Advanced Physiology: Respiratory Flashcards

Terms Definitions
What is the WHOLE POINT of internal cellular respiration?
-Cells take in energy from food
-combine it with O2
-using metabolic reactions we get
---Energy in the form of ATP
---Energy in heat (75%)
---Byproduct of CO2
What structure lies superior in the gross anatomy of the respiratory system?
Clavicular line.
Which structure of the body lines the bottom of the respiratory system?
Diaphragm
What structure occupies the majority of the Thoracic Cavity?
The lungs
What is the primary purpose of the respiratory system?
To provide the means for internal respiration
What are the 2 functions of the external respiratory system?
-Creates a system that transports O2 from the environment to the site of internal respiration.

-Eliminates CO2 from the site of production at the cells to the external environment
When we talk about Structure and Function of respiration are we referring to internal or external respiration?
External Respiration
What are serous membranes and what do they produce?
Sheets of connective tissue

-Produce Serous fluid
Where can you find serous fluid?
In the cavity between adjacent serous membranes
What is the correct way to describe a serous membrane in the thoracic cavity?
Pleural membrane
The visceral membrane has what function?
The pleural membrane that directly covers the right and left lung (covers the viscera)
What does the parietal membrane do?
The pleural membrane that lines the interior thoracic cavity wall
Describe the intrapleural space.
The space between the Parietal and Visceral membranes and is filled with intrapleural fluid
The arrangement of the thoracic cavity membranes is vital in which two functions?
-The function of the lungs

-The airflow within the lungs
Is the pressure within the thoracic cavity ever allowed to equilibrate with the external environment?
NO NEVER!
What happens if the "air tight seal" of the thoracic cavity is broken?
Real problems with breathing will occur
What protective and movable structures surround the thoracic cavity?
-Rib cage
-intercostal muscles
What is the convergence point for air entering the nose and the mouth?
Back of the throat (pharynx)
Where does air flow after it has hit the pharynx?
Larynx -->Trachea
What is the composition of the trachea?

What is the purpose of this material?
Very strong cartilaginous rings

-Rings line the trachea and designed to prevent collapse of the airway
What is the original bifurcation of the respiratory system?
The split into Right and Left bronchi from the trachea
How are bronchiolar airways designed to maximize airflow to the lower lung?
Designed to make many bifurcation points that are always smaller than the branch point from which they originated
What are the branches called after the original bifurcation?
Bronchioles
What change in tissue occurs from the Main branching point of the lungs down to the bronchioles?
Starts with cartilagenous rings --. replaced with smooth muscle lining the walls of the bronchioles
Name the last portion of the airway that does not engage in gas exchange.
Terminal Bronchiole
Where does gas exchange first occur in the lungs and how would you describe this portion?
Respiratory bronchioles

-has small sacs called alveoli that come off of theses small airways.

-The sacs are not bundled at this point
What are the sacs on the respiratory bronchioles called and what is their function?
Alveolar sacs

-Where the majority of gas exchange occurs
How does blood get TO the capillaries in the alveolar sacs?
Pulmonary artery
Is the blood sent through the pulmonary artery oxygenated?
No, deoxygenated
Where does Oxygenated Blood from the lungs go to get back to the body?
Pulmonary VEIN
Where can you find Pores of Kohn?
In the alveolar sacs
What is the funciton Pores of Kohn?
Allow equal distribution of the air throughout the alveolar sac as soon as air occupies the sac
What are Pores of Kohn designed to do?
Maximinze contact between the air in the alveolar sac and the blood in the pulmonary capillaries
What are the pulmonary capillary walls composed of?
capillary endothelial cells
What is the RBC diameter in relation to the capillary diameter?
RBCs diameter are sometimes a little bit bigger than the pulmonary capillaries and they have to squeeze through.
How does the diameter of the RBCs in the pulmonary capillaries contribute to gas exchange?
-The equal diameters minimize the distance between the alveolar space were O2 is and the RBC (which contains Hb)
What do Type I alveolar cells do?
Compose the walls of the alveolar sacs
What functional purpose do Type II alveolar cells serve in the sacs?
They produce pulmonary surfactant
How does pulmonary surfactant help with gas exchange?
Surfactant is a detergent

-breaks up the surface tension of water in the sacs

-prevents the sacs from collapsing in on eachother
What cells help in the immune response of the alveoli?
Alveolar macrophages

-phagocytose dust particles, debris, inhaled bacteria etc
Is this limited space between the alveolar sac and pulmonary capillary intentional or by chance?
Intentional: minimizes the distance for gas exchange
How do you generally define gas exchange?
The movement of CO2 and O2 in opposite directions across the capillary walls (along their concentration gradients)
Does gas exchange require energy expenditure?
No, it is done by passive diffusion
Which law is maximized by the simple diffusion of gases?
Fick's Law
The partial pressure of gases in the body is equivalent to what?
The concentration of that gas in the body
760mm Hg is described as?
The total atmospheric pressure at sea level
The total atmospheric pressure is derived from?
The force of movement of gaseous particles in the air that are colliding with anything that is containing the air.
Do individual molecules exert different pressures?
No, they exert equivalent amounts of pressure. Their overall amount is dependent on their current proportion.
What is the atmospheric partial pressure of O2?
160mm Hg
Does deoxygenated blood that enters the lungs have a partial pressure lower than 160mm Hg?
Yes, this allows for O2 exchange passively into the blood.
How many times does the Po2 drop as it enters the lungs?
twice
What happens to Po2 in the "first drop" in the upper airway?
Because the airway is humidified air, the oxygen that we breathe in gets diluted down to and drops to a Po2 of 150 mm Hg
Why does the second drop in our airway only reach 100mm Hg?
Becuase we do not expel all of the air out of our lungs with each breath
During restful breathing, how much air in our lower airway if from newly inspired air?
ONLY 15%
How do we increase the turnover of used newly inspired air in our lower airway?
We increase the rate and depth of each breath
What is the advantage of the 15% turnover rate in breathing?
We keep this stability whether we are inhaling or exhaling
What is the key purpose for the stability of turn over rate?
To allow for gas exchange to occur whether we are inhaling or exhaling
What constant Po2 is maintained in the alveolar that allows for stability?
100mm Hg
What is the Po2 of deoxygenated blood that enters the lungs?
40mm Hg
What is the size of the Po2 gradient between deoxygenated blood in the lungs and the O2 in the alveolar space?
100mm Hg - 40mm Hg = 60mm Hg

O2 immediately flows into the blood and will stop when the pressure has equilibrated
What Po2 does the blood have the goes BACK to the heart?
100mm Hg
How does the magnitude of the PCO2 gradient different from the PO2 gradient?
PCO2 gradient is lower
What is atmospheric PCO2?
.03mm Hg
What is the PCO2 in the alveolar and why?
40mm Hg

-Because only 15% of the air in the alveolar space is inspired.
What 2 important ways does CO2 work in the body?
1. Respiratory Control

2. Buffering system of the blood
What controls our breathing?
Our CO2 levels
Is there a problem with a pt whose breathing is being controlled by O2 levels?
They are most likely in a state of distress.
What does CO2 help buffer?
The pH levels in the body to maintain pH homeostasis
What is the PCO2 of venous blood?
46mm Hg
What is the partial pressure griadient for CO2 in the lungs?
6
What are Fick's factors that are relevant to gas exchange?
-More SA
-Steeper PP gradient
-Thinner diffusion barrier
-all give more exchange

-The amount of gas transported [diffused/exchanged]=(SAavailable for exchange x Px)/(thickness of diffusion barrier)
What feature of the lungs maximizes SA?
Bronchiole branching to a tremendous number of sacs.
What is the average alveolar SA for a healthy adult?
75 m2 (size of a tennis court)
What SA would our lungs have if the alveolar were just sacs?
0.01 m2
List the 6 barriers that O2 and CO2 must cross?

What is the thickness of these barriers added together.
1. Layer of surfactant
2. Alveolar epithelial cell
3. Interstitial space
4. Capillary endothelial cell
5. Plasma
6. RBC Plasma Mem

-Added together 0.5 micrometer!!
I a pt is suffering a condition that reduces the number of functional alveoli, what aspect of Fick's Law is altered?
They have reduced SA which reduces gas exchange
If chronic inflammation is present in a pt which results in scarring, which aspect of Fick's law will be altered?
They will have a thicker barrier for diffusion which will limit gas exchange
When a pt is struggling to ventilate, what factor in Fick's law is decreased?
The concentration (partial pressure) gradient. The delievery of O2 to the alveoli affects PPG
The gas exchange of a resident of Denver will be limited by what factor?
-The atmospheric pressure is less than sea level, 750mm Hg, and thus the partial pressure gradient between alveoli and atmosphere is less.

This will ultimately reduce the rate of diffusion of CO2/O2
What is the vehicle for gas transport?
The blood
What two general ways do we carry O2 throughout the body?
1. Dissolved in plasma

2. Chemically bound to Hb
What percentage of O2 is carried dissolved in plasma?
only 1.5%
What determines how much O2 bind to Hb?
The amount of O2 physically dissolved in plasma
What does our PO2 value tell us?
How much O2 is physically dissolved in plasma
Does O2 bound to Hb contribute to PO2?
No, only the O2 dissolved in plasma
What percentage of O2 is bound to Hb?
98.5%
What test indicates the % of O2 bound to Hb
Pulse Oximetry
In general, what are hemoglobin?
A large, intracellular protein composed of 4 subunits (2 alpha and 2 beta)
What are the binding sites for O2
The iron containing heme group on each subunit of Hb
How many O2 can on single Hb carry?
4
What does Oxyhemoglobin mean?
Hb is completely saturated --> 4 O2 are bound
When a Hb does not have 4 O2 bound, what state is the Hb in?
Deoxyhemoglobin (unsaturated state)
Which of the 4 O2 that can bind to Hb is the hardest to bind?
The first!
Once the first O2 has bound to Hb, what happens?
a conformational change takes place which allows for the 2nd - 4th O2 to bind easily and progressively faster.
What type of curve describes the binding of O2 to Hb?
Sigmoid Curve
Can O2 bypass plasma to bind to Hb?
No, there is no bypassing!
What tissue type constanly consumes O2 and may have a PO2 of 40mm Hg or less?
Metabolic tissue
The PO2 of plasma depends on?
the environment that the blood occupies
Where does O2 go first once it enters the blood?
It dissolves in plasma which raises the PO2 of that plasma.
Once O2 binds to Hb, what happens to the plasma?
The PO2 level drops allowing more O2 to be dissolved into it. Allows for the partial pressure gradient to be prolonged
When does O2 stop binding to Hb?
When the level of PO2 in the blood is equal to 100mm Hg
What do small changes in PO2 do to % of Hb saturation?
Create big corresponding changes in % Hb saturation
Does the phenonmenon of quick O2 attachment to Hb at high PO2 levels require energy?
No, it is just a property of Hb protein. It is how it works
When PO2 is high, are you more or less likely to find O2 attached to Hb?
More likely.
What is the % of Hb saturation at the plateau of the S-Curve?
97.5%
What PO2 of the tissues allows for quick unloading of O2?
Tissues have PO2 of 40mm Hg so O2 is pushed into the tissues passively and quickly
What is the first step in unloading O2 to the tissues?
O2 must move from the plasma into the tissue space first
Once O2 from plasma has entered the tissues, what result or second step occurs?
The PO2 drops which signals O2 to unload from Hb and thus diffuse into the tissue
What is the ending PO2 level and Hb saturation % once O2 has entered the tissues
PO2= 40

Hb Saturation ~74%
What 3 microenvironmental factors can change the relationship of O2 and Hb?
1. CO2 content
2. Acidity
3. Temperature
What happens if the S curve shifts to the left?
For any value of PO2, Hb saturation is HIGHER.

Hb holds onto O2 more tightly
What happens if the S curve shifts to the RIGHT?
Hb is less saturated at any value of PO2
When we exercise, what are we increases and where does the S curve shift?
-Increasing CO2 --> increases acidity levels
-Temperature rises

-The Hb curve shifts to the right -->delievers more O2 in the most metabolically active tissue
What kind of environment would Hb be more likely to hold onto O2?
One that is not metabolically active

-low CO2
-low acidity
-lower temperature
In general, what are the 3 ways that CO2 is carried in the blood?
1. Small % is dissolved in plasma
2. CO2 binds to Hb
3. In the form of bicarbonate
Does CO2 compete for space with O2 on Hb?
No, they have different attachment sites
What % of CO2 is found bound to Hb?
~30%
When CO2 is bound to Hb, what happens to O2's affinity for Hb?
It decreases because of a shape change
What is the Haldane/Bohr effect?
Mechanism behind the S curve shift to the right due to higher plasma acidity.
What % of CO2 is found as bicarbonate?
~60%
Is bicarbonate a weak or strong base?
Weak
What is the conjugate of bicarbonate?
The weak acid carbonic acid
What is a buffer system?
One that can regulate drastic changes in pH by taking up or release H+
Where does the conversion of CO2 to bicarbonate take place?

What does it use to complete the conversion?
ONLY in RBCs

-Uses carbonic anhydrase which is only in RBC
How does bicarbonate get out of the cell?
uses a bicarbonate chloride exchanger on the surface of the RBC
What type of transport system is used to get bicarbonate out of the cell?
secondary active transport
What is unique about the bicarbonate/chloride exchanger system?
This exchanger can change direction!!
If bicarbonate concentration is higher in the cell, what will happen?
Bicarbonate will flow out

-will pull out Chloride in the opposite direction
What occurs when HCO3- is greater outside the cell?
Bicarbonate will move into the cell pushing Cl- out.
What is the name of the phenomena where chloride levels shift into or out of the cell depending on CO2 levels?
Chloride shift
Where does Cl- travel when CO2 levels in the blood are high?
Into the RBC
What is the overall effect of transferring Cl- with HCO3-
The cell is able to remain electrically neutral
Higher PCO2 causes what reactions?
-Higher binding of CO2 to Hb
-Higher production of Bicarbonate by RBC
Does bicarbonate contribute to the PCO2?
No, only dissolved CO2 in plasma
When blood enters the lungs, how does CO2 get expelled?
-PCO2 starts to decrease (equilibrates with alveolar PCO2)
-CO2 leaves plasma
-CO2 unbinds from Hb (less HCO3- is formed)
-
-
What two ways does our body measure CO2 levels?
1. Partial pressures of CO2
2. acidity (carbonic acid levels)
Define ventilation
Delivery of air to the intra-alveolar space

-V
What is perfusion?
Delivery of blood flow to an area.

-Q
What is the best value for V/Q?
1

-we want to maximize gas exchange and therefore want ventilation=perfusion
Where do we ideally want to ventilate?
The intra-alveolar space
between what two things does gas exchange occur? (detailed)
Intra-alveolar space and the capillary blood.
How much should we ventilate the intra-alveolar space for optimal exchange?
In similar amounts as we deliver blood to that capillary space
What is the first region we must ventilate to have any form of gas exchange?
The terminal bronchioles must be completely ventilated

-Then the respiratory bronchioles can conduct gas exchange
What must we ventilate prior to ventilating our respiratory space?
A significant amount of anatomical dead space
Define anatomical dead space.
All of the neutral parts of the airway where gas exchange is not occurring.

-Everything before the respiratory bronchioles
During restful breathing, what % of total ventilation is used to fill dead space?
30%
How do you decrease dead space ventilation?
Exercise (deeper breathing helps deliver a greater portion of total vent to respiratory ventilation.
What % of total ventilation will occupy dead space during fast and shallow breathing?
100%

-won't allow for gas exchange because air is not getting to respiratory bronchioles
If a pt suffers from a lung tumor, what can this do to the ventilation?
It can cause a physiological dead space and thus reduce overall ventilation
What is the apex of the lungs?
The anatomical top of the lung
What is the name for the anatomical bottom of the lung?
The base
Perfusion of the lungs is done through what process?
pulmonary circulation
Is the right side of the heart strong?
No, because it doesn't have to pump the blood very far

-AND pulmonary circulation operates at low pressure scales
What levels do system arteries operate at?
Average systolic/diastolic values for BP
Distribution of perfusion in pulmonary circulation is highly dependent on what?
Body Position
What is the number one factor for perfusion rate in reference to body position?
GRAVITY
If a person is standing on their head, where is the greatest perfusion of the lungs?
At the apex, due to gravity.
If the perfusion of the lungs is concentrated to the dorsal part, what body position is the person in?
lying on their back
What 2 factors determine regional variations of perfusion in the lungs?
Gravity and body position
What is the V/Q ratio?
It is the comparison of the ventilation and perfusion regionally in the lungs
The V/Q rate is dominated by?
perfusion pattern across the lungs
For a person who is standing upright, which is greater at the APEX, V or Q?
Ventilation V
Where is perfusion greater than ventilation in an standing pt?
At the base
Is the perfusion range (Q[bottom] - Q[top]) greater than or less than the ventilation range (V[bottom] - V [top])?
Perfusion range is larger.
How does exercise help close the Ventilation/Perfusion gap?
As the heart pumps faster, BP increases --> pulmonary circulatory pressure increases --> enables the force of gravity to have LESS of an influence over distribution of perfusion.
what benefit does exercise have on gas exchange?
It enhances it and therefore oxygen delivery
How is ventilation controlled locally?
Determined by bronchiolar constrction or dilation

-contriction --> V downstream goes down

-dilation --> V downstream goes up
How is perfusion locally controlled?
-Constriction of pulmonary arteries--> Q goes down

-Dilation of pulmonary arteries --> Q goes up
Overall, how do we modify V
We influence bronchiolar width
How do we modify Q?
We influence pulmonary arteriolar width
What gas is bronchiolar smooth muscle sensitive to?
Local CO2 levels
Pulmonary arteries are sensitive to influence from?
Local O2 levels
What effect will a drop in CO2 levels have on bronchiolar smooth muscle?
It will cause constriction and thus limits ventilation to that area.

-shunts ventilation to a part of the lung where perfusion is higher
What will occur in bronchiolar smooth muscle if CO2 levels are higher than O2?
Bronchiolar SM will relax causing enhanced ventilation to match the perfusion.
What is the reaction of pulmonary arterioles when Q>V?
-O2 removal > rate of O2 delivery from ventilation.
-Local O2 levels drop and pulmonary arterioles CONSTRICT
-blood can be shunted away
When V>Q, what is the response of pulmonary arterioles?
-O2 delivery is high
-Causes DILATION of the arteriole
-Perfusion level will go up to match the higher ventilation
Which arteries are the only ones in the body to CONSTRICT when O2 levels are low?
Pulmonary Arteries
What two processes occur at the same time when O2 levels are low?
-Pulmonary arteries will CONSTRICT
-Systemic arterioles DILATE
What 5 things are needed for gas exchange to occur?
1. O2 pressure gradient
2. CO2 pressure gradient
3. Ventilation
4. Perfusion
5. Relative matching of V/Q
To inhale, should the intrapulmonary pressure be < or > atmospheric pressure
Less than atmospheric pressure
What happens when the intra alveolar pressure is greater than the atmospheric pressure?
We exhale
How does the intrapleural pressure compare to the intra-alveolar and atmospheric pressures?
It is less than both
What is the purpose of the intraPLEURAL pressure?
To keep the lungs from collapsing

-its negative pressure keeps the lungs inflated
What would happen if you introduced a detergent into the intrapleural space?
The lungs would collapse do to a break in surface tension
Does the intra-alveolar space need surface tension?
No, it would make breathing nearly impossible
Describe intrapleural fluid cohesiveness
The tendency for water to stick to itself

-ex. two glass slides held together with water. They can slide but cannot be pulled apart
When is the P atm= P alveolar?
1. At the end of each breath
2. In between breaths
What is transmural pressure?
There are 2

1. Pressure across the thoracic cavity wall (760 on outside, 756 on inside)

2. Pressure across the lung wall (760 on inside and 756 on outside)
What happens to the chest wall when the lungs collapse?
The wall actually expands
How do we create an alternating pressure gradient that draws in/out of the lung?
By changing lung volume!
When the lungs expand, the volume increases. This does what?
-Causes a drop in pressure and air flows in
What allows for a change in thoracic cavity volume to change the lung volume?
The surface tension of the intrapleural space!
Which muscles are responsible for inhalation?
-Diaphragm

-External intercostals
What muscle in the body is under both voluntary and subconscious control?
The diaphragm
What muscle does the phrenic nerve innervate?
the diaphragm
What nerves innervate the the external intercostals?
Intercostal nerves
What action of the diaphragm contributes to inhalation?
Contraction, flattening to expand thoracic cavity vertically
What direction of volume occurs when external intercostals contract?
Increase in horizontal volume
Why does the intrapleural pressure decrease during inhalation?
Because its volume is also expanding, creating enough negative pressure to pull on the lung (causes lung expansion)
How do we exhale?
We relax the diaphragm and the external intercostals to decrease lung volume and push air out.
What do you need to do to take in a deep breath?
You must recruit accessory muscles for forceful inhalation (voluntarily or when exercising)
LIst the accessory muscles involved in deep breathing.
-sternocleidomastoid
-scalene muscles
If a pt comes in with labored breathing (using accessory muscles) what does this indicate>?
Respiratory distress
Do forceful exhalations require energy?
YES! You must recruit more muscles to be involved
What accessory muscles are involved with forceful exhalation?
1. Internal intercostals (pull rib cage in)

2. Abdominal muscles (displaces diaphragm upward, shrinking thoracic cavity slightly)
What is the advantage of forcefully exhaling air?
-Creates an even greater change in volume in your next inhalation!
What is compliance?
A compliant lung does not need a lot of effort for expansion

-Measure in how much effort we need to stretch the lungs
Do we want high lung compliance?
Yes, we don't want to put in a lot of effort to fill the lungs
What is elastic recoil?
Describes how readily the lungs recoil back after being stretched
What is the optimal lung behavior?
High compliance, low recoil
What is the benefit of having elastin fibers in the lungs?
-When airways are expanding, they pull on neighboring airways, promoting their expansion because they are connected to each other
Pulmonary elasticity is dependent on which 2 factors?
1. Presence of highly elastic CT in the lungs

2. Minimization of alveolar surface tension
Breathing follows what type of cycle?
Rhythmic
What is the result of a spinal chord injury that takes place above C3, C4 or C5?
Will require lifelong mechanical inspiration
What comprises the medullary respiratory center?
1. The Dorsal respiratory group
2. Ventral respiratory group
3. Pre-Botzinger Complex
What specific aggregate sets the respiratory rate?
the Pre-Botzinger complex
What cells are present in the Dorsal respiratory group and what do they control?
-Neuronal cells
-Drive inspiration
-Lead the contraction on muscles involved in restful breathing
What action does the DRG take on the VRG to invoke forceful breathing?
The DRG may recruit the VRG cells to stimulate the sternocleidomastoid and scalenes
Is there any activity in the DRG during exhalation?
No, it is a passive process.

No APs fired
What is the function of the VRG?
Composed of cells that are involved in recruiting accessory muscles for forceful breathing

-Only fires during forceful breathing
What controls the stimulation of the DRG-controlled muscles?
The Pre-Botzinger complex
Are cell bodies of the phrenic and intercostal nerves pace setters for respiration?
No, only the aggregates in the brainstem are!
What are the 2 nuclear aggregates in the pons also known as>
Pontine respiratory centers
What is the general function of the Pontine respiratory centers?
To modulate the rate and depth of breathing by determining the duration of the in-breath
Why is the pontine respiratory center very precise and accurate?
Because the control from the pons centers are constantly based on feedback coming into the brain from the body

-regarding the body's metabolic demands and situation your body is in)
What is the function of the Pneumotaxic center?
Has a tendency to shorten the i-breath
What is the function of the Apneustic center?
Has a tendency to prolong in-breath
What would the result of a sever belong the VRG?
Deep breathing would stop
If we sever above Pre-Boltzinger, what remains? What is lost?
You will still regulate breathing in an involuntary way.

-You have lost the pontine centers
If you sever the sensory input section of the brain, how will you breath?
It will be huge gasps
What is the most important aspect in the brains modulation of breathing?
Sensory input coming into the brain
If you remove sensory input AND cut between the pontine centers what happens?
Apenuisis: Exaggerated, long and deep gasps followed by very short expiration

Prolonged in-breaths
What are three major pulmonary receptor types?
1. Pulmonary stretch receptors
2. Pulmonary Irritant Receptor
3. Pulmonary J Receptors (Juxtacapullary)
What is the purpose of pulomonary receptors?
To PROTECT the lung tissue from overinflation an damage due to inhaled irritants
Where are the PSR located?
Between smooth muscle cells that line bronchiolar airwys
What are PSR most sensitive to?
Stretch
What is triggered by the PSR when the lungs begin to stretch?
What does it do?
Triggers the Hering-Bruer Reflex

-protects the lungs from overinflation
What type of breathing is noticed when the Hering-Bruer Reflex is triggered?
Fast, but shallow breaths to reduce tidal volume
Which respiratory receptors are dispersed among the ciliated columnar epithelium?

What are they most sensitive to?
Pulmonary Irritant Receptors

-Sensitive to irritants
What reaction is seen when the PIR are triggered?
-Bronchiolar constriction: which ill limit the irritant's access to the tract

-Gasping: which helps keep some level of inhalation
Which pulmonary receptors alert the brain of the presence of irritants at the site of gas exchange?
Pulmonary J Receptors (Juxtacapillary)

-These are also primarily sensitive to irritants
What does the BRAIN use to control arterial PO2 and PCO2?
SENSORY information that is meant to reflect respiratory needs
What are the 3 major chemical factors that influence respiration?
1. PO2 of arterial blood
2. PCO2 of arterial blood
3. [H+] of arterial blood: may be non CO2 derived acid.
What chemicals are peripheral chemoreceptors (PCR) sensitive to and to what degree?
1. PCO2 (mildly)
2. PO2 (moderately)
3. pH (highly sensitive)
Which chemoreceptor will sense a drop in PO2?
peripheral chemoreceptors
What PO2 would the blood have to drop in order to stimulate the PCRs?
60mm Hg

-this regulation is used in emergency situations
What Hb saturation would remain if the PO2 levels dropped to 60mm Hg?
We would still have 90%
Before a drop in PO2 is discovered, what will the body sense?
A rise in PCO2
What is the locations of the peripheral chemoreceptors?
1. Carotid bodies of the Carotid Sinus
2. Aortic bodies of the aortic arch
What info do the carotid bodies send to the brain?
The status of the blood specifically perfusing the brain
The brain receives info about the blood entering general circulation from which PCR?
Aortic bodies in the aortic arch.
Which chemoreceptor cannot directly sense changes in pH?
Central chemoreceptor
If acidosis is occuring as a result of non-respiratory acid, what is the overall change in breathing actually doing?
It is COMPENSATING for the acid, not necessarily trying to maintain breathing.
Which chemoreceptors will be the first to respond to change in PCO2?
Central CRs, but only indirectly!!
What action will the respiratory center take when a person is in alkalosis?
Breathing will slow down to try and increase PCO2 and thus carbonic acid.

-This will compensate for the high base concentration and bring pt back to pH homeostasis
What are the only chemoreceptors to mediate compensation?
Peripheral chemoreceptors
What are the central chemoreceptors sensitive to and to what degree?
-changes in plasma PCO2 (highly)
-Changes to plasma PO2 (weakly)
What does the CCRs sense even more than the PCO2?
the CO2 that is converted into bicarb and carbonic acid once int the brain!
What are the CCRs PRIMARILY extremely sensitive to?
the rise in acidity in the BRAIN due to CO2 that has been converted into carbonic acid in the brain!
What does the CCR actually sense INDIRECTLY?
the plasma PCO2 levels in the brain
Once the CCR has seen a rise in acidity, what does it stimulate?
the medullary respiratory centers to increase respiration
Can you hold your breath to death?
No! At some point the PCO2 will get so high that it will force you to breath by triggering the CCRs!
Are we typically under voluntary or involuntary control of our breathing?
Typically voluntary
What are 2 ways that have been thought to help increase length of breath holding?
-Purging: getting rid of a ton of CO2

-Staying completely still
Where are central chemoreceptors located?
In the brain stem close to the medullary respiratory center
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