Download Respiratory system

9/13/16
Respiratory system
Dr. Dinithi Peiris
Dept. of Zoology
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Respiration
n
n
n
n
Ventilation: Movement of air into and out
of lungs
External respiration: Gas exchange between
air in lungs and blood
Transport of oxygen and carbon dioxide
in the blood
Internal respiration: Gas exchange between
the blood and tissues
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Function of the respiratory
system
Regulation of blood pH: Altered by changing blood
carbon dioxide levels
Voice production: Movement of air past vocal
folds makes sound and speech
Olfaction: Smell occurs when airborne molecules
drawn into nasal cavity
Protection: Against microorganisms by
preventing entry and removing them
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Divisions of respiratory
system
n
Upper tract
n
n
Nose, pharynx
and associated
structures
Lower tract
n
Larynx, trachea,
bronchi, lungs
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Nose & pharynx
n
Nose
n
n
n
External nose
Nasal cavity
n
Functions
n
n
n
n
n
Passageway for air
Cleans the air
Humidifies, warms air
Smell
Along with paranasal
sinuses are resonating
chambers for speech
Pharynx
n Common opening
for digestive and
respiratory systems
n Three regions
n Nasopharynx
n Oropharynx
n Laryngopharynx
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Larynx
n
Functions
n Maintain an open
passageway for air
movement
n Epiglottis and vestibular
folds prevent swallowed
material from moving into
larynx
n Vocal folds are primary
source of sound
production
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Tracheobronchial Tree
n
Conducting zone
n
n
n
n
Trachea to terminal bronchioles which is
ciliated for removal of debris
Passageway for air movement
Cartilage holds tube system open and
smooth muscle controls tube diameter
Respiratory zone
n
n
Respiratory bronchioles to alveoli
Site for gas exchange
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Airways Condition Air Before It
Reaches The
n
Warm air to body temperature
n
Humidify air
n
Filter foreign material
n Ciliated epithelial line the trachea and
bronchi
n Secrete mucus and dilute saline
solution
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Inspiration
n
n
Air flows due to pressure gradients created by a
pump.
During inspiration the muscles of the thoracic cage
contract, moving the rib cage
n
n
Thoracic cavity expands (increased volume)
pressure decreases
Air movement ceases when pressure inside is
equal to pressure outside
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Inspiratory Muscles
n
n
External intercostals and scalene
muscles contract and pull ribs
upward and out (expanding lungs
Diaphragm, intercostals and
scalenes are the primary muscles
for breathing during rest.
n
During increased ventilation,
other muscles of the chest and
abdomen may be used
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Expiration
n
n
At the end of inspiration, impulses from somatic
motor neurons to the inspiratory muscles cease and
the muscles relax.
Elastic recoil of the lungs returns the diaphragm and
rib cage to their original relaxed position.
n
n
Passive expiration
Volume of thoracic cavity and lungs decreases and
air pressure increases.
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Exercise
n
n
During exercise pressure differences
become greater occurs when ventilation is
greater than 30-40 breaths per minute
Active expiration—
n
Uses intercostals muscles and abdominal
muscles.
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Ventilatory Muscles
n
n
Internal intercostals muscles line the inside
of the rib cage.
n Contracted—pull ribs inward, reducing volume
of the thoracic cavity.
Internal and external intercostals acts as
antagonistic muscle groups to alter the
position and volume of the rib cage during
ventilation.
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Ventilatory Muscles
n
Diaphragm has no antagonistic forces (stays
relaxed in active expiration), so abdominal
muscles contract and pull the lower rib cage
inward to decrease abdominal volume.
n
Displaced intestines and liver push the
diaphragm up into the thoracic cavity,
decreasing volume even more.
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Breathing
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Breathing
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E expenditure for breathing
n
n
n
About 3-5% of the body s energy expenditure is
used for quiet breathing.
During exercise energy required for breathing
increases substantially.
Factors that influence amount of work needed
for breathing:
Compliance
Resistance
Surfactant
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Compliance
The ease with which the lungs and thorax
expand during pressure changes
n
Greater compliance = greater ease of expansion
n
n
§
A high-compliance lung stretches easily and
requires less force from the inspiratory muscles to
stretch it
Diseases which decrease compliance also
increase the energy required for
breathing;
asthma,
bronchitis,
pulmonary edema
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Resistance
n
n
n
n
n
Length of the system (constant)
Viscosity of the substance flowing through the system
(constant)
Radius of the tubes (main variable)
~ 90% of airway resistance due to trachea and
bronchi—rigid structures with smallest total crosssectional area (supported by cartilage and bone—so
they don t move as easily).
Mucus accumulation can increase resistance
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Resistance
n
Bronchiole constriction
(decrease air flow)
1. Parasympathetic N.S.
(muscarinic R)
2. Histamine
(paracrine)
Bronchiole dilation
(increase air flow)
1. Sympathetic N.S.
(β2 R)
2. CO2 (paracrine)
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Surfactant
n
Mixture of lipo-proteins
n
n
n
n
E.g. DPPC (dipalmitoyl phosphoticylcholine)
Alveoli have a natural tendency to collapse
Surfactant helps prevent collapse by decreasing
the surface tension
If surfactant production decreases (pneumonia)
high pressures may be required to maintain lung
expansion
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Pulmonary function tests
n
n
n
Quantifies air moving during quiet breathing
and during maximum effort
n Determine health of lungs
Spirometer—instrument measures volume of
air moving with each breath
Obstructive lung disease is when air flow
during expiration is diminished due to
narrowing of the bronchioles
n chronic bronchitis
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Lung Volumes
n
n
IRV
n
IC
VC
TV
4 Volumes
4 Capacities
TLC
Sum of 2 or
more lung
volumes
ERV
FRC
RV
RV
Tidal Volume (TV)
n
IRV
IC
VC
TV
TLC
Volume of air
inspired and
expired during
normal quiet
breathing
ERV
FRC
RV
RV
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Inspiratory Reserve Volume (IRV)
n
IRV
IC
VC
TV
TLC
ERV
FRC
RV
RV
The maximum
amount of air
that can be
inhaled after a
normal tidal
volume
inspiration
Expiratory Reserve Volume (ERV)
n
IRV
IC
VC
TV
TLC
Maximum
amount of air
that can be
exhaled from
the resting
expiratory level
ERV
FRC
RV
RV
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Residual Volume (RV)
n
IRV
IC
VC
TV
Volume of air
remaining in the
lungs at the end
of maximum
expiration
TLC
ERV
FRC
RV
RV
Vital Capacity (VC)
n
IRV
IC
VC
TV
TLC
ERV
n
FRC
RV
n
RV
n
Volume of air that
can be exhaled
from the lungs
after a maximum
inspiration
FVC: when VC
exhaled forcefully
SVC: when VC is
exhaled slowly
VC = IRV + TV +
ERV
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Inspiratory Capacity (IC)
n
IRV
IC
VC
TV
TLC
ERV
FRC
RV
n
Maximum
amount of air
that can be
inhaled from the
end of a tidal
volume
IC = IRV + TV
RV
Functional Residual Capacity
(FRC)
n
IRV
IC
VC
TV
TLC
n
ERV
FRC
RV
RV
n
Volume of air
remaining in the
lungs at the end of
a TV expiration
The elastic force of
the chest wall is
exactly balanced by
the elastic force of
the lungs
FRC = ERV + RV
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Total Lung Capacity (TLC)
n
IRV
IC
VC
TV
TLC
ERV
FRC
RV
n
Volume of air in the
lungs after a
maximum
inspiration
TLC = IRV + TV +
ERV + RV
RV
Pulmonary Function Tests
n
Evaluates 1 or more major aspects of
the respiratory system
n
Lung volumes
n
Airway function
n
Gas exchange
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Indications
n
n
n
n
n
Detect disease
Evaluate extent and monitor course of
disease
Evaluate treatment
Measure effects of exposures
Assess risk for surgical procedures
Total pulmonary ventilation
n
Total pulmonary ventilation =
Ventilation rate X tidal volume
12
X
500 = 6 L / min
n
n
Anatomical dead space (air remains in
conducting air ways)
= 150 ml
Alveolar ventilation =
ventilation rate X [tidal volume – dead space]
12
X
[500 – 150]
= 4200 ml / min
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Total pulmonary ventilation
n
Physiological dead space =
anatomical dead space – vol. of nonfunctional
alveoli
Normally, PDS = ADS
n
Respiratory disease- alveolar walls begin to
degenerate and increase the PDS by 10X ADS
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Minute volume / ventilation
n
n
Minute volume- TV X RR (amount of
gas inhaled and exhaled in one minute)
Minute alveolar ventilation- amount of
inspired gas available for gas exchange
during one minute; (TV – DS) X RR
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Blood flow
n
During rest some capillaries in the lungs
are closed off
n
n
blood diverted to other capillaries
During exercise the closed capillaries will
open maximum oxygenation
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Atmospheric gases
concentration
n
n
n
n
n
n
Nitrogen- 78.62% or 597 torr
Oxygen- 20.84% or 159 torr
Carbon dioxide- 0.5% or 0.3 torr
Water vapor- 6.2% or 3.7 torr
Combined partial pressure of gases equal to
100% or 760 torr @ sea level
Measured in mm HG; 1 torr = 1mm Hg
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Atmospheric gases composition
n
Nitrogen- 74.9% or 569 torr
n
Oxygen- 13.7% or 104 torr
n
Carbon dioxide- 5.2% or 40 torr
n
Water vapor- 6.2% or 47 torr
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Why difference of gases in
the body?
n
n
n
Air entering body is humidified
Exchange of O2 and CO2 between
alveoli and blood
Incomplete emptying of alveoli with
expiration
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Pulmonary circulation
n
n
n
Inspired gas enters the lungs; the respiratory
system brings O2 to the blood and removes
CO2
Blood low in O2 converges in the heart;
passes through the R heart and into the lungs
through the pulmonary artery
Alveoli fill and empty 15,000X day
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Pulmonary circulation
n
n
n
Alveoli filled with O2 have pressure gradient
required for gas exchange
O2 moves into capillaries and CO2 into alveoli
to be exhaled
Blood rich in flows into pulmonary veins L
atrium, L ventricle, aorta and tissues
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Partial pressures
n
n
n
Differences in partial pressures of O2 and
CO2 on the two sides of the respiratory
membrane (alveoli) result in diffusion of O2
into the blood and CO2 into the alveoli
Capillary blood PO2 rises and PCO2 falls
Stops when alveolar and capillary partial
pressure equalize
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Partial pressures
n
n
n
Exchange is so rapid that the blood leaving
the lungs has nearly the same PO2 and PCO2
as alveolar air
PO2 of blood returning to heart from veins is
40 mm Hg & alveoli is 100 mm Hg
PCO2 of blood returning to heart from veins
is 46 mm Hg & alveoli is 40 mm Hg
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Partial pressures
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What changes gas exchange?
n
Loss of surface area of alveoli or an increase in
distance between alveoli decrease gas exchange
in the alveoli
n
Hypoxia—too little oxygen in the cells.
n
Hypercapnia—elevated concentrations of CO2
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Oxygen transport
1.
O2 is slightly soluble in fluid—transported by 2 ways:
Hemoglobin (Hb)—O2-binding protein in red blood cells
n
>98% of oxygen transported
n
Each hemoglobin molecule binds up to four oxygen
molecules
n
HbO2 (oxyhemoglobin—hemoglobin bound to O2)
n
PO2 of cells determines how much oxygen will be
release by Hb
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Oxygen transport
Dissolved in the plasma
2.
n
n
n
Only 3 mL of oxygen/liter of blood (5 L
blood/minute)
15 mL of dissolved oxygen through the
systemic tissues each minute
not enough to meet the needs of the tissues
(<10% of metabolic needs)
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Oxygen dissociation curve
Oxygen-hb
dissociation curve
shows that hb is
almost completely
saturated when P02
is 80 mm Hg or
above.
At lower
partial
pressures,
the hb releases
oxygen
49
Factors affecting dissociation
curve
A shift of the curve to the left because of
n Increase in pH
n Decrease in carbon dioxide
n Decrease in temperature - increase in the
ability of hemoglobin to hold oxygen
n 2.3-bisphosphoglycerate increases the ability
of hemoglobin to release oxygen
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Factors affecting dissociation
curve
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Carbon dioxide
Hydrogen Ion:
•Increased H+ (decreased pH) increases H+ binding
to Hb and reduces O2 affinity
(HbO2+H+↔HbH++O2).
• Carbon Dioxide (Bohr s effect):
•Increased PCO2 increases CO2 binding to Hb and
reduces O2 affinity (increased O2 delivery to tissue).
•Increased PCO2 increases H+ and reduces O2 affinity
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Bohr effect
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Temperature effect
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2,3-diphosphoglycerate
No 2,3-DPG
High amount of
2,3-DPG
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Fetal curve
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Shifting the curve
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Transport of carbon dioxide
Mainly 3 ways
1. Bicarbonate ions (70%)
2. In combination with blood proteins (23%)
3. In solution with plasma (7%)
Haldane effect
In tissue capillaries, carbon dioxide combines
with water inside RBCs to form carbonic acid
which dissociates to form bicarbonate ions and
hydrogen ions
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Haldane effect
n
In lung capillaries, bicarbonate ions and
hydrogen ions move into RBCs and chloride
ions move out. Bicarbonate ions combine
with hydrogen ions to form carbonic acid.
The carbonic acid is converted to carbon
dioxide and water. The carbon dioxide
diffuses out of the RBCs.
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Carbon dioxide & Cl- movement
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THE CHALLENGES OF
HYPOXIA
Barometric pressure decreases with alt. and
partial pressure of O2 is a constant 20.9%.
CO2 and water vapor dilute alveolar O2 .
water vapor a function of T b,
47 mm Hg at normal T b
eg. On Mt. Everest BP=253 mm Hg
water vapor 47, CO2 8, O2 40!
Saturation of Hb:
10,000 ft PO2 =110 %Hb sat = 90
20,000 ft PO2 = 73 %Hb sat = 73
30,000 ft PO2 = 26 %Hb sat = 24
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CHEYNE STOKES BREATHING
Alternating periods of slow and rapid breathing.
Diffusion gradient for CO2 does not decrease with altitude,
but the gradient for O2 diffusion decreases substantially.
Small stimulus to breathing due to hypoxia is sufficient to
reduce arterial O2 which results in decreased breathing.
Decreased breathing increases & allows CO2 to build up
again along with hypoxia.
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THE EFFECTS OF HYPOXIA
Acute effects: beginning at about 12,000 ft.
drowsiness, mental and muscle fatigue, headache,
nausea. Progress to twitching and seizures at 18,000
ft. and coma at 23,000 ft.
Acclimation effects:
Days to weeks -- increased pulmonary ventilation,
increased hematocrit (erythropoietin mediated),
increased diffusion capacity of lungs, increased
capillarity.
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THE EFFECTS OF HYPOXIA
Acute mountain sickness (few hrs and couple of days
after ascent): Cerebral edema and pulmonary edema
(due to pulmonary vascular reactivity).
Chronic mountain sickness (days to weeks after ascent):
Exceptionally high hematocrit, high pulmonary arterial
pressure, enlargement of right heart, fall in peripheral
pressure, congestive heart failure.
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Special
adaptations
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Diving Animals
•
•
•
Emperor bird dive up to 500m, cetaceans
up to 1000m & sperm whale more than
1km. They exhale before diving.
Contains massive organs filled with waxes;
spermaceti oil – buoyancy
Echolocations enable to
distance, size & direction
locate
prey
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Diving Animals
•
•
•
Humans : with short distance, large amount of
blood in to thoracic cavity causing lung
compressed.
Diving animals : lungs & chests collapse as
pressure increases. Diaphragm set oblique &
hence lungs collapse to a fraction of the original
size.
Air is forced through windpipes & nasal cavity
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Diving Animals
•
•
Humans: hydrostatic
neurological syndromes
pressure
causes
Divers: inhibitory feedback on their CNS
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Diving Animals
•
•
•
Humans: N partial pressure . N is absorbed
in to arteries & tissues which reduce mental
& motor capabilities.
Decompression causes gases to expand; in
arteries N bubbling occur. The Bends
Divers: N tension is lower & concentration is
limited by total lung collapse
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Diving Animals
•
•
Humans: brain anoxia due to diffusion of O
in to arteries. Lung expansion causes further
reduction in O tension. Further decrease in
O tension will reduce pressure less than
venous pressure
Divers: reduce lung-blood gas exchange.
Much lower partial pressures of O in their
brains
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DIVING BRADYCARDIA IN MARINE MAMMALS
Heart rate falls during dive. Shut
down of peripheral arteries results in
blood flowing primarily to brain, eyes,
and heart. Other tissues become
hypometabolic
At end of dive, heart rate returns,
tissues are re-perfused, but oxygen
payback is much less than what would
have been total metabolic expenditure
if seal had not dived.
Diving bradycardia occurs in humans
when face is submerged and it occurs
during birth.
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Diving Animals
Other adaptations of divers:
• Muscles act aerobically during diving. Lactic
acid produced is diffuse out of muscles &
burn out by the heart.
•
During short dives, they get enough O to
burn off excess lactic acid.
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High Altitude
n
Unlike high altitude animals, humans do not have
left shifted- dissociation curve.
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Regulation of respiration
74
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Respiratory areas in brainstem
n
Medullary respiratory center
n
n
n
Dorsal groups stimulate the diaphragm
Ventral groups stimulate the intercostal and
abdominal muscles
Carbon-dioxdie, oxygen and pH influence
breathing
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Medulla oblongata
Dorsal resp. group
ventral resp. group
Somatic motor neurons
Somatic motor neurons
(Inspiration)
(Expiration)
Scalene
external
Mu.
Int. Cost. Mu.
Diaphragm
Mu.
Internal
Int. Cost. Mu.
Abdominal
Mu.
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senses
Chemo receptors
Mechano receptors
Decrease oxygen
Decrease pH
Irritant receptors
Increase PCO2
Hering-breuer reflex
Exercise (TV > 1 L)
Stretch receptors
Signal brain to IB
respiration
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senses
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Chemo receptors
Peripheral chemo receptors
Carotid & aortic
bodies
pH
Central chemo receptors [CNS]
PCO2
Cross BB
barrier
Resp. centers in
the brain
PO2
Converted to H+ & HCO3H+
Triggers chemo receptors
PCO2
ventilation
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