RespirationRespiration

AP BiologyUnit 6

Types of Respiratory Systems

• Animals typically do gas exchange through one (or more) of the following means: – Skin (body surface) – Gills (internal or external) – Lungs – Tracheal System

Respiratory Media

• Both air and water can serve as respiratory media (what is being “breathed” in)– Ex. Fish respire water, humans respire air

• What are the advantages of respiring air versus water?

Air as a respiratory media

• Advantages – Lighter

– Contains more O2

• Disadvantages– Membranes dry out more easily (moisture

needed)

Water as a media

• Advantages– Keeps membrane moist (so they continue

functioning properly)

• Disadvantages– Heavier

– Contains less O2

Respiratory Systems: Gills

• Fish use their gills as a respiratory surface

• Water flows in through mouth, across the gills, then out through the operculum

• As the water flows across the gills, O2 diffuses into the capillaries in the gills, CO2 diffuses out.

Respiratory Systems: Gills

• Water flows across the gills in the opposite direction as the blood flowing in the capillaries = Countercurrent Flow

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Respiratory Systems: Gills• Why is countercurrent exchange an

effective way to get O2 from water?

(especially compared to concurrent flow)

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Respiratory Systems: Gills

• Countercurrent flow is an effective way to get O2 because as the blood flows, it always meets water that is more highly oxygenated allows O2 to diffuse into the blood along the entire length of the gills

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Tracheal Systems• Insects have spiracles which

open up to the outside

• Air flows in from the spiracles and through the tracheae

• The tracheal system is so extensive that this allows air to flow right next to the body cells

Question…

• How does the tracheal system allow insects to maintain a high metabolic rate despite having an open circulatory system?– They don’t use their circulatory system to

transport O2 to cells– flows directly from tracheae to cells open circulatory system not a factor

Respiratory Systems: Birds

• Birds have air sacs and lungs

• Air sacs = for storing air (no gas exchange occurs here)

• Lungs – where gas exchange (O2 into blood and CO2 out) occurs

Respiratory Systems: Birds

• Birds have one way flow through their lungs

• Animation

Question…

• How does a bird’s respiratory system allow it to maintain high levels of activity, even at high altitudes (where there is less O2)?

– One way flow means that the most oxygenated air is always flowing across the lung surfaces

– There is no “old/stale” air left over in the lungs that takes up space

Mammalian Respiratory System

• Pathway of air

• Nasal cavity & mouth pharynx (back of throat trachea bronchi bronchioles alveoli

Mammalian Respiratory System

• Trachea– Windpipe– Lined with rings of cartilage

for structural support

• Bronchi– Main branches leading from

trachea

• Bronchioles– Smaller branches (no

cartilage rings)

Alveoli

• Air sacs with very thin walls• Surrounded by lung

capillaries• Where gas exchange occurs • Random fact: You have

approximately 300 million alveoli in your lungs– surface area is equivalent to ¼ of a basketball court

Inhalation

• Inhalation = taking air into the lungs

• Diaphragm contracts (flattens) space in chest cavity expands (pressure lowered) air from outside is sucked in (flows from high to low pressure)

Exhalation

• Exhalation = air leaves the lungs

• Diaphragm relaxes (moves up) less space in chest cavity air is pushed out of lungs

Diffusion of Gases in the Alveoli

• Diffusion of O2 and CO2 in the lungs (alveoli) is caused by differences in partial pressure

• Partial pressure = pressure due to one particular gas (kind of like concentration)– PO2 = partial pressure due to O2

– PCO2 = partial pressure due to CO2

Diffusion of Gases

• Oxygen diffuses into the capillaries from the alveoli (PO2 in the capillaries is lower than PO2 in the alveoli)

• CO2 diffuse into the alveoli from the capillaries (PCO2 in the capillaries is higher than PCO2 in the alveoli)

Transport of Oxygen in the Blood

• Oxygen is transported by hemoglobin in red blood cells – Each hemoglobin molecule can carry 4 O2

molecules

– Cooperative binding = once the first O2 binds, the next 3 are able to bind more easily

Bohr Effect

• pH changes hemoglobin’s affinity (ability to bind) for oxygen Bohr effect

• At lower pHs, hemoglobin doesn’t bind O2 as well lets it go into the surrounding tissues

Question…

• Why would it make sense to drop off more O2 when the pH is lower?

– Lower pH is due to lactic acid from fermentation

– This means the cells in that region need more O2 hemoglobin drops it off more readily

Hemoglobin affinity

• Certain organisms also have hemoglobin with a high affinity for oxygen – Fetus has a higher affinity

for O2 compared to its mother

– Llamas have a higher affinity for O2 compared to animals who live at sea level

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Question…

• Why would a fetus have hemoglobin with a higher affinity for O2 than its mother?

• The only way for a fetus to get O2 is from its mother (umbilical cord) it has to be able to have hemoglobin that can “grab” O2 from its mother’s bloodstream

Question…

• Why would a llama have hemoglobin with a higher affinity for O2 compared to other

mammals?

• At higher altitudes, there is less O2 in the air (lower PO2) llamas have to be able to grab more O2 at a lower PO2 to get enough to survive.

Transport of CO2

• CO2 is mostly transported as HCO3

- (bicarbonate ions) in the blood plasma

• After CO2 diffuses into the blood from the body cells, carbonic anhydrase (enzyme in RBC) converts CO2 into bicarbonate ions

Transport of CO2

• When the bicarbonate reaches the lungs, the carbonic anhydrase converts it back into CO2 gas it diffuses out into the alveoli

Control of Respiration

• Regulated by brain (medulla oblongata and pons) that controls the diaphragm and rib muscles to change rate or depth of breathing

• Sensors send messages to brain from elsewhere in body

Control of Respiration

• Messages include those about: – O2 concentration (only

when very low) – pH of blood (related to

CO2 concentration)

Control of Respiration

• CO2 / blood pH has a much stronger effect

on breathing rate than O2 levels

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Question…

• How would holding your breath affect your blood pH? – It would cause pH to drop since CO2 is not

being eliminated

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Marine Mammal Diving Reflex

• When marine mammals dive, their heart rate goes way down– sometimes it goes down to 3 or 4 beats a minute

• This is the diving reflex

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Marine Mammal Diving Reflex

• Blood is sent primarily to the brain, eyes and adrenal glands

• Blood flow to muscles is shut off – it just uses the O2 stored in the myoglobin in muscles – Myoglobin is an oxygen

carrying molecule in muscles

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Marine Mammal Diving Reflex

• What adaptations does the marine mammal have to allow them to stay underwater for a long time (sometimes up to 2 hrs)?– Lots of myoglobin to store O2 in muscles

– More blood to store more O2

– Huge spleen

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Human Diving Reflex

• Humans have a similar reflex

• When your face is submerged, your heart rate goes down

• Might be a protective response during birth when the pressure can prevent O2 from getting to the baby from the umbilical cord slowing down blood flow slows down O2 depletion in blood

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