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Animal physiology (Circulation and Gas Exchange (Gas Exchange Across…

- - - - Body plan w/ cells touching environment
      - Circulatory system
    - - Gastrovascular cavity - digests and distributes substances throughout body
      - Cnidarians; flatworms
      - Flat body optimizes exchange by increasing area & decr. diffusion distances
    - - heart - powers circ by using metabolic energy to elevate BP
      - Circ syst connects body cells to exchanging organs
      - Open circ syst - body cells bathed in hemolyph (interstitial fluid)
        
        Heart contractions pump hemolyph thru vessels into sinuses
        
        Relaxation draws hemolyph back in thru pores
        
        Less costly than closed syst
      - Closed circ syst - blood confined to vessels
        
        Chem exchange occurs betw blood & interstitial fluid, and betw interstitial fluid & body cells
        
        Higher BP => better delivery of O2 and nutrients for larger, more active animals
    - - cardiovasc syst - circ syst of vertebrates
      - arteries - carry blood from heart to organs
        
        arterioles - smaller branches of arteries
        
        capillaries - micro vessels w/ thin, porous walls
        
        capillary beds - networks of capillaries that infiltrate tissues and deliver O2 and nutrients to every cell in body
      - veins - vessels carry blood to heart from organs
        
        venules - smaller branches of veins
        
        capillaries
        
        capillary beds
      - Arteries and veins distinguished by direction of blood flow
      - atria - chambers in heart that receive blood
      - ventricles - chambers in heart responsible for pumping blood out
      - Single Circulation
        
        2 chambers
        
        Bony fishes, rays, sharks
        
        single circ - deox blood goes from heart to lungs, then directly to rest of body
        
        Not very efficient
      - Double Circulation
        
        2 circuits (heart => lungs, heart => body)
        
        Right side of heart delivers blood to lungs
        
        Left side of heart delivers blood to body
        
        pulmonary circuit - capillaries only in lungs
        
        pulmocutaneous circuit - capillaries in lungs and skin (reptiles)
        
        systemic circuit - blood going from heart to body and back
        
        BP higher than single circuit, more efficient
      - Evolutionary Variation in Double Circulation
        
        3 chambers - amphibians; allows them to adjust circulation underwater and breathe solely thru skin
        
        3 chambers w/ incomplete septum - turtles, snakes, lizards; enables ctrl of amt of blood going to lungs and body
        
        4 chambers - crocodilians; pulmonary & systemic valves connected, allowing them to shunt blood flow away from lungs when underwater
        
        Birds & mammals can’t vary blood flow to lungs w/o varying blood flow to rest of body
        
        Endotherms use 10x as much energy as = sized ectotherms
        
        4 chambered heart arose independently in mammal and bird ancestors; convergent evolution
  - - - cardiac cycle - Pumps blood @ contraction (systole); fills blood when relaxes (diastole)
      - cardiac output - V of blood each ventricle pumps/min
        
        heart rate - BPM
        
        stroke volume - amt of blood pumped in each ventricle contraction
        
        HR and stroke vol affect cardiac output
      - 4 valves in heart prevent backflow, move blood in right direction
        
        atrioventricular (AV) valves - betw atria & ventricles
        
        semilunar valves - @ 2 exits of heart: L ventricle=>aorta & R ventricle=>pulmonary artery
        
        Valves pushed open by pressure gen’d during ventricle contractions
      - heart murmur - sound produced when blood squirts backward thru defective valve
    - - Some cardiac muscles autorhythmic
      - sinoatrial (SA) node - pacemaker; sets rate & timing for all cardiac muscle cells to contract
      - SA node gens electric impulses that are conducted to skin; can be picked up by electrocardiogram (ECG/EKG)
      - Impulses make atria contract 1st
      - Atrioventricular (AV) node - relay pt, delays SA impulses by 0.1 sec; allows for atria to empty completely b4 ventricles contract
      - Phys cues can alter heart tempo
        
        Sympathetic nervous syst speeds up pacemaker
        
        Parasympathetic syst slows down pacemaker
        
        Hormones like epinephrine (fight-or-flight)
        
        Body temp
  - - - Blood vessel central lumen lined w/ endothelium (single layer flat epithelial cells)
      - Capillaries only endothelium and basal lamina
      - Exchange betw blood and interstitial fluid @ capillaries bc they’re the only vessels thin enough to allow it
      - Veins & arteries: endothelium => Smooth muscle => connective tissue
      - Arteries: thick & strong, recoil whenheart relaxes to keep BP high
      - Veins: lower BP, don’t need thick walls; contain valves to prevent backflow
    - - Blood slows down @ capillaries
      - Total cross section area of capillaries bigger than any other part of circ syst
      - Blood speeds up after entering veins, but BP is lower than arteries
    - - Changes in BP During Cardiac Cycle
        
        Systolic pressure - BP @ highest pt when heart contracts during ventricular systole
        
        pulse - rhythmic bulging of artery walls w/ heartbeat
        
        Pressure surge partly bc of narrow arteriole openings
        
        diastolic pressure - arteries snap back; lower BP when ventricles relax
      - Regulation of BP
        
        Homeostasis regs arterial BP by alt’ing arteriole diameter
        
        vasoconstriction - when muscles in arterioles contract, they narrow; increases BP
        
        vasodilation - arteriole diameter decreases when muscles relax; decrease BP
        
        Nitric oxide (NO) induces vasodilation; endothelin induces vasoconstriction
        
        Vasodilation/constriction work w/ heart to ensure blood flow
      - BP & Gravity
        
        BP affected by gravity
        
        BP must overcome gravity to reach brain
        
        Animals w/ longer necks need higher BP
        
        Veins use valves and smooth muscle to return blood from legs to heart against gravity
    - - Blood can be diverted from 1 destination to another
      - constriction/dilation and precapillary sphincters used to alter blood flow to capillary beds
      - Reg’d by nerve impulses, hormones, & chems
      - 2 forces ctrl mvmnt of fluid betw capillaries and tissues
        
        BP drives fluid out of capillaries
        
        Blood proteins pull fluid back in
      - osmotic pressure - pressure produced by diff in solute concentration across membrane; dissolved proteins resp for much of this
      - Capillaries more likely to lose fluid than gain
    - - Fluid & proteins lost from capillaries return to blood via lymphatic syst
      - lymphatic system - incl network of belles intermingled among capillaries of CV syst as well as larger vessels
      - lymph - fluid from capillaries w/ ~ same comp as interstitial fluid
      - Lymphatic syst drains into larger CV veins @ neck
      - Valves, vessel wall contractions, & skel muscle contractions help move lymph
      - edema - fluid accumulation in tissues caused by disruption in lymph flow
      - lymph nodes - filter lymph, multiply WBC, & trap circulating cancer cells
  - - - plasma - liquid matrix that suspends blood cells
      - Plasma
        
        Dissolved ions buffer blood, maintain osmotic balance, affect comp of interstitial fluid, & play role in muscle/nerve activity
        
        Proteins act as buffer and help reg osmotic balance; antibodies;
        
        Apoliproteins escort lipids
        
        Fibrinogens - clotting factors that help plug leaks in blood vessels
        
        Carry nutrients, metabolic wastes, respiratory gases, and hormones
      - Cellular Elements
        
        platelets - cell frags of bone marrow involved in clotting
        
        erythrocytes - RBC; lack nuclei (make space for hemoglobin), shape increases surface area, lack mitochondria (anaerobic respiration)
        
        sickle-cell disease - alters shape of RBC; can get lodged in vessels
        
        leukocytes - WBC; fight infections; phagocytes, B-cells, T-cells
      - Stem Cells & Replacement of Cellular Elements
        
        stem cells - cells dedicated to replenishing blood cell pop
        
        Found in red marrow in bones
        
        When stem cell divides, one stays stem cell & other takes on spec function
        
        erythropoietin - hormone made by kidneys to stimulate gen of more RBCs
      - Blood Clotting
        
        fibrinogen - inactive coagulant (fibrin)
        
        thrombin - turns fibrinogen into fibrin
        
        Positive feedback causes thrombin to catalyze more thrombin until complete clot
        
        hemophilia - disease char’d by excessive bleeding & bruising
        
        thrombus - clot w/in blood vessel, blocking flow of blood
    - - Atherosclerosis, Heart Attacks, & Stroke
        
        atherosclerosis - hardening of arteries bc of accumulation of fatty deposits
        
        cholesterol - important role in atherosclerosis; maintain membrane fluidity in cells
        
        Low-density lipoprotein (LDL) - delivers cholesterol to cells for membrane production
        
        High-density lipoprotein (HDL) - collects excess cholesterol for return to liver
        
        Ppl w/ high ratio of LDL to HDL have increased risk of atherosclerosis
        
        Heart attacks and strokes can result from atherosclerosis; plaque @ hard vessel site can break off and get lodged in major artery in heart or brain, cutting off circulation and killing tissue
      - Risk Factors & Treatment of CV Disease
        
        Leading healthy lifestyle decreases risk
        
        Statins can lower LDL
        
        Aspirin can help prevent recurrence of heart attacks
        
        C-reactive protein (CRP) can indicate risk of CV disease
        
        hypertension - high BP; contributes to heart attack & stroke
  - - - partial pressure - pressure exerted by partic gas in mix of gases
      - Can be used to predict net mvmt of gas @ exchange surface
    - - air is thinner than water and easier to move thru small passageways
      - O2 dissolved in water harder to exchange; more demanding & less O2 available
    - - Where orgs do gas exchange
      - Always moist bc of plasma
      - Gas exchange is fast when area for diffusion is large and path for diffusion is short
      - Resp surfaces tend to be large & thin
      - In some orgs, skin is resp organ
      - Most animals, body lacks surface area needed for exchange; resp organs extensively folded & branched
    - - outfoldings of body surface suspended in water
      - Total surface area oft > rest of body’s exterior
      - ventilation - mvmt of resp medium over resp surface; maintains partial pressure of O2 & CO2 nec for exchange
      - Orgs need to move their gills or move water to help ventilation
      - countercurrent exchange - exchange of substance/heat betw 2 fluids moving opposite directions; makes O2 flow from water to blood along entire length of capillary
    - - tracheal system - network of sir tubes that branch throughout body
      - Largest tubes (tracheae) open to outside; branches inside contact most cells to exchange gases
      - Doesn’t need to use circ syst for gas exchange
      - Big insects move limbs to expand/compress air tubes
    - - Localized resp organs w/ folds & typically subdivided pockets
      - Needs circ syst to connect gas exchange to rest of body
      - Amphibians (small lungs & skin), reptiles (&birds), mammals, some fish
      - Mammalian Resp Systs: A Closer Look
        
        Lungs in thoracic cavity
        
        Nostrils => nasal cavity => pharynx => larynx (w/ vocal chords/folds) => trachea => bronchi => bronchioles => alveoli
        
        Looks like inverted tree w/ trachea as trunk
        
        Mucus in lungs trap particle contaminates & cilia move it up pharynx to be swallowed
        
        WBC patrol alveoli & engulf foreign particles
        
        sulfactant - coats alveoli & reduces surface tension to keep them from collapsing
  - - - positive pressure breathing - inflate lungs w/ forced air flow
    - - 8/9 air sacs on sides of lungs keep air flowing
      - parabronchi instead of alveoli
      - 2 cycles of inhalation/exhalation
      - When breathing, pass air over gas exchange surface in 1 direction
      - Incoming fresh air doesn’t mix w/air that already did gas exchange
    - - negative pressure breathing - pull air into lungs rather than force it; inhalation active, exhalation passive
      - Expand thoracic cavity w/ rib muscles & diaphragm
      - Double membranes around lungs: inneradheres to outside of lungs, outer adheres to wall of thoracic cavity
      - During exercise, muscles in neck, back, & chest increase vol of thoracic cavity by raising rib cage
      - tidal volume - vol of air inhaled/exhaled w/ each breath
      - vital capacity - tidal vol during max inhalation/exhalation
      - residual volume - air that remains after forced exhalation
      - Inhalation mixes fresh air w/ O2-depleted air
    - - breathing ctrl centers - neural circuits in medulla oblongata that est breathing rhythm
      - CO2 w/ water makes carbonic acid
      - Medulla uses pH as an indicator of blood CO2 concentration
      - When O2 drops low, , sensors in aorta and carotid arteries send signal to breathing ctrl centers, which respond by increasing breathing rate
  - - - Inhale: fresh air mixes w/ air left in lungs => net diffusion moves O2 into cells and CO2 into alveoli => blood exits lungs w/ same gas values as alveoli => blood returns to heart & pumped they syst circuit
      - In syst capillaries: net diffusion of O2 out & CO2 into blood (mitochondria of cells take up O2) => blood returns to heart & pumped into lungs => exchanges CO2 for O2 across alveoli => exhale CO2
    - - O2 has low solubility in water; issue for animals w/ circ syst
      - respiratory pigments - proteins that transport O2, oft contained w/in spec cells
      - Increase amt of O2 carried in circ; decreases nec cardiac output
      - Metal bound to protein gives it distinct color (iron in hemoglobin)
      - 4 hemoglobin = 4 O2 molecules held; reversible bond
      - When there is less PO2 in tissues (when cells use more O2 during exercise), hemoglobin dumps more O2
      - Bohr shift - low oH decreases affinity of hemoglobin for O2
      - Carbon Dioxide Transfer
        
        CO2 diffuses into RBC => H+HCO3
    - - Lots of blood for storing O2
      - myoglobin - O2-storing protein in muscles; hi concentration in diving mammals
      - Swim/glide w/ little muscular effort
      - HR and O2 consumption decrease; most blood routed to CNS & adrenal glands
      - When cells deplete of O2, get ATP from fermentation
      - All mammals have diving reflex: HR & blood flow decrease
- - - - osmolarity - unit of measure for solute concentration; # of moles of solute/L of solution
      - isoosmotic - 2 solutions w/ same osmolarity
        
        Water crosses membrane @ = rate in both directions; no net mvmt
      - hyperosmotic - higher concentration of solutes betw 2 solutions
      - hypoosmotic - more dilute of 2 solutions
    - - 2 ways to maintain water balance
        
        osmoconformer - to be isoosmotic w/ surroundings (always marine animals)
        
        osmoregulator - ctrl internal osmolarity indep of external environ; allows animals to live in freshwater/terrestrial conditions or move betw habitats
      - Osmoconformers' habitats stable
      - Osmoregulators must discharge excess water in hypoosmotic environ; must take in water in hyperosmotic environ
      - stenohaline - when animals can't tolerate extreme changes in osmolarity (most animals)
      - euryhaline - when animals can survive large changes in osmolarity (barnacles, salmon)
      - Freshwater Animals
        
        All fish hyperosmotic; drink almost 0 water & excrete lots of dilute urine, take up salts from environ thru gills
        
        Salmon move from fresh to salt water; pump salt out like marine fish
      - Shark tissues have hi concentration of urea; considered osmoconformers even tho have lower salt concentration than seawater
      - Animals that Live in Temporary Waters
        
        dedication - extreme dehydration
        
        anhydrobiosis - dormant state some animals enter when habitats dry up
        
        Tardigrades & some round worms; contain lots of sugars when dormant
      - Land Animals
        
        Subject to dehydration
        
        Adaptations: exoskeleton, snail shells, keratinized skin cells, nocturnality
        
        Lose Water by urine, feces, skin, & gas exchange organs; must drink and eat moist food
    - - Active transport
      - Minimizing osmotic diff beta body fluids & surrounding environ decreases energy cost of osmoreg
    - - Most animals do indirect osmoreg by managing solutes content of internal body fluid
      - transport epithelia - layer(s) of epithelial cells spec'd for moving partic solutes; typ tubular networks w/ extensive surface areas
      - Also oft function in disposing metabolic wastes
  - - - Ammonia
        
        Can only be tolerated @ very low concentrations
        
        Most common in aquatic species
      - Urea
        
        Product of metabolic cycle, ammonia+CO2
        
        Low toxicity
        
        Higher energy cost
        
        Terrestrial animals & some marine species
      - Uric Acid
        
        Rel nontoxic
        
        Doesn't dissolve in water well, so excreted as paste w/ little water loss
        
        More energetically expensive
        
        Insects, land snails, reptiles (incl. birds)
    - - Species' phylogeny affects excretion
      - Where animal lives affects form of wastes
      - If it had a permeable or impermeable shell and couldn't/could get rid of wastes
      - Amt of waste produced depends on animal's energy budget
        
        Endotherms eat more and produce more Nitrogenous wastes
      - Wastes linked to diet
        
        Predators excrete more wastes than animals who rely on lipids/carbs
  - - - Body fluid contacts membrane of transport epithelium
      - Hydrostatic pressure drives filtration
        
        Cells, proteins, other large molcs. can't crosss membrane & remain in body fluid while water & small solutes cross membrane
        
        filtrate - produced solution
        
        reabsorption - recovers useful molcs. & water from filtrate to return to body fluids
        
        secretion - adding nonessential solutes/wastes to filtrate by active transport
      - Excretion - filtrate released from body as urine
    - - Protonephridia
        
        Excretory syst of flatworms; form network of dead-end tubules that branch thru-out body
      - Metanephridia
        
        Organs that collect fluid directly from coelom in annelids
      - Malpighian Tubules
        
        Organs in arthropods that remove wastes & function in osmoreg
      - Kidneys
        
        Function in osmoreg & excretion in vertebrates & some other chordates
        
        Consist of tubules arranged in org'd manner & closely assoc'd w/ network of capillaries
        
        Produces urine => travels down ureters => stored in urinary bladder => exit thru urethra
        
        renal cortex and medulla - have tightly packed excretory tubules which carry & process filtrate produced from blood entering kidney; nearly all fluid reabsorbed into blood vessels & leaves
        
        renal pelvis - collect remaining fluid as urine inside kidney b4 exiting thru ureter
        
        nephrons - processes filtrates
        
        cortical nephrons - 85% of all kidney's nephrons
        
        juxtamedullary nephrons - essential for production of urine that is hyperosmotic to body fluids
        
        glomerulus - long tubule w/ ball of capillaries
        
        Bowman's capsule - cup-shape swelling surrounding glomerulus
        
        BP forces fluid from blood in glomerulus into lumen of Bowman's cap
        
        proximal tubule, loop of Henle, distal tubule - filtrate passes thru these regions to be processed
        
        collecting duct - receives processed filtrate from nephrons and transports to renal pelvis
        
        afferent/efferent arterioles come to/leave nephrons, converge @ capillaries of glomerulus to form peritubular capillaries, which surround proximal/distal tubules
        
        vasa recta - capillaries that serve renal medulla
  - - - proximal tubule - reabsorption of ions, water & nutrients
        
        Keeps balance of bodily pH
        
        Materials to be excreted become concentrated
        
        Drugs & toxins processed in liver into interstitial fluid is secreted by transport epithelium into lumen of proximal tubule
      - Descending Limb of loop of Henle
        
        aquaporin - proteins that make transport epithelium freely permeable to water; creates water channels
        
        Almost no channels for small solutes so they have low permeability
        
        Osmolarity of interstitial fluid increases progressively from outer cortex to inner medulla of kidney, making it hyperosmotic; makes filtrate lose water and increases solute concentration
      - Ascending Limb of Loop of Henle
        
        Thin segment: concentrated NaCl diffuses out of tubule, helping maintain osmolarity of fluid in medulla
        
        Thick segment: active transport of NaCl into interstitial fluid, making filtrate more dilute
      - Distal tubule
        
        Secretes K+ & reabsorbs NaCl to reg concentration in body fluid
        
        Ctrl'd secretion of H+ & reabsorption of HCO3 to reg pH
      - Collecting Duct
        
        Does final processing of filtrate to form urine
        
        Hormonal ctrl of permeability & transport determines extent of concentration of urine
    - - Urine produced by kidneys is hyperosmotic
      - Concentrating Urine in Mammalian Kidney
        
        Large amt of water & salt reabsorbed from filtrate as it flows thru proximal tubule
        
        Vol decreases but osmolarity remains ~ same
        
        Highest osmolarity @ elbow of loop of Helne; maxes diffusion of salt out of tubule
        
        Countercurrent exch in loop of Henle actively transports salt from filtrate (countercurrent multiplier syst)
        
        Uses a lot of energy, thus has 1 of highest metabolic rates of any organ
  - - - Antidiuretic Hormone
        
        vasopressin - antidiuretic hormone (ADH); ctrls permiability of collecting duct epithelium; increased permeability increases water reabsorption; response to low salt or water in body
      - Renin-Angiotensin-Aldosterone Syst (RAAS) - involves juxtaglomerular apparatus (JGA), a spec'd tissue consisting of cells and around afferent arteriole
        
        JGA releases renin to initiate seq of steps that cleave plasma protein antiotensinogen => angiotensin II
        
        Happens when BP or vol drops
        
        Angiotensin II - raises BP by constricting arterioles and stimulates adrenal glands to release aldosterone
        
        aldosterone - causes distal tubules & collecting duct to reabsorb more Na & water, raising BP
        
        Drop in BP & vol => renin release => rise in BP & vol => reduce release of renin
      - Coordination of ADH & RAAS Activity
        
        ADH responds to increase in blood osmolarity (e.g. dehydration)
        
        RAAS for when both salt & body fluids lost (e.g. major wound or diarrhea)
        
        Partners in homeostasis
        
        atrial natriuretic peptide (ANP) - opposes RAAS; released in response to increase in BP & vol, inhibits release of renin