chapter 7 p3

Question 1

Components of the lung volume:

Answer 1

Tidal volume
Vital capacity
Inspiratory reserve volume
Expiratory reserve volume
Residual volume
Total lung capacity

Question 2

Tidal volume

Answer 2

the volume of air that moves into and out of the lungs with each resting breath. It is around 500 cm in most adults at rest, which uses about 15% of the vital capacity of the lungs.

Question 3

Vital capacity

Answer 3

the volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath.

Question 4

Inspiratory reserve volume

Answer 4

the maximum volume of air you can breathe in over and above a normal inhalation.

Question 5

Expiratory reserve volume

Answer 5

the extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out.

Question 6

Residual volume

Answer 6

the volume of air that is left in your lungs when you have exhaled as hard as possible. This cannot be measured directly.

Question 7

Total lung capacity

Answer 7

the sum of the vital capacity and the residual volume.
Recordings from a spirometer show the different volumes of air moved in and out of the lungs.

Question 8

diagram of Components of the lung volume:

Answer 8

Question 9

The pattern and volume of breathing changes as

Answer 9

the demands of the body change.

Question 10

breathing rate

Answer 10

the number of breaths taken per minute.

Question 11

ventilation rate

Answer 11

the total volume of air inhaled in one minute.

Question 12

ventilation rate formula

Answer 12

tidal volume x breathing rate (per minute)

Question 13

what happens When the oxygen demands of the body increase

Answer 13

, for example during exercise, the tidal volume of air moved in and out of the lungs with each breath can increase from 15% to as much as 50% of the vital capacity.
The breathing rate can also increase. In this way the ventilation of the lungs and so the oxygen uptake during gaseous exchange can be increased to meet the demands of the tissues.

Question 14

worked breathing calculation

Answer 14

Question 15

Gaseous exchange systems in insects:

Answer 15

Many insects are very active during parts of their life cycles and are mainly land-dwelling animals with relatively high oxygen requirements.
However, they have a tough exoskeleton through which little or no gaseous exchange can take place.
They do not usually have blood pigments that can carry oxygen.
They need a different way of exchanging gases.
The gaseous exchange system of insects has evolved to deliver the oxygen directly to the cells and to remove the carbon dioxide in the same way

Question 16

diagram of Gaseous exchange systems in insects:

Answer 16

Question 17

How does gas exchange take place in insects?:

Answer 17

Along the thorax and abdomen of most insects are small openings known as spiracles.
Air enters and leaves the system through the spiracles, but water is also lost.
Just like mammals, insects need to maximise the efficiency of gaseous exchange, but minimise the loss of water.
In many insects the spiracles can be opened or closed by sphincters.
The spiracle sphincters are kept closed as much as possible to minimise water loss.

Question 18

Effect of oxygen on spiracles:

Answer 18

When an insect is inactive and oxygen demands are very low, the spiracles will all be closed most of the time.
When the oxygen demand is raised or the carbon dioxide levels build up, more of the spiracles open.

Question 19

The tracheae:

Answer 19

Leading away from the spiracles are the tracheae.
These are the largest tubes of the insect respiratory system, up to 1 mm in diameter, and they carry air into the body.
They run both into and along the body of the insect.
The tubes are lined by spirals of chitin, which keep them open if they are bent or pressed.
Chitin is the material that makes up the cuticle.
It is relatively impermeable to gases and so little gaseous exchange takes place in the trachea.

Question 20

Tracheoles:

Answer 20

• The tracheae branch to form narrower tubes until they divide into the tracheoles, minute tubes of diameter 0.6-0.8 pm.
• Each tracheole is a single, greatly elongated cell with no chitin lining so they are freely permeable to gases.
• Because of their very small size they spread throughout the tissues of the insect, running between individual cells.
• This is where most of the gaseous exchange takes place between the air and the respiring cells.

Question 21

Role of diffusion:
part 1

Answer 21

In most insects, air moves along the tracheae and tracheoles by diffusion alone, reaching all the tissues.
The vast numbers of tiny tracheoles give a very large surface area for gaseous exchange.
Oxygen dissolves in moisture on the walls of the tracheoles and diffuses into the surrounding cells.
Towards the end of the tracheoles there is tracheal fluid, which limits the penetration of air for diffusion.

Question 22

Role of diffusion:
part 2

Answer 22

However, when oxygen demands build up - when the insect is flying, for example - a lactic acid build up in the tissues results in water moving out of the tracheoles by osmosis.
This exposes more surface area for gaseous exchange.
All of the oxygen needed by the cells of an insect is supplied to them by the tracheal system.
The extent of gas exchange in most insects is controlled by the opening and closing of the spiracles.

Question 23

How do certain energetic insects, like larger beetles, locusts, grasshoppers, bees, wasps, and flies, increase gaseous exchange to meet their higher oxygen needs?:

Answer 23

• mechanical ventilation of the tracheal system
• collapsible enlarged tracheae or air sacs, which act as air reservoirs

Question 24

• mechanical ventilation of the tracheal system

Answer 24

air is actively pumped into the system by muscular pumping movements of the thorax and/or the abdomen.
These movements change the volume of the body and this changes the pressure in the tracheae and tracheoles.
Air is drawn into the tracheae and tracheoles, or forced out, as the pressure changes

Question 25

• collapsible enlarged tracheae or air sacs, which act as air reservoirs

Answer 25

these are used to increase the amount of air moved through the gas exchange system.
They are usually inflated and deflated by the ventilating movements of the thorax and abdomen.

Question 26

Discontinuous gas exchange cycles in insects:

Answer 26

In DCG spiracles have the states - closed, open, and fluttering.

• When the spiracles are closed no gases move in or out of the insect.
  Oxygen moves into the cells by diffusion from the trachae and carbon dioxide diffuses into the body fluids of the insect where it is held in a process called buffering.
• When the spiracles flutter, they open and close rapidly.
  This moves fresh air into the trachea to renew the supply of oxygen, while minimising water loss.
• When carbon dioxide levels build up really high in the body fluids of the insect, the spiracles open widely and carbon dioxide diffuses out rapidly.
  There may also be pumping movements of the thorax and abdomen when the spiracles are open to maximise gaseous exchange.

Question 27

Evolving Theories and Ongoing Research on DCG

Answer 27

Originally scientists thought discontinuous gas exchange was an adaptation for water conservation in insects.
Now the evidence suggests this is not the case and there are a number of conflicting theories about the adaptive advantages of discontinuous gas exchange for insects, which include helping gaseous exchange in insects that spend at least part of their lives in enclosed spaces such as burrows, or reducing the entry of fungal spores, which can parasitise an insect.
This is still an area of very active research and argument.