Respiration

Gas Exchange requires moist surfaces P. 871 Gills (left), Alveoli (right)

Gas Exchange 42.18

Gill Structure and Function Gills are skin projections into which coelomic fluid moves. Parapodia are used for gills, swimming, crawling. Long, flattened page-like tissues. Feathery gills under exoskeleton. 42.19

Insects Have spiracles leading to trachea (branched tubes) Air sacs are present near organs Pix 42.22

Gills in Fish 42.20 Water is pumped through the mouth and over gill arches. Each gill arch has 2 filaments made of plate like lamellae.

Countercurrent Exchange 42.21 Blood picks up more and more oxygen as the water has higher and higher concentrations. (oxygen poor vessels on right, oxygen rich vessels on left)

Bird Respiration 42.25 Air sacs maximize oxygen withdrawal from air.

Negative Pressure Breathing 42.24 Air is pulled (not pushed) into the lung. On inhalation the volume of the thoracic cavity is increased- decreasing pressure-air rushes in.

Terminology Tidal Volume-volume inhaled and exhaled per breath. Vital Capacity-Maximum tidal volume (forced). Residual volume-the air that cannot be expelled from the lungs.

Breathing Control Centers Two regions of the brain-medulla oblongata and pons. Medulla set rhythm, monitors carbon dioxide levels in blood (mostly using pH) and adjust breathing as needed. CO2 + water forms carbonic acid-lowers pH. Low pH triggers increased breathing rate and depth. Very low O2 sensors in aorta and carotid respond with signal to breathing centers-breathing rate increases. Hyperventilation- very deep breathing may purge blood of carbon dioxide-stops impulses to expand thorax until levels build up. Bypasses usual set-up-Co2 and O2 levels are related. 42.26

Gas Exchange 42.27 Gas diffuses down pressure gradients. Partial Pressures are the portions of atmospheric pressure contributed by individual gases. e.g.: air is 21% oxygen. Pressure of atmosphere is 760 mmHg PP of O2 is .21 x 760= 160mmHg 42.27

More Partial Pressure Gas will always diffuse from a higher partial pressure to a lower partial pressure. At the lung the PO2 in the blood is low and the PO2 in the lung is higher so oxygen moves into the blood. At the lung the PCO2 in the blood is higher than in the lung, so carbon dioxide moves into the lung from the blood. This works at the tissues too.

Hemoglobin Dissociation Curve 42.28 Hemoglobin is a respiratory pigment (protein) which carries oxygen. Arthropods have hemocyanin.

Hemoglobin Made of four subunits, each with a cofactor called a heme group and each with an iron atom at the center. The binding of oxygen with one subunit causes a shape change which causes the other three to bind more easily. This is cooperativity. This is seen in the dissociation curve for hemoglobin over different partial pressures of oxygen. When the partial pressure falls the hemoglobin hangs onto the oxygen until it is pretty low, then lets go of all of it at once. The Bohr shift shows an increase in o2 release when the pH is lower-more carbon dioxide.

Blood CO2 Transport CO2 is carried to the lungs in a variety of ways. 7% is carried in the blood plasma 23% binds to amino groups of hemoglobins 70% is carried as bicarbonate ions in the blood. CO2 diffuses into blood plasma then into RBC’s where it is converted to bicarbonate CO2 first reacts with water (enzyme here is carbonic anhydrase) to form carbonic acid. Most H+ attach to hemoglobin. Bicarbonate diffuses out into plasma. 42.29

Hemoglobin Curves In fetus

Special Adaptations Oxygen storage in blood and muscle may be doubled. Less left in lung 36% to 5% in seal Spleen is large and may store huge amounts of blood. Lots of myoglobin- an oxygen storing protein- in muscle Conserve oxygen ATP from fermentation