Chapter 47: Respiratory System

Question 1

What are gas exchange systems made up of?

Answer 1

1) Specialized body surfaces where gases are exchanged
2) Ventilation mechanisms (move air/water over environmental side of body surfaces)
3) Perfusion/Circulation mechanisms (for ECF on internal side)

Question 2

What is diffusion?

Answer 2

Means of gas exchange in which molecules move from areas of high concentration to low concentration
- can occur in water or air

Question 3

Describe the relationship between gas molecules and pressure.

Answer 3

Gas molecules increase, pressure increases

Question 4

What is partial pressure? Provide an example.

Answer 4

Concentrations of different gases in a mixture.
Ex: At sea level the atmospheric pressure is 760 mmHg

Question 5

What does the amount of gas in a liquid depend on?

Answer 5

1) Partial pressure of gas
2) Solubility of gas
*For gases in solution, concentration is not equal to partial pressure, but partial pressure drives diffusion

Question 6

Is O2 content higher in air or water?
Does O2 diffuse faster in air or water?
Is more energy needed to move water or air over a gas exchange surface?

Answer 6

Air
Air
Water

Question 7

How does slow diffusion of O2 affect air and water breathing animals? Provide examples.

Answer 7

• Animal cells with low metabolic rates can’t function even a few millimeters away from O2 source in water
• Size and shape limits are present in invertebrates that lack internal systems to distribute O2
  Ex:
  1) Marine Flatworms: flat, thin body with large external surface area
  2) Sponges: bodies made of cells surrounding water channels through which external mediums flow

Question 8

How does increasing temperature affect terrestrial animals vs aquatic animals?

Answer 8

Terrestrial animals: No effect
Aquatic Animals:
- most are ectotherms (get heat from surrounding environment)
- body temperature and metabolic rate are correlated with water temperature
- more O2 is needed in warmer water but warmer water holds less dissolved O2 which creates respiratory problems

Question 9

Describe the solubility of oxygen when compared with temperature?

Answer 9

Oxygen is more soluble at lower temperatures and less soluble at higher temperatures.

Question 10

How does altitude affect partial pressure?

Answer 10

Higher altitude = lower partial pressure O2 meaning less oxygen available
- Amount of gas/volume decreases
- Mt. Everest is about 1/3 partial pressure of sea level

Question 11

How does CO2 interact with air-breathing animals?

Answer 11

• CO2 diffuses out as O2 diffuses in (rate of diffusion depends on partial pressure of gases)
• For air-breathing animals, partial pressure of CO2 from the body –> environment is large
• CO2 is very water-soluble and easy for aquatic animals to exchange (causes less problems for aquatic animals than not having O2)

Question 12

What is hypocapnia?

Answer 12

A state of reduced CO2 in the blood usually from hyperventilation

Question 13

What is breathing and cellular respiration?
What’s the formula for cellular respiration?

Answer 13

Breathing: exchange of gases (O2 and CO2)
Cellular Respiration: obtaining energy by oxidizing food molecules
Glucose + 6O2 + 6H2O = 6CO2 + 12H2O + energy (ATP)

Question 14

How does oxygen affect the brain?

Answer 14

Brain is very sensitive to oxygen levels, low anaerobic metabolism
- 4-5 min without oxygen = brain damage

Question 15

What are the bends and how does it occur?

Answer 15

Decompression sickness in scuba divers
1) Scuba divers breath through a regulator that equalizes air pressure in lungs to pressure of water on body
2) At depth, partial pressure of N2 is high and it diffuses from lungs into tissues via blood
3) If a diver comes up too fast, N2 comes out of solution in tissues and blocks blood vessels which lead to pain or death

Question 16

How does air travel in the human respiratory system?

Answer 16

1) Air enters lung from mouth or nose which join in the pharynx
2) Below the pharynx, the trachea leads to the lungs
3) Trachea branches into 2 bronchi (right and left), then into bronchioles, and then alveoli (gas exchange sites)

Question 17

What do alveoli do and how many are present in the human body?

Answer 17

Alveoli = sites of gas exchange
300 million alveoli in EACH lung (600M total)
- surface area of alveoli is about 70m^2

Question 18

How do capillaries help alveoli?

Answer 18

• alveoli have thin walls surrounded by capillaries, diffusion path between blood and air is less than 2 micrometers

Question 19

What are common diseases that take place in bronchioles and alveoli and how are they caused?

Answer 19

1) Emphysema: inflammation damages and destroys alveoli walls
- caused by smoking/air pollution
- 3rd leading cause of death in US

Question 20

What do mammalian lungs secrete that help with ventilation? How does that help?

Answer 20

Mucus and surfactant
- Mucus is secreted by cells lining airways to trap dirt and microorganisms
- Other cells have cilia beating constantly to sweep mucus and other dirt up to pharynx where it is swallowed or spit out (ex: Cigarette smoke paralyzes cilia and you cough to clear the mucus since your mucus elevator is broken)

Question 21

What is surfactant and how does it work?

Answer 21

Surfactant = fatty, detergent-like substance that reduces surface tension of a liquid and lowers work needed to inflate lungs

Question 22

How does surface tension work in lungs?

Answer 22

Surface tension gives the surface of a liquid the properties of an elastic membrane
- results from attraction between water molecules
- fluid covering the inside of alveoli has surface tension to make the lungs elastic

Question 23

What is the anatomy of the breathing organs?

Answer 23

• Lungs are in the thoracic cavity which have a diaphragm at the bottom and pleural membranes covering each lung
• Pleural space (thin, moist, slippery) contains fluid to help membranes slide past each other during breathing

Question 24

How does inhalation (active process) work?

Answer 24

• A larger chest cavity is created by contracting 2 muscles
  1) Diaphragm: pulls down on thoracic cavity and pleural membranes
  2) Intercostal muscles: muscles between ribs;
  a) External intercoastal muscles: lift ribs up and outward to expand thoracic cavity

Since air pressure outside is higher than in the lungs, the oxygen moves from environment –> lungs

Question 25

How does expiration (passive process) work?

Answer 25

- Diaphragm and intercoastal muscles relax 1) Diaphragm: pulls up via elastic recoil 2) Intercostal Muscles: decrease volume by pushing ribs down and inward a) Internal Intercostal Muscles: pull ribs down and inward to decrease thoracic cavity

Question 26

How does the pressure of the alveoli and pleural space compare with the external environment

Answer 26

Intra-alveolar pressure is the same as atmospheric pressure. Interpleural pressure is still negative to keep lungs from collapsing. (Inhalation causes interpleural pressure to become negative which causes intra-alveolar pressure to become negative to pull air into lungs)

Question 27

What happens to the pleural membranes when the thoracic cavity expands?

Answer 27

Increases the tension between them

Question 28

What happens when you have collapsed lung?

Answer 28

A punctured thoracic cavity can lead to collapsed lung as air can leak into the space between pleural membranes and cause lung to deflate. - Air is pulled between pleural membranes and alveoli aren't ventilated

Question 29

How does oxygen exchange occur?

Answer 29

Oxygen exchange occurs across a concentration gradient. Lungs --> blood --> tissues As a tissue gets depleted, more O2 is released there.

Question 30

What is hemoglobin and what is it made of?

Answer 30

Hemoglobin = a red blood cell protein that transports O2 (increases the capacity of blood to carry more O2, making higher rates of metabolism possible) - 4 peptide chains containing 1 heme Heme = Fe which binds O2 - each hemoglobin can carry 4O2 molecules - affinity for O2 changes with binding of O2

Question 31

How does carbon monoxide affect Hgb? What is CO produced from?

Answer 31

CO is made from an incomplete combustion of fuels. CO binds to Hgb with 240x higher affinity than O2 which prevents Hgb from transporting O2 ~ 500 deaths/year from CO poisioning

Question 32

What is positive cooperativity and how does it work?

Answer 32

Positive cooperativity refers to high oxygen affinity O2 is picked up where partial pressure is high and released where partial pressure is low. Low partial pressure of O2 changes the hemoglobin structure making it easier for other subunits to bind to hemoglobin.

Question 33

How is hemoglobin distributed to the body?

Answer 33

- Hgb leaving lungs is 100% saturated (4 O2 molecules) and only tends to drop 1 O2 molecule as it circulates throughout the body (75% saturated when it returns to lungs) **When tissue is starved of O2 and partial pressure of O2 is below 40 mmHg, small decreases in the partial pressure of O2 release lots of O2 in tissues

Question 34

What is myoglobin and how does it function?

Answer 34

Myoglobin = O2-binding molecule in muscle cells; single polypeptide molecule (can only bind 1 O2 molecule) - has a higher affinity for O2 than Hgb and binds it at low partial pressure O2 values when Hgb molecules release their O2 - provides reserves for when metabolic demands are high and blood flow is interrupted

Question 35

What is the functional different between fetal and adult Hgb?

Answer 35

Fetal Hgb has a higher affinity for O2 than adult Hgb which facilitates O2 transfer in placenta - lower affinity for O2 causes high metabolism and lowers pH of blood - low O2 level increase BPG (bisphosphoglyceric acid)

Question 36

What factors affect Hgb Oxygen Affinity?

Answer 36

1) Concentration of O2 in blood plasma 2) Hemoglobin consumption a) Normal adult: 2 alpha and 2 beta chains b) Fetus: 2 alpha and 2 gamma chains (fetus gets O2 from adult Hgb via blood) 3) Blood pH (Bohr effect) - as blood passes through metabolically active/exercising muscle, it picks up metabolites and blood pH lowers and is more acidic 4) Presence of 2,3-BPG + Hgb (deoxygenated) lowers its affinity for O2 and more O2 is released to tissues *#4 is higher in pregnant women, elevated altitudes, and active people

Question 37

Why does blood carry CO2 away from tissues?

Answer 37

CO2 is: 1) highly soluble in blood 2) readily diffuses in plasma 3) mostly converted into bicarbonate ions (HCO3-)

Question 38

What does carbonic anhydrase do?

Answer 38

CO2 from tissues is transported to lungs in the form of HCO3- and then converted back to CO2 to be exhaled. CO2 dissolves in water to form H2CO3 which dissociates to make HCO3-. CO2 + H2O <--> H2CO3 <---> H+ + HCO3- The reaction among CO2 and H2O is typically slow in the ECF but in endothelial cells and RBCs carbonic anhydrase speeds up the conversion of CO2 --> H2CO3 - Carbonic anhydrase reduces partial pressure of CO2 and helps with diffusion from tissue --> endothelial cells **Carbonic anhydrase only speeds up the reversible reaction, it does NOT determine direction

Question 39

What happens when CO2 binds with Hgb?

Answer 39

- In the lungs, the conversion reaction is reversed, CO2 diffuses from the blood into the alveoli and is exhaled

Question 40

How does carbon dioxide exchange occur?

Answer 40

- It is exchanged across a concentration gradient tissues --> blood --> lungs Transported 3 ways: 1) 20% hemoglobin 2) 5% transported in plasma as CO2 3) 75% is transported as bicarbonate (HCO3-)

Question 41

How is breathing regulated?

Answer 41

- Breathing is controlled by neural circuits in brainstem (involuntary process of CNS) Phrenic nerve = axons of respiratory motor neurons in medulla - innervates diaphragm and starts inhalation and controls rhythmic inspiration and expiration - includes the pons (controls medulla inspiration center) Chemoreceptors in brainstem sense H+ concentration **Higher brain areas modify breathing to accommodate speech, eating, coughing, and emotional states

Question 42

How is partial pressure of CO2 sensed?

Answer 42

Partial pressure of CO2 is the primary metabolic feedback for breathing in mammals - Small rise in arterial partial pressure CO2 causes a large increase in ventilation **Different from water-respiring animals as O2 is the primary feedback stimulus for gill ventilation Ventral surface of the medulla is sensitive to partial pressure of CO2,

Question 43

How is partial pressure of O2 monitored?

Answer 43

1) Carotid bodies 2) Aortic bodies in blood vessels leaving the heart - When partial pressure of O2 or blood supply falls, chemoreceptors send nerve impulses to the brain stem to stimulate breathing.

Question 44

What are inspiratory and expiratory reserve volumes?

Answer 44

Additional amounts of air that we can forcefully inhale or exhale - Vital capacity (VC) = Tidal volume (TV) + IRV + ERV *Athletes have a high VC and VC decreases with age because lung tissue stiffens

Question 45

What is residual volume?

Answer 45

Air that cannot be expelled from lungs - can be measured using the helium dilution method: a) a person breathes from a reservoir of a known volume of air with a known volume of helium in it, since helium isn't absorbed the initial and final volumes are the same Functional residual volume (FRV): FRV = ERV + RV

Question 46

How do you measure lung ventilation?

Answer 46

- Fresh air breathed in at rest is diluted by air remaining in lungs so partial pressure of O2 in lungs is lower than in the atmosphere - RV contributes to FRV and dilution of O2 in inhaled air - Diseases that increase RV (like emphysema) impact respiratory ability in a detrimental way