Respiratory physiology

Question 1

What are the key functions of the respiratory system?

Answer 1

-gas exchange; regulation of pH body fluids; temperature control; voice production

Question 2

What are the 2 key respiratory gases?

Answer 2

O2 and CO2

Question 3

What is partial pressure?

Answer 3

the amount of pressure exerted by a particular gas in a mixture

Question 4

What is a gas exchange membrane? How do gases get to the exchange membrane? How do they cross it?

Answer 4

• layers of tissues(s) that separates the internal tissues from the external environment
• gases reach the membrane by convection transport (ventilation and circulation) and cross the membrane by diffusion

Question 5

What factors control the rate of gas diffusion?

Answer 5

• high partial pressure to low
• affected by: membrane surface area, difference in partial pressures, distance between two partial pressures, the gas, temperature, the phase, membrane permeability

Question 6

Why is it advantageous to have an expansive, but very thin gas exchange membrane?

Answer 6

bigger surface area

Question 7

List the parts of the respiratory system

Answer 7

-nasal passages, pharynx, larynx, trachea, bronchi, bronchioles, aveoli, intercostal muscles, diaphragm, pulmonary artery & vein

Question 8

What are the major muscle groups involved in breathing in mammals? In birds?

Answer 8

-mammals: external intercostals, diaphragm, internal intercostals, abdominal muscles

Question 9

Describe how air moves through the airways in mammals.

Answer 9

• composition of air in alveoli is different from the atmosphere
• not all of the “stale” air is cleared from the alveoli after each breath and the inhaled “fresh” air makes up only a small percent of air in the alveoli
• lower pO2 and higher pCO2 than conducting airways

Question 10

What are the different roles of the larynx?

Answer 10

voice box, part of the airway

Question 11

What is the difference between conducting and respiratory airways?

Answer 11

• conducting: passages that bring air to/from exchange surface
• respiratory: where gas exchange occurs, high surface area and good blood supply

Question 12

What is the role of the avian air sacs?

Answer 12

NOT the site of gas exchange; they help move air through the parabronchi because birds to not have a diaphragm

Question 13

Explain the muscular processes involved with inspiration and how these processes lead to air
being drawn into the lungs in mammals.

Answer 13

• requires coordinated muscle contraction by the intercostal muscles and diaphragm (ATP use)
• rib cage pulled up and out, diaphragm descends and creates a vacuum, lungs volume expands, air pulled into airways

Question 14

Explain the processes of expiration in mammals. How (and when) are muscles involved in expiration in mammals?

Answer 14

• muscle relaxation- elastic recoil
• neurons of inspiration are inhibited, muscles relax, rib cage returns to “normal” position; pressure increases pushes air out of alveoli
• forced expiration may be necessary and used the internal intercostals and the abdominal muscles (needs ATP)

Question 15

Explain the muscular processes involved with inspiration and how these processes lead to air
being drawn into the lungs in birds.

Answer 15

• posterior ribs expand and sternum swings forward and down

- air sacs expand: inhale

Question 16

Explain the muscular processes involved with of expiration in birds and how these processes
lead to air leaving the lungs.

Answer 16

• contraction by abdominal and external intercostals
• ATP required
• air sacs empty: exhale

Question 17

Why is the composition of air in the alveoli different from that in the atmosphere?

Answer 17

not all of the stale air is cleared from alveoli after each breath and the inhaled fresh air makes up only a small percent of air in the alveoli

Question 18

Explain/define all the different subdivisions of lung volume. What is the tidal volume?

Answer 18

• tidal volume: amount of air that comes into and out of the lungs during each breath
• vital capacity: maximum amount of air that can move into and out of the lungs during breathing
• residual volume: amount of air that cannot be forcefully expired from the lungs

Question 19

What factors determine how much air enters the lungs each minute?

Answer 19

respiratory minute volume

Question 20

Explain how and why respiration can have both voluntary and non-voluntary components?

Answer 20

-normal breathing is reflexive (done without thinking)

Question 21

What areas of the brain are involved with the control of respiratory rate?

Answer 21

medulla, pons

Question 22

What different “chemical” factors regulate the respiratory rate? How? Why?

Answer 22

pre-Botzinger complex; initiate the breathing rhythm

Question 23

What is the normal blood pH of homeotherms and why is it important to keep this range very tight?

Answer 23

~7.4; anything different will alter protein function

Question 24

Explain all of the processes involved with CO2 moving from the tissues to the blood. Include
discussion of how and where it is converted to bicarbonate and where the bicarbonate ion is primarily found. Also include discussion of how the H+ formed during HCO3- formation is buffered in the blood (and how that varies based on where the HCO3- was made).1

Answer 24

1. O2 is used by the tissues to produce ATP and CO2 is produced
2. CO2 diffuses out of the muscle (tissue) from high PCO2 to low PCO2 in the bloodstream
3. Most CO2 diffuses from the bloodstream into the red blood cell
4. of the CO2 that diffuses into the RBC, some of the CO2 may combine with the amino group of hemoglobin to form a carbamate ion + H+
5. The majority of the CO2 in the RBC is converted to HCO3- + H+ by carbonic anhydrase in the RBC
6. The HCO3- produced in the RBC is transported out into the plasma in exchange for Cl- (enters the RBC) = chloride shift

Question 25

Why does it make sense to link CO2 capacity/affinity with the oxygenation status of the blood?

Answer 25

Carbonic anhydrase (CA) greatly increases the rate of HCO3- formation

Question 26

How does the Haldane effect work? In what way(s) is it in opposition to the Bohr effect?

Answer 26

- Opposes the Bohr effect - hemoglobin deoxgenation promotes CO2 uptake, oxygenation promotes CO2 unloading - Deoxygenation increases buffering capacity of Hb, because Hb can either bind O2 or H+ - More efficient H+ buffering, allows more HCO3 to be carried in the blood - O2 is released in the tissues which is where CO2 is produced; allows efficient removal of the CO2

Question 27

What are the key buffers in the blood (including the specific parts of the molecules)?

Answer 27

1- hemoglobin: intracellular buffer (inside RBC) - terminal amino groups of globin 2- plasma proteins: extracellular buffer (not in RBC) - charged chains of aa can take up or give off H+ ions

Question 28

Why is blood buffering important in ensuring that maximum amounts of CO2 can be carried by the blood?

Answer 28

Amount of HCO3- in the blood is dependent on the buffering capacity (ability to remove H+) of the blood -more buffering = more H+ ions "neutralized" = more bicarbonate can be carried in the blood

Question 29

What is the primary form of CO2 in the blood?

Answer 29

HCO3-

Question 30

Other than oxygen transport, what else does hemoglobin do?

Answer 30

it is an intracellular buffer

Question 31

Explain how the Bohr Effect helps to ensure efficient oxygen delivery to tissues under normal circumstances.

Answer 31

- the O2 dissociation curve in the tissues is shifted to the right of the O2 dissociation curve in the lungs - due to the combine effects of higher PCO2 and lower pH in the tissues than in the lungs - encourages efficient O2 loading onto hemoglobin in the lungs and efficient O2 unloading in the tissues where the O2 is needed - allows for the greatest amount of O2 possible to be delivered to the tissues where it can be diffused and be used to make ATP

Question 32

What are the factors that affect the affinity of hemoglobin for oxygen? For each of these factors explain how they affect the affinity and why. Be able to show how the oxygen dissociation curve will move if changes occur to each of these factors (independently).

Answer 32

- many of the same factors that affect respiratory rate (bohr effect) - increase PCO2 = decrease affinity - decrease pH = decrease affinity - temperature: increase temp = decrease affinity - metabolic byproducts may decrease infinity - type of hemoglobin (myoglobin) = myoglobin has a greater affinity for O2 at tissue PO2 than blood hemoglobin

Question 33

What do we mean when we say that hemoglobin’s affinity for oxygen is high under a certain physiological situation?

Answer 33

Certain physiological effects can influence it; temperature, metabolic byproducts, etc

Question 34

What drives oxygen movement from the blood into the tissues and how does this relate back to the oxygen dissociation curve?

Answer 34

-oxygen must be released from the hemoglobin to diffuse across membranes into the tissues, so it is beneficial for less O2 to be bound to hemoglobin in the tissues (where lowest PO2 exists)

Question 35

What is an oxygen dissociation curve and what does it tell us? Be able to draw the shape of the curve (and know some of the key numbers- ie. lungs, systemic tissues and tissues during exercise)

Answer 35

-the graphical representation of the relationship between Hb oxygenation and O2 partial pressure

Question 36

What is meant by the term ‘oxygen carrying capacity’?

Answer 36

- the oxygen content of the blood when all hemoglobin is saturated with O2 - dependent on how much hemoglobin is in the blood

Question 37

What sets of membranes does O2 need to cross to get from the alveoli to bind to hemoglobin?

Answer 37

- alveolar membrane (into and out of cell) - capillary endothelium (into and out of cell) - RBC membrane (into cell)

Question 38

In what form (ie. dissolved, bound, etc.) is the majority of blood oxygen?

Answer 38

bound

Question 39

What are the key roles of hemoglobin?

Answer 39

- increase the O2 carrying capacity of blood ** - assist with regulation of blood pH - Co2 transport through the blood

Question 40

Describe the structure of hemoglobin and how it may vary based on the tissue.

Answer 40

- heme (ring structure) + globin (protein chain) - 1 oxygen/heme group - varies within a species across tissues - blood hemoglobins = 4 heme+globin molecules - muscle myoglobins: 1 heme+globin

Question 41

What factors regulate the respiratory rate in birds?

Answer 41

- CNS control in the pons and medulla - chemoreceptors for PCO2, PO2, and pH - mechanoreceotprs - thermoreceptors

Question 42

Describe air flow through the avian respiratory system during inspiration and expiration.

Answer 42

Inspiration: - posterior air sacs filled with "fresh" air - anterior air sacs filled with "stale" air - movement through the parabronuhi is always posterior to anterior Exhalation: - air is pushed out of air sacs - "fresh" air from the posterior air sacs directed to the parabronchi - "stale" air from bronchi and anterior air sacs is exhaled via the primary bronchi - the majority of exhaled gas has passed over the exchange surfaces by the end of the inhalation-exhalation cycle - movement through the parabronchi is always posterior to anterior

Question 43

Aside from chemical mediators, what else may be involved in controlling respiration during exercise?

Answer 43

psychological factors: exercise excitement activates the sympathetic nervous system

Question 44

What non-chemical factors can regulate respiratory rate?

Answer 44

- motor neurons - sensors in limbs - thermoregulation - psychological factors