In this chapter of I/GCSE Biology, we will discuss about Breathing and Gas exchange (Part 2).
The Mechanism of Breathing
To inhale:-
- Create an area of lower pressure by enlarging the volume of the thorax.
- Do this by CONTRACTING intercostal muscles (which moves the ribs up and out) and the diaphragm, which flattens from its relaxed domed shape.
- Air will then rush in until the inside pressure is equal to the outside pressure.
To exhale:-
- Create an area of higher pressure inside the thorax by reducing the volume of the thorax.
- Do this by RELAXING intercostal muscles (so ribs move down and in) and the diaphragm which resumes its domed shape.
- The air inside will move out until the pressure inside is equal to the pressure outside.
Refer to I/GCSE Biology, after inhaling comes Gas Exchange – adaptations of alveolus and capillary network.
At the end of each bronchiole is an ALVEOLUS. These are adapted for their function:
- Very thin walled for fast diffusion into and out of the alveolus
- A very large surface area (the inside of each is folded to increase its surface area) which speeds up diffusion of gases.
- Rich blood capillary network for rapid gas exchange
- The inside surface is moist so that the gases dissolve . They can then diffuse across the membrane.
Investigation to show how the rate of exercise affects breathing rate
Key Variables to Control
In I/GCSE Biology, same subjects for each exercise regime - then take an average
- same age
- same sex
- same level of fitness
- same food intake
Or you could use a range of subjects - BUT THEN they must all do the same exercise at every level
Same type of exercise
Same time for exercise period
Example - number of star jumps per minute (6 different rates).
Every exercise period lasting for exactly 5 minutes.
Variable to be varied
When it comes toI/GCSE Biology,the intensity of the exercise, so you might vary the pace of the exercise or its intensity.
(Rather than the TIME of the exercise period as this would simply introduce an additional variable)
Other precautions
Health and Safety considerations
ENSURE that you establish the breathing rate at rest - and ensure that the subjects return to their resting rate before beginning the next level of exercise.
We're done with this topic! Well Done!
