The Respiratory System
Chemical & Neural Control of
Breathing
• Your breathing rate is regulated by neural and
chemical mechanisms.
Neural = Nerves/electrical
Chemical = amount of oxygen, carbon dioxide &
acid levels in blood
• Our breathing or respiration is controlled by
the respiratory centre.
• This is an area located in the brain stem, found
between the spinal cord and the upper brain.
• The respiratory centre controls both the depth
and rate of breathing and does this through
neural and chemical control.
• Your breathing is controlled by automatic
messages sent from the brain to nerves that
stimulate respiratory muscles to contract.
• The main respiratory muscle is the diaphragm.
This works with your intercostal muscles
• How fast the nerves fire is influenced by the
concentration of oxygen, carbon dioxide and
the acidity of the blood.
Chemical Control
• There are chemoreceptors in the brain and the
heart that detect the amount of oxygen, carbon
dioxide and acid present in the body.
• As a result, they increase or decrease the
respiratory rate to compensate for any changes
in balance of any of these chemicals.
• Too much carbon dioxide or acidity and too little
oxygen cause the respiratory rate to increase and
vice versa.
Neural Control
Based on what the chemoreceptors detect in the
blood the respiratory centre in the brain will
send messages to the respiratory muscles to
contract a certain number of times per minute
The normal respiratory rate in adults is between 12
and 18 breaths per minute.
Other Regulators
• Respiratory rate is also regulated by lung stretch
receptors.
• The stretch receptors sense the over-inflation of the
lungs, which leads to decreases in the respiratory
rate.
• Blood pressure receptors in the aorta and carotid
arteries also influence breathing rate. Low blood
pressure causes an increase in breathing rate and
vice versa.