Mechanism of Breathing

Question 1

Is breathing (or ventilation) a voluntary or involuntary process?

Answer 1

involuntary process.

Question 2

What is the average rate of breathing for an adult?

Answer 2

An adult at rest normally breathes about 12 to 18 times per minute.

Question 3

Define inhalation

Answer 3

Inhalation means breathing in

Question 4

List the steps of inhalation (7)

Answer 4

1. The brain controls the rate of breathing.
2. Normally a message is sent from the brain to the intercostal muscles and the diaphragm.
3. These muscles use energy (in the form of ATP) to contract. For this reason inhalation is said to be an active process.
4. The ribs are pulled up and out and the diaphragm curves down.
5. The volume or size of the chest cavity (or thorax) increases.
6. The pressure in the chest cavity decreases.
7. The external air pressure is now higher than the air pressure in the chest. As a result air is forced into the lungs. This is called inhalation or inspiration.

Question 5

List the steps of exhalation (5)

Answer 5

1. The intercostal muscles and diaphragm relax. As a result exhalation is a passive process.
2. The ribs move down and in and the diaphragm curves up.
3. The volume or size of the chest cavity (or thorax) decreases.
4. The pressure in the chest cavity increases.
5. Air is forced out of the lungs.