Respiratory System Flashcards
respiration
cumulation of steps involved in receiving O2 and expelling CO2
ventillation
making O2 flow into lungs->change P
gas exchange
O2/CO2 into/out of blood
gas in blood
O2 through circulatory system to tissue
gas exchange
diffusion at source
cellular respiration
mitochondria use O2 and nutrients to create ATP and CO2 and H2O
pleural cavity
surrounds lungs, results in negative pressure
tidal volume
volume of each breath
-avg=1/2L per breath
vital capacity
largest possible inspiration
inspirational reserve
what you breathe in
FRC
functional residual capacity
- Expiratory reserve+residual volume
- changes with each breath
V(dot)
TVXRR
L/min of air into/out of lungs
AV(dot)
alveolar ventilation
-how much air reaches alveoli per minute
(TV-ADS)XRR
-most efficient to increase tidal volume rather than rate to increase ventillation
anatomical deadspace
space normally ventilated but not participating in gas exchange
-airways average about 150 ml
pleural sac
forms a double membrane surrounding the lung, similar to a fluid-filled balloon surrounding an air filled balloon
-pleural fulid has a very small volume
intrapleural space
has pressure less than that of atmospheric
flow
deltaP/R
-need alveolar pressure to be less than atmospheric pressure for flow to occur
intrapleural pressure
allows lungs to stay in place
-pressure drops when inspiring
changing intrapleural pressure
changes through diaphragm, which changes lung pressure, flow of )2 into alveoli
-if negative pressure in intrapleural space leaves, lung collapses
steps of inspiratoin
- muscles of inspiration contract
- diaphragm, external intercostal, sternocleidomastoids, scalenes - intrathoracic volume increases
- intrathoracic pressure decreases
- lungs expand and alveolar volume increases
- the expansion of the lungs requires working against the force of surgace tension and the elasticity of the lung wall - alveolar pressure decreases to below atmospheric pressure
- when alveolar pressure is less than atmospheric pressure, air flows in
- air continues to flow until the alveolar pressure equals atmospheric pressure
steps of expiration
- muscles of inspiration relax
- during forceful breathing expiratory muscles may be used: internal intercostal, abdominal - intrathoracic volume decreases
- intrathoracic pressure increases
- surface tension and elastic recoil decreases lung volume: alveolar volume decreases
- alveolar pressure increases to above atmospheric pressure
- when alveolar pressure is greater than atmospheric pressure, air flows out
- air continues to flow until the pressure equals the atmospheric pressure
compliance
deltaV/deltaP
low compliance
will cause inspiration to be difficult because large pressures are required to change volume
- pulmonary fibrosis is a low compliance disease where the lung becomes stiffer and less elastic
- respiratory distress syndrome is a low compliance disease where there is too much surface tension due to insufficient pulmonary surfactant
high compliance
will cause expiration to be difficult because the elastic and/or surface tension forces are not sufficient for passive expiration
-one of the problems associated with emphysema is high compliance because the alveolar walls break down, creating larger alveoli. LaPlace tells us that the effects of surface tension will be reduced in alveoli of large radius
restrictive pulmonary diseases
low compliance problems
obstructive pumonary diseases
high airway resistance problems
COPD
chronic obstructive pulmonary diseases
-most common are chronic bronchitis and emphysema
partial pressures
O2 and CO2 concentrations in the blood
- using these units, diffusion can be predicted across the interface between gaseous air and dissolved gasses in the blood
- however, partial pressures of different dissolved gasses cannot be compared to each other, nor can we determine the actual molar concentration of a dissolved gas by knowing only its partial pressure
- in the gaseous form, the partial pressure of a gas is its percentage of the total gas concentration times the total gas pressure
- at sea level, where P=760mmhg:
- -air is 21% O2 and 78% N2, so P)2 is 160 mmhg and PN2 is 590 mmHg. PCO2 at sea level is about 0.3 mmHg
concentrations of O2 in air compared to dissolved in partial pressure vs. concentration at equilibrium
PO2 air=100mmHg [O2]=5.2mmol/L PO2 dissolved=100mmhg [O2}=.15mmol/L -low O2 solubility levels
air vs dissolved concentration vs. PP of CO2 at equilibrium
PCO2 air=100mmHg
[CO2]=5.20
PCO2 dissolved=100mmhg
[CO2]=8.7mmol/L
PCO2=/=PO2
partial pressures of different gasses cannot be compared
gas concentrations in the alveoli
tidal volume is mixed with FRC
- PO2=100mmHg
- PCO2=40mmHg
gas concentrations in the tissues
- mitochondria are using O2 and producing CO2 so..
- PO2=40mmHg
- PCO2=46 mmHg
- concentrations vary depending on activity of tissue
blood leaving the lung/ arterial blood should have concentrations…
blood leaves the tisues and perfuses the pulmonary capillaries, the gasses equilibrate across the alveolar walls
PO2=100mmHg
PCO2=40mmHg
as blood passes through the systemic capillaries, the gasses equilibrate across the capillary walls, so venous blood should have approxiately…
PO2=40mmHg
PCO2=46mmHg
ventilation-perfusion matiching
various factors (gravity, lung mechanics) can influence the ventilation of a particular alveolus to be mismatched with the perfusion of that alveolus
physiological dead space
overventilated and underperfused
how do bronchiole and pulmonary arteriole smooth muscles respond to PCO2 and PO2 differently to adjust air and blood flow to each alveolus
- high PO2 and low PCO2-bronchoconstriction and pulmonary vasodilation
- high PCO2 and LOW PO2-bronchodilation and pulmonary vasoconstriction
how does gravity effect the blood in the lungs
brings more to base of the alveoli, more perfused (hyperperfused)
how do pulmonary arterioles and systemic arterioles differ
pulmonary arterials do the opposite of systemic
-increase O2, pulmonary vasodilate
increase CO2, pulmonary vasoconstrict
Gases in the blood
s
what carries O2 in the blood
hemoglobin (hb)
- blood without hemoglobin caries only about 1/60 as much O2
- each Hb molecule has 4 globins, each with a heme group. each Heme contains an iron atom that can bind to an O2 molecule, so each Hb can bind $ O2
cooperative binding of O2
binding graph gives a sigmoid curve
saturation of Hb at PO2 100mmHg
98% saturated.
-arterial blood
saturation of Hb at PO2 of 40 mmHg
65% saturated
-venous blood
arterial venous difference in saturation
represents O2 that was delivered to the tissue
-delivery of O2 can be increased in several ways if the tissue needs more O2
ways to increase O2 delivery to tissue
- if tissue PO2 decreases, venous O2 saturation will decrease, increasing delivery
- several factors that change in active tissue cause a shift of the binding curve to the right (i.e. decreased affinity and increased delivery)
- decreased pH
- increased PCO2
- increased temperature
- 2,3-diphosphoglycerate (DPG)-an intracelllar message triggered by hypoxia in RBC - notice these factors will only affect unloading of the Hb because:
- these conditions will not be found in the lung
- the shape of the binding curve is such that the effect of PO2 on loading is small
changes in Hb affinity
- increase affinity in lungs so O2 binds
- decrease affinity in tissues so O2 drops off
Carbon dioxide in the blood
-dissolved CO2 is converted to carbonic acid and bicarbonate by the enzyme carbonic anhydrase
CO2 breakdown reaction
CO2+H2OH2CO3H+ + HCO3-
-> in systemic calpillaries
CO2 from peripheral tissues is carried in venous blood in three different ways
- about 7% is carried as dissolved gas
- 23% binds to hemoglobin and is carried as HbCO2 (1 molecule per Hb)
- 70% is converted to HCO3- by carbonic anhydrase inside RBC, and is moved into the plasma where it is carried in venous blood
- HCO3- is moved out of the cell and into the plasma in exchange for Cl-. the resultant movements of Cl-, into the RBCs in the venous blood and into the plasma in arteriole blood are known as the chloride shift
- the H+ produced by the carbonic anhydrase reaciton is buffered by Hb
interaction of O2 and CO2 systems
-notice that some of the CO2 diffusing into the RBC from the tissue and the H+ produced by the carbonic anhydrase bind to the Hb. This binding is what shifts the Hb O2 binding curve to the lower affinity form
cl- concentrations in venous vs arterial blood
- high cl- in venous blood, low [cl-] in plasma
- arterial blood has high [cl-] in plasma
Control of ventilation
s
use of negative feedback system
maintain our arterial blood gasses at a constant at all times with a negative feedback control system for ventillation
peripheral chemoreceptors
measure arterial PCO2, PO2, and pH
- located in aortic and carotid sinuses, and called aortic and carotid bodies
- increased PCO2, decreased pH or decreased P)2 lead to increase action potential frequency in the chemoreceptor axons
- O2 sensors have K+ channel that closes when PO2 decreases
central chemoreceptors
measure pH of the cerebrospinal fluid
-located in the medulla oblongata
how ventilation changes because of pH or PCO2 compared to PO2
- any small change in PCO2 or pH will cause a change in ventilation
- only a large drop in PO2 (below 60mmHg) will increase ventilation