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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