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Physiology > Exam 3: Ch 16 Respiratory Physiology > Flashcards

Exam 3: Ch 16 Respiratory Physiology Flashcards

1
Q

Respiration Encompasses 3 related functions:

A
  • ventilation,
  • gas exchange,
  • 02 utilization (cellular respiration)
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2
Q

02 utilization (cellular respiration)

A

Ventilation = breathing;

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3
Q

Ventilation = breathing;

A

moves air in & out of lungs for gas exchange (which occurs via passive diffusion) with blood

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4
Q

external respiration)

A

gas exchange between air and blood in lungs =

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5
Q

internal respiration

A

Gas exchange between blood & tissues, & O2 use by tissues =

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6
Q

Air passes from

A

from mouth to pharynx to the trachea to right & left bronchi to bronchioles to terminal bronchioles to respiratory bronchioles to alveoli

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7
Q

Gas exchange occurs only in

A
  • respiratory bronchioles & alveoli (= respiratory zone)

- All other structures constitute the conducting zone

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8
Q

Gas exchange occurs across the

A
  • 300 million alveoli (60-80 m2 total surface area)

- Only 2 thin cells are between lung air & blood: 1 alveolar & 1 endothelial cell

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9
Q

Alveoli

A
  • Are polyhedral in shape & clustered at ends of respiratory bronchioles, like units of honeycomb
  • Air in 1 cluster can pass to others through pores
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10
Q

Conducting Zone

A
  • Warms & humidifies inspired air
  • Mucus lining filters & cleans inspired air
    • Mucus moved by cilia to be expectorated
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11
Q

Thoracic Cavity is created by

A

the diaphragm, a dome-shaped sheet of skeletal muscle

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12
Q

Above the diaphram is

A

heart, large blood vessels, trachea, esophagus, thymus, & lungs

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13
Q

Below diaphragm is

A

abdominopelvic cavity; contains liver, pancreas, GI tract, spleen, & genitourinary tract

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14
Q

Intrapleural space is

A

is thin fluid layer between visceral pleura covering lungs & parietal pleura lining thoracic cavity walls

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15
Q

Ventilation results from

A

from pressure differences between the conducting zone and the terminal bronchioles induced by changes in lung volumes

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16
Q

Air moves from

A

higher to lower pressure

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17
Q

Compliance, elasticity, & surface tension of lungs influence

A

ease of ventilation

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18
Q

Boyle’s Law (P = 1/V)

A

States that changes in intrapulmonary pressure (pressure in alveoli and the rest of lungs) occur as a result of changes in lung volume

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19
Q

Pressure of gas is

A
  • inversely proportional to volume
    • Increase in lung volume decreases intrapulmonary pressure causing inspiration
    • Decrease in lung volume raises intrapulmonary pressure causing expiration
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20
Q

Compliance

A

= how easily lung expands with pressure

Is reduced by factors that cause resistance to distension

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21
Q

Elasticity

A

Is tendency to return to initial size after distension

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22
Q

Elasticity is due to

A

high content of elastin proteins that resist distention

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23
Q

Elastic tension increases

A

during inspiration & is reduced by recoil during expiration

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24
Q

Surface Tension (ST)

A

created by intermolecular forces within fluid molecules that attract molecules to each other

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25
Q

ST and elasticity are forces that promote

A

alveolar collapse & resist distension

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26
Q

Lungs secrete & absorb fluid

A
  • normally leaving a thin film of fluid on alveolar surface
    • This film causes ST because H20 molecules are attracted to other H20 molecules; force of ST is directed inward, raising pressure in alveoli
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27
Q

Fluid absorption occurs by

A
  • osmosis

driven by Na+ active transport

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28
Q

Fluid secretion is driven by

A

active transport of Cl- out of alveolar epithelial cells

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29
Q

Surfactant

A

Consists of phospholipids secreted by alveolar cells

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30
Q

Surfactant Lower ST by

A

by getting between H20 molecules, reducing their ability to attract each other via hydrogen bonding

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31
Q

Surfactant Prevents ST from

A

collapsing alveoli

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32
Q

Surfactant secretion begins

A

in late fetal life

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33
Q

Premies are often born with

A
  • immature surfactant system (= Respiratory Distress Syndrome or RDS) and
    have trouble inflating lungs
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34
Q

In adults, septic shock

A
  • (↓ BP due to widespread vasodilation) may cause acute respiratory distress syndrome (ARDS) which decreases compliance & surfactant secretion
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35
Q

Pulmonary ventilation consists of

A

inspiration (= inhalation) & expiration (= exhalation)

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36
Q

Pulmonary ventilation Accomplished by

A

alternately increasing & decreasing volumes of thorax & lungs

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37
Q

Inspiration occurs mainly because

A

diaphragm contracts, increasing thoracic volume vertically

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38
Q

Q: If volume ↑ what happens to pressure?

A

decreases

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39
Q

Parasternal & external intercostal contraction

A

contributes a little by raising ribs, increasing thoracic volume laterally

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40
Q

Expiration is due to

A

passive recoil

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41
Q

Deep Breathing:

Inspiration involves

A

contraction of extra muscles to elevate ribs: scalenes, pectoralis minor, & sternocleidomastoid muscles

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42
Q

Deep Breathing:

Expiration involves

A

contraction of internal intercostals & abdominal muscles

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43
Q

Pulmonary Function Tests Assessed clinically by

A

spirometry, a method that measures volumes of air moved during inspiration & expiration

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44
Q

Anatomical dead space is

A

is air in conducting zone where no gas exchange occurs

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45
Q

Tidal volume

A

amount of air expired/breath in quiet breathing

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46
Q

Vital capacity is

A

amount of air that can be forcefully exhaled after a maximum inhalation

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47
Q

maximum inhalation

A

sum of inspiratory reserve, tidal volume, & expiratory reserve

48
Q

Pulmonary Disorders Are frequently accompanied by

A

dyspnea = a feeling of shortness of breath; unpleasant or labored breathing

49
Q

Asthma results from

A

episodes of obstruction of air flow thru bronchioles

50
Q

Asthma caused by

A

inflammation, mucus secretion, & broncho- constriction

51
Q

inflammation contributes to

A

to increased airway responsiveness to agents that promote bronchial constriction

52
Q

Inflammation provoked by

A

by allergic reactions, by exercise, by breathing cold, dry air, or by aspirin

53
Q

Pulmonary Disorders Treated with

A

glucocorticoid drugs ex: epinephrine

54
Q

Emphysema

A
  • is a chronic, progressive condition that destroys alveolar tissue, resulting in fewer, larger alveoli;
  • reduces surface area for gas exchange & ability of bronchioles to remain open during expiration
55
Q

collapse of bronchiole during expiration causes

A

air trapping, decreasing gas exchange

56
Q

collapse of bronchiole commonly occurs in

A

long-term smokers

57
Q

cigarette smoking stimulates

A

macrophages & leukocytes to secrete protein-digesting enzymes that destroy tissue

58
Q

Pulmonary fibrosis:

A
  • sometimes lung damage leads to instead of emphysema

- Characterized by accumulation of fibrous connective tissue

59
Q

Pulmonary fibrosis: Occurs from

A

inhalation of particles <6m in size, such as in black lung disease (anthracosis) from coal dust

60
Q

Partial pressure

A

is pressure that a particular gas in a mixture exerts independently

61
Q

Dalton’s Law

A

states that total pressure of a gas mixture is the sum of partial pressures of each gas in mixture

62
Q

Gas Exchange in Lungs Is driven by

A

differences in partial pressures of gases between alveoli & capillaries

63
Q

Gas Exchange in Lungs Is facilitated by

A
  • enormous surface area of alveoli
  • short diffusion distance between alveolar air & capillaries
  • tremendous density of capillaries
64
Q

Partial Pressures of Gases in Blood

A

When blood & alveolar air are at gaseous equilibrium the amount of O2 in blood reaches a maximum value

65
Q

Henry’s Law says

A
  • that this value depends on solubility of O2 in blood (a constant), temperature of blood (a constant), & partial pressure of O2
    • So the amount of O2 dissolved in blood depends directly on its partial pressure (PO2), which varies with altitude
66
Q

Blood PO2 & PCO2 Measurements

A

Provide good index of lung function

67
Q

normal PO2 systemic arterial blood has

A

about 100 mmHg and PC02 about 40 mm Hg

68
Q

PO2 is about

A

40 mmHg in systemic veins and PC02 is 46 mmHg in systemic veins

69
Q

Disorders Caused by High Partial Pressures of Gases

A
  • Total atmospheric pressure increases by 1 atmosphere for every 10m (33 ft) below sea level
    • ex. a sea dive of 10 m below doubles the partial pressures of each gas
    • At depth, increased dissolved O2 & N2 can be dangerous to body
    • Breathing 100% O2 at < 2 atmospheres can be tolerated for few hrs
70
Q

O2 toxicity

A
  • can develop rapidly at > 2.5 atmospheres
    • Can lead to coma or death
    • probably because of oxidation damage
71
Q

At sea level, nitrogen is

A
  • physiologically inert and it dissolves slowly in blood

- but under hyperbaric conditions N2 takes more than hour for dangerous amounts to accumulate

72
Q

Nitrogen narcosis

A

resembles alcohol intoxication

73
Q

Amount of nitrogen dissolved in blood as diver ascends

A

decreases due to decrease in PN2 (excess N2 is expired over time)

74
Q

if diver ascends is too rapid

A

decompression sickness occurs as bubbles of nitrogen gas form in tissues & enter blood, blocking small blood vessels & producing “bends”

75
Q

Automatic breathing is generated by

A

by a rhythmicity center in medulla oblongata

76
Q

Automatic breathing Consists of

A

inspiratory neurons that drive inspiration & expiratory neurons that inhibit inspiratory neurons

77
Q

Automatic breathing

Inspiratory neurons stimulate

A

spinal motor neurons that innervate respiratory muscles

78
Q

Automatic breathing

Expiration is

A

passive & occurs when inspiratory muscles are inhibited

79
Q

Pons Respiratory Centers

A

Activities of medullary rhythmicity center are influenced by centers in pons:
Apneustic center and Pneumotaxic center

80
Q

Apneustic center

A

promotes inspiration by stimulating neurons in medulla

81
Q

Pneumotaxic center

A

antagonizes apneustic center, inhibiting inspiration

82
Q

Automatic breathing is influenced by

A

by activity of chemoreceptors that monitor blood PC02, P02, & pH

83
Q

Central chemoreceptors are in

84
Q

Peripheral chemoreceptors are in

A

large arteries near heart (aortic bodies) & in carotids (carotid bodies)

85
Q

Chemoreceptors modify ventilation to maintain

A

normal CO2, O2, & pH levels

86
Q

PCO2 is most crucial because

A

of its effects on blood pH (combines with H2O forming carbonic acid)
H20 + C02  H2C03  H+ + HC03-

87
Q

Hyperventilation causes

A

low C02 (hypocapnia) and pH rises

88
Q

Hypoventilation causes

A

high C02 (hypercapnia) and a fall in pH

89
Q

Brain chemoreceptors are responsible for

A

for greatest effects on ventilation

90
Q

H+ can not cross BBB but C02 can

A

which is why it is monitored & has greatest effects

91
Q

Rate and depth of ventilation is adjusted to

A

maintain arterial PC02 of 40 mm Hg

92
Q

Peripheral chemoreceptors

A

(in aortic and carotid bodies) do not respond to PC02, only to H+ levels

93
Q

Low blood P02 (hypoxemia)

A
  • has little affect on ventilation
    • Does influence chemoreceptor sensitivity to PC02
    • P02 has to fall to about half (from ~ 100 mm Hg to below 70 mmHg) before ventilation is significantly affected
      = hypoxic drive rather than PC02
94
Q

Lungs have receptors that

A

influence brain respiratory control centers via sensory fibers in vagus nerve (CNX)

95
Q

Unmyelinated C fibers

A
  • sensory neurons in lungs
    stimulated by noxious substances such as capsaicin
    • Causes apnea followed by rapid, shallow breathing
96
Q

Irritant receptors

A
  • in wall of larynx and other receptors in lungs called rapidly adapting receptors
  • respond to smoke, smog, & particulates
  • cause cough
97
Q

Hering-Breuer reflex

A

mediated by stretch receptors activated during inspiration

98
Q

Hering-Breuer reflex Inhibits

A

respiratory centers to prevent over inflation of lungs

99
Q

Loading of Hb with O2 occurs in

A
  • lungs;

- unloading in tissues

100
Q

Most 02 in blood is bound to

A

Hb inside RBCs as oxyhemoglobin

101
Q

Methemoglobin contains

A

ferric iron (Fe3+) – the oxidized form; lacks electron to bind with 02 ; blood normally contains a small amount

102
Q

Carboxyhemoglobin is

A

heme combined with carbon monoxide; Bond with carbon monoxide is 210 times stronger than bond with oxygen; so heme can not bind 02

103
Q

02-carrying capacity of blood depends on

A
  • on its Hb levels
    • In anemia, Hb levels are below normal;
    • In polycythemia (higher than normal RBC), Hb levels are above normal
104
Q

Hb production controlled by

A

erythropoietin (EPO); Production stimulated by low P02 in kidneys

105
Q

Hb levels in men are higher because

A

androgens promote RBC production

106
Q

High P02 of lungs favors

A
  • loading;

- low P02 in tissues favors unloading

107
Q

Ideally, Hb-02 affinity should allow

A

maximum loading in lungs & unloading in tissues

108
Q

Blood in systemic arteries has

A

PO2 = 100 mm Hg (20 ml O2/100 ml blood) = 97% oxyhemoglobin saturation

109
Q

Venous blood has

A

PO2 = 40 mm Hg (15.5 ml O2/100 ml blood) = 75% oxyhemoglobin saturation)

110
Q

Oxyhemoglobin dissociation curve gives

A
  • gives % of Hb sites that have bound 02 at different P02s

- Reflects loading & unloading of 02 (~22% = 4.5 of 20 ml O2/100 ml blood)

111
Q

Oxyhemoglobin Dissociation Curve:

Differences in % saturation

A
  • in lungs & tissues are shown at right

- In steep part of curve, small changes in P02 cause big changes in % saturation

112
Q

Oxyhemoglobin Dissociation Curve:is affected by

A

changes in Hb-02 affinity caused by pH & temp.

113
Q

Oxyhemoglobin Dissociation Curve affinity decreases when

A
  • pH decreases (Bohr Effect) or temp increases
    • Occurs in tissues where temp, C02 & acidity are high
    • Ex. Skeletal muscle
  • Causes Hb-02 curve to shift right indicating more unloading of 02 to tissues
114
Q

C02 transported in blood as

A

dissolved C02 in plasma (10%), carbaminohemoglobin attached to an amino acid in Hb (20%), & bicarbonate ion, HC03-, (70%)

115
Q

In RBCs carbonic anhydrase catalyzes

A

catalyzes formation of carbonic acid (H2CO3) from C02 + H2O

Physiology (27 decks)

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