Circulation and Gas Exchange

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Circulation and Gas Exchange

• Chapter 42
• A.P. Biology
• Mr. Knowles
• Liberty Senior High

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Its all because of cellular respiration!

• C6H12O6 6O2 --gt 6CO2 6H2O
  (ATP)

And Eliminate This!
We Need This!
To Make This!
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• Concept 42.5 Gas exchange occurs across
  specialized respiratory surfaces
• Gas exchange supplies oxygen for cellular
  respiration and disposes of carbon dioxide.

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• Animals require large, moist respiratory surfaces
  for the adequate diffusion of respiratory gases
• Between their cells and the respiratory medium,
  either air or water.

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• Overview Trading with the Environment
• Every organism must exchange materials with its
  environment
• And this exchange ultimately occurs at the
  cellular level

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• In unicellular organisms
• These exchanges occur directly with the
  environment.
• For most of the cells making up multicellular
  organisms
• Direct exchange with the environment is not
  possible.

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• Concept 42.1 Circulatory systems reflect
  phylogeny
• Transport systems
• Functionally connect the organs of exchange with
  the body cells.

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• Most complex animals have internal transport
  systems
• That circulate fluid, providing a lifeline
  between the aqueous environment of living cells
  and the exchange organs, such as lungs, that
  exchange chemicals with the outside environment

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External Respiration

• Uptake of O2 and the release of CO2 into the
  environment- external respiration.
• Dry Air 78 N2, 21 O2 , 0.93 argon and
  other inert gases, and 0.03 CO2 .
• Amount of air changes at altitude, but not
  composition.
• Each gas exerts a fraction of total atmospheric
  pressure- partial pressure (PN2, PO2, PCO2)

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Remember the Plasma Membrane?

• Like H2O, O2 and CO2 diffuse through the
  phospholipid bilayer.
• Membrane must have H2O on both sides for its
  integrity (hydrophobic).
• All terrestrial organisms obtain gas diffusion
  across a moist membrane, never dry. Dissolved
  gases (O2 and CO2 ) diffuse through.

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Intracellular Diffusion of Gases is Passive
CO2 is lower
Aerobically Respiring Cell
CO2 is higher
O2 is lower
O2 is higher
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Dissolved Oxygen in Water

• Factors that affect O2 solubility in H2O
• 1. PO2 in air, decreases with altitude. Less PO2
  , less dissolved O2 in the H2O.
• 2. Temperature of the H2O. Inversely related.
• 3. Concentration of other solutes in H2O.
  Inversely related.

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What happens to the oxygen level when tides go
out?

• The Story of the Tarpon
• Discovery Blue Planet- Tidal Seas

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Problems in External Respiration

• Simple diffusion- limited to a distance of 0.5
  mm.
• As organisms become larger, their surface area to
  volume ratio decreases.
• Keep Intracellular O2 lt Extracellular O2. If
  not, there is no net movement of O2 by diffusion.

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Invertebrate Circulation

• The wide range of invertebrate body size and
  form
• Is paralleled by a great diversity in circulatory
  systems

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Evolution of External Respiration

• Unicellular bacteria and protists simple
  diffusion.
• Problem Limits size of organism.
• Jellyfish (Phylum Cnidaria) have no respiratory
  system. Very thin and slow down metabolism to
  allow diffusion of gases. (an unusual case)

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Gastrovascular Cavities

• Simple animals, such as cnidarians
• Have a body wall only two cells thick that
  encloses a gastrovascular cavity.
• The gastrovascular cavity
• Functions in both digestion and distribution of
  substances throughout the body.

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• Some cnidarians, such as jellies
• Have elaborate gastrovascular cavities

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The Jellyfish Life!

• Discover Blue Planet- Seasonal Seas

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Cyanea capillata 7 ft. bell, 120 ft tentacles
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Creating a Water Current

• Sponges (Phylum Porifera) diffusion directly
  from surrounding water set up a current using
  cilia. Beating cilia replace water over the
  diffusion surface.

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Sponges (Porifera)
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Sponges (Porifera)
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Sponges and Corals

• Discovery Blue Planet- Coral Seas

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Creating a Water Current

• Problem Limited to aquatic environments not
  efficient for really large organisms.

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But sponges are aquatic! What about terrestrial
organisms?

• Enter Cutaneous Respiration!

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Cutaneous Respiration

• Cutaneous Respiration gas exchange occurs
  directly across an animals body surface.
• Problem Must stay moist for gas diffusion must
  increase body surface area limits size.

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The Worms!

• Flatworms (Phylum Platyhelminthes) very thin to
  permit direct diffusion from surrounding fluid
  (tapeworms-host fluid).
• Roundworms (Phylum Nematoda) and Earthworms
  (Phylum Annelida) - direct diffusion requires a
  moist cuticle often secret mucous to keep skin
  wet.

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• Many segmented worms have flaplike gills
• That extend from each segment of their body.

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So why do earthworms die on your driveway after a
rain?

• They dry out and, therefore, suffocate!
• Mouth-to-skin, anyone?

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What are the down sides to cutaneous respiration?

• The Worlds Largest Earthworm
• Video Nigel Marvins Giant Creepy Crawlies

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Scolex
Proglottids
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Cutaneous Respiration in a Tapeworm

• Video The Body Snatchers

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Increasing the Diffusion Surface Area

• Advanced Invertebrates (Phylum Echinodermata,
  Mollusca, Arthropoda) increase surface area and
  bring external fluid close to internal fluid.
• Use a primitive gill - increases diffusion
  surface area.

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• In some invertebrates
• The gills have a simple shape and are distributed
  over much of the body

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Primitive Gill

• Phylum Echinodermata use a primitive gill
  called papulae.

papula
O2
CO2
Epidermis
Body Cavity
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• The gills of clams, crayfish, and many other
  animals
• Are restricted to a local body region.

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Axolotl- permanent salamander larvae
External Gills
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O2
CO2
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The External Gills

• Some, like the axolotl (aquatic salamander)
  physically moves its external gills through the
  water for improved gas exchange.
• A problem with external gills Difficult to
  circulate water past surfaces constantly.
• Problem external gills are fragile and offer
  resistance in water.

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Brachial Chambers

• Brachial chambers a muscular, internal pouch
  used to pump water over the gills.
• Phylum Mollusca use an internal mantle cavity
  that pumps water over gills. Ex. Squid and
  octopi.

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Internal Gills

• Cartilaginous Fishes (Sharks and Rays) force
  water through mouth over internal gills by
  constant swimming. Water flows out gill slits.
• Swim with mouth open to force water over gills
  ram ventilation.
• Problem Must stay in motion or suffocate.

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Filament
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• The feathery gills projecting from a salmon
• Are an example of a specialized exchange system
  found in animals.

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The Best Brachial Chamber

• Bony Fishes have opercular cavities. Gills are
  between mouth and opercular cavities.
• Opercula (Gill Covers) are flexible and they
  pull water through cavity, like a bellows.
• Each gill two rows of gill filaments and each
  filament has rows of lamellae parallel to
  direction of water movement (see Fig. 46.6).

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• The effectiveness of gas exchange in some gills,
  including those of fishes
• Is increased by ventilation and countercurrent
  flow of blood and water.

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The Gill Filament

• In each lamella, blood flows in a direction
  opposite the direction of water movement
  countercurrent flow.
• Maximizes the differences in O2 between the water
  and blood (see Fig. 46.7).
• Most efficient respiratory organ known 85
  available oxygen is removed.

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Countercurrent Flow in Gills
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What if youre not aquatic?

• Why do fish die out of water?
• They suffocate.

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The Problem of Terrestrial Respiration

• Water 5-10 ml of O2 per liter
• Air 210 ml O2 per liter (rich in O2)
• Gills dont work in air
• Air is less buoyant than water, fragile lamellae
  collapse and reduce surface area and not enough
  gas diffusion.
• Water diffuses into air by evaporation. Gills
  provide too much surface area for water loss.

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Terrestrial Organisms

• Use two types of internal passage ways for gas
  diffusion sacrifice efficiency for reduced
  evaporation.
• Terrestrial Insects use tracheae air-filled
  passages connecting the surface of the insect to
  all potions of its body. Diffusion directly with
  internal cells and no circulatory system.
• Use openings called spiracles along the abdomen
  that can be controlled. Effective for small
  animals.

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Tracheal Systems in Insects

• The tracheal system of insects
• Consists of tiny branching tubes that penetrate
  the body

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• The tracheal tubes
• Supply O2 directly to body cells.

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How large can an insect become?

• Video Nigel Marvins Giant Creepy Crawlies

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First Terrestrial Organism

• Problem Tracheal breathing limits the size of
  the organism. Ventilation is by movement of
  organism.

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Lungs

• Spiders, land snails, and most terrestrial
  vertebrates
• Have internal lungs (simple sacs).

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Other Terrestrial Organ

• Lung moves air through a moist, internal,
  tubular passage and back out same passage.
• Benefit minimizes evaporation.
• Problem lower efficiency than gill, but O2 more
  abundant in air.
• Four variations of the terrestrial, vertebrate
  lung.

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The First Terrestrial Animals?
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Class Amphibia

• Amphibian Lung simple sac with a folded
  membrane has trachea with a valve glottis.
• Can breathe through nose and mouth.
• Perform positive pressure breathing create a
  positive pressure outside and forces air into
  lungs (throat breathing in frogs).

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I supplement by lung breathing with cutaneous
respiration, too!
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Problems with the Amphibian System

• Lung is not very efficient poor surface area.
• Cutaneous Respiration requires moist skin.
  Limited to moist environments and/or secrete
  mucous covering. Dependent on water.
• Cannot be very active slower metabolism.

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Class Reptilia

• Living completely on land, no connection to
  water. Made water-tight skin (scales) to prevent
  evaporation.
• Little or no cutaneous respiration.
• Reptile Lung contains many small air chambers
  increase surface area.

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Class Reptilia

• Reptiles use negative pressure breathing
  intercostal muscles and diaphragm to expand
  thoracic cavity and create a negative pressure in
  lungs.
• Air is pulled into lungs rather than pushed.
• Also called body cavity breathing or chest
  breathing.

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Class Mammalia

• Must maintain constant body temperature need
  more efficient lung.
• Use millions of sacs, clustered like grapes
  alveoli (alveolus sing.)
• Each cluster connected to a short, branching
  passageway bronchiole.
• Bronchioles connect into left and right bronchi
  (bronchus sing.)
• Bronchi are connected to superior trachea.

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How a Mammal Breathes

• Mammals ventilate their lungs
• By negative pressure breathing, which pulls air
  into the lungs.

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Bronchioles
Bronchi
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(No Cartilage)
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Oxygenated Blood
Deoxygenated Blood
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About 1 µm
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80 m2 of Surface Area!
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Mechanics of Human Breathing

• Trachea and Bronchi have hyaline cartilage, but
  not bronchioles.
• Bronchioles are surrounded by smooth muscle.
• Bronchoconstriction nervous system or hormones
  (histamine) signal smooth muscle to contract and
  narrow bronchioles (asthma).
• Bronchodilation - nervous system or hormones
  (epinephrine) signal smooth muscle to relax and
  open bronchioles.

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Mechanics of Human Breathing

• Visceral Pleural Membrane surrounds outside of
  lung.
• Parietal Pleural Membrane lines thoracic
  cavity.
• Pleural Cavity is fluid-filled space between
  connects lung to wall of cavity.

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Mechanics of Human Breathing

• One-cycle pump.
• Inspiration intercostal muscles and diaphragm
  contract increase volume of thoracic cavity.
• Pleural membranes are coupled, lungs expand.
• Air pressure in lungs is decreased and air is
  pulled in negative pressure breathing.

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Mechanics of Human Breathing

• One-cycle pump.
• Expiration Intercostal muscles and diaphragm
  relax, elastic recoil of thoracic cavity
  decrease volume of cavity and lungs.
• Air pressure in lungs is increased, forces air
  out.

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Mechanics of Human Breathing

• Tidal Volume amount of air moved into and out
  of lungs at rest (500 ml).
• Functional Residual Capacity amount of air left
  in lungs after normal expiration at rest.
• Residual Volume amount of air left after
  forceful, maximum expiration.

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Mechanics of Human Breathing

• Anatomical Dead Space constant amount of air
  trapped in trachea, bronchi, bronchioles (150
  ml).
• Vital Capacity max. amount of air exhaled after
  a forceful, maximum inhalation (VC TV IRV
  ERV).
• Total Lung Capacity TV IRV ERV RV

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Class Aves

• Flight requires more ATP.
• Avian lung is a two-cycle pump (Fig. 46-9).
• Uses a system of anterior and posterior air sacs
  and a lung.
• Gas exchange occurs in lung only.

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How a Bird Breathes

• Besides lungs, bird have eight or nine air sacs
• That function as bellows that keep air flowing
  through the lungs.

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1
3
4
2
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Two-Cycle Breathing

• 1st Inspiration air travels down trachea to
  posterior air sacs.
• 1st Expiration air flows from sacs to lung.
• Lung gas exchange.
• 2nd Inspiration air flows from lung to anterior
  air sacs.
• 2nd Exhalation air flows from sacs out through
  trachea.

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Benefits to Avian Breathing

• Unidirectional flow of air through lung no
  dead volume of air left in lung. Always fully
  oxygenated air.
• Flow of blood is perpendicular to air flow
  cross-current flow.
• Very efficient at extracting oxygen from air.
• Most efficient terrestrial respiration.

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Gas Transport and Exchange

• If transport were by simple diffusion, then O2
  would require three years to travel from lung to
  toe.
• Use a circulatory system but plasma could only
  carry 3 ml O2 per l.
• Use RBC with hemoglobin to carry 200 ml O2 per l.

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Erythrocyte
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Hemoglobin (Hb)

• Accounts for 95 of proteins inside the RBC.
• 280 million Hbs in each RBC.
• Hb binds to and transports O2 and CO2.

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Hb Molecule

• Each Hb molecule four protein chains 2 alpha
  chains 2 beta chains of polypeptides.
• Each chain is a globular subunit and has a heme
  group.
• Heme a porphyrin which is a ring compound with
  an iron in the center.
• Iron has a charge and can bind to O2 (negative).

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• Like all respiratory pigments
• Hemoglobin must reversibly bind O2, loading O2 in
  the lungs and unloading it in other parts of the
  body

Figure 42.28
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Quaternary Structure of Hemoglobin
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Hb Molecule

• When hemoglobin binds to O2 it becomes
  oxyhemoglobin (bright red).
• Very weak interaction easy to separate.
• At the tissues, some oxyhemoglobin releases its
  O2 becomes- deoxyhemoglobin (dark red).

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Oxygenated Blood
PO2 105 mm Hg
PO2 100 mm Hg
Deoxygenated Blood
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Oxygen Transport

• Lungs are efficient 97 of hemoglobin in RBCs
  is fully saturated.
• At capillaries, extracellular fluid has lower PO2
  and O2 diffuses into tissues.
• Venous blood leaving tissues has PO2 40 mm Hg.
• Only about 22 of oxyhemoglobin has releases O2
  into tissues.

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O2 is higher
Body Tissues
O2 is lower
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Figure 42.27
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Why so little O2 released into tissues?

• Blood can supply oxygen needs during exercise.
• Blood has enough oxygen to maintain life 4 or 5
  minutes without breathing.

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How does Hb know when to let go?

• In RBC, CO2 H2O H2CO3 , lowers pH.
• Hbs affinity for O2 decreases with lower pH.
  Releases oxygen into tissue.
• Hbs affinity for O2 inversely related to
  temperature. Metabolically active tissues are
  warmer. Cause release of O2 into tissues.

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What about the CO2?

• As Hb releases O2, a binding site on protein
  absorbs CO2. CO2 does not bind to heme group
  (20).
• 8 dissolved in the blood plasma.
• 72 diffuses from plasma ? RBC cytoplasm and
  converted by enzyme into H2CO3 ?HCO3- H ions.

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Control of Breathing in Humans

• The main breathing control centers
• Are located in two regions of the brain, the
  medulla oblongata and the pons

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Controlling Breathing

• Respiratory Control Center Medulla Oblongata in
  brain.
• Impulses sent to diaphragm and intercostal
  muscles? contraction and expand thoracic cavity
  (inhalation).
• No impulse, muscles relax and cavity becomes
  smaller (exhalation).
• Part of ANS but can be voluntary.

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Controlling Breathing

• If breathing stops, the PCO2 of plasma rises.
• Causes pH to drop (increase in H).
• Peripheral chemoreceptors in walls of aorta and
  coratid arteries detect increase in H.
• Send signals to respiratory control center.
• Initiates breathing.

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What does exercise do?

• Working tissue causes ? PCO2 in plasma and ?in
  pH.
• As H ?, chemoreceptors cause an ? in
  respiratory rate.
• Can you indefinitely hyperventilate?
• Why can people hold their breath longer if they
  hyperventilate first?

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The Ultimate Endurance Runner

• The extreme O2 consumption of the antelope-like
  pronghorn
• Underlies its ability to run at high speed over
  long distances

Figure 42.31