The Respiratory System - Warner Pacific Collegeclasspages.warnerpacific.edu/BDupriest/BIO 420/Unit 3...

The Respiratory

System

RESPIRATORY SYSTEM

Primary functions

Major functional events

Pulmonary ventilation

Diffusion of O2 & CO2 between

alveoli & blood

Transport of O2 & CO2 in

blood and body fluids

Regulation of ventilation

2

Respiratory Gasses

What essential function does O2 serve?

How is CO2 produced and why do we need to

get rid of it?

3

True or false: The oxygen you breathe in gets

converted into carbon dioxide that you then

breathe out.

A) True

B) False

4

Review of Respiratory Structures

Upper vs. lower respiratory tracts

Thoracic cavity

Diaphragm

See Fig. 37-8

5


Respiratory tree

Trachea

Bronchi

Bronchioles

Alveolar sacs

Alveoli

See Fig. 37-8 6


Structural characteristics

Cartilage

Cilia

Mucus glands

Smooth muscle

See Fig. 37-8

7


Respiratory membrane

Blood-air barrier

Epithelial characteristics

Type I cells

Type II cells

Produce surfactant

See Fig. 37-8 8


Pleurae (membranes)

Parietal pleura

Visceral pleura

Pleural cavity

Serous fluid

Lungs “float” in pleural

cavities

9

Fluids in the respiratory system have all of

these functions except…

A) Reducing friction of lung against chest wall

B) Reducing surface tension in the lung

C) Allowing gasses to diffuse across

epithelium

D) Transporting metabolic fuels to body

tissues

10

Mechanics of Breathing

Boyle’s Law

P1V1 = P2V2

The pressure of a gas varies

inversely with its volume

volume, pressure

= inhalation

volume, pressure

= exhalation

Air moves from area of high

pressure to area of low

pressure

11


Muscular events during inspiration

Diaphragm contracts & flattens inferiorly

External intercostals contract & elevate rib cage

thoracic volume

Fig. 37-1 12


Muscular events during expiration

Diaphragm relaxes & moves superiorly

External intercostals relax, rib cage depressed

thoracic volume

Normal breath - recoil due to elasticity of

lungs/thoracic cage

13 Fig. 37-1


Heavy breathing Inspiration

Raise rib cage

Exhalation

Compress rib cage

14 Fig. 37-1


Thoracic pressures

Intrapulmonary pressure (alveolar pressure)

Pressure within alveoli

Equalizes with atmospheric pressure

15


Thoracic pressures


Intrapleural pressure

Pressure of fluid within pleural cavity

< alveolar pressure

Low pressure created by fluid draining into

lymphatic capillaries

Fluid/pressure causes visceral pleura to “stick” to

parietal pleura

as thoracic cavity expands, lungs expand

Elasticity of lungs causes recoil, aids expiration

Equalization with alveolar pressure = collapse 16


Thoracic pressures


Intrapleural pressure

Transpulmonary pressure

Difference between intrapulmonary and

intrapleural pressures

Represents the elastic forces of the lungs

17

Thoracic Pressures

Fig. 37-1 18

Environmental pressure equalizes with which of

the following pressures?

A) Transpulmonary pressure

B) Pleural pressure

C) Alveolar pressure

D) All of the above

19

Lung Compliance

Relationship of lung expansion and

transpulmonary pressure

Every 1 cm H2O increase in transpulmonary

pressure results in 200 ml expansion in lung

volume

Characteristics determined by elastic forces

of lungs

Elasticity of lung tissue

Surface tension within alveoli

20

Lung Compliance

Tissue elasticity

High percentage of elastic fibers in connective

tissue of lungs

Elastin & collagen

Stretched during expansion then recoil

21

Lung Compliance

Alveolar surface tension

Alveolar surfaces covered with fluid

Forms water-air surface

Increases rate of gas diffusion

Creates tension between water molecules

Cohesive forces of water

Surface tension

Surfactants decrease surface tension

Interfere with water cohesion

Degree of recoil reduced

22

Lung Compliance

Factors reducing lung compliance

Reduced tissue elasticity

Reduced surface tension

Increased airway resistance

Mucus buildup

Bronchial constriction

23

Lung compliance is affected by all of the

following except…

A) Alveolar surface tension

B) Elastic forces of lungs

C) Airway resistance

D) Size of alveoli

24

Pulmonary Volumes

Tidal volume (VT)

Normal

inspiration/expiration

~ 0.5 L

Inspiratory reserve

volume (IRV)

Air forceably inspired

beyond VT

~ 3 L

Fig. 37-6

25

Pulmonary Volumes

Expiratory reserve volume

(ERV)

Air forcibly expired beyond VT

~ 1.1 L

Residual volume (RV)

Air that cannot be

forcibly expired

~ 1.2 L

26

Fig. 37-6

Pulmonary Capacities

Inspiratory capacity (IC)

Max. air inspired after normal

expiration

TV + IRV

~ 3.5 L

Functional residual

capacity (FRC)

Air remaining in lungs

after normal expiration

ERV + RV

~ 2.3 L

27

Fig. 37-6

Pulmonary Capacities

Vital capacity (VC)

Max. air inspired after normal

expiration

IRV + TV + ERV

~ 4.6 L

Total lung capacity

(TLC)

VC + RV

~ 5.8 L

28

Fig. 37-6

Other Respiratory Measurements

Minute respiratory volume

Amount of air moved into respiratory passages

each minute

TV (ml) x respiratory rate (bpm)

Dead space

Air filling respiratory passages but not reaching

gas exchange areas

~ 0.15 L

29

The amount of air remaining in your lungs after

a normal expiration is the…

A) Expiratory reserve volume

B) Functional residual capacity

C) Total lung capacity

D) Residual volume

30

Determining Respiratory Volumes

Functional residual capacity (He dilution

method)

Fill spirometer with known vol of air + known vol

of He

Expire normally then breathe from spirometer

Air remaining in lungs = FRC

[He] diluted by FRC gasses

Calculate degree of dilution

31

Fig. 37-6


Residual volume and total lung capacity

Use FRC value

RV = FRC - ERV

TLC = FRC + IC or VC + RV

32

Fig. 37-6


Dead space

Breathe normally then take deep breath of pure O2

Exhale into nitrogen meter

First air expired = dead space all O2

[N2] as alveolar air is expired

[N2] plateaus as original alveolar concentration

reached

Area to left of curve =

dead air space

Fig. 37-7 33

Alveolar Ventilation

Rate at which “new” air reaches gas

exchange area

Good index of effective ventilation

AVR (ml/min) = frequency x (VT - dead space)

E.g., AVR = 12 b/min x (500 ml/b - 150 ml/b) = 4200 ml/min

What this indicates…

Slow/deep breaths ventilation


Rapid/shallow breaths ventilation


34

If you want to increase the amount of new air in

the lungs, you should…

A) Breathe more quickly

B) Breathe more deeply

35

Gas Exchange Across Respiratory Membranes

Dalton’s Law of Partial Pressures

Total gas pressure = sum of partial pressures of

gasses within the mixture

36


Partial pressure of atmospheric gasses (sea level)

mmHg %

N2 597.0 78.62

O2 159.0 20.84

CO2 0.3 0.04

H2O 3.7 0.50

Total 760.0 100.00

See Table 39-1 37


Henry’s Law

When a gas mixture is in contact with a liquid,

each gas will dissolve in proportion to its partial

pressure and relative to its solubility in the liquid

conc. of dissolved gas partial pressure = solubility coefficient solubility, more gas can dissolve without

building up excess partial pressure

38


Solubility coefficients of important respiratory gasses

PO2 0.024

PCO2 0.570

PCO 0.018

PN2 0.012

PHe 0.008

39


Diffusion coefficient

Relative rates at which different gasses at same

pressure levels will diffuse

Depends on molecular weight of the gas & solubility

O2 1.0

CO2 20.3

CO 0.81

N2 0.53

He 0.95

40


Diffusing capacity

Volume of gas that will diffuse through the

membrane each minute at a partial pressure

difference of 1 mmHg

41

Diffusing Capacity

O2 (at rest)

~ 21 ml/min/mmHg

Pressure difference across membrane ~ 11 mmHg

O2 diffusion = 11 x 21 = 230 ml/min (same as

use rate)

Fig. 39-10 42

Diffusing Capacity

O2 (during exercise)

~ 65 ml/min/mmHg (max)

~ 3x increase due to…

Increased pulmonary

circulation (dilation)

Increases diffusing

capacity

Increased ventilation-

perfusion ratio

Fig. 39-10 43

Diffusing Capacity

CO2

~ 400-450 ml/min/mmHg (at rest)

Theoretical

~20x O2

Pressure difference across

membrane > 1 mmHg

Less pressure difference

but higher solubility &

diffusion coefficients

Fig. 39-10

44

The diffusing capacity of a membrane for a

particular gas depends on all of these except:

A) diffusion coefficient of the gas

B) pressure difference of the gas across

membrane

C) thickness of membrane

D) absolute concentration of the gas in the

blood

45

Alveolar Air

Composition differs from atmosphere

Humidified

Continual diffusion of CO2 into alveoli

Continual diffusion of O2 into blood

See Table 39-1 46

Alveolar Air

Only partially replaced

FRC ~2.3 L, only ~350 ml “fresh” air enters alveoli

Takes multiple breaths (16+) to completely replace

Slow replacement important to prevent sudden

changes in gas concentration in the blood

Fig. 39-2 47

Alveolar air is replaced slowly, over the course

of ~16 breaths, because…

A) the volume of air breathed in is small in

relation to dead space

B) the volume of air breathed in is small in

relation to the functional reserve capacity

C) the old air prevents new air from coming

into the lung well

D) the speed of air intake is insufficient to

push old air out

48

Factors Influencing Rate of Diffusion Through Membrane

Membrane thickness

Averages ~0.6 m

thickness (i.e., edema), diffusion

Fig. 39-9 Fig. 39-8 49

Factors Influencing Rate of Diffusion Through Membrane

Membrane thickness

Averages ~0.6 m

thickness (i.e., edema), diffusion

Surface area

~60-70 m2

Partial pressure gradients

Gas solubilities

50

Diffusion of O2 & CO2 Across the Respiratory & Cellular Membranes

Fig. 40-1 & 3 Fig. 40-6 & 5

O2 CO2

51

Systemic PO2

Fig. 40-2

52

Carbon dioxide moves from alveolar capillaries

into alveoli because…

A) Concentration of oxygen is higher in

alveoli than in the blood

B) Partial pressure of carbon dioxide is higher

in alveoli than in the blood

C) Concentration of carbon dioxide is higher

in blood than in alveoli

D) Partial pressure of carbon dioxide is higher

in blood than in alveoli

53

Ventilation-Perfusion Coupling

Synchronization of blood flow with gas

concentrations

Function

Redirect blood to where it is most needed for gas

exchange

54


Alveolar capillaries

Respond to PO2

PO2 arterioles around reduced perfusion (inadequate alveoli constrict (blood flow) ventilation)

Less O2 reduce blood flow around affected alveoli

PO2 arterioles around increased perfusion (adequate alveoli dilate (blood flow) ventilation)

More O2 increase blood flow around affected alveoli

55


Bronchioles

Respond to PCO2

Alveoli Bronchioles

PCO2 Dilate (increase expiration volume)

PCO2 Constrict

56

Ventilation-Perfusion Ratio

Reflects respiratory exchange when alveolar

ventilation (VA) and blood flow (Q) are

imbalanced

V-P ratio = VA/Q

VA = alveolar ventilation, Q = blood flow

ratio compared to normal

Adequate blood flow but poor ventilation

Alveolus [O2/CO2] equilibrates with pulmonary

capillary blood

Blood shunted away from affected capillaries

(physiologic shunt)

Reduced oxygenation of pulmonary venous

blood 57

Ventilation-Perfusion Ratio

Reflects respiratory exchange when alveolar

ventilation (VA) and blood flow (Q) are

imbalanced

ratio compared to normal

Adequate ventilation but poor blood flow

Alveolus [O2/CO2] equilibrates with inspired air

Physiologic dead space (wasted ventilation)

58

Ventilation-perfusion coupling imbalances may

result in…

A) Increased physiological dead space

B) Wasting of energy due to unnecessary

ventilation

C) Poor oxygenation of blood

D) All of the above

59

Transport of O2 in Blood

Bound to hemoglobin

~97%

Dissolved in plasma

~3%

60

Hemoglobin (Hgb)

Hemoglobin

Tetramer

Globin polypeptides

& chains most

common

1 heme / chain

Heme group

Porphyrin ring with Fe

core

Pigment

See Fig. 32-6

61

Hemoglobin (Hgb)

O2 binding

1 O2 / heme group

4 heme groups / Hgb ( 4 O2 / Hgb)

62

O2 binding & pigment development

Causes conformational change in heme group

Oxyhemoglobin (HgbO2) = bright red

Deoxyhemoglobin (HHgb) = dark red

lungs

HHgb + O2 HgbO2 + H+

tissues

Hemoglobin (Hgb)

63

Hemoglobin (Hgb)

O2 binding & Hgb saturation

1st O2 binds

Partial saturation

Conformational change increases uptake of

additional O2

Remaining 3 O2 bind

Full saturation

64

Oxygen binds to…

A) The alpha chain of hemoglobin

B) The beta chain of hemoglobin

C) The heme portion of hemoglobin

D) All of the above

65

O2/Hgb Dissociation Curve

Reflects affinity of O2 for Hgb at different PO2

Observations to note

At PO2 of 40 (venous blood), Hgb is still ~70%

saturated

Venous reserve

Fig. 40-8 66


Reflects affinity of O2 for Hgb at different PO2

Observations to note

Decreased alveolar PO2 can still allow adequate O2

binding ( elevation)

67 Fig. 40-8


Changes in metabolic factors can shift curve

& affect O2 loading/unloading

Shift to right → increase O2 unloading

Shift curve to left → increase O2 loading

68 Fig. 40-8

unloading

loading

Factors Influencing O2/Hgb Dissociation Curve

Any increase in the following factors

shifts the curve to the right

Temperature

H+

PCO2

BPG (2,3-bisphosphoglycerate)

Method

O2 affinity for Hgb

dissociation (unloading)

Fig. 40-10

69

Oxygen can be offloaded more easily when…

A) Carbon dioxide partial pressure is

increased

B) Blood is more alkaline

C) Body temperature falls

D) All of the above

70

Transport of CO2 in Blood

Dissolved in plasma

~7-10%

Bound to Hgb

~20-30%

Carbaminohemoglobin (HgbCO2)

Binds to globin doesn’t compete with O2

binding sites on heme

Binds most rapidly to HHgb than HgbO2

71

Transport of CO2 in Blood

Dissolved in plasma

~7-10%

Bound to Hgb

~20-30%

As bicarbonate ions in plasma

~60-70%

carbonic anhydrase

CO2 + H2O H2CO3 HCO3- + H+

carbonic acid bicarbonate

72

Bicarbonate Buffering System

Dissociation of carbonic acid (H+)

RBC

H+ + Hgb HHgb

Buffering

Weakens HgbO2 enhances O2 unloading

See Fig. 40-13 73


Dissociation of carbonic acid (HCO3-)

Chloride shift

Diffusion of HCO3- from RBC to plasma

Countered by influx of Cl- from plasma into RBC

Maintains charge balance

Gradient favors anabolic action of carbonic anhydrase

See Fig. 40-13 74


CO2 transport to lungs

PCO2 in blood

See Fig. 40-13

75

True or false: Carbonic anhydrase may catalyze

opposite reactions depending on conditions.

A) True

B) False

76

Bohr Effect

Effect of changes in pH and CO2 on the unloading / loading of O2 with hemoglobin Tissues

Uptake of CO2…

carbonic acid ( H+)

O2-Hb curve shifts right

O2 affinity for Hgb ( O2 unloading)

77

Bohr Effect

Effect of changes in pH and CO2 on the unloading / loading of O2 with hemoglobin Lungs

Removal of CO2…

carbonic acid ( H+)

O2-Hb curve shifts left

O2 affinity for Hgb ( O2 loading)

78

Haldane Effect

Effect of O2/Hgb binding on the displacement & uptake of CO2

Lungs

HgbO2 formation (O2 loading) releases H+

tendency of Hgb to form HgbCO2

Drives catabolic action of carbonic anhydrase (CO2 formation)

79

Haldane Effect

Effect of O2/Hgb binding in the displacement & uptake of CO2

Tissues

HgbO2 dissociation (O2 unloading) frees Hgb

Favors HHgb & HgbCO2 formation

H+ utilization drives anabolic action of carbonic anhydrase

80

The ability of protons to influence O2 loading to

hemoglobin is the…

A) Haldane effect

B) Bohr effect

81

Regulation of Respiration

Respiratory centers in medulla oblongata &

pons

Dorsal respiratory group (DRG)

Inspiratory center (sets respiratory rhythm)

Sensory input from vagus & glossopharyngeal

nerves

Chemoreceptors

Baroreceptors

Sensory

receptors within

lungs

Fig. 41-1

82



pons

Dorsal respiratory group (DRG)

Output to primary respiratory muscles (phrenic

nerve)

“Ramp signal”

Gradually increases contraction

Steady increase in lung volume

Abrupt stop (expiration); recoil

83



pons

Ventral respiratory group (VRG)

Inspiration & expiration

Respiratory “overdrive”

Inactive during normal respiration

Activated with forced/increased breathing

Stimulate

muscular

activity of both

inspiration &

expiration

84



pons

Pneumotaxic center

Controls rate & pattern of breathing by limiting

duration of inspiration

Controls DRG ramp “switch-off” point

Strong signal shortens ramp-up time

inspiration rate (30-40 bpm)

inspiration depth

85



pons

Pneumotaxic center

Controls rate & pattern of breathing by limiting

duration of inspiration

Controls DRG ramp “switch-off” point

Strong signal lengthens ramp-up time

inspiration rate (3-5 bpm)

inspiration depth

86

Hering-Breuer Inflation Reflex

Response of lung inflation to limit respiration

Functions to protect against excess stretch

Inflation of lungs increases output signal from

baroreceptors

Increased stimulus (vagal afferents) inhibits DRG

Terminates inspiration (ramp-off)

Sensory receptors within lungs

Deflation of lungs decreases output signal from

baroreceptors

Decreased stimulus (vagal afferents), DRG not

inhibited

Begins ramp-up 87

Which center in the medulla is primarily

responsible for setting respiratory rate?

A) Dorsal respiratory group

B) Pneumotaxic center

C) Ventral respiratory group

D) All of the above

88

Chemical Control of Respiration

Goal of respiration

Maintain O2, CO2, H+ concentrations in blood &

tissues

Control of respiration

Response to changes in O2, CO2, H+ concentrations

CO2 & H+ act centrally on respiratory centers

O2 input from peripheral locations

89

CO2, Blood pH and Regulation of Breathing

Fig. 41-3 90

CO2, H+ & Respiratory Control

Chemosensitive area of respiratory center

blood [CO2] provides indirect stimulation

CO2 diffuses into chemosensitive area

Reacts with H2O in tissues

blood PCO2 tissue PCO2 H+

Effect

ventilation

91 Fig. 41-2

CO2, Blood pH and Regulation of Breathing

Carbonic acid-bicarbonate buffering system

CO2 + H2O H2CO3 HCO3- + H+

pH drives equilibrium

pH ( H+)

Drives equation left

Rapid / deep breathing

Releases more CO2 raises pH (removes free H+)

pH ( H+)

Drives equation right

Slow / shallow breathing

Retains more CO2 lowers pH (increases free H+)

92

O2 & Respiratory Control

Peripheral chemoreceptors

Stimulated by arterial PO2

Lesser extent by CO2 & H+

Primarily carotid & aortic bodies

Carotid bodies

Afferents (Hering’s glossopharyngeal)

Synapse at DRG

Aortic bodies

Afferents (vagus)

Synapse at DRG

Fig. 41-4 93

O2 & Respiratory Control

Effect of arterial PO2

As PO2 decreases (< 100 mmHg)…

Impulse rate to respiratory centers increases

ventilation

Fig. 41-5 Fig. 41-6 94

True or false: Oxygen drives breathing rate

more than carbon dioxide.

A) True

B) False

95

Respiratory Insufficiency

Hypoxia

Inadequate delivery of O2 to tissues

Cyanosis

Skin, mucosa, nail beds turn “blue”

Depressed mental activity (may lead to coma)

Reduced muscle activity

Cell death

96


Asthma

Hypersensitivity (allergy) to airborne substances

Reaction

Immune response

Release of leukotrienes, bradykinin, histamine,

etc.

Localized edema (walls of bronchioles)

Smooth muscle spasm (bronchioles)

Increased airway resistance (decreased

ventilation)

Expiration difficulty

May cause dyspnea 97


Asthma

Common treatments

Bronchodilators

Simulate sympathetic response (bronchiole

dilation)

Immediate relief

Corticosteroid aerosols

Long term therapy

Reduce frequency / intensity of attacks

98


Effect of CO

Competes with O2 for heme sites on Hb

~250x affinity for Hb

At PCO of 0.4 mmHg in alveoli, competes equally

with O2 for Hb

Treatment

PO2 (pure O2)

Greater pressure differential displaces CO

PCO2

Increase ventilation

99

True or false: Oxygen drives breathing rate

more than carbon dioxide.

A) True

B) False

100

The Respiratory System - Warner Pacific Collegeclasspages.warnerpacific.edu/BDupriest/BIO 420/Unit 3...

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