1. This is wrong. This book says that vertebrates use Hb & arthropods use hemocyanin (Cu-based) as their respiratory pigment. 2. Hmm… Zee insect obviouzly ‘as trrouble sustaining aerrobic rezpiracion in zee wadairr. 3. This insect must be an endotherm with a high BMR & high O2 demand. 4. I think maybe the insect stores O2 in this way. The aquatic air-breathing insect Notonecta has tracheal cells (cells lining the respiratory passages) that contain hemoglobin. What advantage would this metallo-protein serve in a diving, air-breathing insect?

Learning Objectives: Gas Exchange in Animals (2/23/09) Describe the requirements for a respiratory surface, using examples. Describe countercurrent exchange of e.g. gases. Discuss the advantages and disadvantages of air as a respiratory medium. Contrast the mechanics of respiration in a variety of air-breathing vertebrates. Describe the structure and function of the human respiratory system. Explain how breathing is controlled in humans. Describe the mechanism of gas exchange and the factors that affect its rate. Discuss the function of Hb as a respiratory protein, esp. in response to regulatory factors. Describe the mechanism of CO2 transport, and the significance of the enzyme carbonic anhydrase.

Gas Exchange in Animals Describe the 4 functional processes involved in most animal respiration. Compare to gas exchange in plants.

Respiratory Organs Identify each type of respiratory adaptation, and relate to lifestyle. Compare (if applicable) ventilation, gas exchange at the respiratory organ, transport of gases, and gas exchange at the tissues.

Challenges of Gas Exchange related to Environment Air vs. Water: 20X more oxygen in air than in water (at the same temp.) Diffusion of gas molecules is more rapid in air Air is less viscous than water ventilation (air) requires 1/10 the energy of water breathing

Diversity in gills Describe the dual function of gills in bivalves and polychaetes. Two of these animals utilize structures for body movement in gas exchange as well. Describe. p. 983

Gill Structure in Fish p. 983 If fish gills are so efficient at gas exchange, why can’t most fish survive out of water?

Gill Ventilation in Fish In order to have bulk flow of water over the respiratory surface, what must be created? Discuss the negative pressure component in gill ventilation. Discuss the positive pressure component of gill ventilation.

Countercurrent Mechanism for Gas Exchange p. 984 Nearly 80% of the O2 is removed from the water as it passes over the gills. Atmospheric Is this more or less efficient than gas exchange at the lungs? Why ? Draw a similar picture showing blood flow and water flow in the same direction. How would oxygen diffusion change?

Tracheal System in Insects (May serve as storage reserve) Each cell has a nearly direct means of gas exchange via the tracheal system (2-4 spiracles on the thorax, 6-8 on abdomen). What is the advantage of such a system for a small, fast animal? Do insects have respiratory pigments in their hemolymph? Significance? p. 984

The abdomen in large, active insects like grasshoppers, is used like a bellows to force air out of tracheae with contraction of skeletal muscles. What happens when these muscles relax? The experiment illustrated (first performed by the insect physiologist Gottfried Fraenkel) shows that there is a one-way flow of air through the grasshopper. The liquid seals at either end of the tubing move to the right as air enters the first four pairs of spiracles in the thorax and is discharged through the last six pairs in the abdomen. Rubber diaphragm Liquid seal Liquid seal (air) (air) How is this different from ventilation in mammals? How does it compare to ventilation in birds? Explain.

Mechanics of Respiration: positive pressure breathing Do amphibians have completely separate pulmonary and systemic circulatory systems? What other organ(s) may be used in respiration?

Ventilation in Birds p. 987 Compare the size and complexity of the respiratory system in birds and amphibians (previous slide), and explain any differences. Compare the direction of airflow in birds and mammals. What does this imply regarding the pressure gradients at the transport epithelium?

Mammalian Respiratory System

Mechanics of Respiration: negative pressure breathing How do the serous membranes that cover the surfaces of the lungs and line the thoracic cavity facilitate breathing?

Gas Exchange at Lungs Four factors affect the rate of gas diffusion across a selectively permeable barrier: Solubility of the gas in the membrane Thickness of the membrane _____________________

The Function of Hemoglobin Would you expect insects (tracheal system) to have a respiratory pigment in their hemolymph? Explain. Hemoglobin is the only respiratory pigment in vertebrates, but it is a common respiratory pigment among invertebrates as well. Hemocyanin, a blue copper-containing protein, carries oxygen in crustaceans and most mollusks, within hemolymph. Describe the respiratory organs in these animals.

Hemoglobin Dissociation Curves How is the function of Hb similar to that of enzymes? Under what conditions does Hb act as a strong acid…as a weaker acid?

Transport of Carbon Dioxide Carbonic anhydrase catalyzes the chemical reaction in both directions. Explain how this is possible… What “drives” the diffusion of bicarbonate out of RBCs? Is there a “potential” problem associated with the loss of HCO3- ? (pun intended ) p. 992

Regulation of Breathing monitor CO2 (& pH) p. 988 How does hyperventilation affect the control centers of breathing? Should you hyperventilate just before your underwater swim test? Why or why not?