Download iphy 3430 9-15

IPHY 3430 9-15-11
RESPIRATORY SYSTEM
Purpose:
Maintain blood levels of O2 and
CO2 as homeostatic variables
F
Additional parts of anatomy
involved in respiration
Nervous system: Pons, Medulla
Phrenic nerve and other motor
nerves
Physical Principles
1. Gas flows from area of high pressure
to low pressure
2. The rate of flow depends on the
pressure gradient: the greater the
gradient, the faster the flow and the
larger the volume of air that moves
3. When gas is compressed in a smaller
volume, the pressure increases.
INHALATION
1. Medulla sends signal via motor nerves to
diaphragm and external intercostals, causing
contraction
2. Those muscles cause expansion of the
volume of the thoracic cavity
3. The increased volume of the thoracic cavity
causes the lungs to expand
4. The expansion of the lungs causes a
decrease in air pressure in the lungs relative to
outside air
5. Air flows into lungs down pressure
gradient until air pressure equalized.
During inhalation/exhalation at rest:
pressure differential of about 1 mm
760
760
759
mmHg
Inhalation at rest
761
Exhalation at rest
EXHALATION AT REST
1. Air flow in during inhalation stops when pressure
equalized
2. Stimulus from medulla ceases, causes muscles to
relax.
3. Elastic properties of the muscles and rib cage cause
decrease in volume of thoracic cavity, which causes a
decrease in lung volume
4. Decrease in volume of lungs causes increase in air
pressure in lungs relative to outside
5. Air rushes out of lungs until pressure equalized.
During inhalation/exhalation at rest:
pressure differential of about 1 mm
760
760
759
mmHg
Inhalation at rest
761
Exhalation at rest
VARIATION IN RESPIRATORY
EXCHANGE DURING EXERCISE
1. In exercise, increased muscle
contraction leads to greater expansion of
thoracic cavity and decrease in air
pressure in lungs
2. Decreased air pressure in exercise
leads to greater air inhalation and
exhalation
3. Increased number of breaths/min
During exercise, pressure differentials greater than 1
mm generated due to greater numbers of muscles
contracting with greater force, resulting in larger
expansion of thoracic cavity and lungs.
Inhalation
760
mmHg
750
Exhalation
760
770