This document discusses the process of breathing and its importance. It describes that breathing involves two processes: inhalation, which is an active process using muscle contraction to draw air into the lungs, and exhalation, which is a passive process that relies on muscle relaxation to push air out of the lungs. It also mentions that breathing is controlled homeostatically to regulate carbon dioxide levels in the body.

1. LIFE SCIENCES
GASEOUS EXCHANGE (BREATHING)

2. LESSON OBJECTIVES
• Understand what is breathing and why is it important.
• Understand the two distinct processes of breathing.
• Understand the homeostatic control of breathing.

3. • BREATHING
• Is the process of taking air into and expelling it from the lungs.
• Air moves in and out of the lungs as a result of differences in
atmospheric air pressure and the air pressure inside the lungs
• This process involves different muscles and volume and
pressure changes in the thoracic cavity.
• It involves 2 distinct processes: inhalation and exhalation.

4. Inhalation – Is an active process involving muscle
contraction and movement of air into lungs.
• diaphragm muscle contracts, it
flattens and moves downwards
• external intercostal muscles
between the ribs contract
• ribcage lifts upwards and pushes
outwards
• air pressure in the lungs decreases
as the chest volume increases
• atmospheric pressure is greater than
the pressure inside the lungs and air
flows in

5. Exhalation – is a passive process involving muscles
relaxation and air being pushed out of the lungs.
• diaphragm relaxes and moves
upwards
• external intercostal muscles relax
• ribcage moves down and inward
• air pressure in lungs increases
relative to the outside air pressure
• air is forced out to equalize the
pressure
• exhalation

6. HOMEOSTATIC CONTROL OF
BREATHING
(THE REGULATION OF
CARBON DIOXIDE LEVELS IN
THE INTERNAL
ENVIRONMENT)

7. Deep breaths are
like little love notes
to yourself, so,
breathe.