State whether muscles relax or contract as a person is breathing in or out.When breathing...INOUTThe diaphragm and intercostal muscles...

When breathing:

1. IN (Inhalation)

• The diaphragm contracts and moves downward.
• The intercostal muscles contract, raising the ribcage.
• This increases the volume of the thoracic cavity and decreases the pressure inside, allowing air to flow into the lungs.

2. OUT (Exhalation)

• The diaphragm relaxes and moves upward.
• The intercostal muscles relax, lowering the ribcage.
• This decreases the volume of the thoracic cavity and increases the pressure inside, forcing air out of the lungs.

Summary:

• Inhalation: Muscles contract (diaphragm and intercostal muscles).
• Exhalation: Muscles relax (diaphragm and intercostal muscles).