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29 Cards in this Set

  • Front
  • Back

Nonrespiratory Air Movements

• Processes other than breathing that
moves air in or out of lungs
• May modify normal respiratory rhythm
• Most result from reflex action; some
voluntary
• Examples include-cough, sneeze, crying,
laughing, hiccups, and yawns

External respiration

–diffusion of gases in lungs

Internal respiration

–diffusion of gases at body tissues

Both internal and external respiration involve:

– Physical properties of gases
– Composition of alveolar gas

• Anatomical dead space

–No contribution to gas exchange in
alveoli
–TV is 500 ml, ~350ml involved in
ventilation
–Air remaining in passageways; ~150 ml

Alveolar dead space

–non-functional alveoli due to collapse or obstruction

Total dead space

-sum of anatomical and alveolar dead space

• Dalton’s law

how gas behaves when part of a mixture
• Total pressure exerted by mixture of gases
= sum of pressures exerted independently
by each gas

Partial pressure

– Pressure exerted by each gas in mixture
– Directly proportional to its percentage in
mixture

Henry’s law

how gases move into and out of liquid
• Gas mixtures in contact with liquid
– when a mixture of gases is in contact with a
liquid each gas will dissolve into the liquid in
proportion it its partial pressure
– Partial pressure abbreviated P followed by
gas formula: Examples: PO2, PCO2

Perfusion

-blood flow reaching alveoli from pulmonary capillaries

Ventilation

-amt. of gas reaching alveoli

What must be matched (coupled) for efficient gas exchange?

Ventilation and perfusion

Why are ventilation and perfusion Never balanced for all alveoli?

due to
• Regional variations due to effect of
gravity on blood and air flow
• Some alveolar ducts plugged with
mucus

Perfusion
–Changes in Po2 in alveoli cause
changes in diameters of arterioles

•Where alveolar O2 is high, arterioles
dilate
•Where alveolar O2 is low, arterioles
constrict

CO2 transported in blood in three forms

– 70% transported as bicarbonate ions
(HCO3
–) in plasma
– 20% bound to globin of hemoglobin
(carbaminohemoglobin)
– 7 to 10% dissolved in plasma

• Molecular O2 carried in blood two ways

– 98.5% loosely bound to each Fe of
hemoglobin (Hb) in RBCs
– 1.5% dissolved in plasma
• Oxygen is poorly soluble so very little
(~1.5%) is transported dissolved in
plasma

Hypoxia

– Inadequate O2 delivery to tissues  cyanosis

– Anemic hypoxia

–too few RBCs; abnormal or too little Hb

– Ischemic hypoxia


–impaired/blocked circulation

– Histotoxic hypoxia

–cells unable to use O2, as in metabolic poisons

– Hypoxemic hypoxia

–abnormal ventilation; pulmonary disease

– Carbon monoxide poisoning

–especially from
fire; 200X greater affinity for Hb than oxygen

Influence of CO2 on Blood pH
• Hypoventilation:

allows CO2 to
accumulate in blood (produce CO2 faster
than you exhale) results in raising [H+]
which lowers pH (acidosis)

causes of hypoventilation

Congestive heart failure, emphysema, sleep
apnea; slip into coma → fatal

Hyperventilation:

increased depth and
rate of breathing that exceeds the body’s
need to remove CO2 which raises pH i.e.,
alkalosis; change in arrow direction!
CO2 + H2O ← H2CO3 ← HCO3
- + H+

causes of hyperventilation


– Extreme anxiety and stress or extreme pain,
become dizzy, faints, tetany in hands and face,
overstimulation of CNS, convulsions, fatal if
untreated

Carbonic acid–bicarbonate buffer
system

–resists changes in blood pH
– If H+ concentration in blood rises, excess H+ is
removed by combining with HCO3
–  H2CO3
– If H+ concentration begins to drop, H2CO3
dissociates, releasing H+
– HCO3
– is alkaline reserve of carbonic cidbicarbonate
buffer system

Changes in respiratory rate and depth
affect blood pH

– Slow, shallow breathing  increased CO2 in
blood drop in pH
– Rapid, deep breathing  decreased CO2 in
blood  rise in pH