THE EXCHANGE OF GASES BETWEEN AN ORGANISM AND ITS ENVIRONMENT Respiration.
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Transcript of THE EXCHANGE OF GASES BETWEEN AN ORGANISM AND ITS ENVIRONMENT Respiration.
THE EXCHANGE OF GASES BETWEEN AN ORGANISM AND ITS ENVIRONMENT
Respiration
2 types:
Organismic Oxygen taken up from environment and delivered to
individual cells Simple diffusion Respiratory systems
Aerobic cellular respiration Cells use O2 as final electron acceptor to produce
energy CO2 created as waste
Gas Exchange
Requires MOIST MEMBRANES
Air Higher concentration of O2
Less viscous than water O2 diffuses quickly
Water Less threat of dessication More energy needed
Respiratory Surfaces
Body Surface High SA : Volume Low metabolic rate
Tracheal Tubes Air enters through
spiracles Branching tubules Fluid-filled tracheoles
= gas exchange
Gills Folded or split into
filaments Capillaries deliver
blood to filaments Countercurrent exchan
ge
Lungs Terrestrial Ingrowth of body
cavity
Mammalian Respiratory System
Nostrils/Nasal Cavity Filter Moisture Warmth
Pharynx/Larynx Cartilage give support Epiglottis closes off larynx during swallowing to
prevent choking
Trachea
Divides into 2 bronchi – lead to each lung Further divides into bronchioles Ends at alveoli
Surfactants
Ventilation: The Mechanics of Breathing
Inhalation/Inspiration Thoracic cavity is closed Diaphragm contracts & moves downward Ribs may also move upward Air pressure in lungs falls Air from outside moves to area of lower pressure
Ventilation, cont.
Exhalation/Expiration Diaphragm relaxes Pressure in cavity increases Air sacs deflate
http://www.smm.org/heart/lungs/breathing.htmhttp://sprojects.mmi.mcgill.ca/resp/
inspiration.htm
Total air in and out during normal/resting breath = tidal volume
Maximum amount exhaled after maximum filling = vital capacity
Gas Exchange at Alveoli
Made possible by thin epithelium Alveoli Capillaries
Dalton’s Law of Partial Pressure PO2 = 160 mm Hg PCO2 = 0.3 mm Hg
Flick’s law of diffusion
http://www.wisc-online.com/objects/index_tj.asp?objID=AP2404
Gas exchange at tissues
PO2 in arteries ~ 100 mm Hg
PO2 in tissues = 0 – 40 mm Hg
PO2 in veins ~ 40 mm Hg
Respiratory Pigments
Combine reversibly with O2
Examples: Hemocyanin Hemoglobin Myoglobin
Increases amount of O2 blood can carry from 0.25 mL/100mL to 20 ml/100 mL
% O2 saturation Affected by pH, temperature, CO2 concentration
CO2 Transport
Transported in blood in 3 forms: Dissolved in plasma (10%)
Hb in RBCs (30%) Causes release of O2
HCO3-
Combination of CO2 & H2O forms carbonic acid In cells, catalyzed by carbonic anhydrase Dissociates into H+ & HCO3
-
Hb buffers H+ HCO3
- diffuses out of cell into plasma At lung, reaction reverses
Regulation of Breathing
Medulla regulates basic rhythm
Pons – controls inhalation/exhalation transition
Chemoreceptors in medulla/aorta/carotid arteries detect changes in CO2 concentration Increased CO2 lowers blood pH
Respiratory rate increases to get rid of excess CO2