Ventilation Flashcards
airflow is governed by
the same principles of flow, pressure, and resistance that govern blood flow
atmospheric pressure drives
respiration
intrapulmonary pressure is
the pressure within the alveoli, also reffered to as alveolar pressure
direction that air flows depends on
the gradient between atmospheric pressure and intrapulmonary pressure
Boyle’s Law
states that the pressure of a gas in a closed container is inversely proportional to the volume of its container, at a constant temperature
Charles’ Law
states that the volume of a gas in a closed container is directly proportional to its absolute temperature, at a constant pressure
ex. basketball in cold
Dalton’s Law
states that each gas in a mixture exerts a partial pressure (p) independent of the partial pressures of the other gases in the mixture
Henry’s Law
states that the amount of gas that dissolves in a liquid is directly proportional to its solubility in that liquid and its partial pressure
for air flow into lungs,
intrapulmonary pressure must be lower than atmospheric air pressure and this is accomplished by increasing the volume of the lungs
-Boyles law is important here.
when diaphragm and external intercostal muscles contract,
volume of the thoracic cavity increases
contraction of the diaphragm
increases the volume of the thoracic cavity from top to bottom
contraction of the external intercostal muscles
pulls the ribs upward and outward to increase volume of thoracic cavity from front to back
because the visceral and parietal pleurae adhere strongly to one another,
lung volume will expand as the volume of the thoracic cavity expands
increasing the volume of the lungs causes
a drop in intrapulmonary pressure
- so atmospheric air pressure is now greater than intrapulmonary pressure, so air rushes into lungs along pressure gradient
- Boyles law
normal inspiration is
an active process
normal inspiration can be increased by
contracting additional chest muscles, which further enlarges volume of thoracic cavity and decreases intrapulmonary pressure
inspiration
air flow into lungs
expiration
air flow out of lungs
for air flow out of lungs,
intrapulmonary pressure must be higher than atmospheric air pressure and this is accomplished by decreasing the volume of the lungs
when diaphragm and external intercostal muscles relax,
volume of the thoracic cavity decreases
-volume of the thoracic cavity returns to normal, which forces lungs to become smaller
decreasing the volume of the lungs cause
a rise in intrapulmonary pressure (boyles law)
-intrapulmonary pressure is now greater than atmospheric air pressure, so air rushes out of lungs along pressure gradient
normal expiration during quiet breathing is
a passive process that can be made active by contracting abdominal and internal muscles to compress the thoracic cavity
resistance affects
airflow
pulmonary compliance
the ease with which the lungs expand relative to a change in the pressure gradient between the atmosphere and the lungs
high compliance means that
the lungs will expand easily, low compliance means lungs will resist expansion
degenerative lung diseases
decrease compliance (tuberculosis)
____________ controls resistance
diameter of the bronchioles
bronchoconstriction can be triggered by
airborne irratants, cold air, parasympathetic innervation, or histamines
bronchodilation can be triggered by
sympathetic innervationor epinephrine
________ must be overcome for lungs to expand during each inspiration
alveolar surface tension
surfactant
a mixture of phopholipids and lipoproteins that lowers surface tension to reduce tendency of alveoli to collapse and adhere to each other during expiration
surfactant deficiency in premature babies leads to
respiratory distress syndrome, causes alveoli to collapse at end of each expiration
some air always remains in non-respiratory airways as
anatomic dead space volume
a normal, healthy adult averages ________ per minute
12 quiet breathing cycles
a spirometer measures
volume of air exchanged during a breathing cycle
spirometry is used to
measure pulmonary function
restricitve lung disorders
reduce pulmonary compliance; limits inflation of lungs, which causes reduction in vital capacity
obstructive lung disorders
interfere with airflow, which makes it harder to exhale
tital volume
the volume of air exchanged during one breathing cycle
-about 500 mL
inspiratory reserve volume
the volume of air that can be inhaled in excess of tidal volume with maximal effort
expiratory reserve volume
the volume of air that can be exhaled in excess of tidal volume with maximal effort
residual volume
the volume of air that remains in lungs after maximum exhalation and it keeps the alveoli open
vital capacity
the maximum volume of air that can be moved into and out of the lungs during one forced breathing cycle
inspiratory capacity
the maximum volume of air tha can be inhaled after a normal expiration
functional residual capacity
the resting lung volume
total lung capacity
the sume of all pulmonary volumes
the basic rhythm of breathing is controlled by
neurons in the medulla oblongata and pons
inspiratory and expiratory neurons
travel down the spinal cord to the phrenic nerve and intercostal nerves to innervate diaphragm and intercostal muscles
the medullary rhythmicity area has
ventral (VRG) and dorsal (DRG) respiratory groups
inspiratory neurons from the ventral respiratory group
send impulses to stimulate muscles needed for inspiration
after about 2 seconds the impulses from the inspiratory neurons
cease and inspiratory muscles relax, which allows passive expiration for about 3 seconds
expiratory neurons from the ventral respiratory group
fire and output stops
dorsal respiratory group
integrates input from stretch receptors and chemoreceptors
the pons contains a pontine respiratory group to
modify the rate and depth of breathing that is established by the ventral respiratory group
respiratory centers in the brainstem
receive input from a variety of sources
input from the limbic system and hypothalamus
allows pain/emotion to affect respiration
input from chemoreceptors
adjust breathing to maintain homeostasis
stretch receptors in the bronchial tree and visceral peura
monitor lung inflation
Hering-Breuer reflex is
a protective mechanism that inhibits inspiratory neurons to prevent overinflation of lungs
voluntary control over ventilation originates in
the frontal lobe of the cerebral cortex
Ondine’s curse
can be caused from brainstem damage from poliomyelitis or from an accident
automatic respiratory functions are disabled and individual must constantly remember to take each breath.
he/she cannot go to sleep without ventilator
