6.7- THE MECHANISM OF BREATHING

Question 1

What is done to maintain diffusion of gases across the alveolar epithelium?

Answer 1

air constantly moved in and out of lungs

Question 2

What is the process of air constantly moving in and out of the lungs called?

Answer 2

breathing or ventilation

Question 3

When is air forced into the lungs?

Answer 3

when air pressure of atmosphere greater than air pressure inside lungs

Question 4

What is the process of air being forced into the lungs called?

Answer 4

inspiration (inhalation)

Question 5

When is air forced out of the lungs?

Answer 5

when air pressure in lungs greater than that of atmosphere

Question 6

What is the process of air being forced out of the lungs called?

Answer 6

expiration (exhalation)

Question 7

What are the three sets of muscles that cause the pressure change within the lungs?

Answer 7

diaphragm
internal intercostal muscles
external intercostal muscles

Question 8

What is the diaphragm?

Answer 8

sheet of muscle that separated the thorax from the abdomen

Question 9

Where does the intercostal muscles lie between?

Answer 9

between the ribs

Question 10

What does the contractions of the internal intercostal muscles lead to?

Answer 10

contraction leads to expiration

Question 11

What does the contraction of external intercostal muscles lead to?

Answer 11

contraction leads to inspiration

Question 12

What sort of process is breathing in?

Answer 12

active process

Question 13

Why is breathing in an active process?

Answer 13

it uses energy

Question 14

How breathing in occurs: intercostal muscles (1)

Answer 14

external intercostal muscles contract, while internal intercostal muscles relax

Question 15

How breathing in occurs: ribs (2)

Answer 15

ribs pulled upwards + outwards, increasing volume of thorax

Question 16

How breathing in occurs: diaphragm (3)

Answer 16

diaphragm muscles contract, causing it to flatten, which also increases volume of thorax

Question 17

How breathing in occurs: increased volume of thorax (4)

Answer 17

increased volume of thorax results in reduction of pressure in lungs

Question 18

How breathing in occurs: atmospheric pressure (5)

Answer 18

atmospheric pressure now greater than pulmonary pressure + air forced into lungs

Question 19

What sort of process is breathing out?

Answer 19

largely passive process

Question 20

Why is breathing out a largely passive process?

Answer 20

does not require much energy

Question 21

How breathing out occurs: intercostal muscles (1)

Answer 21

internal intercostal muscles contract, while external intercostal muscles relax

Question 22

How breathing out occurs: ribs (2)

Answer 22

ribs move downwards + inwards, decreasing volume of thorax

Question 23

How breathing out occurs: diaphragm (3)

Answer 23

diaphragm muscles relax + so it’s pushed up again by contents of abdomen that were compressed during inspiration
volume of thorax further decreased

Question 24

How breathing out occurs: decreased volume of thorax (4)

Answer 24

decreased volume of thorax increases pressure in lungs

Question 25

How breathing out occurs: pulmonary pressure (5)

Answer 25

pulmonary pressure now greater than that of atmosphere, + so air forced out of lungs

Question 26

What is the main cause of air being forced out during normal quiet breathing?

Answer 26

recoil of elastic tissue in lungs

Question 27

When do the various muscles play a major part in breathing?

Answer 27

only under more strenuous conditions i.e. exercise