1. PHED 1 Applied Physiology Control of Breathing
AS PE
PHED 1
Applied Physiology
Control of Breathing

2. Co2 Co2 is produced as a waste product of muscular contraction
The more intense the exercise the more Co2 is produced
So – High Co2 levels in the body indicate to the brain that we are exercising
Co2 is poisonous in high concentrations and we must get rid!

3. How do we transport Co2? Co2 diffuses in to the blood
7% dissolves into the blood plasma
23% combines with the haemoglobin
70% is transported as hydrogen carbonate ions

4. The control of breathing and the role of Co2
Controlled by the respiratory centre (rate and depth) in the medulla oblongata of the brain.
The RC uses both nerves (neural) and chemicals to control the rate and depth of breathing

5. Breathing at Rest
The RC is split into an inspiratory and expiratory centre.
The inspiratory centre send a nerve impulse to the respiratory muscles and we breath in
After 2 seconds the inspiratory centre ceases and the respiratory muscle relax causing us to expire

6. During exercise – chemical control
Acidity levels in the blood is the main cause of a change of rate and depth in breathing – they are:
Increase in Co2 causing blood acidity
Increase in lactic acid causing blood acidity
These changes are detected by chemoreceptor's which are located in the aorta.
They send a message to the respiratory centre to increase ventilation until the blood acidity is normal

7. During exercise – neural control
The brain will also change your breathing rate when one or more of the following occur:
Stimulation of proprioceptors in the joints and muscles
Anticipation of exercise causing increased brain activity and release of adrenaline
Increase in body temp
When the alveoli have inflated a nerve feedback to the respiratory centre causes the breathing muscles to stop.

8. Past paper exam question

9. Mark Scheme