Respiration AP Biology Unit 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 O 2 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 O 2

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, O 2 diffuses into the capillaries in the gills, CO 2 diffuses out.

Respiratory Systems: Gills Water flows across the gills in the opposite direction as the blood flowing in the capillaries = Countercurrent Flow Image taken without permission from

Respiratory Systems: Gills Why is countercurrent exchange an effective way to get O 2 from water? (especially compared to concurrent flow) Image taken without permission from

Respiratory Systems: Gills Countercurrent flow is an effective way to get O 2 because as the blood flows, it always meets water that is more highly oxygenated  allows O 2 to diffuse into the blood along the entire length of the gills Image taken without permission from

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 O 2 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 (O 2 into blood and CO 2 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 O 2 )? –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 O 2 and CO 2 in the lungs (alveoli) is caused by differences in partial pressure Partial pressure = pressure due to one particular gas (kind of like concentration) –P O2 = partial pressure due to O 2 –P CO2 = partial pressure due to CO 2

Diffusion of Gases Oxygen diffuses into the capillaries from the alveoli (P O2 in the capillaries is lower than P O2 in the alveoli) CO 2 diffuse into the alveoli from the capillaries (P CO2 in the capillaries is higher than P CO2 in the alveoli)

Transport of Oxygen in the Blood Oxygen is transported by hemoglobin in red blood cells –Each hemoglobin molecule can carry 4 O 2 molecules –Cooperative binding = once the first O 2 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 O 2 as well  lets it go into the surrounding tissues

Question… Why would it make sense to drop off more O 2 when the pH is lower? –Lower pH is due to lactic acid from fermentation –This means the cells in that region need more O 2  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 O 2 compared to its mother –Llamas have a higher affinity for O 2 compared to animals who live at sea level Image taken without permission from

Question… Why would a fetus have hemoglobin with a higher affinity for O 2 than its mother? The only way for a fetus to get O 2 is from its mother (umbilical cord)  it has to be able to have hemoglobin that can “grab” O 2 from its mother’s bloodstream

Question… Why would a llama have hemoglobin with a higher affinity for O 2 compared to other mammals? At higher altitudes, there is less O 2 in the air (lower P O2 )  llamas have to be able to grab more O 2 at a lower P O2 to get enough to survive.

Transport of CO 2 CO 2 is mostly transported as HCO 3 - (bicarbonate ions) in the blood plasma After CO 2 diffuses into the blood from the body cells, carbonic anhydrase (enzyme in RBC) converts CO 2 into bicarbonate ions

Transport of CO 2 When the bicarbonate reaches the lungs, the carbonic anhydrase converts it back into CO 2 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: –O 2 concentration (only when very low) –pH of blood (related to CO 2 concentration)

Control of Respiration CO 2 / blood pH has a much stronger effect on breathing rate than O 2 levels 5 slides left

Question… How would holding your breath affect your blood pH? –It would cause pH to drop since CO 2 is not being eliminated 4 slides left

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 3 slides left

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 O 2 stored in the myoglobin in muscles –Myoglobin is an oxygen carrying molecule in muscles 2 slides left

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 O 2 in muscles –More blood to store more O 2 –Huge spleen 1 slide left

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 O 2 from getting to the baby from the umbilical cord  slowing down blood flow slows down O 2 depletion in blood Last slide!