obj 5 pt 2 Flashcards by Kaitlyn Dominie

what are the 2 phases of pulmonary ventilation?

inspiration
expiration

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gases flow into lungs

inspiration

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gases exit lungs

expiration

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pressure exerted by air surrounding the body

atmospheric pressure

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pressure in alveoli
fluctuates with breathing
always eventually equalizes with atmospheric pressure

intrapulmonary pressure

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pressure in pleural cavity
fluctuates with breathing
always a negative pressure in order to keep lungs inflated

intrapleural pressure

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difference between intrapulmonary and intrapleural pressures
determines the size of the lungs
if equal, causes lung collapse

transpulmonary pressure

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consists of inspiration and expiration
mechanical process that depends on volume changes in thoracic cavity
volume changes lead to pressure changes
pressure changes lead to the flow of gases to equalize pressure
gases always move from an area of high pressure to an area of low pressure

pulmonary ventilation

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active process involving inspiratory muscles (contraction of diaphragm and external intercostals)
As thoracic cavity volume increases, lungs are stretched as
they are pulled out with thoracic cage
Intrapulmonary pressure drops
Because of difference between atmospheric and
intrapulmonary pressure, air rushes into lungs until
intrapulmonary and atmospheric pressures are equalized

inspiration

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what are the actions of the diaphragm?

when dome-shaped diaphragm contracts, moves inferiorly and flattens out; there is an increase in thoracic volume

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what are the actions of the intercostal muscles?

when external intercostals contract, rib cage is lifted up and out
results in increase in thoracic volume

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passive process
depends on lung elasticity more than muscle contraction
inspiratory muscles relax, thoracic cavity volume decreases, lungs recoil
volume decrease causes intrapulmonary pressure to increase so air flows out of lungs down its pressure gradient until intrapulmonary pressure is equal to atmospheric pressure

expiration

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may modify normal respiration rhythm
most result from reflex action, although some are voluntary

non-respiratory air movements

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what are the 3 factors that influence the ease of air passage and the amount of energy required for ventilation?

airway resistance
alveolar surface tension
lung compliance

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major non-elastic source of resistance to gas flow
decreases air passage
causes breathing movements to become more strenuous
greatest resistance to airflow occurs in midsize bronchi
F(gas flow) = P/R

airway resistance

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the attraction of liquid molecules to one another at gas-liquid interface

surface tension

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tends to draw liquid molecules closer together and reduce contact with dissimilar gas molecules
resists any force that tends to increase surface area of liquid
tends to cause alveoli to shrink to smallest size- that is, collapse
surfactant, a fat-protein complex, prevents alveolar collapse

alveolar surface tension

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measure of how much “stretch” the lung has

lung compliance

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why is lung compliance normally high?

distensibility of lung tissue
surfactant, which decreases alveolar surface tension

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how do we assess ventilation?

Several respiratory volumes can be used to assess
respiratory status
Respiratory volumes can be combined to calculate
respiratory capacities, which can give information on a
person’s respiratory status
Respiratory volumes and capacities are usually abnormal in
people with pulmonary disorders

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amount of air moved into and out of lung with each breath
averages ~500ml

tidal volume

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amount of air that can be inspired forcibly beyond the tidal volume (2100-3200ml)

inspiratory reserve volume

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amount of air that can be forcibly expelled from lungs after a normal tidal expiration (1000-12000ml)

expiratory reserve volume

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amount of air that always remains in lungs

residual volume

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sum of tidal volume + inspiratory reserve volume

inspiratory capacity

sum of residual volume + expiratory reserve volume

functional residual capacity

sum of tidal volume + inspiratory reserve volume + expiratory reserve volume

vital capacity

sum of all lung volumes (TV + IRV + ERV +RV)

total lung capacity

what are the pulmonary functions tests can measure rate of gas movement?

forced vital capacity forced expiratory volume

amount of gas forcibly expelled after taking deep breath

forced vital capacity

amount of gas expelled during specific time interval of FVC

forced expiratory volume

total amount of gas that flows into or out of respiratory tract in 1 min

minute ventilation

flow of gases into and out of alveoli during particular time

alveolar ventilation rate

occurs between lungs and blood as well as blood and tissues

gas exchange

diffusion of gases between blood and lungs

external respiration

diffusion of gases between blood and tissues

internal respiration

what are both external and internal respiration subject to?

* Basic properties of gases * Composition of alveolar gas

the total pressure of a mixture pf gases is the sum of the partial pressures of the individual components

Dalton's law of partial pressures

the pressure exerted by an individual gas in a mixture. is proportional to the percentage of that gas in the gas mixture

partial pressure

PO2 is high PCO2 is low bcuz inspiration occurred

alveoli

PO2 is low PCO2 is high blood just came from tissues

pulmonary capillaries

PO2 is low PCO2 is high bcuz tissues using oxygen

tissues

PO2 is high PCO2 is low because blood just came from lungs

tissue capillaries

* the relative concentration of gases (their partial pressures) does not change as the pressure and volume of the gas mixture changes * so air inhaled into the lungs will have the same relative concentration of gases as atmospheric air. * In the lungs, the relative concentration of gases determines the rate at which each gas will diffuse across the alveolar membranes

Dalton's law

* predicts how gasses will dissolve in the alveoli and bloodstream during gas exchange. * The amount of oxygen that dissolves into the bloodstream is directly relational to the partial pressure of oxygen in alveolar air

Henry's law

what happens for gas mixtures in contact with liquid?

* Each gas will dissolve in the liquid in proportion to its partial pressure * At equilibrium, partial pressures in two phases will be equal

what does the amount of each gas that dissolves depend on?

* Solubility: CO2 more soluble in water than O2 * Temperature: at temp of liquid rises, solubility decreases

what is the composition of alveolar gas?

* Alveoli contain more CO2 and water vaporand less O2 than atmospheric air because: * Gas exchanges in lungs (O2 diffuse out of lungs and CO2 diffuse into lung) * Humidification of air by conducting passages * Mixing of alveolar gas with each breath * Newly inspired air mixes with air that was left in passageways between breaths

what is exchange of external respiration influenced by?

* pressure gradients (Dalton’s Law) and gas solubilities (Henry’s Law) * Thickness and surface area of respiratory membrane * The thicker the membrane, the less diffusion; thinner the membrane, more diffusion. This affects the rate of gas exchange

a steep partial pressure gradient for O2 exists between blood and lungs

partial pressure gradients and gas solubilities

40 mm Hg

venous blood P02

104mm Hg

alveolar P02

what is the partial pressure gradient for CO2?

venous blood PCO2 = 45 mm Hg alveolar PCO2 = 40mm Hg

* Gas movement occurs by diffusion * Rate of diffusion depends on the concentration of the gas and the barrier; especially the thickness of the respiratory membranes * Respiratory membranes are very thin * 0.5 to 1 m thick * Large total surface area of the alveoli is 40 the surface area of the skin

thickness and surface area of the respiratory membrane

what are the 2 ways molecular O2 is carried in the blood?

* dissolved in plasma * bound to hemoglobin (Hb) in RBCs

hemoglobin-O2 combination

oxyhemoglobin

hemoglobin that has released O2

deoxyhemoglobin

all four heme groups carry O2

fully saturated

when only one to three hemes carry O2

partially saturated

what are the factors that influence hemoglobin saturation?

* PO2 * Other factors such as: * Temperature * Blood pH * PCO2 * Concentration of BPG

what is the influence of PO2 on hemoglobin saturation?

PO2 heavily influences binding and release of O2 with hemoglobin

what is the influence of PO2 on hemoglobin saturation in arterial blood?

* Hgb is 98% saturated * Further increases in PO2 (as in deep breathing) produce minimal increases in O2 binding

what is the influence of PO2 on hemoglobin saturation in venous blood?

* Hgb is still 75% saturated * Venous reserve: oxygen remaining in venous blood that can still be used

what are the 3 forms that CO2 is transported in blood?

* dissolved in plasma as PCO2 * bound to hemoglobin * Accumulating CO2 lowers blood pH * Depletion of CO2 in blood raises blood pH

what is carbon dioxide transport?

* Most carbon dioxide molecules entering the plasma quickly enter RBCs. The reactions that convert carbon dioxide to bicarbonate for transport mostly occur inside RBCs because they contain carbonic anhydrase, an enzyme that reversibly catalyzed the conversion of carbon dioxide and water to carbonic acid. * Hydrogen ions are released during the reaction bind to hemoglobin triggering the bohr effect. The carbon dioxide loading enhances oxygen release. * In systemic capillaries, after bicarbonate is created, it quickly diffuses from RBCs to plasma * This outpouring of bicarbonate from RBCs is balanced as chloride moves into RBCs from plasma (chloride shift) * In pulmonary capillaries, the process occurs in reverse * Bicarbonate moves into RBCs while Chloride moves out of RBCs back into plasma * Bicarbonate binds with H+ to form H2CO3 (carbonic acid) * Carbonic acid is split by carbonic anhydrase into CO2 and H20 * CO2 diffuses into alveoli

helps blood resist changes in pH

carbonic acid-bicarbonate buffer system

what are respiratory rhythms regulated by?

higher brain centers chemoreceptors other reflexes

involve neurons in reticular formation of medulla and pons

neural controls

clustered neurons in two areas of medulla

medullary respiratory centers

sets normal respiratory rate and rhythm

ventral respiratory group

assists VRG

dorsal respiratory group

* Neurons in this center influence and modify activity of Ventral Respiratory Group (VRG) * Act to smooth out transition between inspiration and expiration and vice versa * Transmit impulses to VRG that modify and fine- tune breathing rhythms during vocalization, sleep, exercise

pontine respiratory centers

determined by how actively the respiratory center stimulates respiratory muscles

depth

determined by how long center is active

rate

what are respiratory centers affected by?

* Chemical factors * Influence of higher brain centers * Pulmonary irritant reflexes * Inflation reflex

* Most important of all factors affecting depth and rate of inspiration * Changing levels of CO2, O2, and pH are most important

chemical factors

located throughout brain stem

central chemoreceptors

found in aortic arch and carotid arteries

peripheral chemoreceptors

* Most potent and most closely controlled * blood PCO2 levels rise (hypercapnia), its most powerful respiratory stimulant * Respiratory centers increase depth and rate of breathing, which act to lower blood PCO2, and pH rises to normal levels * If blood PCO2 levels decrease (hypocapnia), respiration becomes slow and shallow

influence of PCO2

* Peripheral chemoreceptors in aortic and carotid bodies sense arterial O2 levels * Declining PO2 normally has only slight effect on ventilation because of huge O2 reservoir bound to Hgb * Requires substantial drop in arterial PO2 (below 60 mmHg) to stimulate increased ventilation * When excited, chemoreceptors cause respiratory centers to increase ventilation

influence of PO2

* pH can modify respiratory rate and rhythm even if CO2 and O2 levels are normal * Mediated by peripheral chemoreceptors * Decreased pH may reflect CO2 retention, accumulation of lactic acid, or excess ketone bodies * Respiratory system controls attempt to raise pH by increasing respiratory rate and depth

influence of arterial pH

modify rate and depth of respiration

hypothalamic controls

bypass medullary controls

cortical controls

* Receptors in bronchioles respond to irritants such as dust, accumulated mucus, or noxious fumes * Receptors communicate with respiratory centers via vagal nerve * Promote reflexive constriction of air passages * Same irritant triggers a cough in trachea or bronchi or a sneeze in nasal cavity

pulmonary irritant reflexes

* Stretch receptors in pleurae and airways are stimulated by lung inflation * Send inhibitory signals to medullary respiratory centers to end inhalation and allow expiration * May act as protective response more than as a normal regulatory mechanism * a reflex triggered to prevent over-inflation of the lung

hering-breuer reflex