Control of Breathing
1. Breathing
control centers
in the brain
2. Keep
breathing in
tune with body
needs,
3. sensing and
responding
to the CO2
level in the
blood
Brain
Cerebrospinal
fluid
Pons
Medulla
Breathing
control
centers
stimulated by:
Nerve signals
trigger
contraction
of muscles
CO2 increase /
pH decrease
in blood
CO2 and O2
sensors in
aorta
Diaphragm
Rib muscles
Nerve signals
indicating CO2
and O2 levels
Neural Regulation of ventilation rate
 Activity of respiratory
muscles is transmitted to the
brain by the nerves
 Neural centers that control
rate and depth are located in
the medulla
 Normal respiratory rate is
12–15 respirations per
minute
 increased respiratory rate
often due to extra oxygen
needs
Factors Influencing Respiratory Rate and Depth

Chemical factors
 Carbon dioxide levels
 Level of carbon dioxide
in the blood is the main
regulatory chemical for
respiration
 Oxygen levels is Less
effective than changes in
blood CO2 level
 Changes in Co2 and O2
concentration in the blood
are detected by
chemoreceptors in the
aorta and carotid artery
 Information is sent to the
medulla oblongata
Homeostasis of blood CO2 level helps
regulate breathing rate – negative feedback
Factors Influencing Respiratory Rate and Depth

Physical factors
 Increased
body
temperature
 Exercise
 Talking
 Coughing

Conscious
control

Emotional factors
Chronic Bronchitis
Emphysema
airways and air sacs have been
damaged.
need to forcefully blow the air out
in order to empty the lungs --puts pressure on the airways and
causes them to collapse.
walls of the air sacs are
destroyed-- less surface area for
gas exchange..
Emphysema is characterized by
shortness of breath (SOB).
Destruction of tissue
leaves little surface area,
few capillaries, and large
air spaces
Much normal tissue
creates large surface area
with many capillaries,
which are filled with
RBCs (red cells)
Emphysema
 Alveoli enlarge as
adjacent chambers
break through
 Loss of elastic recoil of
lung tissue
 Over-inflation of the
lungs leads to a
permanently expanded
barrel chest
 Cyanosis appears late
in the disease
Cyanosis--A bluish discolouration of the skin
and mucous membranes; a sign that oxygen in
the blood is dangerously diminished --as in
carbon monoxide poisoning
Asthma -- reference only
 Chronic inflamed hypersensitive bronchiole passages
 Response to irritants with dyspnea*, coughing, and
wheezing
Dyspnea--Difficult or laboured respiration
Volume of air
moved in / out of
the Lungs
1. Between which points is air moving into the lungs?
2. Between which points is air moving out of the lungs?
3. At which point is the lungs most inflated / lung volume
largest?
1. Between which points is air moving into the lungs? A1-A3
2. Between which points is air moving out of the lungs? A3-A5
3. At which point is the lungs most inflated / lung volume
largest? A3 / C2