This document discusses the mechanics and control of respiration. It covers topics like pressure relationships in the thoracic cavity, pulmonary ventilation, respiratory volumes and tests, gas exchange in the body, transport of respiratory gases by blood, and neural control of breathing. It also addresses factors that influence respiration like exercise, altitude, and chemoreceptors.

1. Respiration

2. Mechanics of breathing

3. Pressure relationships in the
thoracic cavity
Atmospheric pressure is the pressure
exerted by the gases surrounding the body.
Intrapulmonary pressure is the pressure
within the alveoli of the lungs.

5. Intrapleural pressure is the pressure within
the pleural cavity.
Transpulmonary pressure is the difference
between the intrapulmonary and intrapleural
pressures, which keeps the lungs from
collapsing.
A pneumothorax is the presence of air in the
intrapleural space.

6. Pulmonary ventilation
Boyle’s law is the relationship between
pressure and volume, such that P1V1=P2V2,
which states that there is an inverse
proportionality between pressure and
volume.

7. Inspiration is the period when air is flowing
into the lungs.
The inspiratory muscles are the diaphragm
and the external intercostal muscles.
Expiration is the period when gases are
leaving the lungs.

12. Physical factors influencing
pulmonary ventilation
Surface tension is the preferential attraction
of water molecules toward each other,
rather than to the gas molecules, that
produces a state of tension at the liquid
surface.
Surfactant is a detergent-like complex of
lipids and proteins that interferes with the
cohesiveness of water molecules.

13. Respiratory volumes and
pulmonary function tests
Tidal volume (500 ml) is the amount of air
inhaled or exhaled with each breath under
resting conditions.
Inspiratory reserve volume (3100 ml) is the
amount of air that can be forcefully inhaled
after a normal tidal volume inhalation.

16. Expiratory reserve volume (1200 ml) is the
amount of air that can be forcefully exhaled
after a normal tidal volume exhalation.
Residual volume (1200 ml) is the amount of
air remaining in the lungs after a forced
exhalation.

17. Inspiratory capacity (3600 ml) is the
maximum amount of air that can be inspired
after a normal expiration.
Functional residual capacity (2400 ml) is
the volume of air remaining in the lungs
after a normal tidal volume expiration.

18. Vital capacity (4800 ml) is the maximum
amount of air that can be expired after a
maximum inspiratory effort.
Total lung capacity (6000 ml) is the
maximum amount of air contained in the
lungs after a maximum inspiratory effort.

19. Anatomical dead space is the volume of air
that fills the conducting respiratory
passageways, and never contributes to gas
exchange.
Alveolar dead space is the volume of air in
the lungs when the alveoli cease to act in
gas exchange.

20. Total dead space is the sum of the
anatomical dead space and the alveolar dead
space.
A spirometer is an instrument that makes a
graphic recording of respiratory volumes.
Total ventilation is the total amount of gas
that flows into or out of the respiratory tract
in 1 minute.

21. Forced vital capacity measures the amount
of gas expelled when a subject takes a deep
breath and then forcefully exhales as
rapidly as possible.
Forced expiratory volume determines the
amount of air expelled during specific time
intervals of the FVC test.

22. Alveolar ventilation rate measures the flow
of fresh gases in and out of the alveoli
during a particular time, taking into account
the volume of air wasted in the dead spaces.

23. Nonrespiratory air movements
Nonrespiratory air movements are processes
other than breathing that move air into or
out of the lungs, such as coughing,
sneezing, laughing, and crying.

24. Gas exchanges in the body

25. Dalton’s law of partial pressures
Dalton’s law of partial pressure states that
the total pressure exerted by a mixture of
gases is the sum of the pressures exerted
independently by each gas in the mixture.
The pressure exerted by each gas is its
partial pressure, and is directly proportional
to its percentage in the total gas mixture.

26. Henry’s law states that when a mixture of
gasses is in contact with a liquid, each gas
will dissolve in the liquid in proportion to
its partial pressure.
Oxygen toxicity develops when PO2 is
greater than 2.5-3 atmospheres, due to the
large numbers of free radicals.

30. Transport of respiratory gases
by blood

31. Oxygen transport
Oxyhemoglobin is the hemoglobin-oxygen
combination formed when 4 iron atoms in
the hemoglobin bind with 4 molecules of
oxygen.
Deoxyhemoglobin is the hemoglobin
complex after oxygen has been released.

35. The Bohr effect occurs as a result of
declining pH due to increased
concentrations of CO2, which weakens the
oxygen-hemoglobin bond and thus
accelerates oxygen unloading.

36. Hypoxia is inadequate oxygen delivery to
body tissues.
Carbon monoxide poisoning is a type of
hypoxia that results when CO, which has an
affinity for hemoglobin 200 times greater
than that of O2, is introduced into the blood.

37. Carbon dioxide transport
Between 20% and 30% of transported CO2
is carried within RBCs as
carbaminohemoglobin.
Most CO2, 60%-70%, is transported in the
plasma as bicarbonate ions.

38. Carbonic anhydrase is an enzyme found in
erythrocytes that catalyzes the following
reaction:
CO2 + H2O <-> H2CO3 <-> H+ + HCO3-
The chloride shift exchanges Cl- for HCO3-,
by sending chloride ions into erythrocytes,
to compensate for the rapid accumulation of
bicarbonate ions in the plasma.

41. Haldane effect reflects the greater ability of
reduced hemoglobin to form
carbaminohemoglobin and to buffer H+ by
combining with it.
The carbonic acid-bicarbonate buffer
system is important in resisting shifts in
blood pH.

43. Control of respiration

44. Neural mechanisms and
generation of breathing rhythm
The dorsal respiratory group and the ventral
respiratory group are a cluster of neurons in
the medulla oblongata that regulate
respiration.
The dorsal respiratory group appears to be
the pacesetting respiratory center, and is
known as the inspiratory center.

45. Impulses travel along the phrenic intercostal
nerves to excite the diaphragm and external
intercostal muscles.
The pneumotaxic center is located in the
pons, and seems to inhibit the medulla.

47. Factors influencing the rate and
depth of breathing
The inflation reflex prevents over inflation
of the lungs, and is initiated when
baroreceptors in the visceral pleurae and
conducting passages are stimulated due to
over inflation of the lungs.
Chemoreceptors respond to changing levels
of carbon dioxide, oxygen, and hydrogen
ions in the arterial blood.

50. Hypercapnia refers to the lowering of the
pH of cerebrospinal fluid due to an increase
in the PCO2, which excites chemoreceptors
and increases the rate and depth of
breathing.
Hyperventilation is an increase in the rate
and depth of breathing, which enhances
alveolar ventilation.

51. Hypocapnia occurs when low carbon
dioxide levels result from hyperventilation,
which leads to dizziness due to the
constriction of cerebral blood vessels.
Hypoventilation occurs when PCO2 is
abnormally low due to inhibited respiration.

52. Apnea is the complete cessation of
breathing, and may result from
hypoventilation.
Cells sensitive to arterial oxygen levels are
found in the aortic bodies of the aortic arch,
and in the carotid bodies in the carotid
arteries.

53. When PO2 becomes the primary stimulus for
breathing due to insensitivity of CO 2
chemoreceptors following pulmonary
disease, it is called the hypoxic drive.

54. Respiratory adjustments
during exercise and at high
altitudes

55. Effects of exercise
Hyperpnea occurs as breathing becomes
deeper and more vigorous due to exercise,
but metabolic demands match respiratory
changes, as opposed to hyperventilation.

56. Effects of high altitude
Acclimatization occurs when decreased
PO2, which is evident at high altitudes,
increases ventilation, thus lowering arterial
CO2 levels but decreasing hemoglobin
affinity for oxygen.
Erythropoitin secretion by the kidneys may
increase, thus increasing the concentration
of RBCs and the PO2. Go Broncos!