the respiratory system part c (22c)
Hypothalamus and limbic system modify rate and depth of respiration in response to
strong emotions or pain: Breath holding in anger, Gasping with pain or fear, Increased respiratory rate when excited
Declining Po 2 has only minor effect on ventilation because...?
there is huge O 2 reservoir bound to Hb; Hb remains almost fully saturated until Po 2 falls below 60 mm Hg
Unloading of one O 2 makes it easier to
unload the next
*Ability of bronchioles to regulate airflow + ability of arterioles to regulate blood flow =
ventilation/perfusion coupling
VRG
ventral respiratory group
Cerebral motor cortex can exert___________________ ________________ over breathing and bypass...?
voluntary; medullary controls-->voluntarily hold breath
because heat is a byproduct of metabolic activities, we would expect that active tissues are _________than less active tissues
warmer
Decreased blood pH (acidosis) and increased Pco 2 cause Hb O 2 bond to________________; this is referred to as..?
weaken; Bohr effect-->O2 unloading occurs where needed most
VRG is a medullary respiratory center; what is it?
Sets normal respiratory rate and rhythm->Eupnea (12 16 breaths/minute)-->Rhythm generating and integrative center
why do all areas of lungs not have the same amount of O 2 & CO 2 and same blood flow at same time
Some alveoli are well ventilated and some are not, Some regions of lung have sufficient blood moving, through capillaries and some do not, Due to gravity causing regional variations and occasional alveolar ducts plugged with mucus
Hering Breuer Reflex (inflation reflex)
Stretch receptors in pleurae and airways are stimulated by lung inflation
Smooth muscle of bronchioles leading to alveoli and Smooth muscle of arterioles carrying blood to pulmonary capillaries can do what to maximize gas exchange
contract or relax
hypoxia causes______________, which is what?
cyanosis bluish cast seen when Hb saturation falls below 75%
rapid, deep breathing means what in terms of blood pH?
decreased CO2 in blood and a rise in pH
decreased body temp does what to respiratory rate
decreases-->apnea if you jump into cold water
In pulmonary capillaries in lungs CO2
diffuses down its pressure gradient Out of RBC and into plasma, and From plasma and into alveoli
reduced surface area=
emphysema, tumors, inflammation, mucus
why does the respiratory membrane have a large total surface area (40 times that of skin)?
for gas exchange
In the lungs, where PO 2 is high (100 mm Hg), Hb is almost
fully saturated (98%)
***Rising CO2 and H + levels in the brain are the most
important and powerful respiratory stimulant***
what happens when cells metabolize glucose and use O2 and release CO2?
increase Pco2 in capillary blood and increases in H+ in capillary blood
slow, shallow breathing means what in terms of blood pH?
increased CO2 and drop in pH
what happens when ventilation is greater than perfusion?
increased O2 and decreased Co2 in alveoli
increased body temp does what to respiratory rate?
increases
because pontine respiratory centers Influence and modify activity of VRG, this provides for a smooth transition between..?
inspiration and expiration
In the tissues of other organs, Where P O 2 is low (40 mm Hg), Hb is
less saturated with O2 (75%)
Partial pressure gradient for CO 2 in lungs is _____steep than pressure gradient for O2 in lungs
less; Pulmonary artery Pco 2 = 45 mm Hg and Alveolar Pco 2 = 40 mm Hg
In metabolically active tissues (e. exercising muscle), the P O 2 is even____________.At a P O 2 of 20 mm Hg, Hb is only 40% saturated an additional 35% of O 2 has been unloaded for tissue use.
lower
because tissue cells use O2 for metabolism, tissue Po2 is___________than in systemic arterial blood-->
lower; oxygen diffuses from blood to tissues (40 mm Hg versus 100 mm Hg)
ventilation and perfusion must be_______/___________for efficient gas exchange, what is this called?
matched/coupled; ventilation-perfusion coupling
In pulmonary capillaries in lungs, HCO3
reenters RBCs (while Cl moves out) and Binds with H to form H 2 CO 3
*Control of breathing during rest is aimed primarily at
regulating the H concentration ( Pco 2 in the brain*
If arterial Po 2 falls below 60 mm Hg , it becomes major stimulus for
respiration via peripheral chemoreceptors
Several factors can influence activity of
respiratory centers; Most important are changing arterial levels of CO2, O2, and H+
in internal respiration, partial gradients are________________compared to external respiration
reversed
in Hering Breuer Reflex (inflation reflex), vagus nerve sends...?
sends inhibitory signals to medullary respiratory centers to end inhalation/allow expiration; Protective response to prevent over inflation of lungs
At high P O 2, large changes in P O 2 cause___________changes in Hb saturation
small
why does decreased alveolar O2 case arterioles to constrict?
so effort is not wasted on these alveoli
In pulmonary capillaries in lungs, carbonic anhydrase
splits H 2 CO 3 into CO 2 and water
partial pressure gradient for O2 in lungs is
steep (Pulmonary artery Po 2 = 40 mm Hg and Alveolar Po 2 = 104 mm Hg)
Substantial drop in arterial Po 2 (to 60 mm Hg) is required to
stimulate increased ventilation
pulmonary gas exchange (external respiration) is influenced by 3 factors:
Thickness and surface area of the respiratory membrane, Partial pressure gradients and gas solubilities, Ventilation perfusion coupling
In systemic capillaries at tissues HCO 3 diffuses from RBCs into plasma and Transported to lungs to..?
To counter balance rush of HCO 3 out of RBCs->chloride shift occurs (plasma to RBCs)
apnea
breathing cessation/stopping from abnormally low Pco 2; When Pco 2 is abnormally low, respiration is inhibited and becomes slow and shallow
Changes in Pco 2 in alveoli cause changes in diameter of
bronchioles
change in arterial levels of O2, CO2, and H+ are sensed by...?
central & peripheral chemoreceptors
hemoglobin that has released O2=reduced Hb=
deoxyhemoglobin (HHb)
DRG
diagnostic related group
because metabolism produces CO2, tissue Pco2 is_____________than in blood
higher; CO2 diffuses from tissues to blood (45 mm Hg versus 40 mm Hg)
blood flow is greatest around alveoli with
highest Po2
hypoxia
inadequate O 2 delivery to tissues
PCO2 is the most
potent and closely controlled
Increase in temperature, Pco 2 , H + , BPG does what in terms of Hb?
Lowers Hb's affinity for O 2; Enhances O 2 unloading from blood
Temperature, blood pH, Pco 2 , and BPG have what effect on hemoglobin?
Modify Hb's three dimensional structure and ultimately Change Hb's affinity for O 2
O 2 is carried in blood in two ways:
1.5% dissolved in plasma (not very soluble in H 2 O) and 98.5% bound to Fe of hemoglobin ( Hb ) in RBCs 4 O 2 per Hb
partially saturated hemoglobin
3 bound O2
CO2 is transported by blood in _______ways, these are:
3; -7 to 10% dissolved in plasma, 20% bound to globin of hemoglobin carbaminohemoglobin, and 70% transported as bicarbonate ions (HCO 3 --) in plasma
fully saturated hemoglobin
4 bound O2
why does decreased alveolar CO2 cause bronchioles constrict
Allows "postponement" of elimination
Perfusion Is Controlled by
Alveolar Po2
oxygen diffusion (O2 loading)
Alveolar chamber->alveolar type I cell membrane->basement membrane of alveolus->basement membrane of capillary->capillary endothelial cell membrane->plasma and red blood cell membrane
components of the respiratory membrane
Alveolar epithelium and its basement membrane, Capillary endothelium and its basement membrane, Two basement membranes are fused
Peripheral chemoreceptors sense arterial O 2 via....?
Aortic bodies in aortic arch and Carotid bodies* at bifurcation of common carotid artery ( main oxygen sensors
CO2 diffuses from blood to alveoli but not as quickly as O2, how does it diffuse in equal amounts with oxygen?
CO 2 is 20 times more soluble in plasma than O 2
Decreased pH may be caused by ____________ _____________or other metabolic factors including:
CO 2 retention, Accumulation of lactic acid (exercise), Excess ketone bodies (diabetes)
change in arterial levels of O2, CO2, and H+ are sensed by central & peripheral chemoreceptors, what do these include?
Central: throughout brainstem, including medulla Peripheral sensitive to arterial O 2 levels; Aortic bodies in aortic arch and Carotid bodies* at bifurcation of common carotid arteries
If H concentration in blood rises (low pH), excess H+ is removed by (Carbonic acid bicarbonate buffer system)
Combining with HCO 3 to form H 2 CO 3->raises blood pH
what happens when ventilation is less than perfusion?
Decreased O 2 and increased CO 2 in alveoli
why is it good that pontine respiratory centers Influence and modify activity of VRG, this provides for a smooth transition between inspiration and expiration?
Erratic breathing results if PRC damaged Prolonged inspiration = apneustic breathing
in expiration, what does VRG do?
Expiratory neurons inhibit inspiratory neurons and Result in relaxation of respiratory muscles
If H concentration in blood drops (high pH), it is lowered when (Carbonic acid bicarbonate buffer system)
H 2 CO 3 dissociates; Releases H +-> lowers blood pH
internal respiration
Gas exchange between systemic capillaries and body tissues
what happens when pH drops?
H stimulates central chemoreceptors of brain stem, Chemoreceptors synapse with respiratory centers, rate and depth of breathing increases, flushes CO 2 out of blood lowers blood Pco2, and blood pH rises
increased heat in active tissues decreases______affinity for____________, why?
Hb for O2; allows increased O2 unloading in active tissues
At low P O 2, large changes in P O 2 cause large changes in
Hb saturation
Hb remains saturated even at high altitude or with lung disease, why?
Hb's properties produce a safety margin that ensures that Hb is almost fully saturated even with a substantial PO 2 decrease.
why is ***PCO2 the most closely controlled?
If blood Pco 2 levels rise (hypercapnia ), CO 2 accumulates in brain, and eventually pH drops and acidosis becomes nearer
Hyperventilation
Increase in rate and depth of breathing that exceeds body's need to remove CO 2
why are ***Rising CO2 and H + levels in the brain are the most important and powerful respiratory stimulant***
Increased blood CO 2-> increased CO 2 in brain->forms carbonic acid ->dissociates->releases H +->brain pH drops->central chemoreceptors respond-> send impulses to respiratory centers in brainstem->increases rate and depth of breathing to blow off CO 2
decrease in temperature, Pco2, H+, and BPG does what in terms of Hb?
Increases Hb's affinity for O 2 and Decreases O 2 unloading from blood
DRG does what?
Integrates input from peripheral stretch and chemoreceptors and Sends information to VRG
Control of Respiration involves
Involves higher brain centers, chemoreceptors, and other reflexes->Neurons in reticular formation of Medulla oblongata and Pons
pulmonary gas exchange of________and____________across the....?
O2 and CO2 across the respiratory membrane
the respiratory membrane is a thin barrier that..?
O2 and CO2 diffuse across
"Other Factors" are highest in systemic capillaries where
O2 loading is wanted
why does The amount of oxygen carried by hemoglobin depend on the amount of oxygen (P O2 ) available
P O2 measurements indicate only the amount of O 2 dissolved in plasma and not the amount bound to hemoglobin->This ensures optimal oxygen pickup and delivery
• Rate of loading (binding) and unloading (releasing) of O 2 is regulated by
Po 2, Temperature, Blood pH, Pco 2, Blood concentration of BPG
how do pulmonary irritant reflexes influence respiration?
Receptors in bronchioles respond to irritants Communicate with respiratory centers via vagal nerve and Promote reflex constriction of air passages->Receptors in upper airways initiate cough in trachea or bronchi or sneeze in nasal cavity
carbon dioxide diffusion (CO2 unloading)
Red blood cell membrane and plasma->capillary endothelial cell membrane->basement membrane of capillary->basement membrane of alveolus->alveolar type I cell membrane->alveolar chamber
why does increased alveolar O2 cause arterioles dilate
To pick up O 2 and deliver it to tissues
hypoxia can happen due to a variety of causes, including:
Too few RBCs, Abnormal or too little Hb, Blocked circulation (ischemia), Metabolic poisons (cyanide), Pulmonary disease, Carbon monoxide poisoning (red color)
pontine respiratory centers influence and modify activity of?
VRG
how could emphysema cause reduced surface area of the respiratory membrane
Walls of adjacent alveoli break down and Alveolar chambers enlarge
like blood in the CV system, oxygen in te respiratory system also diffuses down..?
a pressure gradient->from alveoli into pulmonary capillaries
why does increased alveolar CO2 cause bronchioles to dilate?
allows CO2 to be eliminated more rapidly
O2 diffuses from___________to__________
alveoli to blood
perfusion
amount of blood flow to alveoli
ventilation
amount of gas reaching alveoli
how could tumors, inflammation, or mucus cause reduced surface area
blocks gas flow into alveoli and decreases number of functional alveoli
even though cerebral motor cortex can exert voluntary controls over breathing and bypass medullary controls, the brain stem reinstates breathing when...?
blood CO 2 critical; this is why Drowning victims usually have water in their lungs
Carbonic acid bicarbonate buffer system resists changes in
blood pH
Changes in respiratory rate and depth affect
blood pH
CO2 diffuses from___________to_____________
blood to alveoli
arterial pH can modify respiratory rate and rhythm even if CO 2 and O 2 levels are normal, how is this mediated?
by peripheral chemoreceptors
CO 2 combines with water to form____________ ___________(H 2 CO 3 ), which quickly dissociates
carbonic acid-->transport and exchange of CO2
when hyperventilation occurs, this causes decreased CO2 levels-->hypocapnia, which can result in..?
cerebral vasoconstriction and ischemia, dizziness, fainting
pontine respiratory centers transmit impulses to_________________and______________-____________________breathing rhythms during...?
modify and fine-tine; vocalization, sleep, exercise
arterial pH can..?
modify respiratory rate and rhythm even if CO 2 and O 2 levels are normal
alveolar Po2 directs blood to respiratory areas where alveolar oxygen is high for...?
more efficient gas exchange
The amount of oxygen carried by hemoglobin depends on the amount of
oxygen available
in the event that Hb saturation is low, Hb's properties ensure that
oxygen is delivered where it is most needed->when tissues need more, they get more.
hemoglobin+bound O2=
oxyhemoglobin (HbO2)
Respiratory system controls attempt to raise pH by
pH by increasing respiratory rate/depth to eliminate CO 2 from blood
Decreased arterial pH caused by CO 2 retention or metabolic factors act via_______________ ____________ to...?
peripheral chemoreceptors to increase respiratory rate and depth
VRG inspiratory neyrons send impulses via____________and__________nerves to cause contraction of corresponding muscles
phrenic and intercostal (external)
transport and exchange of CO2 occurs in __________, but primarily in RBCs because..?
plasma; RBCs contain carbonic anhydrase that reversibly and rapidly catalyzes reaction->Most CO 2 entering plasma quickly enters RBCs
CO 2 dissolved in_____________and released from Hb also diffuses from____________into_______________
plasma; blood into alveoli
thickened respiratory membrane=
pneumonia and L heart failure (pulmonary edema)->lungs become waterlogged and edematous
Binding of one O 2 causes a shape change in Hb that makes it
progressively easier to bind additional O 2
what happens when Decreased O 2 and increased CO 2 in alveoli results from ventilation being less than perfusion?
pulmonary arterioles constrict and bronchioles dilate
what happens when there is Decreased O 2 and increased CO 2 in alveoli as a result of ventilation being greater than diffusion
pulmonary arterioles dilate and bronchioles constrict