RESPIRATORY PT. 2 Flashcards
(500 cards)
1
Q
How many viruses can cause coryza?
A
Hundreds
2
Q
What group of viruses is responsible for about 40 percent of all colds in adults?
A
Rhinoviruses
3
Q
What does recent research suggest about emotional stress and the common cold?
A
The higher the stress level, the greater the frequency and duration of colds
4
Q
What viruses cause seasonal influenza (flu)?
A
Influenza viruses
5
Q
What are the two types of influenza viruses responsible for seasonal influenza?
A
Influenza type A virus and influenza type B virus
6
Q
What type of disease is influenza?
A
A respiratory disease
7
Q
What do many people mistakenly believe seasonal flu to be?
A
A digestive canal disease
8
Q
Why is it difficult to distinguish between the cold and the flu?
A
Because they have overlapping signs and symptoms
9
Q
How does the onset of the flu differ from the onset of a cold?
A
The flu has an abrupt onset, while a cold has a more gradual onset
10
Q
How do the signs and symptoms of the flu compare to those of a cold?
A
The flu has more intense signs and symptoms, while a cold has milder symptoms
11
Q
What is a common flu symptom that is rare with a cold?
A
Chills and a fever higher than 101°F (33°C)
12
Q
What are some life-threatening complications of the flu?
A
Pneumonia, worsening of heart disease and bronchial asthma, neurological conditions, and respiratory failure
13
Q
What are some less serious complications of a cold?
A
Sinusitis, ear infections, laryngitis, and bronchitis
14
Q
How do general body aches, headaches, fatigue, and weakness compare between the flu and a cold?
A
They are severe with the flu but milder or rare with a cold
15
Q
Which symptoms occur sometimes with the flu but are more common with a cold?
A
Sneezing, stuffy nose, and sore throat
16
Q
What is the ultimate goal of flu vaccination?
A
To create a vaccine that protects against all flu strains and provides long-term immunity
17
Q
Why has this goal not been reached?
A
Because flu strains mutate rapidly and are difficult to predict
18
Q
How do scientists decide which flu strains to include in the vaccine each year?
A
Using data from numerous countries in the northern hemisphere, usually in February
19
Q
Why might the flu vaccine be ineffective some years?
A
Because circulating flu strains can mutate, making the vaccine ineffective
20
Q
What antiviral medications can be taken for the flu?
A
Tamiflu® and Relenza®
21
Q
What do Tamiflu® and Relenza® do?
A
Ease flu symptoms and shorten the duration of the illness
22
Q
When are Tamiflu® and Relenza® most effective?
A
Within 24 hours of the first signs and symptoms
23
Q
What other treatments are available for the flu?
A
Bedrest, decongestants, antihistamines, cough medications, and medications for fever and body aches
24
Q
What is the first way to prevent infection?
A
Wash your hands often with soap and water or use an alcohol-based sanitizer
25
What should you do when coughing or sneezing?
Cover your mouth with a tissue and dispose of it or cough/sneeze into your elbow
26
What should you avoid touching to prevent infection?
Your mouth, nose, or eyes
27
What personal items should you not share to prevent infection?
Makeup, utensils, or sports/office equipment
28
How close should you avoid being to someone with flu-like symptoms?
Within six feet
29
When should you stay home after having flu symptoms?
For seven days after symptoms begin or 24 hours after being symptom-free, whichever is longer
30
What helps maintain the patency of the respiratory system?
Structures or secretions
31
What are some examples of structures that help maintain patency?
Bony and cartilaginous frameworks of the nose, skeletal muscles of the pharynx, cartilages of the larynx, C-shaped rings of cartilage in the trachea and bronchi, smooth muscle in the bronchioles, and surfactant in the pulmonary alveoli
32
What is the function of these structures and secretions?
To keep air passageways free of obstruction
33
What factors can compromise patency?
Crushing injuries to bone and cartilage, a deviated nasal septum, nasal polyps, inflammation of mucous membranes, spasms of smooth muscle, and a deficiency of surfactant
34
What type of epithelium is found in the nasal vestibule?
Nonkeratinized stratified squamous
35
Does the nasal vestibule have cilia?
No
36
Does the nasal vestibule have goblet cells?
No
37
What special feature is found in the nasal vestibule?
Contains numerous hairs
38
What type of epithelium is found in the respiratory region of the nose?
Ciliated pseudostratified columnar
39
Does the respiratory region of the nose have cilia?
Yes
40
Does the respiratory region of the nose have goblet cells?
Yes
41
What special features are found in the respiratory region of the nose?
Contains conchae and meatuses
42
What type of epithelium is found in the olfactory region of the nose?
Olfactory epithelium (olfactory sensory neurons)
43
Does the olfactory region of the nose have cilia?
Yes
44
Does the olfactory region of the nose have goblet cells?
No
45
What is the function of the olfactory region?
Functions in olfaction
46
What type of epithelium is found in the nasopharynx?
Ciliated pseudostratified columnar
47
Does the nasopharynx have cilia?
Yes
48
Does the nasopharynx have goblet cells?
Yes
49
What are the special features of the nasopharynx?
Passageway for air; contains internal nares, openings for auditory tubes, and pharyngeal tonsil
50
What type of epithelium is found in the oropharynx?
Nonkeratinized stratified squamous
51
Does the oropharynx have cilia?
No
52
Does the oropharynx have goblet cells?
No
53
What are the special features of the oropharynx?
Passageway for both air and food and drink; contains opening from mouth
54
What type of epithelium is found in the laryngopharynx?
Nonkeratinized stratified squamous
55
Does the laryngopharynx have cilia?
No
56
Does the laryngopharynx have goblet cells?
No
57
What are the special features of the laryngopharynx?
Passageway for both air and food and drink
58
What type of epithelium is found in the larynx?
Nonkeratinized stratified squamous above the vocal folds; ciliated pseudostratified columnar below the vocal folds
59
Does the larynx have cilia?
No above folds; yes below folds
60
Does the larynx have goblet cells?
No above folds; yes below folds
61
What are the special features of the larynx?
Passageway for air; contains vocal folds for voice production
62
What type of epithelium is found in the trachea?
Ciliated pseudostratified columnar
63
Does the trachea have cilia?
Yes
64
Does the trachea have goblet cells?
Yes
65
What are the special features of the trachea?
Passageway for air; contains C-shaped rings of cartilage to keep trachea open
66
What type of epithelium is found in the main bronchi?
Ciliated pseudostratified columnar
67
Does the main bronchi have cilia?
Yes
68
Does the main bronchi have goblet cells?
Yes
69
What are the special features of the main bronchi?
Passageway for air; contain C-shaped rings of cartilage to maintain patency
70
What type of epithelium is found in the lobar bronchi?
Ciliated pseudostratified columnar
71
Does the lobar bronchi have cilia?
Yes
72
Does the lobar bronchi have goblet cells?
Yes
73
What are the special features of the lobar bronchi?
Passageway for air; contain plates of cartilage to maintain patency
74
What type of epithelium is found in the segmental bronchi?
Ciliated pseudostratified columnar
75
Does the segmental bronchi have cilia?
Yes
76
Does the segmental bronchi have goblet cells?
Yes
77
What are the special features of the segmental bronchi?
Passageway for air; contain plates of cartilage to maintain patency
78
What type of epithelium is found in larger bronchioles?
Ciliated simple columnar
79
Does the larger bronchioles have cilia?
Yes
80
Does the larger bronchioles have goblet cells?
Yes
81
What are the special features of the larger bronchioles?
Passageway for air; contain more smooth muscle than in the bronchi
82
What type of epithelium is found in smaller bronchioles?
Ciliated simple columnar
83
Does the smaller bronchioles have cilia?
Yes
84
Does the smaller bronchioles have goblet cells?
No
85
What are the special features of the smaller bronchioles?
Passageway for air; contain more smooth muscle than in the larger bronchioles
86
What type of epithelium is found in terminal bronchioles?
Nonciliated simple columnar
87
Does the terminal bronchioles have cilia?
No
88
Does the terminal bronchioles have goblet cells?
No
89
What are the special features of the terminal bronchioles?
Passageway for air; contain more smooth muscle than in the smaller bronchioles
90
What type of epithelium is found in respiratory bronchioles?
Simple cuboidal to simple squamous
91
Does the respiratory bronchioles have cilia?
No
92
Does the respiratory bronchioles have goblet cells?
No
93
What are the special features of the respiratory bronchioles?
Passageway for air; gas exchange
94
What type of epithelium is found in alveolar ducts?
Simple squamous
95
Does the alveolar ducts have cilia?
No
96
Does the alveolar ducts have goblet cells?
No
97
What are the special features of the alveolar ducts?
Passageway for air; gas exchange; produce surfactant to maintain patency
98
What type of epithelium is found in pulmonary alveoli?
Simple squamous
99
Does the pulmonary alveoli have cilia?
No
100
Does the pulmonary alveoli have goblet cells?
No
101
What are the special features of the pulmonary alveoli?
Passageway for air; gas exchange; produce surfactant to maintain patency
102
What are the conducting structures of the respiratory system?
NOSE
1. Nasal Vestibule
2. Respiratory Region
3. Olfactory Region
PHARYNX
1. Nasopharynx
2. Oropharynx
3. Laryngopharynx
LARYNX
TRACHEA
BRONCHI
1. Main Bronchi
2. Lobar Bronchi
3. Segmental Bronchi
4. Larger Bronchioles
5. Smaller Bronchioles
6. Terminal Bronchioles
103
What are the gas exchange structures of the respiratiry system?
LUNGS
1. Respiratory Bronchioles
2. Alveolar ducts
3. Pulmonary Alveoli
104
What is the flow of air into and out of the lungs?
Pulmonary ventilation
105
What is another term for pulmonary ventilation?
Breathing
106
Where does air flow between in pulmonary ventilation?
The atmosphere and the pulmonary alveoli of the lungs
107
What causes the alternating pressure differences in pulmonary ventilation?
Contraction and relaxation of respiratory muscles
108
What influences the rate of airflow and the amount of effort needed for breathing?
Alveolar surface tension, compliance of the lungs, and airway resistance
109
When does air move into the pulmonary alveoli of the lungs?
When the air pressure inside the lungs is less than the air pressure in the atmosphere.
110
When does air move out of the pulmonary alveoli of the lungs?
When the air pressure inside the lungs is greater than the air pressure in the atmosphere.
111
What is breathing in called?
Inhalation (inspiration)
112
Just before each inhalation, what is the air pressure inside the lungs equal to?
The air pressure of the atmosphere, which at sea level is about 760 mmHg or 1 atm.
113
For air to flow into the lungs, what must happen to the pressure inside the pulmonary alveoli?
It must become lower than the atmospheric pressure.
114
How is the condition for air to flow into the lungs achieved?
By increasing the size of the lungs.
115
What does Boyle’s law state about the relationship between pressure and volume?
The pressure of a gas in a closed container is inversely proportional to the volume of the container.
116
What happens to pressure if the size of a closed container is increased?
The pressure of the gas inside the container decreases.
117
What happens to pressure if the size of a closed container is decreased?
The pressure inside it increases.
118
What forces air into the lungs when we inhale and out when we exhale?
Differences in pressure caused by changes in lung volume.
119
What must happen for inhalation to occur?
The lungs must expand, which increases lung volume and decreases the pressure in the lungs below atmospheric pressure.
120
What is the first step in expanding the lungs during normal quiet inhalation?
Contraction of the main muscle of inhalation, the diaphragm, with resistance from external intercostals.
121
What is the most important muscle of inhalation?
The diaphragm.
122
What is the diaphragm?
A dome-shaped skeletal muscle that forms the floor of the thoracic cavity.
123
What nerves innervate the diaphragm?
The phrenic nerves, which emerge from the spinal cord at cervical levels 3, 4, and 5.
124
What happens when the diaphragm contracts?
It flattens, lowering its dome, and increases the vertical diameter of the thoracic cavity.
125
During normal quiet inhalation, how far does the diaphragm descend?
About 1 cm (0.4 in.), producing a pressure difference of 1–3 mmHg and inhaling about 500 mL of air.
126
During strenuous breathing, how far can the diaphragm descend?
About 10 cm (4 in.), producing a pressure difference of 100 mmHg and inhaling 2–3 liters of air.
127
What percentage of air that enters the lungs during quiet breathing is due to contraction of the diaphragm?
About 75%.
128
What factors can prevent complete descent of the diaphragm?
Advanced pregnancy, excessive obesity, or confining abdominal clothing.
129
What are the next most important muscles of inhalation after the diaphragm?
The external intercostals.
130
What happens when the external intercostals contract?
They elevate the ribs, increasing the anteroposterior and lateral diameters of the chest cavity.
131
What percentage of air that enters the lungs during normal quiet breathing is due to contraction of the external intercostals?
About 25%.
132
What is intrapleural pressure?
The pressure within the pleural cavity.
133
What is the range of intrapleural pressure during normal quiet breathing?
754–756 mmHg.
134
Why does the pleural cavity function as a vacuum?
Because intrapleural pressure is always negative, lower than atmospheric pressure.
135
What happens to the lungs when the thoracic cavity increases in size?
The lungs expand.
136
What happens to the lungs when the thoracic cavity decreases in size?
The lungs recoil (become smaller).
137
Just before inhalation, what is intrapleural pressure?
About 4 mmHg less than atmospheric pressure, or 756 mmHg.
138
What happens to intrapleural pressure when the diaphragm and external intercostals contract?
It decreases to about 754 mmHg.
139
What happens to alveolar (intrapulmonic) pressure as the volume of the lungs increases?
It drops from 760 mmHg to 758 mmHg.
140
Why does air flow into the lungs during inhalation?
Because air always flows from a region of higher pressure to a region of lower pressure.
141
When does air stop flowing into the lungs?
When there is no longer a pressure difference between the atmosphere and the pulmonary alveoli.
142
What causes most of the increase in lung volume during inhalation?
The lengthening and expansion of alveolar ducts and the increase in size of the openings into the alveoli.
143
What happens during deep, forceful inhalation?
Accessory muscles of inspiration participate in increasing the size of the thoracic cavity.
144
When do the accessory muscles of inhalation contract?
During exercise or forced breathing.
145
What are the accessory muscles of inhalation?
Sternocleidomastoid muscles, scalene muscles, and pectoralis minor muscles.
146
What is the function of the sternocleidomastoid muscles during inhalation?
They elevate the sternum.
147
What is the function of the scalene muscles during inhalation?
They elevate the first two ribs.
148
What is the function of the pectoralis minor muscles during inhalation?
They elevate the third through fifth ribs.
149
Why is inhalation considered an active process?
Because both normal quiet inhalation and inhalation during exercise or forced breathing involve muscular contraction.
150
The volume of a gas varies inversely with its pressure.
Boyle's Law
151
During normal, ___, the diaphragm and external intercostals contract, the lungs expand, and air moves into the pulmonary alveoli of the lungs; during normal,___, the diaphragm and external intercostals relax and the lungs recoil, forcing air out of the pulmonary alveoli of the lungs.
quiet inhalation; quiet exhalation
152
Air moves into the lungs when alveolar pressure is ___ than atmospheric pressure, and out of the lungs when alveolar pressure is greater than atmospheric pressure.
less
153
What is breathing out called?
Exhalation (expiration)
154
What causes exhalation?
A pressure gradient, where the pressure in the lungs is greater than the pressure of the atmosphere.
155
How does normal exhalation during quiet breathing differ from inhalation?
It is a passive process because no muscular contractions are involved.
156
What causes exhalation if no muscular contractions are involved?
Elastic recoil of the chest wall and lungs.
157
What is the natural tendency of the chest wall and lungs after they have been stretched?
To spring back due to elastic recoil.
158
What are the two inwardly directed forces that contribute to elastic recoil?
(1) The recoil of elastic fibers that were stretched during inhalation, and (2) the inward pull of surface tension due to the film of intrapleural fluid between the visceral and parietal pleurae.
159
When does exhalation start?
When the inspiratory muscles relax.
160
What happens to the diaphragm when it relaxes?
Its dome moves superiorly due to its elasticity.
161
What happens to the external intercostals when they relax?
The ribs are depressed.
162
What effect do these movements (diaphragm and external intercostals relaxing) have on the thoracic cavity?
They decrease the vertical, lateral, and anteroposterior diameters of the thoracic cavity.
163
What happens to lung volume when the thoracic cavity decreases in size?
Lung volume decreases.
164
What happens to alveolar pressure as lung volume decreases?
It increases to about 762 mmHg.
165
Why does air flow out of the lungs during exhalation?
Because air flows from the area of higher pressure in the pulmonary alveoli to the area of lower pressure in the atmosphere.
166
When does exhalation become an active process?
During forceful breathing, such as while playing a wind instrument or during exercise.
167
What muscles are involved in forceful exhalation?
The abdominal and internal intercostals muscles.
168
What happens when the muscles of exhalation contract?
It increases pressure in the abdominal region and thorax.
169
What happens when the abdominal muscles contract?
They move the inferior ribs downward and compress the abdominal viscera, forcing the diaphragm superiorly.
170
What happens when the internal intercostals contract?
They pull the ribs inferiorly.
171
How do the internal intercostals extend between adjacent ribs?
They extend inferiorly and posteriorly.
172
What happens to intrapleural pressure during a forceful exhalation?
It may briefly exceed atmospheric pressure, such as during a cough.
173
What drives airflow during inhalation and exhalation?
Air pressure differences.
174
Besides air pressure differences, what three other factors affect the rate of airflow and the ease of pulmonary ventilation?
Surface tension of the alveolar fluid, compliance of the lungs, and airway resistance.
175
What is a thin layer of alveolar fluid that coats the luminal surface of pulmonary alveoli and exerts a force?
Surface tension
176
What causes surface tension to arise at all air–water interfaces?
Polar water molecules are more strongly attracted to each other than they are to gas molecules in the air.
177
What happens when liquid surrounds a sphere of air, such as in a pulmonary alveolus or a soap bubble?
Surface tension produces an inwardly directed force.
178
Why do soap bubbles “burst”?
They collapse inward due to surface tension.
179
What causes the pulmonary alveoli to assume the smallest possible diameter?
Surface tension
180
What must be overcome during breathing to expand the lungs during each inhalation?
Surface tension
181
What accounts for two-thirds of lung elastic recoil, decreasing the size of pulmonary alveoli during exhalation?
Surface tension
182
What is present in alveolar fluid that reduces its surface tension below the surface tension of pure water?
Surfactant (a mixture of phospholipids and lipoproteins)
183
What causes respiratory distress syndrome in premature infants?
A deficiency of surfactant causes respiratory distress syndrome.
184
What happens when the surface tension of pulmonary alveolar fluid is greatly increased in respiratory distress syndrome?
Many pulmonary alveoli collapse at the end of each exhalation.
185
What is needed at the next inhalation to reopen the collapsed pulmonary alveoli?
Great effort is needed at the next inhalation.
186
What refers to how much effort is required to stretch the lungs and chest wall?
Compliance
187
What does high compliance mean in relation to the lungs and chest wall?
The lungs and chest wall expand easily.
188
What does low compliance mean in relation to the lungs and chest wall?
The lungs and chest wall resist expansion.
189
What is an analogy for high compliance?
A thin balloon that is easy to inflate.
190
What is an analogy for low compliance?
A heavy and stiff balloon that takes a lot of effort to inflate.
191
What are the two principal factors related to compliance in the lungs?
Elasticity and surface tension.
192
Why do the lungs normally have high compliance and expand easily?
Because elastic fibers in lung tissue are easily stretched and surfactant in alveolar fluid reduces surface tension.
193
What is a common feature in pulmonary conditions that scar lung tissue, cause lung tissue to become filled with fluid, produce a deficiency in surfactant, or impede lung expansion?
Decreased compliance.
194
What is an example of a condition that scars lung tissue, leading to decreased compliance?
Tuberculosis.
195
What is an example of a condition that causes lung tissue to become filled with fluid, leading to decreased compliance?
Pulmonary edema.
196
What is an example of a condition that produces a deficiency in surfactant, leading to decreased compliance?
Deficiency in surfactant.
197
What is an example of a condition that impedes lung expansion, leading to decreased compliance?
Paralysis of the intercostal muscles.
198
What condition leads to increased lung compliance due to destruction of elastic fibers in alveolar walls?
Emphysema.
199
What does the rate of airflow through the airways depend on?
Both the pressure difference and the resistance.
200
How is airflow calculated?
Airflow equals the pressure difference between the pulmonary alveoli and the atmosphere divided by the resistance.
201
What offers some resistance to the normal flow of air into and out of the lungs?
The walls of the airways, especially the bronchioles.
202
What happens to the bronchioles as the lungs expand during inhalation?
The bronchioles enlarge because their walls are pulled outward in all directions.
203
What happens to airway resistance when larger-diameter airways are present?
Airway resistance decreases.
204
What happens to airway resistance during exhalation?
Airway resistance increases as the diameter of the bronchioles decreases.
205
What regulates the diameter of the airways?
The degree of contraction or relaxation of smooth muscle in the walls of the airways.
206
What causes relaxation of bronchiolar smooth muscle (bronchodilation)?
Signals from the sympathetic division of the autonomic nervous system (ANS).
207
What is the result of bronchodilation?
Decreased resistance.
208
What causes contraction of bronchiolar smooth muscle (bronchoconstriction)?
Signals from the parasympathetic part of the ANS.
209
What is the result of bronchoconstriction?
Increased resistance.
210
What increases resistance in the airways, requiring more pressure to maintain the same airflow?
Any condition that narrows or obstructs the airways.
211
What is the hallmark of asthma or chronic obstructive pulmonary disease (COPD) such as emphysema or chronic bronchitis?
Increased airway resistance due to obstruction or collapse of airways.
212
What is respiratory distress syndrome (RDS)?
A breathing disorder of premature newborns in which the pulmonary alveoli do not remain open due to a lack of surfactant.
213
What does surfactant do in the lungs?
Surfactant reduces surface tension and is necessary to prevent the collapse of pulmonary alveoli during exhalation.
214
What happens the more premature the newborn is?
The greater the chance that RDS will develop.
215
What factors make RDS more common in infants?
Infants whose mothers have diabetes, males, and European Americans (compared to African Americans).
216
What are the symptoms of RDS?
Labored and irregular breathing, flaring of the nostrils during inhalation, grunting during exhalation, and perhaps a blue skin color.
217
How is RDS diagnosed?
It is diagnosed on the basis of chest radiographs and a blood test.
218
What treatment may a newborn with mild RDS require?
Supplemental oxygen administered through an oxygen hood or through a tube placed in the nose.
219
What treatment may be used in severe cases of RDS?
Oxygen may be delivered by continuous positive airway pressure (CPAP) through tubes in the nostrils or a mask on the face. In such cases, surfactant may be administered directly into the lungs.
220
What is the term for the normal pattern of quiet breathing?
Eupnea (ūp- NĒ-a; eu- = good, easy, or normal; -pnea = breath).
221
What can eupnea consist of?
Shallow, deep, or combined shallow and deep breathing.
222
What is the term for shallow (chest) breathing?
Costal breathing.
223
What causes costal breathing?
The upward and outward movement of the chest due to contraction of the external intercostal muscles.
224
What is the term for deep (abdominal) breathing?
Diaphragmatic breathing (dī′-a- frag- MAT- ik).
225
What causes diaphragmatic breathing?
The outward movement of the abdomen due to the contraction and descent of the diaphragm.
226
What are some emotional expressions facilitated by breathing?
Laughing, sighing, and sobbing.
227
What actions use breathing to expel foreign matter from the lower air passages?
Sneezing and coughing.
228
How are breathing movements modified during talking and singing?
Breathing movements are modified and controlled during talking and singing.
229
Are modified breathing movements reflexes or voluntary actions?
These movements are reflexes, but some of them can also be initiated voluntarily.
230
A long- drawn and deep inhalation followed by a complete closure of the rima glottidis, which results in a strong exhalation that suddenly pushes the rima glottidis open and sends a blast of air through the upper respiratory passages. Stimulus for this reflex act may be a foreign body lodged in the larynx, trachea, or epiglottis.
Coughing
231
Spasmodic contraction of muscles of exhalation that forcefully expels air through the nose and mouth. Stimulus may be an irritation of the nasal mucosa.
Sneezing and coughing.
232
A long- drawn and deep inhalation immediately followed by a shorter but forceful exhalation
Sighing
233
A deep inhalation through the widely opened mouth producing an exaggerated depression of the mandible. It may be stimulated by drowsiness or someone else’s yawning, but the precise cause is unknown.
Yawning
234
A series of convulsive inhalations followed by a single prolonged exhalation. The rima glottidis closes earlier than normal after each inhalation so only a little air enters the lungs with each inhalation.
Sobbing
235
An inhalation followed by many short convulsive exhalations, during which the rima glottidis remains open and the vocal folds vibrate; accompanied by characteristic facial expressions and tears.
Crying
236
The same basic movements as crying, but the rhythm of the movements and the facial expressions usually differ from those of crying. Laughing and crying are sometimes indistinguishable.
Laughing
237
Spasmodic contraction of the diaphragm followed by a spasmodic closure of the rima glottidis, which produces a sharp sound on inhalation. Stimulus is usually irritation of the sensory nerve endings of the digestive canal.
Hiccuping
238
Forced exhalation against a closed rima glottidis as may occur during periods of straining while defecating
Valsalva maneuver
239
The nose and mouth are held closed and air from the lungs is forced through the auditory meatus into the middle ear. Employed by those snorkeling or scuba diving during descent to equalize the pressure of the middle ear with that of the external environment.
Pressurizing the middle ear
240
What factors affect the amount of air moving into and out of the lungs during inhalation and exhalation?
Varying amounts of air depend on many factors related to various characteristics of healthy individuals and pulmonary disorders.
241
What are the two types of air amounts classified into?
(1) Lung volumes, which can be measured directly by use of a spirometer, and (2) lung capacities, which are combinations of different lung volumes.
242
What is the apparatus used to measure lung volumes and capacities called?
A spirometer (spī-ROM-e-ter; spiro- = breathe; -meter = measuring device) or respirometer (res′-pi- ROM-e- ter).
243
What is the record of lung volumes and capacities called?
A spirogram.
244
How is inhalation recorded on a spirogram?
Inhalation is recorded as an upward deflection.
245
How is exhalation recorded on a spirogram?
Exhalation is recorded as a downward deflection.
246
In general, who tends to have larger lung volumes and capacities?
Males, taller individuals, younger adults, people who live at higher altitudes, and those who are not obese tend to have larger lung volumes and capacities.
247
How are various disorders diagnosed in relation to lung volumes and capacities?
Disorders may be diagnosed by comparison of actual and predicted normal values for a person’s gender, height, and age.
248
How many breaths per minute does a healthy adult average while at rest?
A healthy adult averages 12 breaths per minute.
249
What is the volume of air moved in and out of the lungs with each inhalation and exhalation?
About 500 mL of air.
250
What is the volume of one breath called?
Tidal volume (Vt).
251
What percentage of the tidal volume reaches the respiratory zone and participates in external respiration?
About 70% (350 mL) of the tidal volume.
252
What percentage of the tidal volume remains in the conducting airways and does not participate in respiratory exchange?
30% (150 mL) of the tidal volume.
253
What is the term for the conducting airways where air does not undergo respiratory exchange?
The anatomic (respiratory) dead space.
254
What is the rule of thumb for determining the volume of your anatomic dead space?
The volume of your anatomic dead space is about the same in milliliters as your ideal weight in pounds.
255
What is the volume of air called that is inhaled beyond the tidal volume?
The inspiratory reserve volume (IRV).
256
How much is the inspiratory reserve volume (IRV) in an average adult male and female?
About 3100 mL in an average adult male and 1900 mL in an average adult female.
257
What is the additional volume of air that can be exhaled after a normal exhalation?
The expiratory reserve volume (ERV).
258
How much is the expiratory reserve volume (ERV) in males and females?
About 1200 mL in males and 700 mL in females.
259
What is the forced expiratory volume in 1 second (FEV1)?
The volume of air that can be exhaled from the lungs in 1 second with maximal effort following a maximal inhalation.
260
How does chronic obstructive pulmonary disease (COPD) affect FEV1?
COPD greatly reduces FEV1 because it increases airway resistance.
261
What is the term for the air that remains in the lungs after exhaling the expiratory reserve volume?
The residual volume (RV).
262
How much is the residual volume in males and females?
About 1200 mL in males and 1100 mL in females.
263
What happens to the intrapleural pressure if the thoracic cavity is opened?
The intrapleural pressure rises to equal atmospheric pressure, forcing out some of the residual volume.
264
What is the air remaining after the residual volume is forced out when the thoracic cavity is opened?
The minimal volume.
265
How is minimal volume used as a medical and legal tool?
The presence of minimal volume can be demonstrated by placing a piece of lung in water and observing if it floats.
266
Why would a stillborn baby's lung not float in water?
Fetal lungs contain no air, so the lung of a stillborn baby will not float in water.
267
are combinations of various lung volumes.
Lung capacities
268
What are lung capacities?
Lung capacities are combinations of specific lung volumes.
269
What is the inspiratory capacity (IC)?
The sum of tidal volume and inspiratory reserve volume (500 mL + 3100 mL = 3600 mL in males and 500 mL + 1900 mL = 2400 mL in females).
270
What is the functional residual capacity (FRC)?
The sum of residual volume and expiratory reserve volume (1200 mL + 1200 mL = 2400 mL in males and 1100 mL + 700 mL = 1800 mL in females).
271
What is the vital capacity (VC)?
The sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume (4800 mL in males and 3100 mL in females).
272
What is the total lung capacity (TLC)?
The sum of vital capacity and residual volume (4800 mL + 1200 mL = 6000 mL in males and 3100 mL + 1100 mL = 4200 mL in females).
273
What is minute ventilation (V . )?
The total volume of air inspired and expired each minute, calculated by tidal volume multiplied by respiratory rate.
274
What is the minute ventilation for a typical adult at rest?
Minute ventilation is about 6000 mL/min (12 breaths per minute × 500 mL = 6000 mL/min).
275
What does a lower-than-normal minute ventilation usually indicate?
A lower-than-normal minute ventilation usually is a sign of pulmonary malfunction.
276
What is the anatomic dead space in the conducting zone of the respiratory system?
The 150 mL in the conducting zone is the anatomic dead space.
277
What is alveolar ventilation (V . a)?
The volume of air per minute that actually reaches the respiratory zone (350 mL).
278
What is the typical alveolar ventilation for a typical adult at rest?
Alveolar ventilation is typically about 4200 mL/min (12 breaths per minute × 350 mL = 4200 mL/min).
279
How does the exchange of oxygen and carbon dioxide occur between alveolar air and pulmonary blood?
The exchange of oxygen and carbon dioxide occurs via passive diffusion, governed by the behavior of gases as described by Dalton’s law and Henry’s law.
280
What is Dalton's law important for understanding?
Dalton’s law is important for understanding how gases move down their pressure gradients by diffusion.
281
What does Henry's law help explain?
Henry’s law helps explain how the solubility of a gas relates to its diffusion
282
According to Dalton's law, what does each gas in a mixture of gases exert?
According to Dalton’s law, each gas in a mixture of gases exerts its own pressure as if no other gases were present.
283
What is the pressure of a specific gas in a mixture called?
The pressure of a specific gas in a mixture is called its partial pressure (Px).
284
How is the total pressure of the mixture calculated?
The total pressure of the mixture is calculated by adding all of the partial pressures.
285
What is atmospheric pressure composed of?
Atmospheric pressure is the sum of the pressures of gases such as PN2, PO2, PAr, PH2O, PCO2, and Pother gases.
286
How can the partial pressure exerted by each component in the mixture be determined?
The partial pressure exerted by each component in the mixture can be determined by multiplying the percentage of the gas in the mixture by the total pressure of the mixture.
287
What are the partial pressures of the gases in inhaled air?
The partial pressures of gases in inhaled air are: PN2 = 597.4 mmHg, PO2 = 158.8 mmHg, PAr = 0.7 mmHg, PH2O = 2.3 mmHg, PCO2 = 0.3 mmHg, Pother gases = 0.5 mmHg, with a total of 760.0 mmHg.
288
What happens to the O2 and CO2 content in alveolar air compared with inhaled air?
Compared with inhaled air, alveolar air has less O2 (13.6%) and more CO2 (5.2%) due to gas exchange and humidification of inhaled air.
289
Why does exhaled air contain more O2 and less CO2 than alveolar air?
Exhaled air contains more O2 (16%) and less CO2 (4.5%) because some of the exhaled air was in the anatomic dead space and did not participate in gas exchange.
290
What does Henry's law state about the quantity of a gas that will dissolve in a liquid?
Henry’s law states that the quantity of a gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility.
291
How does solubility affect the ability of a gas to stay in solution?
The ability of a gas to stay in solution is greater when its partial pressure is higher and when it has a high solubility in water.
292
How does the solubility of CO2 compare to O2 in blood plasma?
The solubility of CO2 in blood plasma is 24 times greater than that of O2.
293
What everyday experience demonstrates Henry’s law?
An everyday experience demonstrating Henry’s law is the hissing sound and bubbles rising in a carbonated beverage when the container is opened, showing CO2 coming out of solution due to decreased pressure.
294
How does Henry’s law explain the condition of nitrogen narcosis in scuba divers?
Henry’s law explains that under high pressure, nitrogen dissolves in plasma and interstitial fluid, leading to nitrogen narcosis, which produces symptoms similar to alcohol intoxication.
295
What happens if a scuba diver ascends too quickly after breathing compressed air?
If a diver ascends too quickly, nitrogen comes out of solution too quickly and forms gas bubbles in tissues, resulting in decompression sickness (the bends), which can cause symptoms such as joint pain, dizziness, and unconsciousness.
296
What is hyperbaric oxygenation?
Hyperbaric oxygenation is a clinical technique where pressure is used to cause more O2 to dissolve in the blood.
297
How does hyperbaric oxygenation help treat patients infected by anaerobic bacteria?
Hyperbaric oxygenation is effective for treating infections caused by anaerobic bacteria (e.g., tetanus, gangrene) because anaerobic bacteria cannot survive in the presence of free O2.
298
What happens during hyperbaric oxygenation?
In hyperbaric oxygenation, the patient is placed in a hyperbaric chamber with O2 at a pressure greater than 1 atmosphere (760 mmHg), allowing tissues to absorb more O2 and kill the bacteria.
299
What conditions can hyperbaric oxygenation treat?
Hyperbaric oxygenation can be used to treat heart disorders, carbon monoxide poisoning, gas embolisms, crush injuries, cerebral edema, bone infections from anaerobic bacteria, smoke inhalation, near-drowning, asphyxia, vascular insufficiencies, and burns.
300
Gases diffuse from areas of __ partial pressure to areas of __ partial pressure.
higher; lower
301
What is external respiration?
External respiration, or pulmonary gas exchange, is the process where O2 diffuses from alveolar air in the lungs into blood in pulmonary capillaries, and CO2 diffuses in the opposite direction.
302
What is the role of external respiration in oxygenating blood?
External respiration converts deoxygenated blood (low in O2) from the right side of the heart into oxygenated blood (high in O2) that returns to the left side of the heart.
303
How does the diffusion of O2 occur during external respiration?
O2 diffuses from the pulmonary alveolar air (with a partial pressure of 105 mmHg) into the blood in the pulmonary capillaries (with a partial pressure of 40 mmHg at rest), continuing until the PO2 of the blood matches that of alveolar air (105 mmHg).
304
What happens to the PO2 of blood as it moves through the pulmonary capillaries?
As blood flows through the pulmonary capillaries, it picks up O2 from the alveolar air, and the PO2 of the blood increases to match the PO2 of the alveolar air (105 mmHg). However, after mixing with blood from non-gas-exchanging areas, the PO2 of the blood in the pulmonary veins is slightly lower (about 100 mmHg).
305
How does CO2 move during external respiration?
CO2 diffuses from the deoxygenated blood (with a partial pressure of 45 mmHg) into the pulmonary alveoli (with a partial pressure of 40 mmHg), continuing until the PCO2 of the blood decreases to 40 mmHg.
306
How does blood flow through pulmonary capillaries affect gas exchange?
The number of capillaries near pulmonary alveoli is very large, and blood flows slowly enough for maximal O2 absorption. However, during vigorous exercise, blood flows more quickly, reducing the time available for gas exchange, although the PO2 still reaches 100 mmHg.
307
What happens in diseases that reduce the rate of gas diffusion?
In diseases that impair gas diffusion, blood may not fully equilibrate with pulmonary alveolar air, especially during exercise. This results in a decline in PO2 and a rise in PCO2 in systemic arterial blood.
308
What does the left ventricle pump into the aorta and through the systemic arteries to systemic capillaries?
Oxygenated blood
309
What is the exchange of O2 and CO2 between systemic capillaries and tissue cells called?
Internal respiration or systemic gas exchange
310
What happens as O2 leaves the bloodstream?
Oxygenated blood is converted into deoxygenated blood.
311
Where does internal respiration occur?
Internal respiration occurs in tissues throughout the body.
312
What is the PO2 of blood pumped into systemic capillaries compared to the PO2 in tissue cells?
The PO2 of blood pumped into systemic capillaries is higher (100 mmHg) than the PO2 in tissue cells (40 mmHg at rest).
313
Why is the PO2 of blood higher in systemic capillaries than in tissue cells?
Because the cells constantly use O2 to produce ATP.
314
What happens to oxygen as it diffuses from systemic capillaries into tissue cells?
Oxygen diffuses out of the capillaries into tissue cells.
315
What is the PO2 of blood when it exits systemic capillaries?
The PO2 of blood drops to 40 mmHg by the time it exits systemic capillaries.
316
In what direction does CO2 diffuse while O2 diffuses from systemic capillaries into tissue cells?
CO2 diffuses in the opposite direction to O2.
317
What is the PCO2 of tissue cells compared to the PCO2 in systemic capillary blood?
The PCO2 of tissue cells is higher (45 mmHg at rest) than that of systemic capillary blood (40 mmHg).
318
Where does CO2 diffuse from and to?
CO2 diffuses from tissue cells through interstitial fluid into systemic capillaries.
319
What is the PCO2 in blood after CO2 diffuses into the systemic capillaries?
The PCO2 in the blood increases to 45 mmHg.
320
Where does deoxygenated blood return to after gas exchange?
Deoxygenated blood returns to the heart and is pumped to the lungs for another cycle of external respiration.
321
What percentage of the available O2 in oxygenated blood do tissue cells need on average when a person is at rest?
Tissue cells need only 25% of the available O2 in oxygenated blood.
322
What percentage of O2 content is retained in deoxygenated blood at rest?
Deoxygenated blood retains 75% of its O2 content.
323
How does exercise affect the O2 content of deoxygenated blood?
During exercise, more O2 diffuses from the blood into metabolically active cells, causing the O2 content of deoxygenated blood to drop below 75%.
324
What factors affect the rate of pulmonary and systemic gas exchange?
The rate of pulmonary and systemic gas exchange depends on several factors.
325
What is required for oxygen to diffuse from pulmonary alveolar air into the blood?
Alveolar PO2 must be higher than blood PO2 for oxygen to diffuse from pulmonary alveolar air into the blood.
326
How does the partial pressure difference affect the rate of gas diffusion?
The rate of diffusion is faster when the difference between PO2 in pulmonary alveolar air and pulmonary capillary blood is larger; diffusion is slower when the difference is smaller.
327
What happens to the partial pressures of O2 and CO2 in pulmonary alveolar air during exercise?
The differences between PO2 and PCO2 in pulmonary alveolar air versus pulmonary blood increase during exercise.
328
What effect do larger partial pressure differences have on the rate of gas diffusion?
Larger partial pressure differences accelerate the rates of gas diffusion.
329
What factors influence the partial pressures of O2 and CO2 in pulmonary alveolar air?
The partial pressures of O2 and CO2 in pulmonary alveolar air also depend on the rate of airflow into and out of the lungs.
330
What effect do certain drugs (like morphine) have on gas exchange?
Certain drugs (like morphine) slow ventilation, thereby decreasing the amount of O2 and CO2 that can be exchanged between pulmonary alveolar air and blood.
331
How does increasing altitude affect the partial pressure of O2?
With increasing altitude, the total atmospheric pressure decreases, as does the partial pressure of O2—from 159 mmHg at sea level to 110 mmHg at 10,000 ft to 73 mmHg at 20,000 ft.
332
What happens to pulmonary alveolar PO2 with increasing altitude?
Pulmonary alveolar PO2 decreases correspondingly, and O2 diffuses into the blood more slowly.
333
What are the common signs and symptoms of high altitude sickness?
The common signs and symptoms of high altitude sickness include shortness of breath, headache, fatigue, insomnia, nausea, and dizziness, due to a lower level of oxygen in the blood.
334
What is the surface area of the pulmonary alveoli?
The surface area of the pulmonary alveoli is huge (about 75 m² or 807 ft²).
335
How many capillaries surround each pulmonary alveolus?
Many capillaries surround each pulmonary alveolus, allowing up to 900 mL of blood to participate in gas exchange at any instant.
336
What effect does a pulmonary disorder that decreases the functional surface area of the respiratory membranes have on gas exchange?
Any pulmonary disorder that decreases the functional surface area of the respiratory membranes decreases the rate of external respiration.
337
What happens in emphysema?
In emphysema, pulmonary alveolar walls disintegrate, so surface area is smaller than normal, and pulmonary gas exchange is slowed.
338
What is the diffusion distance across the respiratory membrane?
The respiratory membrane is very thin, so diffusion occurs quickly.
339
How does the narrowness of capillaries affect diffusion distance?
The capillaries are so narrow that the red blood cells must pass through them in single file, minimizing the diffusion distance from a pulmonary alveolar air space to hemoglobin inside red blood cells.
340
What effect does a buildup of interstitial fluid in pulmonary alveoli have on gas exchange?
A buildup of interstitial fluid between pulmonary alveoli (as occurs in pulmonary edema) slows the rate of gas exchange because it increases diffusion distance.
341
What happens because of the molecular weight and solubility differences between O2 and CO2?
Because O2 has a lower molecular weight than CO2, it could be expected to diffuse across the respiratory membrane about 1.2 times faster. However, the solubility of CO2 in the fluid portions of the respiratory membrane is about 24 times greater than that of O2.
342
How does the solubility of CO2 and O2 affect their diffusion rates?
Taking both molecular weight and solubility into account, net outward CO2 diffusion occurs 20 times more rapidly than net inward O2 diffusion.
343
What typically occurs when diffusion is slower than normal in emphysema or pulmonary edema?
When diffusion is slower than normal, such as in emphysema or pulmonary edema, O2 insufficiency (hypoxia) typically occurs before there is significant retention of CO2 (hypercapnia).
344
Does oxygen dissolve easily in water?
No, oxygen does not dissolve easily in water.
345
What percentage of inhaled O2 is dissolved in blood plasma?
About 1.5% of inhaled O2 is dissolved in blood plasma.
346
What percentage of blood O2 is bound to hemoglobin in red blood cells?
About 98.5% of blood O2 is bound to hemoglobin in red blood cells.
347
How much gaseous O2 does each 100 mL of oxygenated blood contain?
Each 100 mL of oxygenated blood contains the equivalent of 20 mL of gaseous O2.
348
How much of the oxygenated blood's O2 is dissolved in plasma and how much is bound to hemoglobin?
The amount dissolved in plasma is 0.3 mL and the amount bound to hemoglobin is 19.7 mL.
349
What does the heme portion of hemoglobin contain?
The heme portion of hemoglobin contains four atoms of iron, each capable of binding to a molecule of O2.
350
How does oxygen bind to hemoglobin?
Oxygen and hemoglobin bind in an easily reversible reaction to form oxyhemoglobin.
351
What percentage of O2 bound to hemoglobin is trapped inside RBCs?
The 98.5% of O2 that is bound to hemoglobin is trapped inside RBCs.
352
Which oxygen can diffuse out of tissue capillaries into tissue cells?
Only the dissolved O2 (1.5%) can diffuse out of tissue capillaries into tissue cells.
353
Why is it important to understand the factors that promote O2 binding to and dissociation from hemoglobin?
It is important to understand these factors because only the dissolved O2 (1.5%) can diffuse out of tissue capillaries into tissue cells.
354
Most O2 is transported by hemoglobin as __(Hb–O2) within red blood cells; most CO2 is transported in blood plasma as bicarbonate ions (HCO3−)
oxyhemoglobin
355
What is the most important factor that determines how much O2 binds to hemoglobin?
The most important factor is PO2. The higher the PO2, the more O2 combines with Hb.
356
When is hemoglobin said to be fully saturated?
Hemoglobin is said to be fully saturated when reduced hemoglobin (Hb) is completely converted to oxyhemoglobin (Hb–O2).
357
When is hemoglobin considered partially saturated?
Hemoglobin is partially saturated when it consists of a mixture of Hb and Hb–O2.
358
What does the percent saturation of hemoglobin express?
The percent saturation of hemoglobin expresses the average saturation of hemoglobin with oxygen.
359
How is hemoglobin considered 50% saturated?
Hemoglobin is 50% saturated when each hemoglobin molecule has bound two O2 molecules, because each Hb can bind a maximum of four O2.
360
What does the oxygen–hemoglobin dissociation curve illustrate?
The oxygen–hemoglobin dissociation curve illustrates the relationship between the percent saturation of hemoglobin and PO2.
361
What happens when PO2 is high?
When PO2 is high, hemoglobin binds with large amounts of O2 and is almost 100% saturated.
362
What happens when PO2 is low?
When PO2 is low, hemoglobin is only partially saturated with O2.
363
How does the PO2 affect the binding of O2 to hemoglobin?
The greater the PO2, the more O2 will bind to hemoglobin, until all the available hemoglobin molecules are saturated.
364
What happens in pulmonary capillaries?
In pulmonary capillaries, where PO2 is high, a lot of O2 binds to hemoglobin.
365
What happens in tissue capillaries?
In tissue capillaries, where PO2 is lower, hemoglobin does not hold as much O2, and the dissolved O2 is unloaded via diffusion into tissue cells.
366
What is the average PO2 of tissue cells in a person at rest?
The average PO2 of tissue cells in a person at rest is 40 mmHg.
367
At what PO2 is hemoglobin still 75% saturated with O2?
Hemoglobin is still 75% saturated with O2 at a PO2 of 40 mmHg.
368
How much of the available O2 unloads from hemoglobin at rest?
Only 25% of the available O2 unloads from hemoglobin and is used by tissue cells under resting conditions.
369
What is the saturation of hemoglobin when PO2 is between 60 and 100 mmHg?
When PO2 is between 60 and 100 mmHg, hemoglobin is 90% or more saturated with O2.
370
What happens when PO2 is as low as 60 mmHg?
Blood picks up a nearly full load of O2 from the lungs even when the PO2 of alveolar air is as low as 60 mmHg.
371
What does the Hb–PO2 curve explain?
The Hb–PO2 curve explains why people can still perform well at high altitudes or when they have certain cardiac and pulmonary diseases, even though PO2 may drop as low as 60 mmHg.
372
How saturated is hemoglobin at a PO2 of 40 mmHg?
At a PO2 of 40 mmHg, hemoglobin is still 75% saturated with O2.
373
What happens to oxygen saturation of hemoglobin at 20 mmHg?
The oxygen saturation of hemoglobin drops to 35% at 20 mmHg.
374
What happens between 40 and 20 mmHg in terms of oxygen release?
Between 40 and 20 mmHg, large amounts of O2 are released from hemoglobin in response to only small decreases in PO2.
375
What happens in active tissues such as contracting muscles?
In active tissues, such as contracting muscles, PO2 may drop well below 40 mmHg, causing a large percentage of O2 to be released from hemoglobin, providing more O2 to metabolically active tissues.
376
As PO2 ___, more O2 combines with hemoglobin
increases
377
What is the most important factor that determines the percent O2 saturation of hemoglobin?
PO2 is the most important factor that determines the percent O2 saturation of hemoglobin.
378
What do several other factors influence regarding hemoglobin's binding of O2?
These factors influence the tightness or affinity with which hemoglobin binds O2.
379
How do these factors affect hemoglobin's affinity for O2?
These factors shift the entire curve either to the left (higher affinity) or to the right (lower affinity).
380
What is the effect of acidity (pH) on the affinity of hemoglobin for O2?
As acidity increases (pH decreases), the affinity of hemoglobin for O2 decreases, and O2 dissociates more readily from hemoglobin.
381
What is the Bohr effect?
The Bohr effect refers to the shift in the oxygen–hemoglobin dissociation curve to the right when pH decreases. This means that at any given PO2, Hb is less saturated with O2.
382
How does an increase in H+ affect hemoglobin's ability to bind O2?
An increase in H+ in blood causes O2 to unload from hemoglobin, and the binding of O2 to hemoglobin causes unloading of H+ from hemoglobin.
383
What happens when H+ ions bind to amino acids in hemoglobin?
When H+ ions bind to amino acids in hemoglobin, they alter its structure slightly, decreasing its oxygen-carrying capacity.
384
How does lowered pH affect O2 availability for tissue cells?
Lowered pH drives O2 off hemoglobin, making more O2 available for tissue cells.
385
How does elevated pH affect hemoglobin's affinity for O2?
Elevated pH increases the affinity of hemoglobin for O2 and shifts the oxygen–hemoglobin dissociation curve to the left.
386
How does the partial pressure of carbon dioxide (PCO2) affect hemoglobin's release of O2?
As PCO2 rises, hemoglobin releases O2 more readily, shifting the curve to the right.
387
What happens when CO2 enters the blood?
When CO2 enters the blood, much of it is temporarily converted to carbonic acid (H2CO3), which dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3−), causing pH to decrease.
388
What is the relationship between PCO2 and pH?
PCO2 and pH are related because low blood pH results from high PCO2.
389
How does an increased PCO2 produce a more acidic environment?
An increased PCO2 produces a more acidic environment, which helps release O2 from hemoglobin.
390
What happens during exercise regarding lactic acid and blood pH?
During exercise, lactic acid, a by-product of anaerobic metabolism in muscles, decreases blood pH, further promoting the release of O2 from hemoglobin.
391
What effect does decreased PCO2 (and elevated pH) have on the oxygen-hemoglobin dissociation curve?
Decreased PCO2 (and elevated pH) shifts the saturation curve to the left.
392
How does temperature affect O2 release from hemoglobin?
As temperature increases, so does the amount of O2 released from hemoglobin.
393
What is the effect of heat on O2 release from hemoglobin?
Heat, a by-product of metabolic reactions, promotes the release of O2 from oxyhemoglobin, especially in metabolically active tissues like muscle fibers.
394
How does fever affect O2 release from hemoglobin?
Fever produces a similar result as heat, promoting the release of O2 from hemoglobin.
395
What happens during hypothermia in terms of O2 release from hemoglobin?
During hypothermia, O2 remains more tightly bound to hemoglobin as the body’s metabolic rate slows down, shifting the curve to the left.
396
What role does BPG (2,3-bisphosphoglycerate) play in O2 release from hemoglobin?
BPG decreases the affinity of hemoglobin for O2, helping to unload O2 from hemoglobin.
397
How is BPG formed in red blood cells?
BPG is formed in red blood cells when they break down glucose to produce ATP in a process called glycolysis.
398
What effect does BPG have on the binding of O2 to hemoglobin?
When BPG combines with hemoglobin, it causes hemoglobin to bind O2 less tightly at the heme group sites, promoting the release of O2.
399
What happens when the level of BPG increases?
The greater the level of BPG, the more O2 is unloaded from hemoglobin.
400
Which hormones increase the formation of BPG?
Hormones such as thyroxine, human growth hormone, epinephrine, norepinephrine, and testosterone increase the formation of BPG.
401
What is the level of BPG like in people living at higher altitudes?
The level of BPG is higher in people living at higher altitudes.
402
As pH decreases or PCO2 increases, the affinity of hemoglobin for O2 declines, so less __ combines with hemoglobin and more is available to tissues.
O2
403
As temperature increases, the affinity of hemoglobin for O2 ___.
decreases
404
How does fetal hemoglobin (Hb-F) differ from adult hemoglobin (Hb-A)?
Fetal hemoglobin (Hb-F) differs from adult hemoglobin (Hb-A) in structure and its affinity for O2.
405
Why does Hb-F have a higher affinity for O2 than Hb-A?
Hb-F has a higher affinity for O2 because it binds BPG less strongly.
406
How much more O2 can Hb-F carry compared to Hb-A when PO2 is low?
Hb-F can carry up to 30% more O2 than maternal Hb-A when PO2 is low.
407
Why is the higher affinity of Hb-F for O2 important?
The higher affinity of Hb-F for O2 is important because it allows O2 to be transferred from maternal to fetal blood, even when maternal blood PO2 is low in the placenta.
408
What might happen if fetal hemoglobin had the same affinity for O2 as maternal hemoglobin?
If fetal hemoglobin had the same affinity for O2 as maternal hemoglobin, the fetus might suffer from hypoxia.
409
has a higher affinity for O2 than does adult hemoglobin
Fetal hemoglobin
410
What is carbon monoxide (CO)?
Carbon monoxide (CO) is a colorless and odorless gas found in exhaust fumes from automobiles, gas furnaces, space heaters, and tobacco smoke.
411
How is carbon monoxide produced?
Carbon monoxide is a by-product of the combustion of carbon-containing materials such as coal, gas, and wood.
412
How does carbon monoxide affect hemoglobin?
CO binds to the heme group of hemoglobin, just as O2 does, but the binding of CO to hemoglobin is over 200 times as strong as the binding of O2.
413
At what concentration will carbon monoxide reduce the oxygen-carrying capacity of blood by 50%?
At a concentration as small as 0.1% (PCO = 0.5 mmHg), CO will combine with half the available hemoglobin molecules and reduce the oxygen-carrying capacity of the blood by 50%.
414
What is the result of elevated blood levels of carbon monoxide?
Elevated blood levels of CO cause carbon monoxide poisoning, which can cause the lips and oral mucosa to appear bright cherry-red.
415
How can carbon monoxide poisoning be treated?
Carbon monoxide poisoning can be treated by administering pure oxygen, which speeds up the separation of carbon monoxide from hemoglobin.
416
How is carbon dioxide (CO2) transported in the blood?
CO2 is transported in the blood in three main forms: dissolved CO2 (~7%), carbamino compounds (~23%), and bicarbonate ions (HCO3−) (~70%).
417
What percentage of CO2 is dissolved in blood plasma?
About 7% of CO2 is dissolved in blood plasma.
418
How is CO2 transported as carbamino compounds?
About 23% of CO2 combines with the amino groups of amino acids and proteins in blood to form carbamino compounds, mainly bound to hemoglobin.
419
What is carbaminohemoglobin?
Carbaminohemoglobin is hemoglobin (Hb) that has bound CO2.
420
How does CO2 transport as carbaminohemoglobin change in different capillaries?
In tissue capillaries, PCO2 is high, promoting the formation of carbaminohemoglobin, while in pulmonary capillaries, PCO2 is low, causing CO2 to split and enter the alveoli.
421
What is the major form of CO2 transported in blood?
About 70% of CO2 is transported in blood plasma as bicarbonate ions (HCO3−).
422
What is the chloride shift?
The chloride shift occurs when HCO3− moves out of RBCs into blood plasma, and Cl− moves into RBCs to maintain electrical balance.
423
How does the Haldane effect relate to CO2 transport?
The Haldane effect states that the lower the amount of oxyhemoglobin (Hb–O2), the higher the CO2-carrying capacity of the blood. Deoxyhemoglobin binds more CO2 and buffers more H+, promoting the conversion of CO2 to HCO3−.
424
What forms of CO2 are present in deoxygenated blood returning to the pulmonary capillaries?
Deoxygenated blood contains CO2 dissolved in plasma, CO2 combined with globin as carbaminohemoglobin (Hb–CO2), and CO2 incorporated into HCO3− within RBCs.
425
How is CO2 released in the pulmonary capillaries?
In the pulmonary capillaries, CO2 dissolved in plasma and CO2 dissociated from carbaminohemoglobin (Hb–CO2) diffuse into the pulmonary alveolar air and are exhaled.
426
What happens when O2 diffuses into RBCs in the lungs?
Oxygen diffuses into RBCs and binds to hemoglobin, forming oxyhemoglobin (Hb–O2).
427
What occurs to HCO3− and H+ in the pulmonary capillaries?
H+ combines with HCO3− inside RBCs, releasing CO2, which is exhaled, and forming water (H2O).
428
What happens to HCO3− in RBCs during the process?
As HCO3− decreases inside RBCs, it diffuses in from blood plasma in exchange for Cl− (the chloride shift).
429
How does oxygenated blood leaving the lungs differ from deoxygenated blood?
Oxygenated blood leaving the lungs has increased O2 content and decreased CO2 and H+ levels.
430
What happens in systemic capillaries regarding O2 and CO2?
In systemic capillaries, O2 is used by cells, and CO2 is produced, reversing the chemical reactions described in the lungs.
431
inside red blood cells transports O2, CO2, and H+.
Hemoglobin
432
How much O2 is used by body cells at rest?
At rest, about 200 mL of O2 is used per minute by body cells.
433
How much can O2 use increase during strenuous exercise?
During strenuous exercise, O2 use typically increases 15- to 20-fold in normal adults and up to 30-fold in elite endurance-trained athletes.
434
What helps match breathing effort to metabolic demand?
Several mechanisms help match breathing effort to the metabolic demand during exercise.
435
What alters the size of the thorax during breathing?
The size of the thorax is altered by the action of breathing muscles, which contract and relax in response to nerve impulses.
436
Where are the nerve impulses for breathing sent from?
The nerve impulses for breathing are sent from clusters of neurons located in the brain stem, collectively known as the respiratory center.
437
What are the two main areas of the respiratory center?
The two main areas of the respiratory center are: (1) the medullary respiratory center in the medulla oblongata, and (2) the pontine respiratory group in the pons.
438
What are the two collections of neurons in the medullary respiratory center?
The two collections of neurons in the medullary respiratory center are the dorsal respiratory group (DRG) and the ventral respiratory group (VRG).
439
What muscles are involved in normal quiet breathing?
In normal quiet breathing, the diaphragm and external intercostal muscles are involved.
440
How does the DRG contribute to breathing?
The DRG generates impulses to the diaphragm and external intercostal muscles, causing inhalation. The impulses are released in bursts, causing muscle contraction followed by relaxation for exhalation.
441
What is the pre-Bötzinger complex and its function?
The pre-Bötzinger complex in the VRG is believed to generate the rhythm of breathing, similar to a pacemaker in the heart.
442
When does the VRG become activated?
The VRG becomes activated during forceful breathing, such as during exercise, playing wind instruments, or at high altitudes.
443
What muscles are involved in forceful inhalation?
During forceful inhalation, the sternocleidomastoid, scalenes, and pectoralis minor muscles are activated.
444
What muscles are involved in forceful exhalation?
During forceful exhalation, the internal intercostals, external abdominal oblique, internal abdominal oblique, transversus abdominis, and rectus abdominis muscles are activated.
445
is composed of neurons in the medullary respiratory center in the medulla plus the pontine respiratory group in the pons.
Respiratory center
446
During normal quiet breathing, the ___ respiratory group is inactive; during forceful breathing, the ___ respiratory group activates the ventral respiratory group.
ventral;dorsal
447
What is the function of the pontine respiratory group (PRG)?
The PRG transmits nerve impulses to the DRG in the medulla and may modify the basic rhythm of breathing, especially during activities like exercising, speaking, or sleeping.
448
Where is the pontine respiratory group located?
The PRG is located in the pons.
449
What areas does the PRG influence?
The PRG influences the DRG in the medulla, which controls the basic rhythm of breathing.
450
When is the PRG active?
The PRG is active during both inhalation and exhalation.
451
What role does the cerebral cortex play in breathing?
The cerebral cortex allows for voluntary control over breathing patterns, enabling actions like holding the breath temporarily or altering the rate of breathing.
452
What is the protective aspect of voluntary control over breath?
Voluntary control helps prevent harmful substances, like water or irritating gases, from entering the lungs.
453
What happens when CO2 and H+ levels increase in the body?
When PCO2 and H+ levels rise, the DRG neurons are strongly stimulated, leading to involuntary breathing as nerve impulses are sent to respiratory muscles.
454
What limits voluntary breath-holding?
Voluntary breath-holding is limited by the buildup of CO2 and H+, which triggers involuntary breathing when these levels reach a critical point.
455
Why is it impossible for small children to harm themselves by holding their breath?
Children cannot harm themselves through breath-holding because breathing resumes automatically when consciousness is lost due to high levels of CO2 and H+.
456
How can emotional stimuli affect breathing?
Emotional stimuli from the hypothalamus and limbic system can alter breathing, such as during laughing or crying.
457
are sensory neurons that respond to changes in the levels of certain chemicals in the body.
Chemoreceptors
458
An increase in arterial blood PCO2 stimulates the
dorsal respiratory group (DRG).
459
What do certain chemical stimuli modulate?
Certain chemical stimuli modulate how quickly and how deeply we breathe.
460
What is the function of the respiratory system?
The respiratory system functions to maintain proper levels of CO2 and O2.
461
What are chemoreceptors?
Chemoreceptors are sensory neurons that are responsive to chemicals, as introduced in Chapter 21.
462
Where are central chemoreceptors located?
Central chemoreceptors are located in or near the medulla oblongata in the central nervous system.
463
What do central chemoreceptors respond to?
Central chemoreceptors respond to changes in H+ concentration or PCO2, or both, in cerebrospinal fluid.
464
Where are peripheral chemoreceptors located?
Peripheral chemoreceptors are located in the aortic bodies and the carotid bodies.
465
What are the peripheral chemoreceptors sensitive to?
Peripheral chemoreceptors are sensitive to changes in PO2, H+, and PCO2 in the blood.
466
What cranial nerves are involved with peripheral chemoreceptors?
The vagus (X) nerves are involved with aortic bodies, and the glossopharyngeal (IX) nerves are involved with carotid bodies.
467
How does CO2 diffuse into cells?
CO2 is lipid-soluble, so it easily diffuses into cells, where it combines with H2O to form carbonic acid (H2CO3).
468
What happens when carbonic acid breaks down?
When carbonic acid (H2CO3) breaks down, it forms H+ and HCO3−.
469
What causes an increase in H+ inside cells?
An increase in CO2 in the blood causes an increase in H+ inside cells.
470
What is hypercapnia?
Hypercapnia is the condition where there is a slight increase in PCO2.
471
What happens when PCO2 increases slightly?
When PCO2 increases slightly, the central chemoreceptors are stimulated, responding to the increase in H+ level.
472
What do peripheral chemoreceptors respond to?
Peripheral chemoreceptors respond to high PCO2, high H+, and a deficiency of O2.
473
What happens when PO2 falls below 50 mmHg?
When PO2 in arterial blood falls below 50 mmHg, severe deficiency of O2 depresses central chemoreceptors and DRG activity.
474
How does the chemoreceptor feedback system work?
The chemoreceptors participate in a negative feedback system that regulates CO2, O2, and H+ levels in the blood.
475
What happens when PCO2, pH (H+), or PO2 levels increase?
When PCO2 increases, pH decreases (increased H+), or PO2 decreases, the DRG becomes highly active, increasing the rate and depth of breathing.
476
What is hyperventilation?
Hyperventilation is rapid and deep breathing that allows more O2 to be inhaled and more CO2 to be exhaled.
477
What happens if arterial PCO2 is lower than 40 mmHg?
If arterial PCO2 is lower than 40 mmHg (hypocapnia), the chemoreceptors are not stimulated and the DRG neurons set their own moderate pace.
478
What happens when people hyperventilate and cause hypocapnia?
People who hyperventilate and cause hypocapnia can hold their breath longer than usual, but this is risky.
479
Why was hyperventilation risky for swimmers?
Hyperventilation was risky for swimmers because it could cause the O2 level to fall dangerously low, leading to fainting before the PCO2 rises high enough to stimulate inhalation.
480
What happens as soon as you start exercising?
Your rate and depth of breathing increase, even before changes in PO2, PCO2, or H+ level occur.
481
What is the main stimulus for these quick changes in respiratory effort?
The main stimulus is input from proprioceptors, which monitor the movement of joints and muscles.
482
What do nerve impulses from the proprioceptors stimulate?
Nerve impulses from the proprioceptors stimulate the DRG of the medulla.
483
What else feeds excitatory impulses into the DRG?
Axon collaterals (branches) of upper motor neurons from the primary motor cortex (precentral gyrus) feed excitatory impulses into the DRG.
484
What is hypoxia?
Hypoxia is a deficiency of O2 at the tissue level.
485
How can hypoxia be classified?
Hypoxia can be classified into four types based on the cause.
486
What causes hypoxic hypoxia?
Hypoxic hypoxia is caused by a low PO2 in arterial blood as a result of high altitude, airway obstruction, or fluid in the lungs.
487
What causes anemic hypoxia?
Anemic hypoxia is caused by too little functioning hemoglobin in the blood, which reduces O2 transport to tissue cells.
488
What are some causes of anemic hypoxia?
Causes of anemic hypoxia include hemorrhage, anemia, and failure of hemoglobin to carry its normal complement of O2, as in carbon monoxide poisoning.
489
What causes ischemic hypoxia?
Ischemic hypoxia occurs when blood flow to a tissue is so reduced that too little O2 is delivered to it, even though PO2 and oxyhemoglobin levels are normal.
490
What causes histotoxic hypoxia?
Histotoxic hypoxia occurs when the blood delivers adequate O2 to tissues, but the tissues are unable to use it properly because of the action of some toxic agent, such as cyanide poisoning, which blocks an enzyme required for the use of O2 during ATP synthesis.
491
What are stretch-sensitive receptors in the walls of bronchi and bronchioles called?
Stretch-sensitive receptors in the walls of bronchi and bronchioles are called baroreceptors or stretch receptors.
492
What happens when these stretch receptors become stretched during overinflation of the lungs?
When these receptors become stretched during overinflation of the lungs, nerve impulses are sent along the vagus (X) nerves to the dorsal respiratory group (DRG) in the medullary respiratory center.
493
What is the response of the DRG when it is inhibited by the stretch receptors?
When the DRG is inhibited by the stretch receptors, the diaphragm and external intercostals relax, stopping further inhalation and initiating exhalation.
494
What happens when the lungs deflate and stretch receptors are no longer stimulated?
When the lungs deflate and the stretch receptors are no longer stimulated, the DRG is no longer inhibited, and a new inhalation begins.
495
What is the reflex called that prevents overinflation of the lungs?
The reflex that prevents overinflation of the lungs is referred to as the inflation reflex or Hering–Breuer reflex.
496
When does the Hering–Breuer reflex function in infants?
In infants, the Hering–Breuer reflex appears to function in normal breathing.
497
When does the Hering–Breuer reflex activate in adults?
In adults, the Hering–Breuer reflex is not activated until tidal volume reaches more than 1500 mL.
498
What is the role of the Hering–Breuer reflex in adults?
In adults, the reflex is a protective mechanism that prevents excessive inflation of the lungs, especially during severe exercise
499
What system is stimulated when anticipation of activity or emotional anxiety occurs, affecting the rate and depth of breathing?
Limbic system stimulation increases the rate and depth of breathing.
500
How does body temperature affect the rate of breathing?
An increase in body temperature (such as during a fever or vigorous muscular exercise) increases the rate of breathing, while a decrease in body temperature decreases the breathing rate.
