit collagen & calcium phosphate • Haversian canals for blood and nerves • Marrow  blood cells • Blood • RBC, WBC, platelets • Extracellular matrix = plasma

Tissues 3) Muscle • Long cells of muscle fibers w/contractile proteins actin & myosin • Three types: • Skeletal (striated) • Cardiac • Smooth

Tissues 4) Nervous • Senses stimuli, transmits signals • Cell = neuron • Dendrite  body  axon • Depolarization  Action potential (48.10&11)

Blood is usually classified as which one of the following tissue types? • Muscle • Epithelial • Connective • Nervous

Action potentials are closely associated with which one of the following tissue types? • Muscle • Epithelial • Connective • Nervous

Ch. 40: Introduction to Animal Structure and Function Overview • Functional anatomy • Types of tissues • Introduction to Homeostasis • Positive and negative feedback loops • Introduction to Bioenergetics & Thermoregulation • (Ch. 41 Digestive System) • Feedback loops (in Ch. 40 notes) • Blood sugar • Appetite • (Ch. 42 Circulatory & Respiratory Systems)

Homeostasis • “Steady state” • Relatively stable internal environment in a cell (or organism) • Fluctuations do occur • Homeostatic control system (40.8): • Three parts (e.g., blood pressure): • Receptor: detects change in internal environment (neurons of carotid artery) • Control center: processes info, signals effector (medulla) • Effector: area of body that responds to change (ventricles of heart)

Homeostasis • Relatively stable internal environment • Homeostatic control system: • Negative feedback: depresses stimulus, counters further change • E.g., Body temp. (40.16), blood sugar (45.12) • Positive feedback: enhances stimulus, creates further change • E.g., uterine contractions

Homeostatic regulation: blood sugar • Blood sugar = glucose • Excess stored in liver and muscle • Hepatic portal vein carries blood from small intestine to liver • Negative feedback loop (45.12):

Homeostatic regulation: blood sugar • Negative feedback loop: • Blood glucose too high: pancreas secretes insulin (beta cells) • (Hormone: Commun./coord. between different parts of body) • Insulin  liver & muscles store glycogen •  cells increase uptake of sugar •  glucose level drops • Blood sugar too low: pancreas secretes glucagon (alpha cells) • Glucagon------> glycogen  glucose •  glucose level rises • High fructose corn syrup: Body does not regulate blood fructose levels

Hormonal feedback loops and appetite regulation (41.23) Suppressors target hypothalamus: • Leptin • Pancreas  Insulin • S.I.  PYY • Also stimulates reward/pleasure center in frontal cortex • Also regulates emptying of stomach Stimulant: • Stomach wall  Ghrelin

Homeostatic regulation: caloric intake Feedback loop stabilizing body weight: • Adipose cells produce leptin  suppresses appetite • HFCS inhibits leptin production! • Increase in adipose  increase in leptin levels suppresses appetite & increases burning of fat • Loss of adipose  decrease in leptin  hunger •  Weight ~stabilizes

Intro to bioenergetics • Flow of energy through an organism (40.17) • Metabolism • How much energy is needed just to stay alive? • Vs. walk, run, fly, reproduce, etc.?

Bioenergetics • Metabolic rate = Amount of energy used per unit time • Rate relates to thermoregulation • Endotherms > ectotherms • Endothermy: • Metabolism produces body heat • Energetically costly • Benefit: intense, long-duration activity over wide range of temps

Bioenergetics • Metabolic rate relates to body size • A mouse consumes same/more/fewer calories per gram than an elephant? • Inverse relationship • E.g., Mouse consumes 20x more calories/g than elephant • Smaller =: • More calories per gram body weight • Higher respiration rate • Higher blood volume (relative to size) • Higher heart rate (up to 1000+ beats/minute)

Bioenergetics • Basal metabolic rate (BMR) • Endotherm’s rate at rest w/no digestion, no stress • Humans: female = 1300 to 1500 kcal/day; male = 1600 to 1800 • = ___ 75W light bulbs? • 1 • vs. Standard metabolic rate (SMR)=Ectotherm at rest • Daily energy consumption • Most animals: 2 to 4 x (BMR or SMR) • Humans: 1.5-2 x BMR

Energy budget: Body size and endothermy (40.20)

Thermoregulation • Cold environments: •  muscular activity (incl. shivering) • nonshivering thermogenesis • Mitochondria • Brown adipose • Trap more air in fur or feathers • Subnivean lifestyle • Adaptive hypothermia • Daily = torpor: e.g., Hummingbirds • Hibernation: e.g., Marmots, ground squirrels (40.21) • 85 kCal/day  1 kCal/day • Not bears! • Warm environments: • Evap. Cooling; avoid heat of day

Ch. 40: Introduction to Animal Structure and Function Overview • Functional anatomy • Introduction to Homeostasis • Positive and negative feedback loops • Introduction to Bioenergetics & Thermoregulation Ch. 41 Nutrition & Digestion • Feedback loops (in Ch. 40 notes) • Blood sugar • Appetite • Food processing

Food Processing • Ingestion  digestion (mechanical & chemical)  absorption  elimination • Chemical summary: Fig. 41.13 • Digestive tract + accessory glands: • Salivary glands • Pancreas • Liver • Gall bladder

Digestion • Mouth: Physical and chemical digestion • Teeth: • make food easier to swallow •  surface area of food • Saliva: • lubricates food • prevents tooth decay (neutralizes acids) • antibacterial • salivary amylase: starch & glycogen  smaller polysacchs. & maltose

Digestion • Pharynx • epiglottis covers glottis of trachea • Esophagus - Peristalsis (41.11) • Stomach • Storage & chem. digestion • Little absorption • Smooth muscles churn food • Gastric juices (pH 2) contain pepsin (protein digestion: protein  small polypeptides) • Nutrient-rich broth = ‘acid chyme’: • Pyloric sphincter  Small intestine

Digestion • Small intestine (~6m) - (1st part = duodenum) • Digestion & absorption • Extra- & intra-cellular digestion: lumen & epithelials • Villi and microvilli increase SA: ~tennis court (~41.15) • Hepatic portal system

Digestion • Small intestine Fats: - Bile: liver  gall bladder  S.I. - Emulsifies lipids • Lipase: pancreas  S.I. • chemically breaks down lipids

Digestion • Small intestine Carbohydrates: • Pancreatic amylase • Polysaccharides  maltose • Disaccharidases (SI epith) • Disacch.  Monosacch. Nucleic acids: • Pancreatic nuclease, and nucleotidase & nucleosidase (from SI epithelium): DNA, RNA  nucleotides  sugars, phosphates, N-bases

Digestion • Small intestine Pancreatic trypsin and aminopeptidase (from SI ep.), etc.: • Polypeptides  amino acids • Large intestine (=colon) • w/cecum (w/appendix) (41.21) • Note pigeon ceca (red arrows) • Absorption of water • Symbiotic bacteria •  vitamins: B, K, folic acid… ( Rectum) - Fecal storage

Ch. 42: Circulation and Gas Exchange: Overview • Functions of Circulatory system • Blood • Components • Clotting • Vertebrate circulatory systems • Single vs. double • Fish, amphibians, reptiles, birds, mammals • Blood vessels and blood pressure • Respiratory system

Circulatory System • Functions (in vertebrates): • Transport gases • Transport nutrients • Immune • Conserve or dissipate heat • Endocrine

Circulatory System • Blood = Plasma + formed elements • Plasma • Water • Ions (e.g., sodium, potassium, etc.) • Dissolved proteins (e.g. fibrinogen), gases and nutrients

Circulatory System Blood • Plasma • Formed elements (42.14) Produced in bone marrow, stored in spleen: • Erythrocytes • 1 RBC contains 250 million hemoglobin molecules •  1 bil. oxygen molecules • Leukocytes • WBCs: defense/immunity (Ch. 43) • Platelets • Clotting

Leukocyte summary • Eosinophils: Non-specific defense against large invaders • Neutrophils: Non-specific, phagocytic • Monocytes: Non-specific, phagocytic • Form macrophages • Basophils: Non-specific, inflammation • Secrete histamine & prostaglandins • Lymphocytes: Immunity • B cells • T cells

(Homeostatic) Blood clotting (42.16) - Blood vessel damaged  - Platelets adhere to collagen fibers at wound site  - Platelets and tissue release thromboplastin + other clotting factors 

Blood clotting - Plasma protein prothrombin  thrombin  - Plasma protein fibrinogen  fibrin  - Fibrin entangles platelets & erythrocytes (= clot)

Blood clotting - Blood enzyme prothrombin  thrombin  - Blood protein fibrinogen  fibrin  - Fibrin entangles platelets & erythrocytes (= clot) • Hemophiliacs lack platelet clotting factor • Irreducible complexity? Darwin’s Black Box

Ch. 42: Circulation and Gas Exchange: Overview • Functions of Circulatory system • Blood • Components • Clotting • Vertebrate circulatory systems (review: read) • Single vs. double • Fish, amphibians, reptiles, birds, mammals • Blood vessels and blood pressure (lab) • Respiratory system • Ch. 43

Circ. Systems • Fish: Single w/2 chambers • Other verts. (42.3b,c): • Double circ. system • Amphibians & (most) reptiles: 3 chambers • 2 atria, 1 ventricle (partly divided in reptiles) • (Crocodiles), birds, humans : 4 chambers • 2 atria, 2 ventricles

Circulatory System • Mammalian (42.4): superior/inferior (ant./post.) vena cava  R atrium  R ventricle pulmonary artery  lungs  pulmonary vein  L atrium  L ventricle aorta  arteries  arterioles  capillaries  venules  veins  vena cava  …

Circulatory System • Blood vessels: Artery, vein, capillary (42.8) • Capillary thinnest (1 layer of epith.) • Artery thickest • Withstand high pressure, rapid flow • Elastic, maintains BP when heart relaxes • Systolic vs. diastolic (42.13) • Veins • Low pressure: BP lost at capillary beds • Large veins have valves • Blood flow aided by: • Smooth venous muscles • Muscle contractions • Breathing

Respiratory System • Mammalian respiration: Lungs (42.23) • Nasal passages  pharynx  (epiglottis)  glottis  larynx  trachea  bronchi  bronchioles  alveoli • SA=100 sq. m • Cartilage rings • Diaphragm • Smooth muscle

Animal Structure and Function: Tissues and Homeostasis