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Lecture 14 Outline (Ch. 49)
I. Overview
II. Respiration in different organism
III. Methods – bulk flow vs. diffusion
IV. Gas exchange and partial pressures
V. Inhalation/exhalation
VI. Brain control
VII. Respiratory problems
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If you are an athlete who trains at high elevations, what happens if you compete at a lower elevation?
Thought Question:
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Living things process energy
• They need oxygen for this - Why?
Overview
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Cellular respiration uses O2 and produces CO2
• C6H12O6 + O2 CO2
+ H2O + ATP energy
• Breathing – respiration supports this process by exchanging gasses
Overview
Cell
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Exchanging gasses
• Moist surface – Gasses dissolve in water
to move in/out of cells
• Thin • Large surface area
Gas Exchange Systems
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Who needs a respiratory system?
• I don’t!• Moist environment• Small (or thin)• Low energy demand
• I do!• Dryer environment• Large or thick-bodied• High energy demand
Gas Exchange Systems
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Respiratory systems enable gas exchange
• Bulk flow– Fluids move in bulk– Air/water move to respiratory
surface– Blood moves through vessels
• Diffusion– Individual molecules move
down concentration gradients– Gas exchange across
respiratory surface– Gas exchange in tissues
Gas Exchange Systems
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Gills• Aquatic gas exchange
Gas Exchange Systems
• Elaborately folded ( surface area)
• Contain capillary beds
• Gill size inversely related to [O2]
• Large gills = low [O2]
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Fish Efficiency
• Dissolved O2 is < 1% of water (21% of air)
• Countercurrent exchange increases efficiency
Gas Exchange Systems
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Terrestrial respiration
• Internal– Stay moist &
supported
• Insects have tracheae– Air enters/exits
through spiracles– Branching channels
(trachioles) allow gas exchange with cells
Gas Exchange Systems
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Vertebrate respiration• Terrestrial use of lungs
– Evolved from accessory respiratory organs of freshwater fish
• Amphibians are weird– Remain tied to water– Larval gills to adult lungs– Moist skin transfers
gasses
Gas Exchange Systems
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Reptiles & Mammals use lungs exclusively
• Lack permeable skin• Lungs are more efficient
– Especially birds!
Gas Exchange Systems
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Human Respiration
• Air enters through nose and mouth to pharynx
• Travels through larynx (voice box)
• Epiglottis directs travel
Mammals
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On to the lungs
• Trachea • Bronchi • Bronchioles Alveoli
Human Respiration
Air is warmed & cleaned
• Dust & bacteria trapped by mucus • Swept up and out by cilia
• Microscopic chambers provide enormous surface area
• Surfactant keeps surface moist• Association with capillaries
– Diffusion of gasses
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Diffusion
• Blood arrives from pulmonary artery
• Low in O2
– Higher concentration in air diffuses into blood
• High in CO2
– Higher concentration in blood diffuses into air
Lungs
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Human Respiration
• Gas exchange is driven by differences in pressures
• Blood from body with low O2, has a partial oxygen pressure (PO2) of ~40 mm Hg
• By contrast, the PO2 in the alveoli is about 105 mm Hg
• Blood leaving lungs, thus, normally contains a PO2 of ~100 mm
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CO2 Transport
• CO2 binds hemoglobin loosely
• Dissolved in plasma
• Combines with H20 to form bicarbonate (HCO3
-)
– More CO2 = lower pH
Transport of gasses
The Bohr Effect:
Hemoglobin binds more tightly to O2 when pH is increased and loosely when pH is decreased
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O2 Transport
• Binds to hemoglobin
– Removes O2 from plasma solution
– Increases concentration gradient; favors diffusion from air
Transport of gasses
CO binds more tightly to hemoglobin than O2
Prevents O2 transport
• Outside lung covered by the visceral pleural membrane
• Inner wall of thoracic cavity lined with parietal pleural membrane
• Space between called the pleural cavity– Thin space w fluid– Causes 2 membranes to
adhere– Lungs move with thoracic
cavity
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Breathing Mechanisms
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Breathing Mechanisms• Inhalation:
Contraction of intercostal muscles expands rib cage
Contraction of diaphragm expands the volume of thorax and lungs
• Thoracic cavity expands, produces negative pressure which draws air into the lungs
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Breathing is involuntary
Breathing Mechanisms
• Controlled by respiratory center of the brain• Adjusts breath rate & volume based on
sensory input– Maintain a constant concentration of
CO2
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Asthma• Smooth muscle in bronchioles
becomes irritated and constricts or spasms
• Increased mucus• Can lead to collapse • Linked to air quality and
allergies
Respiratory Problems
• Chronic obstructive pulmonary disease (COPD)– Refers to any disorder that obstructs airflow on a
long-term basis
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Emphysema
• Reduces surface area available for gas exchange
• Labored and difficult breathing
• 80-90% of deaths linked with smoking
Respiratory Problems
• Alveoli rupture or become brittle creating larger but fewer alveoli
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Bronchitis & Pneumonia
• Inflammations of respiratory passages & lungs • Increase in mucus production, decrease in cilia
• Reduces air flow to alveoli
• Causes include bacteria, viruses, fungi, & parasites
Respiratory Problems
Jim Henson, creator of the Muppets, died at age 53 from pneumonia
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Tuberculosis
• Bacteria attack and cause lesions on lung tissue
Respiratory Problems
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200 different toxins!– Includes tar, carbon monoxide, formaldehyde
Smoking
Lung cancer accounts for more deaths than any other form of cancerCaused mainly by cigarette smoking
3 of the Marlboro men died from lung cancer
Lung cancer metastasizes rapidly – usually cancer has spread to other tissues before detected
Chance of recovery poor: only 3% of patients survive > 5 yrs
Lecture 14 Summary
1. Respiration Overview (Ch. 49)- Diffusion- Insects- Gills- Birds, reptiles, mammals
2. Airway Route & gas exchange (Ch. 49)- Hemoglobin- Partial pressures
3. Control (Ch. 49)- Inhalation/exhalation- Brain control
4. Respiratory Problems (Ch. 49)- Asthma, emphysema, lung cancer, bronchitis, pneumonia,
tuberculosis