Chemoreceptors that monitor O2 and CO2 content and pH are located in the _________.
medulla oblongata, carotid arteries, and aorta
Changes in the amount of ________ is the primary stimulus driving changes in ventilation.
CO2
Emphysema causes a loss of septa between individual alveoli, resulting in fewer, but larger, alveoli. What component of gas diffusion would be most affected by emphysema?
surface area
Oxygen is carried in the blood in two ways. Most of it is bound to hemoglobin while the remainder is carried in what form?
dissolved in the plasma
In a healthy respiratory system, if the alveolar PO2 is 85 mmHg, what will arterial PO2 be?
85 mmHg
In what form is most carbon dioxide transported in the blood?
as bicarbonate ion
Central chemoreceptors that monitor composition of cerebrospinal fluid will trigger an increase in ventilation ________.
if either CO2 or H+ increases (resulting in a drop in pH)
Because this factor normally varies, the most important variable that influences the diffusion of respiratory gases is the ________.
concentration gradient
What is the definition of "anemic hypoxia"?
decreased O2 bound to hemoglobin
Which of these blood values are in the normal range?
Arterial PCO2 = 38 mmHg
What is the primary mechanism by which gases move from the alveoli into the blood and cells and back?
simple diffusion
Low alveolar PO2 can be caused by one of two mechanisms. One of them is that the inspired air has a low oxygen content. What is the other reason?
hypoventilation
Which disorder would usually result in a normal alveolar PO2 but a decreased arterial PO2?
pulmonary edema
If alveolar PO2 is normal but arterial PO2 is low, what is the most likely cause?
decreased barrier permeability
At the same pressure, about 25 times more CO2 will dissolve in plasma as O2. Why does this occur?
CO2 has a higher solubility than O2.
High carbon dioxide concentration in body fluids is called
hypercapnia
The partial pressure of carbon dioxide in the cells of peripheral tissues is approximately ________ mm Hg.
45
Of the factors that influence diffusion of respiratory gases, the most variable and, therefore, important factor to consider is the
concentration gradient.
The process by which dissolved gases are exchanged between the blood and interstitial fluids is
diffusion
The lung pathology most likely to result from certain kinds of heart disease is
pulmonary edema.
Hypoxia resulting from fluid accumulation in the alveoli that cannot be corrected by oxygen therapy can lead to
adult respiratory distress syndrome.
If the partial pressure of oxygen in both air and water is 100 mm Hg, then the concentration of the oxygen is the same in the air and water.
False
destruction of alveoli
emphysema
thickened alveolar membrane and decreased lung compliance
fibrotic lung disease
decreased surface area for gas exchange
emphysema
increased airway resistance
asthma
fluid accumulation in interstitial spaces
pulmonary edema
increased diffusion distance
pulmonary edema
increased temperature
decrease
increased pH
increase
increased PCO2
decrease
increased 2,3-DPG
decrease
Too little oxygen in cells is called
hypoxia.
Too little oxygen in cells is often accompanied by too much ________, which is called ________.
carbon dioxide, hypercapnia
Generally, PO2 in arterial blood is ________ than PO2 in venous blood.
55 mmHg higher
Generally, PCO2 in arterial blood is ________ than PCO2 in venous blood.
6mmHg lower
PCO2 tends to be ________ in tissues than in systemic capillaries.
higher
Diffusion rate is directly proportional to
surface area and concentration gradient.
________ is characterized by a decreased surface area for gas exchange in the lungs.
Emphysema
________ is characterized by a thickened alveolar membrane, slowing respiratory gas exchange.
Fibrotic lung disease
In ________, fluid accumulates in the interstitial spaces of the lungs, slowing gas exchange.
pulmonary edema
________ is characterized by an increased airway resistance and decreased ventilation.
Asthma
Diffusion rate is inversely proportional to
membrane thickness.
Jill lives in St. Louis, which is close to sea level. She decides to spend a month of her summer vacation working in the mountains outside of Denver. After a week in the mountains, what kinds of changes would you expect to see as Jill adapts to the higher
decreased PO2 in the alveoli
Low levels of oxygen in the tissues, due to reduced blood flow, is known as __________.
ischemic hypoxia
Emphysema reduces respiratory gas exchange by altering ________.
surface area
Choose the combination of factors that would lead to the greatest oxygen unloading from hemoglobin.
Low pH, high temperature, high PCO2, high 2,3-DPG
Using the Fick equation, calculate cardiac output if a person is consuming 1.41 L O2/min, have an arterial O2 content of 190 ml O2/L, and a venous O2 content of 25 ml O2/L.
8.5 L/min
What is the main difference between fetal and adult hemoglobin?
Fetal hemoglobin has a higher affinity for oxygen.
What would a rightward shift in the oxygen-hemoglobin binding curve indicate?
a decrease in hemoglobin affinity for oxygen
Which change would cause a leftward shift in the oxygen-hemoglobin binding curve?
decreased temperature
What is the chloride shift?
the exchange of Cl? for bicarbonate ions in erythrocytes causing HCO?3 to leave the cell
How is CO2 converted to carbonic acid at the tissues and back to CO2 in the lungs by the same enzyme, carbonic anhydrase?
Carbonic anhydrase catalyzes the reaction in both directions depending upon the concentration of the substrates.
The variables of oxygen consumption, cardiac output, and blood oxygen content are unrelated.
False
Which of the following characteristics makes hemoglobin's structure such a good match for its function as an oxygen carrier?
Each hemoglobin molecule can bind four oxygen molecules.
Most of the oxygen transported by the blood is
bound to hemoglobin.
At a PO2 of 70 mm Hg and normal temperature and pH, hemoglobin is ________% saturated with oxygen.
over 90
Which of the following would make the oxygen-hemoglobin curve shift right?
increased H+ concentration
Chronic hypoxia
increases 2,3-DPG production in blood and can result from anemia.
Most of the carbon dioxide in the blood is transported as
bicarbonate ions.
________ is the enzyme that converts CO2 into bicarbonate ions.
Carbonic anhydrase
For maximum efficiency in loading oxygen at the lungs,
the temperature should be slightly lower than normal body temperature.
A student in your lab volunteers to enter a hypoxic breathing chamber for 10 minutes, and his alveolar PO2 drops to 50 mm Hg. What other change would occur?
decrease in arterial PCO2
A molecule that blocks the activity of carbonic anhydrase would
cause an increase in blood pH.
Approximately what percentage of the total blood oxygen is bound to hemoglobin instead of dissolved in plasma?
98%
A hemoglobin molecule binds to a maximum of how many oxygen molecules?
up to 4
About 23% of the carbon dioxide in blood is carried ________.
by hemoglobin, bound to amino groups
Which area of the brain stimulates the diaphragm to contract to initiate inspiration?
dorsal respiratory group
Which change would cause the greatest stimulus for an increase in ventilation?
arterial PCO2 increasing to 46 mmHg
Which chemical can stimulate ventilation by binding both peripheral and central chemoreceptors?
plasma CO2
In the medulla oblongata, the nucleus tractus solitarius contains the ________ of neurons.
dorsal respiratory group
The most important chemical regulator of respiration is
carbon dioxide.
An increase in the level of carbon dioxide in the blood will
increase the rate of breathing.
The expiratory neurons control the ________ muscles, whereas the inspiratory neurons control the ________ muscles.
abdominal and internal intercostal, diaphragm and external intercostal
If the neural connections between the pons and medulla are severed, breathing will stop.
false
The Hering-Breuer reflex
prevents overexpansion of the lungs.
Protective reflexes of the lungs include
coughing and bronchoconstriction.
The ________ group of neurons contains mostly inspiratory neurons. The ________ group of neurons controls muscles used for active expiration and some inspiratory muscles.
dorsal respiratory, ventral respiratory
The output of the ________ group of inspiratory neurons controls the ________ muscle(s) by way of the ________ nerve.
dorsal respiratory, diaphragm, vagus
Inappropriate relaxation of the ________ muscle(s) during sleep contributes to ________, a sleep disorder associated with snoring.
pharynx and larynx, obstructive sleep apnea
________ in the carotid and aortic bodies are activated by a decrease in PO2 and pH or an increase in PCO2 and they trigger________.
glomus cells, an increase in ventilation
The carotid and aortic bodies contain specialized ________ cells, which can increase ventilation in response to changes in PO2, PCO2, or pH.
glomus
Fear and excitement may affect the pace and depth of respiration by stimulation of portions of the
limbic system.
Carbon dioxide is more soluble in water than oxygen. To get the same amount of oxygen to dissolve in plasma as carbon dioxide, you would have to
increase the partial pressure of oxygen.
The chloride shift occurs when
bicarbonate ions leave the red blood cells.
Blocking afferent action potentials from the chemoreceptors in the carotid and aortic bodies would interfere with the brain's ability to regulate breathing in response to all EXCEPT which of the following?
changes in blood pressure