Lesson 14: Topic 9 and 10 - CO2 Transport and Control of Breathing Flashcards
what direction does the bicarbonate equilibrium reaction go at the cell/tissue?
left to right
what direction does the bicarbonate equilibrium reaction go at the alveoli/lungs?
right to left
why can we not bind all of our CO2 to hemoglobin?
because there is not enough hemoglobin available because most of the hemoglobin still has oxygen bound to it (60-70%)
what is the saturation of O2 to hemoglobin in the arterial vs venous circulation?
- arterial: 98-100%
- venous: 60-70%
why is there not a neutral charge in the red blood cell?
because when H2CO3 –> H+ + HCO3-, the hydrogen ion is lost because it gets converted to HbH
what is the hamburger effect?
also known as the chloride shift
- HCO3 diffuses out of the red blood cell and into the plasma and its replaced by a chloride negative ion
why does the chloride shift happen?
to avoid HCO3 from binding with free floating hydrogen ions and also
- to maintain a neutral charge in the RBC (H+ and Cl- balance) ( keeps the RBC stable)
what is part of why have a humid expiration (when we breath on a window it gets foggy)?
because we are reversing the bicarbonate reaction, therefore breathing our CO2 and H20
the bicarbonate equilibrium reaction accounts for how much % of the CO2 transport?
60%
- (summary of CO2 transport 1/2) at the tissue, increased CO2 moves into blood then RBC drives reaction left to right by?
increasing CO2 concentration
- (summary of CO2 transport 2/2) at the lung, CO2 diffuses from plasma into alveoli, decreasing the CO2 concentration in RBC which drives reaction from right to left by?
decreasing CO2 concentration
metabolic rate produces?
CO2
breathing is generated at the level of?
the medulla in the brain stem
what established arhythmic breathing pattern?
the brain stem
what are the two respiratory groups of the medulla?
- dorsal respiratory group
- ventral respiratory group
both of the medullas respiratory groups have?
inspiratory neurons
which of the medullas respiratory groups have expiratory neurons?
ventral respiratory group
why do we have more neurons dedicated to inspiration?
because we need muscles to inspire at a resting state than expire which is passive
where is the Pre-Botzinger complex?
within the medulla
what does the Pre-Botzinger complex generate?
respiratory rhythm (size, frequency, etc.)
what does mechanoreceptors do? (not important)
- detect changes in pressure, flow or displacement of a structure and sends it to the medulla
- lung and chest wall
- peripheral muscles
what does the metaboreceptors do? (not important)
detect local change in metabolic byproduct concentration like lactate and hydrogen and it can help/send information to control respiratory rhythm as well
what does the pulmonary stretch receptors do? (not important)
- stretch reflex: where your lung stretches and as soon as it gets to a certain level of stretch, it sends an inhibitory message to the brain to stop the diaphragm from contracting
does chemical factors play a role in determining the magnitude of ventilation?
yes
what is O2 and CO2 predominantly sensed by?
chemoreceptors
what are the two types of chemoreceptors?
- peripheral (away from brain, in blood stream)
- central medullary (in the medulla in the brainstem)
what are the two peripheral chemoreceptors?
- Carotid chemoreceptors (dominates/more active)
- aortic chemoreceptors
where are the carotid chemoreceptors located?
in the carotid body
where are the aortic chemoreceptors located?
in the aortic body
what does peripheral chemoreceptors respond to?
both respond to changes in the arterial blood gas partial pressures and they send signals up to the medulla
which peripheral chemoreceptor is more sensitive and plays a larger role that the other?
carotid is more sensitive and plays a larger role than the aortic body
the peripheral carotid chemoreceptor is predominantly a sensor for?
O2
- responds predominantly to fluctuations in oxygen
If you increase or decrease resting PO2 (100mmHg) by 20 or 30 mm, what happens to ventilation? why?
almost no change because of oxygen hemoglobin saturation
what does the carotid chemoreceptor do if it notices a drop in our arterial PO2?
it sends a signal to the brain to tell it to start hyperventilation to increase our PO2
when PaO2 decreases, the receptors _____ their rate of discharge.
increase
true or false: increased ventilation is directly proportional to firing rate
true
is O2 a strong or weak stimulator of ventilation for the chemoreceptors?
weak because it stimulates only during vast changes in PaO2 which would be 40mmHb below resting (100-40mmHb = 60mmHb)
what is another way that ventilation will be stimulated by the chemoreceptor?
if H+ is high (extreme fluid lost, heavy exercise, lactic acid)
what does central chemoreceptors located in the medulla do?
they sense changes within the brains extracellular fluid/cerebrospinal fluid (not blood stream) and responds to changes in H+ (pH) in the medulla
can hydrogen pass the blood brain barrier?
no
can CO2 in the blood pass the blood brain barrier?
yes
when CO2 passes the blood brain barrier, some diffuses into the cerebrospinal fluid. what happens?
it goes from left to right in the bicarbonate equilibrium reaction and ultimately dissociates into hydrogen
the cerebrospinal fluid (CSF) senses hydrogen (response from central chemoreceptors), but where does this hydrogen come from?
from the arterial CO2 from when it crossed the blood brain barrier and a bit leaked into the CSF
if there was an experiment where we could measure three respiratory values, what would they be if they could all go up in perfect correlation with each other?
- measure breathing
- measure arterial CO2 in the brain
- measure hydrogen accumulation in the cerebrospinal fluid
they would all go up in perfect correlation with each other
what does the central chemoreceptors respond to?
CO2 fluctuations in the arterial blood
if O2 decreases, which chemoreceptor regulates it?
carotid peripheral chemoreceptor
if CO2 rises, which chemoreceptor regulates it?
central chemoreceptor
