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Animal Physiology - Coggle Diagram

- - - - Prehension strategies (teeth, beaks, tongues, proboscises) determine particle size and feeding rate; particle size influences the surface area available for digestion
      - Cephalic-phase responses: sensory cues (sight, smell, taste) trigger anticipatory secretion (saliva, gastric acid, insulin) that primes digestive tract and reduces postprandial lag.
    - - Mechanical digestion: Mastication and stomach churning increase surface area and expose substrates to enzymes; segmentation in intestine enhances mixing.
      - Chemical digestion
        
        Proteolysis: Begins with pepsin (stomach) and continues with trypsin/chymotrypsin in small intestine; zymogens are activated in lumen to avoid autodigestion.
        
        Carbohydrate digestion: Salivary and pancreatic amylases break polysaccharides to disaccharides and monosaccharides; brush‑border enzymes (maltase, sucrase) finish hydrolysis.
        
        Lipid digestion: Bile salts emulsify lipids into micelles; pancreatic lipase hydrolyzes triglycerides into monoglycerides and free fatty acids for absorption.
      - pH gradients and enzyme localization: Low gastric pH activates gastric enzymes and sterilizes food; bicarbonate from pancreas neutralizes chyme to optimize pancreatic enzyme activity.
    - - Monosaccharides and amino acids: Enter enterocytes via specific transporters (SGLT1 for glucose/Na⁺ cotransport; GLUT transporters basolaterally), then pass to capillaries and hepatic portal circulation.
      - Lipids: Form micelles, diffuse into enterocytes, reassembled into triglycerides, packaged into chylomicrons with apolipoproteins, and enter lacteals (lymphatics) to bypass first‑pass hepatic uptake initially.
      - Water, electrolytes, vitamins: Water follows osmotic gradients; vitamins vary (fat‑soluble absorbed with lipids; water‑soluble via transporters); B12 requires intrinsic factor and ileal receptors.
      - Enterocyte turnover and barrier: Rapid epithelial renewal maintains absorptive function; tight junction regulation controls paracellular permeability; immune surveillance in gut‑associated lymphoid tissue prevents pathogen translocation.
    - - Large intestine functions: Absorbs water/electrolytes, compacts feces; bacterial fermentation of residual carbs produces short‑chain fatty acids (SCFAs) absorbed as additional energy sources.
      - Microbiome role in elimination: Microbes synthesize vitamins (K, some B), metabolize bile salts, and contribute to fecal bulk; dysbiosis can alter stool consistency and systemic physiology.
      - Defecation reflexes: Coordinated by enteric and central nervous systems (rectal stretch → parasympathetic reflex → relaxation of internal anal sphincter; voluntary control over external sphincter).
  - - - Mechanical processing: Heterodont dentition (incisors, canines, molars) adapted to diet; chewing reduces particle size and mixes with saliva.
      - Saliva composition: Amylase starts starch digestion; mucins lubricate; lysozyme and IgA provide antimicrobial defense; pH buffering begins.
    - - Peristalsis propels bolus; coordinated swallowing reflex protects airway; sphincter mechanisms prevent reflux (upper esophageal and lower esophageal/cardiac sphincter).
    - - Gastric zones and cell types: Parietal cells secrete HCl; chief cells secrete pepsinogen; G cells release gastrin; mucous cells protect epithelium.
      - Mechanical grinding, acid denaturation of proteins, initial proteolysis, controlled chyme release to duodenum to regulate digestion and neutralization.
    - - Duodenum: Receives acidic chyme; secretin and CCK coordinate pancreatic bicarbonate and enzyme secretion and gallbladder contraction.
      - Jejunum/Ileum: Progressive absorption: sugars, amino acids, lipids; ileum specializes in bile salt and B12 reabsorption.
      - Plicae circulares (macroscopic folds) → villi (millimeter) → microvilli (brush border) create ~600× surface increase relative to a smooth tube.
      - Lymphatic and vascular coupling: Lacteals absorb lipids; capillaries feed hepatic portal system for nutrient processing and detoxification.
    - - Haustra and segmentation slow transit to extract water; mucus secretion eases passage.
      - Liver: Central metabolic hub processes absorbed nutrients (glycogenesis, lipogenesis, deaminated nitrogen handling), detoxifies xenobiotics, synthesizes plasma proteins, and secretes bile for fat emulsification.
      - Pancreas: Exocrine acinar cells produce digestive zymogens and bicarbonate; endocrine islets regulate systemic glucose via insulin and glucagon.
      - Gallbladder: Concentrates and times bile release with CCK-triggered contraction to emulsify dietary fats.
    - - Myenteric plexus controls motility; submucosal plexus regulates secretion and blood flow; ENS can operate autonomously but is modulated by sympathetic and parasympathetic inputs.
      - Motility types: Peristalsis for propulsion; segmentation for mixing and absorption; migrating motor complex clears residual material between meals.
  - - - Macronutrients supply calories converted to ATP via cellular respiration: glycolysis → pyruvate oxidation → Krebs cycle → oxidative phosphorylation; net ATP yield differs by substrate
      - glucose ≈ 30–32 ATP; fatty acids yield much more per carbon
    - - Must be obtained in diet; absence halts protein synthesis and growth
    - - (omega‑3/omega‑6): Precursors for inflammatory mediators and maintain membrane properties; deficiency affects growth, immunity, neural development.
    - - Fat‑soluble (A, D, E, K): Stored in tissues; A for vision and epithelial maintenance; D for Ca²⁺ homeostasis; K for clotting.
      - Water‑soluble (B complex, C): Coenzymes (NAD+, FAD, coA, folate) and antioxidant role (C); deficiencies cause defined syndromes (scurvy, beriberi, pellagra).
    - - Electrolytes (Na⁺, K⁺) for membrane potentials
      - Ca²⁺ for signaling/bone
      - Fe for hemoglobin;
      - I⁻ for thyroid hormones; trace elements serve catalytic roles (Zn, Cu, Se).
  - - - overcoming cellulose and anti‑nutrients
      - Foregut (ruminants) or hindgut (horses, rabbits) chambers host fermentative bacteria/archaea/protists that hydrolyze cellulose into SCFAs absorbed by host.
      - Enlarged cecum or multi‑chambered stomachs, elongated intestines to increase retention time and exposure to microbes.
      - Coprophagy in some hindgut fermenters to recover microbial protein and vitamins; selective foraging to balance fiber and nutrient intake.
    - - maximized protein and lipid extraction
      - apid digestion and pathogen suppression; high pepsin and low pH optimize protein breakdown and reduce reliance on microbial fermentation.
      - Sharp carnassial teeth for shearing; powerful bite force for tearing flesh.
    - - flexible morphology and physiology
      - Intermediate gut length, mixed dentition for both tearing and grinding, broad enzymatic repertoire (amylases, proteases, lipases) to exploit variable diets.
      - Opportunistic feeding and learned foraging strategies expand ecological niche.
    - - Microbes assist in complex carbohydrate breakdown, vitamin biosynthesis, bile modification, and training the immune system; host diet strongly shapes microbial composition.
      - Vertical and horizontal transmission, rapid microbial adaptation to diet, and host genetic factors produce co adapted host microbe relationships with fitness consequences.
  - - - Trigger: Stomach distension and presence of peptides stimulate G cells to release gastrin.
      - Action: Gastrin increases HCl secretion by parietal cells and promotes gastric motility, optimizing protein digestion and preparing chyme for downstream processing.
    - - Trigger: Low pH in duodenum (acidic chyme).
      - Action: Secretin stimulates pancreatic duct cells to release bicarbonate-rich fluid, neutralizing acid and creating the pH optimum for pancreatic enzymes.
    - - Trigger: Fatty acids and certain amino acids in duodenum.
      - Action: CCK stimulates pancreatic enzyme secretion and gallbladder contraction; slows gastric emptying to prolong intestinal digestion and absorption.
    - - Nutrients transported via portal vein to liver for detoxification, glycogen storage, lipid packaging, and redistribution; protects systemic circulation from dietary toxins and allows metabolic regulation before peripheral distribution.
    - - In enterocytes, re-esterified lipids plus apolipoproteins form chylomicrons that enter lymphatics; lymph drains into venous circulation bypassing immediate hepatic uptake, enabling peripheral delivery of dietary lipids.
    - - Insulin (fed state): Stimulates glucose uptake (GLUT4 translocation in muscle/adipose), glycogen synthesis (liver/muscle), lipogenesis, and inhibits lipolysis; central to storing excess energy.
      - Glucagon (fasted state): Stimulates hepatic glycogenolysis and gluconeogenesis, mobilizing glucose; promotes lipolysis in adipose to supply energy substrates.
    - - Short‑term
        
        Ghrelin: Secreted by stomach preprandially to stimulate hunger via hypothalamic NPY/AgRP neurons.
        
        PYY and GLP‑1: Released postprandially from intestine to promote satiety and slow gastric emptying; GLP‑1 also enhances insulin secretion (incretin effect).
      - Long‑term
        
        Leptin: Proportional to adipose mass; signals energy sufficiency to hypothalamus, reducing food intake and increasing energy expenditure via melanocortin pathways.
        
        Insulin: Also conveys adiposity signals to central circuits.
    - - ENS modulates motility, secretion, and blood flow; vagal afferents convey mechanical and chemical status to brainstem and hypothalamus for integrated responses.
      - Microbial metabolites (SCFAs, neurotransmitter precursors) influence appetite, mood, and central regulation of metabolism.
- - - - Polarization and morphology
        
        Neurons: Long axons minimize synapse count over distance; myelination increases conduction speed via saltatory conduction
        
        axon hillock concentrates voltage-gated channels to trigger action potential
        
        dendritic spines modulate synaptic strength
        
        Epithelial cells: Apical–basal polarity supports directional transport
        
        apical microvilli boost absorption
        
        basolateral Na⁺/K⁺-ATPase powers nutrient uptake via secondary active transport.
      - Cell to cell matrix communications
        
        Junctions: Tight barriers that can mechanically couple, or electrical/metabolic couple
        
        Integrins/ECM: Cells read stiffness and composition to adapt gene expression
      - Organelles function
        
        Muscle fibers: Dense sarcomeres, T-tubules for rapid Ca²⁺ signaling, sarcoplasmic reticulum for release/reuptake; mitochondria clustered near myofibrils for ATP supply.
        
        Secretory cells: Expanded rough ER and Golgi for protein synthesis and packaging andsmooth ER for steroid synthesis
    - - Epithelial tissue
        
        Types
        
        Simple vs. stratified
        
        squamous
        
        cuboidal
        
        columnar
        
        Barrier and transport:Tight junctions create selective paracellular barriers, transcytosis moves macromolecules; basement membrane provides structural support and signaling.
      - Connective Tissue
        
        ECM design
        
        Collagen I for tensile strength (tendon)
        
        collagen II for cartilage
        
        elastin for recoil (arteries)
        
        proteoglycans and glycosaminoglycans retain water and resist compression
        
        Specialized forms
        
        Bone: Mineralized matrix osteons with Haversian canals optimize strength and nutrient delivery.
        
        Cartilage: Avascular; chondrocytes in lacunae; resilient due to proteoglycan rich matrix.
        
        Adipose: Energy storage and endocrine signaling (leptin, adiponectin)
        
        Blood: Fluid connective tissue for transport and immunity.
      - Muscle Tissue
        
        Skeletal
        
        Fast vs. slow fibers; excitation–contraction coupling
        
        length–tension and force–velocity relationships determine performance.
        
        Cardiac
        
        Intercalated discs with gap junctions synchronize contraction
        
        pacemaker cells (SA node) generate rhythm
        
        calcium-induced calcium release.
        
        Smooth
        
        Calmodulin–MLCK pathway,plasticity for sustained tone in vessels and gut.
      - Nervous Tissue
        
        Neurons plus glia
        
        Astrocytes regulate synapses and blood–brain barrier
        
        oligodendrocytes/Schwann cells myelinate
        
        microglia handle immune surveillance
    - - Heart system
        
        Force generation: Spiral fiber orientation produces efficient wringing contraction; valve mechanics prevent backflow.
        
        Electrical conduction: SA → AV → His–Purkinje ensures timed chamber activation.
        
        Coronary circulation: High O₂ demand met by dense capillary bed and myoglobin; flow autoregulation matches workload.
      - Small intestine system
        
        Surface amplification: Plicae circulares → villi → microvilli produce hierarchical folding.
        
        Cell specialization
        
        Enterocytes absorb via transporters
        
        goblet cells secrete mucus
        
        Paneth cells release antimicrobials
        
        enteroendocrine cells coordinate digestion via hormones.
        
        Immune integration
        
        Peyer’s patches sample antigens
        
        tight barrier balances absorption and defense.
        
        Vascular/lymph coupling
        
        Capillaries drain to hepatic portal vein;
        
        lacteals carry chylomicrons.
    - - Scaling reality
        
        Surface area scales with length squared; volume with length cubed. As size increases, relative surface area drops, constraining diffusion-based exchange.
        
        Implication: Large organisms require specialized exchange structures and transport systems.
      - Exchange enhancement
        
        Fractal branching: Lungs (bronchial tree to alveoli)
        
        vasculature maximize area and minimize diffusion distance.
        
        Hierarchical folding
        
        Intestinal villi/microvilli increase area by orders of magnitude without huge volume cost.
        
        Thin barriers- Alveolar epithelium and capillary endothelium minimize diffusion path length.
      - Transport physics
        
        Fick’s law: Flux increases with surface area and concentration gradient, decreases with barrier thickness; tissues evolve to optimize these terms.
        
        Boundary layers and flow: Cilia, peristalsis, and blood flow reduce stagnant layers, maintaining gradients.
      - Trade-offs and constraints
        
        Strength vs. lightness-Bones balance mass and load via hollow shafts and trabecular networks.
        
        Protection vs. permeability-Skin defends but limits exchange; internalized lungs/gills solve this.
        
        Speed vs. endurance-Muscle fiber composition and tendon elasticity reflect ecological demands.
      - Convergent solutions
        
        Streamlined bodies in swimmers, gliding membranes in gliders, countercurrent exchangers in extremities and gills
        
        different lineages arrive at similar forms under similar functional pressures.
  - - - Relies primarily on external heat sources and behavioral adjustments (basking, seeking shade, choosing microhabitats) to set body temperature.
      - Low energetic cost for basal maintenance but performance (enzymatic rates, locomotion, digestion) varies with ambient temperature
      - many ectotherms use temporal or spatial thermoregulatory strategies to optimize function
    - - Produces the majority of body heat via sustained metabolic processes (high mitochondrial density, elevated basal metabolic rate).
      - Uses specialized tissues and hormones to raise metabolic heat production (thyroid hormones increase basal metabolism; sympathetic activity increases metabolic rate).
      - Provides stable internal temperature across a range of external temperatures, supporting high and sustained activity levels.
    - - Countercurrent arrangements can localize heat retention while permitting temperature control in peripheral tissues.
      - Microstructures (underfur, down feathers) trap air for additional insulation; piloerection or feather fluffing increases trapped air and effective thickness.
      - improved heat retention reduces cooling ability and can impair heat dissipation in warm conditio
    - - Vasodilation increases blood flow to peripheral skin, raising heat transfer to the environment; mediated by autonomic nerves and local metabolites (NO, adenosine).
      - Reduces skin blood flow to conserve core heat; mediated by sympathetic vasoconstrictor tone and local reflexes.
      - Countercurrent arrangements can localize heat retention while permitting temperature control in peripheral tissues.
    - - Heat loss via evaporation (sweating, cutaneous moisture, panting) removes latent heat of vaporization, effective even when ambient temperatures approach body temperature.
      - Mechanisms differ by clade
        
        eccrine sweating (many mammals), panting and tongue-flicking (birds, some mammals), cutaneous evaporation (amphibians)
      - Evaporative cooling is water-costly and thus constrained by hydration state
    - - Rapid, asynchronous muscle contractions produce heat without sustained work output
        
        ontrolled by hypothalamic centers and motor circuits.
      - Increases ATP turnover and O2 demand markedly; effective for acute cold defense but energetically expensive and cannot be sustained
    - - Brown adipose tissue (BAT) contains abundant mitochondria and uncoupling protein 1 (UCP1)
        
        dissipates proton motive force as heat rather than driving ATP synthesis.
      - Activated by sympathetic norepinephrine signaling
        
        important in neonates, small mammals, and some hibernators for rapid, sustained heat
    - - Arteries carrying warm blood run adjacent to veins returning cooler blood
      - heat transfers from arterial to venous blood, conserving core heat and minimizing loss at extremities.
      - Used in limbs, flippers, and gills to maintain core temperature while permitting peripheral cooling or minimizing ice formation.
    - - Reversible adjustments in physiology and biochemistry in response to prolonged environmental change
      - altered enzyme isoforms, membrane lipid composition (to preserve fluidity), hematologic adjustments (hematocrit, hemoglobin affinity), and changes in insulation density.
      - Behavioral plasticity (activity timing, habitat selection) complements physiological shifts
      - acclimatization improves performance but has energetic and time costs.
    - - Thermoregulation integrates neural (hypothalamic set-point, autonomic outputs), endocrine (thyroid hormones, catecholamines), and behavioral responses
      - effectors are coordinated to balance heat production, conservation, and loss.
      - Trade-offs include water versus heat balance (evaporative cooling vs. dehydration), oxygen/energy demand versus heat generation (shivering), and insulation versus cooling ability
    - - Arctic mammals: compact body shape, dense fur/blubber, countercurrent exchangers in extremities, seasonal metabolic upregulation.
      - Desert mammals: nocturnal behavior, high renal water conservation, efficient evaporative cooling with behavioral timing to avoid peak heat.
      - Reptiles: behavioral thermoregulation (basking in morning, retreating to shade midday), seasonal activity shifts
  - - - Maintains internal variables (temperature, pH, osmolarity, blood glucose, blood pressure, ion concentrations) within functional ranges through continuous sensing and corrective action.
      - Involves hierarchical control from local reflexes to central integration and requires energy to oppose entropy
    - - A physiologically determined target or narrow range used by integrators to compute error signals
      - modifiable by circadian rhythms, developmental stage, hormones, and environmental context; they are not fixed constants.
    - - Sttabilizing loop mechanism-sensor detects deviation → control center compares to set point → effector action reduces the deviation.
      - Ex: Glucose control- pancreatic β-cells sense high glucose → secrete insulin → increase muscle/adipose uptake and hepatic glycogen synthesis → blood glucose returns toward set point.
      - Properties- resists perturbations, produces graded responses, can include proportional and threshold components to avoid instability.
    - - amplifying loop for rapid completion
      - Mechanism- an initial change triggers responses that increase that change until an external terminating event occurs.
      - Ex: Hemostasis- local platelet activation and coagulation cascade rapidly amplify clot formation until repair or inhibitory factors stop the process.
      - Use is limited because amplification is destabilizing; systems that use it include built in termination conditions
    - - Sensor: transducer that detects physical/chemical change. Ex:thermoreceptors, baroreceptors, chemoreceptors
      - Control center: integrates inputs, compares to set point, issues commands Ex: hypothalamus, medulla oblongata, pancreatic islets
      - Effector: tissue or organ that carries out corrective action. Ex: sweat glands, skeletal muscle, blood vessels, liver, kidney
    - - achieving stability through change by shifting operating ranges or set points to meet predicted demands.
      - Ex: circadian shifts in hormone rhythms (morning cortisol), stress-induced HPA activation that temporarily raises glucose availbility
    - - Neural signaling: fast, precise, short-duration responses (reflex arcs, autonomic adjustments).
      - Endocrine signaling: slower-onset, long-duration, widespread effects (thyroid hormones, cortisol).
      - Local intrinsic control: tissue-level autoregulation complements systemic commands.
      - Feedforward mechanisms: anticipatory adjustments that reduce corrective lag (salivary/insulin responses to sight or smell of food)
    - - Time constants and delays (sensor transduction, signaling, effector kinetics) shape loop behavior
      - Delays can cause oscillation or overshoot if not buffered.
      - controller “gain” determines response strength to error but effectors have limits and refractory periods; excessive gain risks instability.
      - controller “gain” determines response strength to error but effectors have limits and refractory periods; excessive gain risks instability.
  - - - Energy expenditure per unit time, commonly estimated from oxygen consumption or CO2 production; reflects whole animal ATP turnover supporting maintenance, activity, growth, and thermoregulation
    - - The minimal rate of energy use for an endotherm measured at rest, fasting, in a thermoneutral environment with minimal stress
      - reflects baseline energy required for cellular maintenance, ion pumping, protein turnover, and minimal organ function
      - compares energetic costs between species and across physiological states; deviations indicate pathology, hormonal shifts
    - - The minimal metabolic rate for an ectotherm measured at a specified ambient temperature and at rest
      - because ectotherm metabolism depends on temperature, SMR is always temperature-specific and not directly comparable to BMR without correction for temperature effects
    - - Metabolic rate scales sublinearly with body mass
      - mass-specific metabolism (energy per gram) declines as size increases
      - small animals have higher surface area-to-volume ratios and this greater relative heat loss and higher turnover needs to maintain gradients and tissue function
      - high mass-specific BMR in small mammals drives rapid food intake, high heart/respiratory rates
    - - Also called the thermic effect of food
      - energy expended for mechanical and biochemical processing of a meal: secretion of digestive enzymes, active transport during absorption, protein turnover, and tissue synthesis.
      - SDA magnitude varies with meal size and macronutrient composition