Chapter 16: Respiratory Physiology
sickle cell anemia
-8/11% of african americans -occurs when a person inherits the affected gene from each parents and produces hemoglobin S (differs from hemoglobin A in that one amino acid is substituted for another in beta chains) -under conditions of low Po2, when the hemoglobin is deoxygenated, hemoglobin S polymerizes into long fibers giving the sickle cell shape and reducing flexibility to pass through narrow vessels, reducing blood flow through organs -is treated with HYDROXYUREA: stimulates the production of hemoglobin gamma chains instead of beta chains
what happens in hyperventilation
-CO2 level falls and pH increases
lungs secrete and absorb fluid; what is being absorbed and secreted?
-absorption through osmosis is driven by active transport of Na+ -secretion by active transport of Cl- outside of the alveolar, epithelial cells
importance of oxygen electrode
-blood gas measurement which provides a good measurement of lung function -if partial pressure of oxygen in blood is more than 5mmHg BELOW that of the lungs, gas exchange is impaired
metabolic alkalosis
-caused by either too much bicarbonate or inadequate nonvolatile acids (perhaps as a result of excessive vomiting) -hypoventilate
respiratory alkalosis
-caused by hyperventilation -measured by plasma CO2
respiratory acidosis
-caused by hypoventilation -results in rise in plasma concentration of CO2 and thus carbonic acid
when does the diaphragm contract and relax
-contraction: inspiration -relaxation: exhalation
volatile acid
-example: H2CO3 -can be converted to a gas
Thalassemia
-found predominantly among Medittaranean -alpha thalassemia: decreased synthesis of alpha chains of hemoglobin -beta thalassemia: decreased synthesis of beta chains of hemoglobin -higher resistance to malaria since they cannot live in RBCs that contain abnormal hemoglobin
describe oxygen unloading in systemic arteries
-have a Po2 of 100mmHg -this makes enough oxygen bind to get 97% oxyhemoglobin -20mL O2/100mL of blood
describe oxygen unloading in systemic veins
-have a Po2 of 40mmHg -makes enough oxygen bind to get 75% oxyhemoglobin -15.5mL O2/100mL of blood
what is contained in the thoracic cavity
-heart -trachea -esophagus -thymus -lungs fill rest of cavity
erythropoietin
-hormone made in kidneys -stimulates hemoglobin/RBC production when oxygen levels are low
how does boyle's law correspond to lung volume
-increase in lung volume during inhalation means a decrease in intrapulmonary pressure to subatmospheric pressure -a decrease in lung volume during exhalation means an increase in intrapulmonary pressure above atmospheric levels
describe arteriole response to oxygen in terms of ions and channels
-low oxygen DEPOLARIZES smooth muscle cells of the arteriole wall by inhibiting outward flow of K+ -this opens voltage-gated Ca2+ channels, which stimulate contraction
why must the vascular resistance be low
-low pressure/low resistance pathway -reduces possibility of pulmonary edema
what 2 organs maintain acid-base balance of the blood
-lungs: regulate CO2 concentration of the blood -kidneys: regulate the bicarbonate concentration
purpose of spirometry
-measures lung volumes and capacities -can diagnose restrictive and obstructive lung disorders
rhythmicity center
-medulla oblongata -control of automatic breathing
pneumataxic area
-pons -inhibits inspiration
apneustic area
-pons -promotes inspiration
metabolic acidosis
-result from excessive production of nonvolatile acids -diabetes
unmyelinated C fibers
-sensory neurons in the lungs that can be stimulated by capsaicin which is found in pepper spray -it causes rapid, shallow breathing
Hering-Breuer reflex
-stimulated by pulmonary stretch receptors -it inhibits respiratory control centers during inspiration -makes sure you don't inhale too deeply
describe mechanism seen in pulmonary arterioles in reference to partial pressure of oxygen
-the pulmonary arterioles constrict when the alveoli Po2 is LOW -the pulmonary arterioles dilate as the alveolar Po2 is RAISED **blood flow to the alveoli is increased when they are full of oxygen and decreased when they are not full of oxygen
describe mechanism seen in systemic arterioles in reference to partial pressure of oxygen
-the systemic arterioles constrict when Po2 in tissues is HIGH; this ensures that only tissue that need oxygen are send to the blood -the systemic arterioles dilate when Po2 in tissues is low
what happens as a result of the trapping of hydrogen ions within the red blood cells
-there is also an outward diffusion of bicarbonate -this causes the inside of the red blood to gain a net positive charge and it attracts Cl-, which move into the RBCs as bicarbonate moves out
what are the functions of the conducting zone
-transports air to the lungs -warms and filters the air (mucus traps small particles and cilia move it away from lungs) -voice production in the larynx as air passes over the vocal folds
when is there an increase in the production of 2,3-DPG
-when the total hemoglobin concentration is low (anemia) -when the partial pressure is low (high altitude)
what do chemoreceptors in the medulla do
-when there is an increase in carbon dioxide in fluids of the brain and a drop in pH, it is sensed by chemoreceptors in the medulla and ventilation is increased -responsible for about 70/80% of increased ventilation -slower response than aortic and carotid bodies that mostly respond to H+ levels
the diaphragm divides the body cavity into what 2 parts
1. abdominopelvic cavity 2. thoracic cavity
what is the conducting zone process
1. air travels down the nasal cavity 2. pharynx 3. larynx 4. trachea 5. Right and left primary bronchi 6. secondary bronchi 7. tertiary bronchi 8. terminal bronchioles 9. respiratory zone (enters respiratory bronchioles) 10. terminal alveolar sacs
carbon dioxide is carried in the blood in what 3 forms?
1. as dissolved CO2 in plasma 2. as carbaminohemoglobin 3. as bicarbonate ion (accounts for most CO2)
how to use oxygen electrode
1. calibration of oxygen electrode 2. then it can be inserted into a fluid and partial pressure of oxygen can be determined
what are the 3 physical properties of the lungs
1. compliance 2. elasticity 3. surface tension
What are the two zones of the respiratory system?
1. conducting zone: gets air to the respiratory zone 2. respiratory zone: site of gas exchange between air and blood
discuss the 4 types of neurons in the rhythmicity center identified for different stages of breathing
1. dorsal respiratory group: made up of inspiratory neurons that stimulate neurons of the phrenic nerve 2. ventral respiratory group: made up of inspiratory neurons that stimulate spinal respiratory neurons and expiratory neurons that INHIBIT the phrenic nerve
what are the 3 layers of muscles between the bony portions of the rib cage
1. external intercostal muscles: inspiration 2. internal intercostal muscles: expiration 3. parasternal intercostals: between costal cartilage
what are the 2 receptors that stimulate coughing
1. irritant receptors: in wall of larynx; respond to smoke 2. rapidly adapting receptors: in lungs; respond to excess fluid
what 2 factors change the affinity of hemoglobin for oxygen and what does it ensure
1. pH 2. temperature -it ensures that muscles get more oxygen for exercise
what are the 3 different areas that comprise the brain respiratory system
1. pneumotaxic area: pons 2. apneustic area: pons 3. rhythmicity center: medulla oblongata
what are the 2 types of alveolar cells and their functions?
1. type I: 95-97% of total SA of the lung where gas exchange occurs 2. type II: the cells that secrete pulmonary surfactant and reabsorb Na+ and H2O, thereby preventing fluid buildup in the alveoli
3 functions of respiration
1. ventilation (breathing) 2. gas exchange (between blood and lungs and blood and tissues) 3. oxygen utilization (by the tissues to make ATP)
the motor neurons that stimulate the respiratory muscles are controlled by what 2 tracts
1. voluntary breathing tract: from cerebral cortex 2. involuntary breathing tract: from respiratory control centers of the medulla oblongata and pons
what is the pressure difference between left atrium and pulmonary artery
10mmHg which is the driving pressure in the pulmonary circuit
at a certain point in the glycolitic pathway, a side reaction occurs in the RBCs that results in the product
2,3-DPG
what percent of oxygen is unloaded in tissue
22%
each hemoglobin can carry how many oxygen molecules
4
the blood plasma within arteries normal has a pH between
7.35 and 7.45
what is the atmospheric pressure at sea level
760mmHg
because oxyhemoglobin has a weaker affinity for H+ than does deoxyhemoglobin, what is released
H+ ions are released within the red blood cells which attracts HCO3- from plasma and forms carbonic acid
carbon dioxide is transferred in the blood as primarily
HCO3- = a form of bicarbonate
polycythemia
above normal hemoglobin levels; may occur at high altitudes
what is the respiratory zone process
air enters respiratory bronchioles via terminal branchioles
alveoli
air sacs in the lungs where gas exchange occur
partial pressure of oxygen changes with
altitude/location
an increased concentration of 2,3-DPG causes
an increase in oxygen unloading
boyle's law
as pressure goes up, volume goes down
chemoreceptors
automatic control of breathing is influenced by feedback from chemoreceptors, which monitor pH of fluids in the brain and pH, PCO2, and Po2 of the blood
why does air enter the lungs
because atmospheric pressure is greater than the intrapulmonary pressure
the reaction of carbon dioxide forming with water occurs much more slowly in plasma. Why does it occur so much more quickly in RBCs?
because of the catalytic action of the enzyme CARBONIC ANHYDRASE
why does O2 diffuse from the air to blood
because the concentration of O2 is higher in the lungs than in the blood
why can't RBCs respire aerobically
because they lack both nuclei and mitochondria
anemia
below normal hemoglobin levels
pulmonary ventilation
breathing; accomplished by increasing and decreasing volumes of the thorax and lungs
barometer
can measure atmospheric pressure
when ventilation is inadequate
carbon dioxide levels go up and pH is lowered because the combination of CO2 + H20 = carbonic acid
under conditions of lower PCO2, as occurs in the pulmonary capillaries, carbonic anhydrase catalyzes the conversion of
carbonic acid to carbon dioxide and water
pressure differences between the 2 ends of the conducting zone occur due to
changing lung volumes
surfactant consists of
consists of hydrophobic proteins and phospholipids
visceral pleura
covers the lungs
the hydrogen ions released by the dissociation of H2CO3 are largely buffered by their combination with
deoxyhemoglobin within the red blood cells
transpulmonary pressure
difference between intrapulmonary and intrapleural pressure
CO2 moves from the blood to the air within the lungs by?
diffusing down its concentration gradient
what determines direction of unloading or loading reactions
directions of the reaction depends on partial pressure of oxygen of the environment and affinity for oxygen -high partial pressure for oxygen favors loading
lung compliance
expand easily when inflated; defined as change in lung volume per change in transpulmonary pressure
adult hemoglobin (A) can bind to 2,3-DPG, however ______ hemoglobin cannot-- what does this cause
fetal hemoglobin (F) -since fetal hemoglobin has a higher affinity for oxygen than the mother, it causes the oxygen to be transferred to the fetus
most of the oxygen in blood is bound to
hemoglobin
carboxyhemoglobin
hemoglobin is bound to carbon monoxide
gas exchange between air and blood occurs entirely where
in the lung tissue
intrapleural pressure is always lowest in
inhalation AND exhalation
describe the pressure during inhalation
intrapulmonary pressure < atmospheric pressure
describe the pressure during exhalation
intrapulmonary pressure > atmospheric pressure
oxyhemoglobin/reduced hemoglobin
iron is in reduced form (Fe2+) and can bind with oxygen -deoxyhemoglobin + oxygen
how could lung compliance be reduced
it could be reduced by factors that produce a resistance to dissension; infiltration of connective tissue protein seen in pulmonary fibrosis (as volume of lung goes up, so does the transpulmonary pressure)
what is the effect of blood Po2 on ventilation
it indirectly affects ventilation by affecting chemoreceptors-- sensitivity to PCO2 -low blood O2 makes carotid bodies more sensitive to CO2
what determines the oxygen carrying capacity of blood
it is determined by is hemoglobin concentration
the enzyme that produces 2,3-DPG is inhibited by
it is inhibited by oxyhemoglobin
there is a thin film of fluid normally present in alveolus and it has a surface tension due to
it is produced because the H2O molecules at the surface are attracted more to each other than to air which acts to collapse the alveolus, increases pressure of air within alveolus
what does surfactant do
it reduces the surface tension between water molecules by reducing the hydrogen bonding
purpose of transpulmonary pressure
keeps lungs against the thoracic wall
when is surfactant first produced
late fetal life
parietal pleura
lines the thoracic wall
peripheral chemoreceptors
located in carotid and aortic arteries
central chemoreceptors
located in the medulla
how do lungs maintain elasticity
lungs have tons of elastin fiber and because lungs are stuck to the thoracic wall, they are always under ELASTIC TENSION which increases during inhalation
elasticity
lungs return to initial size after being stretched
percent oxyhemoglobin saturation
measured to assess how well the lungs have oxygenated the blood -the normal value for arterial blood is around 97% -% oxyhemoglobin to total hemoglobin
what do motor neurons of the phrenic nerve do
motor neurons of the phrenic nerve, stimulate the diaphragm and have cell bodies in the cervical region of the spinal cord -phrenic nerve -stimulate diaphragm -cell bodies in cervical region
what motor neurons stimulate respiratory muscles of the rib cage and abdomen
motor neurons that stimulate the respiratory muscles of the rib cage and abdomen have cell bodies in the thoracolumbar region of the spinal cord -stimulate respiratory muscles and abdomen -cell bodies in thoracolumbar region spinal cord
how to measure partial pressure
multiple % of that gas by the total pressure
since the partial pressure of oxygen is very low in mitochondria, what does myoglobin do
myoglobin may act a "go-between" in the transfer of oxygen from blood to the mitochondria within muscle cells -it may also have an oxygen storage function which is important for the heart
what is the difference in inspiration in normal,quiet breathing and in forced ventilation
normal: contraction of diaphragm and external intercostals increasing thoracic and lung volume; decreasing intrapulmonary pressure to about -3mmHg forced: inspiration, aided by contraction of accessory muscles such as the scales and sternocleidomastoid which decreases intrapulmonary pressure to -20mmHg
what is the difference in exhalation in normal, quiet breathing and in forced ventilation
normal: relaxation of the diaphragm and external intercostals, plus elastic recoil of lungs which decreases lung volume and increases intrapulmonary pressure to +3mmHg forced: expiration, aided by contraction of abdominal muscles and internal intercostals muscles which increases intrapulmonary pressure to +30mmHg
what is obstructive lung disorder- give example
obstructive lung disorder: lung tissue is normal. vital capacity is normal, but forced expiration is reduced. example: asthma
oxygen electrode only measures O2 dissolved in
only in blood plasma NOT in RBCs
reverse chloride shift
operates in the pulmonary capillaries to convert carbonic acid to H2O and CO2 gas, which is eliminated in the expired breath
methemoglobin
oxidized iron (Fe3+) can't bind to oxygen
why don't O2 levels change as rapidly
oxygen levels don't change as rapidly because of the oxygen reserves in hemoglobin, so oxygen levels are not a good index for control of breathing
what is internal respiration
oxygen utilization and gas exchange in tissues
intrapleural space
potential space between parietal and the visceral pleura
respiratory distress syndrome (RDS)
premature babies born with lungs that lack sufficient surfactant and their alveoli are collapsed
subatmospheric/negative pressure
pressure below that of atmospheric pressure
intrapulmonary pressure
pressure in the lungs
atmospheric pressure
pressure of air outside the body
intrapleural pressure
pressure within intrapleural space
oxygen electrode
produces an electric current in proportion to the concentration of dissolved oxygen-- blood gas measurement
the rate of blood flow to the lungs is _____ to that through the systemic circuit
rate of blood flow to the lungs is EQUAL to that through the systemic circuit -5.5L/min cardiac output
myoglobin
red pigment found exclusively in striated muscles cells (skeletal and cardiac muscles) -1 heme rather than the 4 heme as seen in hemoglobin -higher affinity for oxygen than hemoglobin
what regulates these motor neurons
regulated by descending axons from the brain
oxygen unloading in tissues at: rest: light exercise: heavy exercise:
rest: 22% light: 39% heavy: 80%
what is a restrictive lung disorder- give example
restrictive lung disorder: lung tissue is damaged. vital capacity is reduced, but forced expiration is normal. example: pulmonary fibrosis and emphysema
what exerts surface tension on the lungs
surface tension is exerted by the fluid secreted in the alveoli; it raises the pressure of the alveolar air as it acts to collapse the alveolus
spirometry
technique in which subject breathes into and out of a device that records volume and frequency of air movement on a SPIROGRAM
why is surfactant important
the ability of surfactant to lower the surface tension in the alveolus improves as the alveoli gets smaller during expiration; this is likely due to having a greater concentration
bohr effect
the affinity of hemoglobin for oxygen is low at a lower pH and the affinity of hemoglobin for oxygen is high at a higher pH
Henry's law
the amount of gas that can dissolve in a liquid depends on: 1. solubility of gas in liquid; physically constant 2. temperature of the fluid (more gas dissolved in cold fluid, but this doesn't change in the blood) 3. partial pressure of the gas; the determining factor
aortic body
the aortic body sends feedback to the medulla along the VAGUS NERVE
what is being referred to in terms of affinity
the bond between oxygen and hemoglobin
carotid body
the carotid body sends feedback to the medulla along GLOSSOPHARYNGEAL NERVE
mediastinum
the central region of the cavities
the buildup of carbonic acid concentration within the RBCs favors
the dissociation of these molecules into hydrogen ions and HCO3- H2CO3 --> H+ and HCO3-
chloride shift
the exchange of anions as blood travels through the tissue capillaries
surface tension
the forces that act to resist distension
the metabolic component of acid base balance is represented by
the free bicarbonate concentration
why is equilibrium of oxygen and carbon dioxide so easily obtained in the alveoli
the large SA of the alveoli and short diffusion distance between alveolar air and the capillary blood help to bring this equilibrium
what are the terminal branchioles
the narroest of alveoli and don't contribute to gas exchange
what serves as the oxygen reserve
the oxygen remaining in the veins
as air enters in the alveoli, the percent of ____ decreases and _____ increases, changing the partial pressure of each gas.
the percent of oxygen decreases and the percent of carbon dioxide increases
the respiratory component of acid base balance is represented by
the plasma carbon dioxide concentration
law of laplace
the pressure thus created in the alveolus is directly proportional to the surface tension and indirectly proportional to the radius of the alveolus; smaller alveolus means a greater pressure
ventilation/perfusion ratios
the response of pulmonary arterioles to low oxygen levels makes sure that ventilation (O2 into the lungs) matches perfusion (blood flow)
carbonic acid is produced mostly in the red blood cells as blood passes through
the systemic capillaries
describe the mechanism of inspiration
the volume of the thoracic cavity/lungs increases vertically when the diaphragm contracts (flattened) and horizontally when parasternal and external intercostals raise the ribs
there is more unloading at a ______ pH
there is more unloading at a lower pH
important of alveoli
they provide a large SA to increase diffusion rate
how do RBCs obtain energy
through anaerobic metabolism of glucose
dalton's law
total pressure of a gas is equal to the sum of pressure of each gas in it
what is external respiration
ventilation and gas exchange in the lungs
describe the mechanism of exhalation
volume of the thoracic cavity and lungs decreases vertically when the diaphragm relaxes (dome) and horizontally when internal intercostals lower the ribs in forced expiration
acidosis
when blood pH falls below 7.35
alkalosis
when blood pH rises above 7.45
what is the loading reaction
when hemoglobin bind to oxygen in the lungs
what is the unloading reaction
when oxyhemoglobin drops off oxygen in tissues
