Chapter 42 Continued Respiratory System

Gas Exchange Moist membrane

Comparative Study Protists: entire cell surface Worms: long, thin shape maximizes surface area; stay in moist area to keep exchange surface wet Animals with gills: aquatic animals; H2O has lower O2 concentration than air Sea star: dermal gills over whole body Polychaete annelids: parapodia -- extensions from each segment Fish, mollusks: finely-divided membrane in localized area

Respiratory surfaces are: • evaginations • invaginations Which are each of these?

Ventilation Movement of medium over exchange surface Fish expend a large amount of energy for this Blood vessel design enhances exchange Countercurrent exchange strategy extracts more oxygen from water by diffusion.

Countercurrent vs. concurrent flow

Insect tracheal system Gases diffuse faster in air than in water; Don’t have to ventilate surfaces as thoroughly Respiratory surface are continually desiccated

Lungs Highly vascularized evaginations Land snails: internal mantle is respiratory surface Spiders: booklungs Frogs: simple balloon-like lungs; limited surface area; positive pressure breathing Mammals: highly subdivided; very large surface area

Negative pressure breathing Intercostal muscles

Lung Air Volumes Determined using a spirometer Tidal: normal, quiet ventilation; 500 ml Vital capacity: max. air lungs inhale/exhale 3400 - 6000ml Residual: remaining air following forced exhalation; about 350ml

Avian ventilation: most complex method; one-way air flow - no gas exchange in air sacs > act as bellows to keep air moving Parabronchi: parallel tubes

Control Centers • Medulla oblongata / Pons • O2 concentration affects - Monitors pH of blood and cerebrospinal fluid • increase in CO2 decreases pH; medulla increases tempo and depth of breathing • O2 concentration affects breathing only if it’s in a severely low concentration • aortic and carotid sensors stimulate centers to pick up rate and depth of breathing • Inhalation: neg. feedback affected by stretch receptors in lungs

Diffusion of Gases Partial pressures PO2 = partial pressure of oxygen; O2 = 21% of atmosphere; therefore PO2 = 160 mm Hg (0.21 x 760 mm Hg = 160 mm Hg) PCO2 = 0.23 mm Hg (0.0003 x 760 mm Hg) Gases diffuse from areas of high partial pressure to areas of low partial pressures

Blood arriving at lungs has lower PO2 and a higher PCO2 than air in alveoli Systemic capillaries: gradient favors diffusion of CO2 into blood

Respiratory pigments Carry oxygen in most organisms because oxygen is not very soluble in water Contain metal atoms; give color to the pigments Hemocyanin: arthropods and mollusks Metal atom is copper; imparts a blue color O2 dissolved directly in plasma; no cells

Hemoglobin Four subunits; contain one heme protein each; iron atom in center of each heme Binding of O2 to Hb is reversible Oxyhemoglobin (HbO2) The first bound O2 induces shape change in Hb which increases affinity for next three O2 (cooperativity) Unloading of O2 from one heme induces conformational change in others which stimulates unloading from the other three

Dissociation curve reveals cooperativity • heme groups change conformation as O2 loads/unloads; a change in affinity for O2 Bohr shift reveals a decrease in oxygen affinity for Hb if pH decreases (important for release of O2 in peripheral tissues)

Carbon Dioxide transport Transported in three different forms Dissolved in plasma (7%) Bound to Hb -- carbaminohemoglobin -- (23%) As bicarbonate ion -- HCO3– (70%) Carbonic anhydrase facilitates conversion to bicarbonate once CO2 diffuses into RBC Assists in buffering blood Bicarbonate diffuses out of RBC in exchange for a chloride ion (Cl–): chloride shift H+ attach to Hb and other proteins: results in the dissociation of O2 from Hb

Cl- Cl-

Deep-diving mammals/oxygen Seals, dolphins, whales Weddell seals Can store 2X amt. of oxygen as human/kg. of weight More myoglobin concentration in muscles than humans have Seals have 70% O2 load in blood vs. 51% in human 5% O2 in lungs vs. 36% in human lungs Seals have 2X blood/kg as human; also large spleen (24 liters!!) Human spleens stores about 200 ml blood (50 ml - 1,000 ml) Myoglobin stores 25% O2 vs. 13% in humans Adaptations support large O2 reserve

More diving adaptations Adaptations to conserve oxygen Diving reflex Slows pulse and O2 consumption Blood rerouted mostly to brain, spinal cord, sense organs, adrenal glands Rerouting causes muscles to consume oxymyglobin and shift over to anaerobic ATP production; extends dives.

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