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Announcements

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Announcements

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    1. 1 Announcements Bring PhysioEx for Human Physiology to Lab tomorrow!!! (if you don’t have it yet, get it!) Read in Chapter 1: Conceptual introduction (pg 1-2) Background on facilitated diffusion (pg 5) Background on Osmosis (pg 7) Pick up lab handout in class today and read before lab tomorrow

    2. 2 Respiration and Gas Exchange (2) Gills and Lungs

    3. 3 Countercurrent exchange

    4. 4 Gill Ventilation Animals use either PUMPS or PADDLES E.g. decopod crustaceans “Scaphognathite” This is a paddle that pulls water over gills Fish use pumps

    5. 5 Opercular pumping in fish Gill chamber is rigid (opercular cavity) Can be sealed by a flap (operculum) Bottom of the opercular chamber is muscular and can be raised or lowered Pump cycle: Mouth open, operculum closed Bottom of chamber drops, chamber fills Mouth closed Bottom of chamber is raised, squeezing water out through operculum

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    7. 7 Gill ventilation is very important Maximizes concentration gradient between water and blood Blood holds more O2 than water does: Ventilation rate must be 6 – 20 X circulation rate in order to keep up!

    8. 8 Ram ventilation Some very active, fast big fish skip pumping altogether Swimming fast with mouth open is sufficient to ventilate gills PRO: Saves them the cost of pumping (For some big active fish they probably couldn’t keep up anyway) CON: They always have to swim Or suffer very reduced oxygen transport

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    10. 10 Gas exchange in terrestrial animals Arthropods Mammals Reptiles Birds

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    12. 12 Insect tracheal system Branching air passages reach within microns of each respiring cell Trachea, tracheoles, air capillaries Insects blood is not important in oxygen transport it does transport nutrients, hormones, and heat! Ventilation is produced by activity - “abdominal pumping” Flight or running. Relies on diffusion of O2 through air Possibly limitation on insect size?

    13. 13

    14. 14 Carboniferous gigantism in insects: Many gigantic arthropods evolved during the Carboniferous Period Dragonflies with 72 cm wingspan Giant spider (34 cm body) Scorpions over 60 cm long All went extinct in the Permian Oxygen [] was ~ 35% PO2 was 76% higher! With higher D[ ], diffusion works faster over greater distances Maybe this is part of why insects got so big!!

    15. 15 Mammalian lungs

    16. 16 Mammalian lungs FUNCTION Lungs are filled through negative pressure Diaphragm and external intercostal muscles contract Expands volume of chest cavity Ideal Gas Law: PV = nRT Increasing volume decreases pressure Air always flows from high to low pressure Reduced pressure creates suction

    17. 17 Mammalian Lungs Lungs are TIDAL (air flows in two directions) Causes dead space … some of the inhaled air never comes into contact with respiratory surfaces This is somewhat inefficient!

    18. 18 Alveoli and Surfactant PROBLEM: Water molecules lining alveolus want to interact with each other Deflated alveoli susceptable to collapse due to force of surface tension Inflated alveoli less influenced by surface tension – tend to stay inflated

    19. 19 Alveoli and Surfactant SOLUTION: Surfactant! Lung produces phospholipids to line alveoli (= surfactant) Lipid lining reduces surface tension (water/water interactions) Thickness of surfactant (hence how well it works) increases as alveoli shrink Pressure to inflate alveoli: With surfactant: 4 mm torr Without surfactant: 21 torr

    20. 20 Respiratory Distress Syndrome (RDS) Leading cause of death and illness in infants, especially premature infants 2 surfactant production pathways One develops 22-24 weeks The other develops at 35 weeks (very soon to birth) If type II alveolar cells do not produce enough surfactant: Lungs collapse easily Hard to inflate – strains diaphragm

    21. 21 Reptilian Lungs Similar to mammalian Not as structurally complex Big bag with sac-like depressions in the wall Not nearly as much surface area as mammalian Generally have less demand for oxygen Lower metabolic needs No diaphragm – ribcage expanded by intercostal muscles alone Movement of limbs also helps expand and contract

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    23. 23 Bird lungs Same concept as mammalian Lots of surface area and blood vessels Fundamentally different circuitry of air Respiratory surfaces are TUBES, not SACS (parabronchi) Multiple sacs serve as bellows to push air through tubes Constant, unidirectional air flow over respiratory surfaces All inhaled air travels through tubes, no dead space Achieves rapid diffusion through better maintenance of the “concentration gradient”. Takes two breaths for air to make the full circuit

    24. 24 Bird lungs Blood is flowing toward YOU “Cross current” exchange

    25. 25 Bird lungs First breath – Inhalation Air into caudal air sac Exhalation Air pushed over respiratory surfaces (Parabronchi) Second breath Inhalation Air pulled into cranial air sac Exhalation Air pushed out

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    27. 27 Ventilation and Locomotion GENERAL PRINCIPLE: Locomotion = free ventilation! Gills Swimming with mouth open = Ram ventilation Sharks and other big fast fish Insect trachea Flapping wings increases air circulation Flying insects Lungs Synchronous breathing & locomotion Kangaroos breathe on each hop Birds and Bats breathe with each flap of wings Galloping mammals breathe with each stride These muscular contractions help circulate air through lungs more cheaply!

    28. 28 Control of Ventilation Ventilation rate is highly tuned to oxygen demand Especially so in birds and mammals (animals with high rates of oxygen demand) Respiratory Control Center In the Medulla Oblongata region of brain stem Controls Breathing rate Breathing depth Constriction of Respiratory passages

    29. 29 Sensing O2 demand is indirect: Signal is CO2 and pH! Sensors are located: Bronchioles Carotid arteries to brain in Aorta near the heart In the medulla itself (detect pH in brain fluid) Neurons from these centers run to the Respiratory Center Open respiratory passages Increase ventilation rate Increase ventilation depth

    30. 30 The Respiratory Center

    31. 31 Control of Respiration

    32. 32 Thought questions: What happens when you hold your breath? If you take several deep breaths in rapid succession, what do you think should happen to your ventilation rate? What should breathing into a paper bag do to your ventilation rate?

    33. 33 Announcements Bring PhysioEx for Human Physiology to Lab tomorrow!!! (if you don’t have it yet, get it!) Read in Chapter 1: Conceptual introduction (pg 1-2) Background on facilitated diffusion (pg 5) Background on Osmosis (pg 7) Pick up lab handout in class today and read before lab tomorrow

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