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Inhalation & Exhalation
Antagonistic Muscle action in ventilation
External and internal intercostal muscles & diaphragm and abdominal
muscles as examples of antagonistic muscle pairs
Ventilation involves 2 pairs of opposite movements that change the
volume and therefore the pressure inside the thorax.
Inspiration
Diaphragm moves downward and flattens
Ribcage moves upward and outward
The volume inside the thorax increases, pressure decreases
Pairs:
Antagonistic
Diaphragm contracts – moves down, pushes abdomen wall out
Muscles in abdomen wall relax
External intercostal muscles contract, move ribcage up and out
Internal intercostal muscles relax
Expiration
Diaphragm moves up and becomes dome shaped
Ribcage moves downward and inward
Volume inside the thorax decreases, pressure increases
Antagonistic Pairs:
Diaphragm relaxes, pushed up into dome shape
Muscles in abdominal wall contract pushing diaphragm up
External intercostal muscles relax
Internal intercostal muscles contract, pulling ribcage in