Download Respiratory System Physiology

Respiratory System Physiology
“Breathing”
Pulmonary Ventilation
Inspiration- in
Expiration- out
• Breathing occurs because
of a pressure gradient
between the lungs and
exterior environment
• Respiratory muscles control
the size of the thoracic
cavity setting up the
gradient
Inspiration
• When the
diaphragm
contracts it
increases size of
thoracic cavity
• Intercostal muscles
aid in expanding
size of rib cage
Expiration
• Is aided by elastic recoil, tendency of thorax and
lungs to return to shape
• When muscles relax it causes a decrease in size of
thorax
• Compliance is the ability of lungs to relax or stretch
Breathing Patterns
• Eupnea- normal quiet breathing
• Hyperpnea- increased breathing
rate and depth to meet need for
O2
• Hyperventilation- increased
breathing rate and depth with out
need for O2
• Hypoventilation- slowed breathing
• Dyspnea- difficult labored
breathing
• Apnea- cessation of breathing
Exchange of Gases
• O2 and CO2 move
across pressure
gradients from the
atmosphere into
the lungs
• Alveolar and
capillary surface
area is extremely
large with thin
walls
• Capillaries in lungs
have a diameter
one cell thick
Transport of O2
• Hemoglobin greatly increases the
amount of O2 that can be dissolved in
the blood
Transport of CO2
• A small amount of CO2
binds amino acid groups
onto hemoglobin
• Most of the CO2 in blood
associates with H2O to
form carbonic acid H2CO3
(bicarbonate)
• H2CO3 once catalyzed by
carbohydrate anhydrase
(enzyme) dissociates into
H+ and HCO3• Increased CO2 in the
blood causes a decrease
in blood pH/increase in
acidity
Systemic Gas Exchange
• As oxygenated blood enters tissues it has high Po2 and low
Pco2 relative to the tissue
• O2 is pulled off the hemoglobin and CO2 binds temporary to
hemoglobin to form carbaminohemoglobin
Respiratory Control Centers
• Ventilation is the rate and
depth of breathing
• The apneustic center stimulates
the inspiratory center thus
increasing respiration
• Ventilation is controlled by
the medullary rhythmicity
centers of the brain
• The pneumotaxic center
inhibits the apneustic center in
the brain
Factors that influence Breathing
• Chemoreceptors in the
medulla measure levels
of CO2
• Low levels of CO2 will
decrease rate and
depth of breathing
• High levels of CO2
increase rate and
depth of breathing
• pH plays a small role in
controlling breath
• Blood levels of O2 seem
to have little effect on
breathing rate
Breathing Reflexes
• Hering-Breuer reflex
maintains normal
breath depth
• Once tidal volume
is reached,
inhalation stretch
receptors trigger
inhibitory impulses
to the inspiratory
centers of the brain
Breathing Reflexes
Breathing can be controlled
voluntarily to a certain
extent
• You cannot hold your
breath till you die, CO2 is too
strong a stimulant
• Sudden stimulation - reflex
apnea
• Sudden cold stimuli - reflex
apnea
• Stimulation of pharynx or
larynx causes choking reflex
• Breathing can be affected
by emotions
Breathing Reflexes
• Cough reflex- caused
by stimulation
• Sneeze reflex- air is
forced out nose and
mouth(100 mph)
• Hiccup- caused by a
spasm of diaphragm
• Yawn- slow and deep
breath with similar
function to a stretch