The Mechanism of Breathing
• http://teachhealthk12.uthscsa.edu/curriculum/pulmonary/pulmo
nary-breathsimulation.asp
(Anatomy of Breathing Flash Animation)
Inhalation
1. The Intercostal muscles
contract, sending the rib
cage upward and outward
2. The Diaphragm contracts,
and moves downward
3. The Volume inside of the
chest cavity increases
4. The Pressure inside the
chest cavity decreases
5. Air enters the lungs to
equalize the pressure
Exhalation
1. The Intercostal muscles
relax, sending the rib cage
downward and inward
2. The Diaphragm relaxes, and
moves upward
3. The Volume inside of the
chest cavity decreases
4. The Pressure inside the
chest cavity increases
5. Air exits the lungs to
equalize the pressure
Another Animation
• http://www.youtube.com/watch?v=43jJGXude
Ps&safety_mode=true&persist_safety_mode=
1&safe=active
Inhaled vs. Exhaled Air
Inhaled Air
Exhaled Air
Oxygen Concentration
21 %
16 %
Carbon Dioxide
Concentration
Nitrogen Concentration
0.04 %
5%
78 %
78 %
Dryness
Drier
Moist
Temperature
Colder or Warmer than
37 C
Dirtier
Warm (close to 37 C)
Cleanliness
*Cleaner (filtered)
*Exhaled air may contain bacteria or viruses, but is cleaner in terms of dust or pollutants
Turbinate Bones
Increase Surface Area
and
Increase the rate of
 Filtering
 Warming and
 Moistening of air
Breathing versus Respiration
• Breathing: The act of bringing air in and out of
lungs; consists of inhalation and exhalation; it
is an external mechanical process
• Cellular (Cell) Respiration: When glucose
(food) and oxygen combine to produce carbon
dioxide, water and ATP energy; occurs in the
mitochondria of cells; it is an internal
chemical process
Equation: C6H12O6 + O2
CO2 + H2O + ATP
How are Breathing and Cell Respiration
Connected?
• In order for cell respiration to occur, oxygen
must move into cells, while carbon dioxide
must move out of cells.
• The exchange is made in the lungs during
breathing
Exchanges made
between the lungs
and the blood are
said to be external
exchanges, because
the lungs are open to
the outside of the
body.
Gas Exchange
• Carbon dioxide and oxygen swap places.
• The gases move by a process called diffusion.
• In animals, oxygen is moved from the air in
the lungs to the blood, and then from the
blood to the cells.
Lungs
• Carbon dioxide
moves in the
opposite
direction
O2
Blood
CO2
Cells
http://www.youtube.com/watch?v=HiT621PrrO0&safety_mode=true&persist_s
afety_mode=1&safe=active
Label and Color the Alveolus Diagram
Use Red for oxygenated blood
and Blue for deoxygenated blood
Conditions required for Gas Exchange
1. Thin walls (air sacs and blood vessels) – so
that gases can pass through the walls
2. Moist walls – so that gases can dissolve and
pass into the blood and cytoplasm of cells
(which need materials in liquid, not gaseous
form)
3. Concentration gradient – so that gases can move by
diffusion; movement of molecules occurs from higher
towards lower concentrations
High
Low
4. Pressure gradient – so that the gases can be pushed
in the direction that they need to move into; molecules
will move from areas of higher towards areas of lower
pressure
Effect of Altitude on Gas Exchange
At Sea Level,
Air Pressure is
Higher
because there
are more air
particles on
top of you
At high altitudes (like up on a mountain):
 There are lots of oxygen molecules
 But oxygen molecules can’t get into the body cells
This is because:
 There isn’t enough pressure
 To push the oxygen from the lungs
 across the air sacs,
 blood vessels,
 and cell membranes
 into the cells where the oxygen is needed.
At HIGH altitudes….
Pressure
Gradient
Diffusion
Gradient
The Diffusion Gradient is in the right direction but the Pressure Gradient is not
Gas Transport
• Oxygen and Carbon dioxide are carried in the
blood stream.
• Oxygen is carried from the lungs to cells
which then use the oxygen for cell respiration.
• Carbon dioxide is produced by cell respiration
and is carried from the cells to the lungs to be
exhaled.
Hemoglobin
• A chemical found inside red blood cells.
• It has 4 binding spots for gas molecules.
• There are many hemoglobin molecules in each
red blood cell.
• Hemoglobin can carry




oxygen
carbon dioxide
hydrogen ions
carbon monoxide
• A hemoglobin molecule consists of 4 Globular
proteins (polypeptide chains) bound to a
central iron (Fe) atom (called a Heme
group)….hence the name Hemo Globin.
Blood Vessel
Fe
Red blood cell
Oxygen Transport
• Oxygen travels through the blood stream in 2
ways:
• Dissolved in the blood plasma (3%)
• Attached to hemoglobin – oxyhemoglobin (97%)
(Hb + O2
HbO2)
• Diagram:
Blood vessel
97
%
•
RBC
3% in plasma
http://www.youtube.com/watch?v=WXOBJEXxNEo&safety_mode=true&persist_safety_mode=1&safe=active
(3 min. Pre-load to avoid ad, stop showing at graph)
Carbon Dioxide Transport
• Carbon dioxide travels through the blood stream
in 3 ways:
• Dissolved in the blood plasma (9%)
• Attached to hemoglobin – carbaminohemoglobin
(27%) (Hb + CO2
HbCO2)
• As a combination of bicarbonate ions dissolved in
blood plasma and hydrogen ions attached to
hemoglobin - acid hemoglobin (64%)
Blood Vessel
(Hb + H+
HHb)
• Diagram:
27%
http://www.youtube.com/watch?v=x2
6TWL3VKMg&NR=1&safety_mode=tru
e&persist_safety_mode=1&safe=active
CO2
64%
H+
9% CO2 and
64% HCO3in plasma
• If carbonic acid were allow to accumulate in the
blood vessels, it would cause respiratory acidosis and
could damage blood vessel walls
• The body solves this problem by buffering the blood
• Once hydrogen ions are generated they are “hidden
away” inside red blood cells – they attach to
hemoglobin to become “acid hemoglobin”
• The bicarbonate ions are benign and can travel
through the blood vessels without causing problems
Carbon Monoxide Transport
• Carbon monoxide (CO) binds to hemoglobin
200X more tightly than oxygen
• Even if there is plenty of oxygen present, the
hemoglobin will choose CO over oxygen,
leading to the death of the person.
• Carbon monoxide is a colorless and odorless
gas that is a by-product of combustion
reactions – found in smoke.
• It is very important to have a carbon monoxide
detector in your home.
Control of Breathing
• Number of breaths per minute taken at rest is
about 14-20
• More when exercising
• Breathing rate and heart rate are tied together
• Breather rate and depth control by the
medulla oblongata and the pons in the brain
Nervous Control of Breathing
• Sensors called
chemoreceptors detect
CO2 levels in blood
• Higher CO2 levels = faster
and deeper breathing
• To speed rate and depth
of breathing, the brain
sends messages to the
diaphragm & intercostal
muscles using
sympathetic nerves
Brain
Nervous
Control of
Breathing
Muscles contract faster to speed up
rate of breathing when CO2 is high
Muscles contract slower to slow
rate of breathing when CO2 is low
Feedback Loops
Exercise
Hold breath
Certain drugs
High
CO2
Levels in
Blood
Chemoreceptors
(medulla &
Pons)
Intercostal
muscles
Diaphragm
Rate of
breathing
Increases
High Altitude Athletic Training
• Training in places with higher elevations (ex. Colorado) in order to
increase lung capacity and thus performance
• At first - breathing & heart rates will be higher than normal
• After a few months of training....
 The lungs have stretched
 Breathing rates return to normal 14-20 breaths/minute
 More capillaries grew around alveoli
to accommodate a faster gas exchange
 More red blood cells will have been added
to the blood stream for a greater
oxygen carrying capacity.
• The athlete then returns to lower
altitudes to compete