Exam 3: Ch 16 Respiratory Physiology Flashcards
1
Q
Respiration Encompasses 3 related functions:
A
- ventilation,
- gas exchange,
- 02 utilization (cellular respiration)
2
Q
02 utilization (cellular respiration)
A
Ventilation = breathing;
3
Q
Ventilation = breathing;
A
moves air in & out of lungs for gas exchange (which occurs via passive diffusion) with blood
4
Q
external respiration)
A
gas exchange between air and blood in lungs =
5
Q
internal respiration
A
Gas exchange between blood & tissues, & O2 use by tissues =
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
7
Q
Gas exchange occurs only in
A
- respiratory bronchioles & alveoli (= respiratory zone)
- All other structures constitute the conducting zone
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
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
10
Q
Conducting Zone
A
- Warms & humidifies inspired air
- Mucus lining filters & cleans inspired air
- Mucus moved by cilia to be expectorated
11
Q
Thoracic Cavity is created by
A
the diaphragm, a dome-shaped sheet of skeletal muscle
12
Q
Above the diaphram is
A
heart, large blood vessels, trachea, esophagus, thymus, & lungs
13
Q
Below diaphragm is
A
abdominopelvic cavity; contains liver, pancreas, GI tract, spleen, & genitourinary tract
14
Q
Intrapleural space is
A
is thin fluid layer between visceral pleura covering lungs & parietal pleura lining thoracic cavity walls
15
Q
Ventilation results from
A
from pressure differences between the conducting zone and the terminal bronchioles induced by changes in lung volumes
16
Q
Air moves from
A
higher to lower pressure
17
Q
Compliance, elasticity, & surface tension of lungs influence
A
ease of ventilation
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
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
20
Q
Compliance
A
= how easily lung expands with pressure
Is reduced by factors that cause resistance to distension
21
Q
Elasticity
A
Is tendency to return to initial size after distension
22
Q
Elasticity is due to
A
high content of elastin proteins that resist distention
23
Q
Elastic tension increases
A
during inspiration & is reduced by recoil during expiration
24
Q
Surface Tension (ST)
A
created by intermolecular forces within fluid molecules that attract molecules to each other
25
ST and elasticity are forces that promote
alveolar collapse & resist distension
26
Lungs secrete & absorb fluid
- 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
27
Fluid absorption occurs by
- osmosis
| driven by Na+ active transport
28
Fluid secretion is driven by
active transport of Cl- out of alveolar epithelial cells
29
Surfactant
Consists of phospholipids secreted by alveolar cells
30
Surfactant Lower ST by
by getting between H20 molecules, reducing their ability to attract each other via hydrogen bonding
31
Surfactant Prevents ST from
collapsing alveoli
32
Surfactant secretion begins
in late fetal life
33
Premies are often born with
- immature surfactant system (= Respiratory Distress Syndrome or RDS) and
have trouble inflating lungs
34
In adults, septic shock
- (↓ BP due to widespread vasodilation) may cause acute respiratory distress syndrome (ARDS) which decreases compliance & surfactant secretion
35
Pulmonary ventilation consists of
inspiration (= inhalation) & expiration (= exhalation)
36
Pulmonary ventilation Accomplished by
alternately increasing & decreasing volumes of thorax & lungs
37
Inspiration occurs mainly because
diaphragm contracts, increasing thoracic volume vertically
38
Q: If volume ↑ what happens to pressure?
decreases
39
Parasternal & external intercostal contraction
contributes a little by raising ribs, increasing thoracic volume laterally
40
Expiration is due to
passive recoil
41
Deep Breathing:
| Inspiration involves
contraction of extra muscles to elevate ribs: scalenes, pectoralis minor, & sternocleidomastoid muscles
42
Deep Breathing:
| Expiration involves
contraction of internal intercostals & abdominal muscles
43
Pulmonary Function Tests Assessed clinically by
spirometry, a method that measures volumes of air moved during inspiration & expiration
44
Anatomical dead space is
is air in conducting zone where no gas exchange occurs
45
Tidal volume
amount of air expired/breath in quiet breathing
46
Vital capacity is
amount of air that can be forcefully exhaled after a maximum inhalation
47
maximum inhalation
sum of inspiratory reserve, tidal volume, & expiratory reserve
48
Pulmonary Disorders Are frequently accompanied by
dyspnea = a feeling of shortness of breath; unpleasant or labored breathing
49
Asthma results from
episodes of obstruction of air flow thru bronchioles
50
Asthma caused by
inflammation, mucus secretion, & broncho- constriction
51
inflammation contributes to
to increased airway responsiveness to agents that promote bronchial constriction
52
Inflammation provoked by
by allergic reactions, by exercise, by breathing cold, dry air, or by aspirin
53
Pulmonary Disorders Treated with
glucocorticoid drugs ex: epinephrine
54
Emphysema
- 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
collapse of bronchiole during expiration causes
air trapping, decreasing gas exchange
56
collapse of bronchiole commonly occurs in
long-term smokers
57
cigarette smoking stimulates
macrophages & leukocytes to secrete protein-digesting enzymes that destroy tissue
58
Pulmonary fibrosis:
- sometimes lung damage leads to instead of emphysema
| - Characterized by accumulation of fibrous connective tissue
59
Pulmonary fibrosis: Occurs from
inhalation of particles <6m in size, such as in black lung disease (anthracosis) from coal dust
60
Partial pressure
is pressure that a particular gas in a mixture exerts independently
61
Dalton’s Law
states that total pressure of a gas mixture is the sum of partial pressures of each gas in mixture
62
Gas Exchange in Lungs Is driven by
differences in partial pressures of gases between alveoli & capillaries
63
Gas Exchange in Lungs Is facilitated by
- enormous surface area of alveoli
- short diffusion distance between alveolar air & capillaries
- tremendous density of capillaries
64
Partial Pressures of Gases in Blood
When blood & alveolar air are at gaseous equilibrium the amount of O2 in blood reaches a maximum value
65
Henry’s Law says
- 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
Blood PO2 & PCO2 Measurements
Provide good index of lung function
67
normal PO2 systemic arterial blood has
about 100 mmHg and PC02 about 40 mm Hg
68
PO2 is about
40 mmHg in systemic veins and PC02 is 46 mmHg in systemic veins
69
Disorders Caused by High Partial Pressures of Gases
- 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
O2 toxicity
- can develop rapidly at > 2.5 atmospheres
- Can lead to coma or death
- probably because of oxidation damage
71
At sea level, nitrogen is
- physiologically inert and it dissolves slowly in blood
| - but under hyperbaric conditions N2 takes more than hour for dangerous amounts to accumulate
72
Nitrogen narcosis
resembles alcohol intoxication
73
Amount of nitrogen dissolved in blood as diver ascends
decreases due to decrease in PN2 (excess N2 is expired over time)
74
if diver ascends is too rapid
decompression sickness occurs as bubbles of nitrogen gas form in tissues & enter blood, blocking small blood vessels & producing “bends”
75
Automatic breathing is generated by
by a rhythmicity center in medulla oblongata
76
Automatic breathing Consists of
inspiratory neurons that drive inspiration & expiratory neurons that inhibit inspiratory neurons
77
Automatic breathing
| Inspiratory neurons stimulate
spinal motor neurons that innervate respiratory muscles
78
Automatic breathing
| Expiration is
passive & occurs when inspiratory muscles are inhibited
79
Pons Respiratory Centers
Activities of medullary rhythmicity center are influenced by centers in pons:
Apneustic center and Pneumotaxic center
80
Apneustic center
promotes inspiration by stimulating neurons in medulla
81
Pneumotaxic center
antagonizes apneustic center, inhibiting inspiration
82
Automatic breathing is influenced by
by activity of chemoreceptors that monitor blood PC02, P02, & pH
83
Central chemoreceptors are in
medulla
84
Peripheral chemoreceptors are in
large arteries near heart (aortic bodies) & in carotids (carotid bodies)
85
Chemoreceptors modify ventilation to maintain
normal CO2, O2, & pH levels
86
PCO2 is most crucial because
of its effects on blood pH (combines with H2O forming carbonic acid)
H20 + C02 H2C03 H+ + HC03-
87
Hyperventilation causes
low C02 (hypocapnia) and pH rises
88
Hypoventilation causes
high C02 (hypercapnia) and a fall in pH
89
Brain chemoreceptors are responsible for
for greatest effects on ventilation
90
H+ can not cross BBB but C02 can
which is why it is monitored & has greatest effects
91
Rate and depth of ventilation is adjusted to
maintain arterial PC02 of 40 mm Hg
92
Peripheral chemoreceptors
(in aortic and carotid bodies) do not respond to PC02, only to H+ levels
93
Low blood P02 (hypoxemia)
- 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
Lungs have receptors that
influence brain respiratory control centers via sensory fibers in vagus nerve (CNX)
95
Unmyelinated C fibers
- sensory neurons in lungs
stimulated by noxious substances such as capsaicin
- Causes apnea followed by rapid, shallow breathing
96
Irritant receptors
- in wall of larynx and other receptors in lungs called rapidly adapting receptors
- respond to smoke, smog, & particulates
- cause cough
97
Hering-Breuer reflex
mediated by stretch receptors activated during inspiration
98
Hering-Breuer reflex Inhibits
respiratory centers to prevent over inflation of lungs
99
Loading of Hb with O2 occurs in
- lungs;
| - unloading in tissues
100
Most 02 in blood is bound to
Hb inside RBCs as oxyhemoglobin
101
Methemoglobin contains
ferric iron (Fe3+) -- the oxidized form; lacks electron to bind with 02 ; blood normally contains a small amount
102
Carboxyhemoglobin is
heme combined with carbon monoxide; Bond with carbon monoxide is 210 times stronger than bond with oxygen; so heme can not bind 02
103
02-carrying capacity of blood depends on
- on its Hb levels
- In anemia, Hb levels are below normal;
- In polycythemia (higher than normal RBC), Hb levels are above normal
104
Hb production controlled by
erythropoietin (EPO); Production stimulated by low P02 in kidneys
105
Hb levels in men are higher because
androgens promote RBC production
106
High P02 of lungs favors
- loading;
| - low P02 in tissues favors unloading
107
Ideally, Hb-02 affinity should allow
maximum loading in lungs & unloading in tissues
108
Blood in systemic arteries has
PO2 = 100 mm Hg (20 ml O2/100 ml blood) = 97% oxyhemoglobin saturation
109
Venous blood has
PO2 = 40 mm Hg (15.5 ml O2/100 ml blood) = 75% oxyhemoglobin saturation)
110
Oxyhemoglobin dissociation curve gives
- 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
Oxyhemoglobin Dissociation Curve:
| Differences in % saturation
- in lungs & tissues are shown at right
| - In steep part of curve, small changes in P02 cause big changes in % saturation
112
Oxyhemoglobin Dissociation Curve:is affected by
changes in Hb-02 affinity caused by pH & temp.
113
Oxyhemoglobin Dissociation Curve affinity decreases when
- 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
C02 transported in blood as
dissolved C02 in plasma (10%), carbaminohemoglobin attached to an amino acid in Hb (20%), & bicarbonate ion, HC03-, (70%)
115
In RBCs carbonic anhydrase catalyzes
catalyzes formation of carbonic acid (H2CO3) from C02 + H2O
