Chapter 17 Flashcards
O2 moves from alveoli to blood at the same rate it is
consumed by cells
CO2 moves from blood to alveoli at the same rate it is
produced by cells
Partial pressure of a gas =
proportion of pressure of entire gas that is due to presence of the individual gas
Partial pressure of a gas depends on
fractional concentration of the gas
Total pressure of gas mixture formula
Pgas = %gas × Ptotal
Composition of air
- 79% nitrogen
- 21% oxygen
- Trace amounts of carbon dioxide, helium, argon, and other gases
- Water can be a factor depending on humidity
partial pressure of a gas affects
the amount of gas that goes into solution
Partial pressures of vaporized and dissolved gases will be
equal at equilibrium
CO2 is ____ soluble than O2 in water (and blood)
more
Gases diffuse ___ pressure gradients
down ; high to low
Diffusion between alveoli and blood is rapid because
Small diffusion barrier
Large surface area
Mixed venous blood
All systemic venous blood returns to the right atrium and is pumped out of the right ventricle and into the pulmonary artery
Amount of O2 and CO2 that is exchanged in a vascular bed depends on?
- metabolic activity of the tissue
- Greater rate of metabolism → greater exchange
Blood in pulmonary artery =
mixed venous blood
Factors affecting alveolar partial pressures
- PO2 and PCO2 of inspired air
- Minute alveolar ventilation
- Rates at which respiring tissues use O2 and produce CO2 (most critical)
Hyperpnea
increased ventilation due to increased demand
Hypoventilation
- ventilation does not meet demands
- Arterial PO2 decreases
- Arterial PCO2 increases
Hyperventilation
- ventilation exceeds demands
- Arterial PO2 increases
- Arterial PCO2 decreases
Dyspnea
labored or difficult breathing
Apnea
temporary cessation of breathing
Tachypnea
rapid, shallow brathing
hypoxia
deficiency of O2 in tissues
hypoxemia
deficiency of O2 in the blood
Hypercapnia
excess of CO2 in the blood
hypocapnia
deficiency of CO2 in the blood
eupnea
normal breathing
Oxygen transport by
hemoglobin
O2 is ____ very soluble in plasma
not
Hb =
deoxyhemoglobin
Hb*O2 =
oxyhemoglobin
Hemoglobin can bind up to ___ oxygen molecules
four
Binding of oxygen to hemoglobin follows the ______
law of mass action
More oxygen →
more binds to hemoglobin
100% saturation →
all four binding sites on hemoglobin have oxygen bound to them
O2-carrying capacity of blood
- 1 g hemoglobin carries 1.34 mL O2
- Normal blood hemoglobin levels
2–17 g/dL - O2-carrying capacity of hemoglobin in blood
200 mL O2 per 1 L blood
Arterial blood
Hemoglobin is 98.5% saturated
Venous blood
Hemoglobin is 75% saturated
Shift right in Hb*O2 dissociation
Less loading of O2 and more unloading
Shift left in Hb*O2 dissociation
More loading of O2 and less unloading
Effects of high temperature on Hb*O2 dissociation curve
Active tissues
Shift right
More O2 unloading in tissues
More O2 delivery to tissues
Bohr effect
Lower pH increases O2 unloading
Active tissues
- Produce more acid; pH decreases in tissues
- Decreased pH causes shift right in saturation curve
- More O2 is unloaded to tissues
Effects of CO2–carbamino effect
- CO2 reacts with hemoglobin to form carbaminohemoglobin
- Hb + CO2 -> HbCO2
- Increased oxygen unloading in active tissue
- lower affinity for oxygen than Hb
Increased metabolic activity →
increases CO2
Effect of 2,3-DPG
- Produced in red blood cells under conditions of low O2 such as anemia and high altitude
- Synthesis inhibited by oxyhemoglobin
- 2,3-DPG decreases affinity of hemoglobin for O2, enhancing O2 unloading
Effect of carbon monoxide
- Hemoglobin has greater affinity for carbon monoxide (CO) than for O2
- Prevents O2 from binding to hemoglobin
CO2 is ___ soluble in plasma than O2, but still not very soluble
more
CO2 can be converted to ______ by erythrocytes, then transported in plasma
bicarbonate
Carbonic anhydrase
Enzyme that converts carbon dioxide and water to carbonic acid
Law of mass action
an increase in CO2 causes an increase in bicarbonate and hydrogen ions
CO2 + H2O -> H2CO3
Inspiration (nerves)
Phrenic nerve → diaphragm
External intercostal nerve → external intercostal muscles
Expiration (nerves)
Internal intercostal nerve → internal intercostal muscles
Brainstem respiratory centers
Inspiratory neurons
Expiratory neurons
Mixed neurons
Inspiratory neurons
Depolarize during inspiration
Expiratory neurons
Depolarize during expiration
Mixed neurons
Have properties of both inspiratory and expiratory neurons
Label figure 17.15
what are the two respiratory control centers located on each side of the medulla
Ventral respiratory group (VRG)
Dorsal respiratory group (DRG)
Inspiratory neurons are hypothesized to control?
motor neurons to inspiratory muscles
Expiratory neurons are hypothesized to control
motor neurons to expiratory muscles and/or inhibit inspiratory neurons
Pontine respiratory group
- Contains inspiratory, expiratory, and mixed neurons
- May regulate transitions between inspiration and expiration
Central pattern generator
- Central pattern generator establishes respiratory cycle
- Location and mechanism of action are unknown
Chemoreceptors
Detect levels of O2 and CO2
Two types
two types of chemoreceptors
- Peripheral chemoreceptors in carotid bodies
- Central chemoreceptors in medulla oblongata
Peripheral chemoreceptors
- Located in carotid bodies near carotid sinus
- Direct contact with arterial blood
- Communicate with afferent neurons via chemical messenger
- Afferent neurons project to medullary respiratory control areas
- Respond mainly to changes in blood pH
Central chemoreceptors
- Located on the ventral surface of medulla
- Respond to changes in pH of the CSF
- Not directly responsive to CO2
- Not responsive to changes in [O2]
Ventilation (V) =
Perfusion (Q) =
rate of air flow
rate of blood flow
- Local ventilation and perfusion are regulated
to match
- VA/Q
If ventilation to certain alveoli decreases
Increased PCO2 and decreased PO2 in blood and air
Increased PCO2 in bronchioles →
bronchodilation
Decreased PO2 in P. arterioles →
vasoconstriction
If perfusion to certain alveoli decreases
Increased PO2 and decreased PCO2 in blood and air
Increased PO2 in P. arterioles →
vasodilation
Decreased PCO2 in bronchioles →
bronchoconstriction
Normal blood pH =
7.4 (range 7.3–7.42)
___ and ___systems regulate blood pH
Respiratory ; renal
Changes in pH alter?
protein activity
Acidosis
blood pH < 7.35
CNS depression
Alkalosis
blood pH > 7.45
CNS over-excitation
Hemoglobin and bicarbonate function as a ?
buffer
Respiratory system regulates ____ ; Kidneys regulate ____
CO2; HCO3-
Respiratory acid-base disturbances
- Respiratory acidosis
(Caused by increased CO2) - Respiratory alkalosis
(Caused by decreased CO2)