Bi 103 Lecture Notes: Chapter 29: Respiration

I. Basics of Respiration

            A. The “Point” :

                        1. Body needs oxygen for cellular respiration (ENERGY!) and produces CO2

                        2. Lungs take in oxygen and release CO2

                        3. Blood distributes oxygen to body, removes CO2

            B. Features of respiratory systems

                        1. Moist surface (gasses dissolve to cross surfaces by diffusion)

                        2. Thin cells lining surface

                        3. Large surface area contacting environment

            C. Methods of gas exchange

                        1. No specialized respiratory system

                                    a. Flatworm: thin, flattened body.

                                    b. Sponges: water circulates though out body

                                    c. Earthworms: Skin and circulatory system

                        2. Specialized respiratory system (involve both diffusion and bulk flow)

                                    a. Terrestrial organisms:  internal system (see human example)

                                    b.  Fish: Gills (aquatic) : use oxygen from water

II. Human Respiratory system

            A. Conducting system: passageways carrying air into/out of lungs

                        1. nasal cavityà pharynx à Larynx à Trachea à Bronchi à Bronchioles

                        2. System warms, air and moistens, mucous traps dust/bacteria

            B. Gas Exchange system: Location of gas exchange between blood and air

                        1. Alveoli: sacs where diffusion happens

                                    a. once cell layer thick, surrounded by capillaries

                                    b. large surface area

                                    c. coated with thin layer of fluid (surfactant)

III. Gas Transport

            A. Lung: Oxygen diffuses into blood, Carbon dioxide diffuses out of blood

            B. Tissues: Oxygen diffuses out of blood, carbon dioxide diffuses into blood

            C. Oxygen transport

                        1. > 98% travels bound to hemoglobin (Carbon monoxide prevents binding)

                        2. remainder dissolved in plasma

            D. Carbon Dioxide transport

                        1. 70% converted to bicarbonate ion, carried in plasma

                        2. 20% bound to hemoglobin

                        3. 10% dissolved directly in plasma      

IV. Breathing (depends on air tight chest cavity

            A. Inhalation: active process

                        1. diaphragm, rib muscles contract

                        2. chest cavity expands, reducing pressure, drawing air in

            B. Exhalation: passive process

                        1. diaphragm, rib muscles relax

                        2. chest cavity shrinks, increasing pressure, forcing air out.

V. Control of respiration

            A. Respiratory center in Medulla, monitors CO2 levels to regulate respiration