Download AS Mechanics_of_Breathing

Respiratory System
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Exchange of oxygen and carbon dioxide
between the blood and the muscle tissues
Exchange of oxygen and carbon dioxide
between the lungs and blood
The breathing of air into and out of the lungs
Mechanics of Breathing
Inspiration:
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External intercostals muscles contract during inspiration
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Diaphragm contracts (downwards and flattens)
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This pulls the rib cage upwards and outwards
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These actions cause the thoracic cavity size to increase
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This decreases the pressure inside the thoracic cavity
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Gases move from areas of high pressure to low pressure
areas
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Therefore oxygen moves from the atmosphere (higher
pressure) into the lungs (now low in pressure)
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During exercise, a more forceful inspiration is required so
extra muscles are involved in this process –
sternocleidomastoid and pectoralis minor
Expiration
 Usually a passive process
 As the intercostals muscles relax the rib cage moves
downwards
 The diaphragm relaxes and returns to its dome shape
 This decreases the size of the thoracic cavity
 This causes the pressure to increase in the thoracic cavity
(smaller volume)
 Therefore gases move out of the lungs (high pressure) into
the atmosphere (lower pressure)
 During exercise breathing rate is increased, expiration is
aided by the internal intercostal muscles and the
abdominal muscles,
 This pulls the rib cage down more quickly and with greater
force
Gaseous Exchange
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Key Terms:
Gaseous Exchange – the process of exchanging O2
and CO2
Partial Pressure - the pressure a gas exerts in a
mixture of gases
Diffusion - The movement of gases from areas of
higher partial pressure to lower partial pressure
Diffusion Gradient - The difference between high and
low pressure of gases. The bigger the gradient the
greater the diffusion.
External Respiration
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Involves the movement of oxygen and carbon
dioxide between the alveoli of the lungs and
capillaries surrounding the alveoli.
The aim of external respiration is to oxygenate
the blood returning from the tissues
As blood circulates through the capillaries
surrounding the alveoli oxygen is picked up and
carbon dioxide is dropped off to be expired
Internal Respiration
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Involves the movement of O2 and CO2
between the capillaries surrounding the muscles
and the muscle tissues
The aim of internal respiration is to oxygenate
the muscles and collect CO2 to return it to the
alveoli
These processes can only happen if a diffusion
gradient is present.
External and Internal Respiration
Showing Changes in O2 and CO2
Oxygen-Haemoglobin Dissociation
Curve
Shows
us how much haemoglobin is saturated
with oxygen
Saturated – when haemoglobin is loaded with
oxygen
Dissociation – where oxygen is unloaded from
the haemoglobin
The higher the partial pressure of oxygen, the
higher percentage of oxygen saturation to
haemoglobin
Oxygen associates with haemoglobin at the
lungs and dissociates at the muscles (because PP
of O2 is high at lungs and low at muscles)
 During exercise a greater amount of dissociation
of O2 at the muscles is required, therefore less
saturation at the muscles has to occur
 Four factors happen in our bodies during
exercise to allow this to occur
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Factors Affecting the saturation of
oxygen to haemoglobin
Increase in temperature – in the blood and muscles during exercise
 Decrease in PP of O2 – within the muscles during exercise, therefore
creating a greater diffusion gradient
 Increase in PP of CO2 – therefore causing a greater CO2 diffusion
gradient
 Increase in acidity – lowering the pH of the blood through
production of lactic acid (more hydrogen ions produced). This is
known as the BOHR SHIFT
All four of these factors (which occur during exercise) increases the
dissociation of oxygen from haemoglobin, which increases the supply
of oxygen to the working muscles and therefore delays fatigue.
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Exam Style Question:
 What happens to the oxygen-Haemoglobin
Dissociation Curve during exercise? (6 marks)
 It shifts to the right
 Because during exercise there is an increase in
blood/muscle temperature
 Decrease in PP of O2 in the muscles
 Increase in PP of CO2 in muscles
 Increase in acidity (more lactic acid)
 Known as Bohr Effect/Shift
Myoglobin
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Has a higher affinity for O2 than haemoglobin
Therefore acts as a store of O2
Even at very low partial pressures of 02 (the
muscles when exercising) it remains saturated
This means that myoglobin still has O2 available
to supply the working muscles.
Respiratory Adaptations to Training
Reduction
in breathing rate during submaximal exercise,
System is more efficient therefore less
breaths required,
No changes in lung volumes except. . . .
Vital capacity – amount of air that can be forcibly
expired after maximal inspiration – increases
slightly, largely due to stronger respiratory
muscles
Therefore spirometer traces are not good
predictors of training or fitness because lung
size/volume do not determine fitness (these are
largely genetic and not adapted due to training)
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Gaseous exchange becomes
efficient
External Respiration - increased
capilliarisation surrounding alveoli
– more opportunity for gaseous
exchange to occur, more O2 enters
the blood
Internal Respiration – increase in
myoglobin within the muscles (this
carries O2 to mitochondria),
therefore leading to improved
efficiency of energy production.
Describe the chemical, physical and neural
changes that cause a change in our breathing
rate.
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Chemical –
Increase in CO2, increase in acidity
Detected by chemoreceptors
Physical –
Movement of muscles and joints
Detected by proprioreceptors
Also stretch receptors in lungs, temperature receptors detect
changes
Neural –
Nervous control
Messages sent to the medulla (respiratory control centre)
Messages to send respiratory muscles via sympathetic nervous
system.
Respiratory System so far . . .
1.
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4.
5.
What is the Oxygen-Haemoglobin
Disassociation Curve?
What happens to the curve during exercise?
What causes this to happen?
What are the effects of the curve shifting to the
right?
What changes occur to the respiratory system
as a result of training?
Lung Volumes
(Average male) ** Learn
Volume Name
Description
Value at Rest
(ml)
Change during
Exercise
Tidal Volume (TV)
Amount of air breathed in or
out per breath
500
Increases
Inspiratory Reserve
Volume (IRV)
Maximal amount of air forcibly
inspired in addition to tidal
volume
3100
Decreases
Expiratory Reserve
Volume (ERV)
Maximal amount of air forcibly
expired in addition to tidal
volume
1200
Decreases
Vital Capacity (VC)
Maximal amount of air exhaled
after a maximal inspiration
(TV + IRV + ERV)
4800
Slight
Residual Volume
(RV)
Amount of air left in the lungs
after a maximal expiration
1200
None
Total Lung Capacity
(TV)
Vital Capacity plus residual
volume
(TV + IRV + ERV + RV)
6000
none
Effects of Exercise on Volumes
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At rest, lungs are ventilated at approx. 6 Litres per minute
During “steady state” endurance exercise maximal ventilation is about 80100 Litres per minute (males) and 45-80 Litres per minute (females) –
smaller lungs!
Brief maximal exercise (800m race) rates may increase to 120-140 Litres
per minute
BREATHING RATES – rise from 12 per minute to 45 per minute
during strenuous exercise
Depth of respiration can increase from 0.5 litres per breath to 2.5 litres
per breath
Training will usually result in little or no change in pulmonary function.
However, swimmers may experience some increase in vital capacity and
maximal breathing capacity (breathing against resistance of the water)
Comparison of marathon runners and sedentary subjects showed no
difference in actual lung functions (FEV1, etc)
Summary
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The respiratory system functions to deliver O2 to the lungs and
remove CO2
The system consists of the nose, trachea, larynx, bronchial tree and
lungs
Inspiration occurs when air is drawn into the lungs by the reduction
of the pressure caused by an increase in the size of the thoracic cavity
Expiration occurs when the pressure increases as the size of the
thoracic cavity decreases and air is forced out
During normal breathing inspiration is produced by the activity of the
diaphragm and intercostal muscles
During exercise both the rate and depth of breathing increase
Respiration is controlled by the MEDULLA of the brain
Total Lung Capacity = Tidal Volume + Inspiratory Reserve Volume
+ Expiratory Reserve Volume and Residual Volume (6000ml)