Chapter 7: Exchange Surfaces and Breathing

Question 1

Outline process of inspiration (active process).

Answer 1

1. External intercostal muscles contract.
2. Ribs move up and outwards.
3. Dome shaped diaphragm contracts.
4. Diaphragm lowers/flattens.
5. Volume increased so pressure is reduced.
6. Pressure of air surrounding lungs < pressure of atmospheric air.
7. Air drawn in through nasal passages, trachea, bronchi, bronchioles and into the lungs.
8. Until pressure inside chest = pressure outside.

Question 2

Outline process of expiration (passive process)

Answer 2

1. External intercostal muscles relax.
2. Ribs move down and inwards.
3. Diaphragm relaxes.
4. Diaphragm moves up into its resting dome shape.
5. Elastic fibres in alveoli return to original length + vol. of thorax decreases.
6. Pressure in thorax > pressure of atmospheric air.
7. Air rushes out of lungs up trachea until pressure inside = pressure outside.

Question 3

Outline process of exhaling forcibly.

Answer 3

1. Internal intercostal muscles contract pulling ribs down hard + fast.
2. Abdominal muscles contract forcing diaphragm up to increase pressure in lungs rapidly.

Question 4

Define tidal volume.

Answer 4

Vol. of air inhaled/exhaled in each breath during steady breathing.

Question 5

Define vital capacity.

Answer 5

Max vol. of air that can be inhaled/exhaled in one breath.

Question 6

Define inspiratory reserve volume.

Answer 6

Max vol. of air you can breathe in over + above a normal inhalation.

Question 7

Define expiratory reserve volume.

Answer 7

Extra vol. of air you can force out of your lungs over + above the normal tidal vol. of air breathed out.

Question 8

Define forced expiratory reserve volume (FEV1).

Answer 8

Vol. of air that can be expired/exhaled in the first second of forced breathing.

Question 9

Define residual volume.

Answer 9

Vol. of air left in lungs after you have exhaled as hard as possible.

Question 10

Define total lung capacity.

Answer 10

Sum of vital capacity and residual volume.

Question 11

Define cardiac output.

Answer 11

Vol. of blood pumped out from left ventricle in 1 min (cm3min-1).

Question 12

Define stroke volume.

Answer 12

Vol of blood pumped from left ventricle in one contraction (cm3).

Question 13

Define heart rate.

Answer 13

No. of contractions per minute.

Question 14

Define breathing rate.

Answer 14

No. of breaths taken per minute.

Question 15

Define ventilation rate.

Answer 15

• Total vol. of air inhaled in one minute.

- Tidal vol x breathing rate.

Question 16

How does exercise affect breathing.

Answer 16

• Tidal vol increases –> panting.
• Breathing rate increases.
• Ventilation rate increases –> to meet demand of tissues.

Question 17

What happens to water flow over the gills when the mouth is open?

Answer 17

1. Mouth open + floor of buccal cavity lowered.
2. Vol. of buccal cavity increases, pressure drops + water moves into buccal cavity.
3. Opercular valve shuts + opercular cavity containing gills expands.
4. Lowers pressure in opercular cavity containing gills.
5. Floor of buccal cavity moves up –> increasing pressure there so water moves from buccal cavity over gills.

Question 18

What happens to water flow over gills when mouth is closed?

Answer 18

1. Mouth closed + floor of buccal cavity raised.
2. Operculum opens + opercular cavity moves inwards.
3. Increases pressure in opercular cavity.
4. Water –> forced over gills + out of operculum.
5. Floor of buccal cavity steadily raised –> maintaining continuous flow of water.

Question 19

Alternate methods of gas exchange in insects.

Answer 19

Mechanical Ventilation of Tracheal System:

• Air —> actively pumped into system by muscular pumping movements of thorax and/or abdomen.
• Movements —> change vol of body and changes pressure in trachea and tracheoles.
• Air drawn in/forced out of trachea and tracheoles as pressure changes.

Collapsible Enlarged Trachea or Air Sacs:

• Acts as reservoirs.
• Increase amount of air moving in through gas exchange system.
• Usually inflated + deflated by ventilating movements of thorax + abdomen.