Lesson 14: Topic 9 and 10 - CO2 Transport and Control of Breathing

Question 1

what direction does the bicarbonate equilibrium reaction go at the cell/tissue?

Answer 1

left to right

Question 2

what direction does the bicarbonate equilibrium reaction go at the alveoli/lungs?

Answer 2

right to left

Question 3

why can we not bind all of our CO2 to hemoglobin?

Answer 3

because there is not enough hemoglobin available because most of the hemoglobin still has oxygen bound to it (60-70%)

Question 4

what is the saturation of O2 to hemoglobin in the arterial vs venous circulation?

Answer 4

• arterial: 98-100%
• venous: 60-70%

Question 5

why is there not a neutral charge in the red blood cell?

Answer 5

because when H2CO3 –> H+ + HCO3-, the hydrogen ion is lost because it gets converted to HbH

Question 6

what is the hamburger effect?

Answer 6

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

Question 7

why does the chloride shift happen?

Answer 7

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)

Question 8

what is part of why have a humid expiration (when we breath on a window it gets foggy)?

Answer 8

because we are reversing the bicarbonate reaction, therefore breathing our CO2 and H20

Question 9

the bicarbonate equilibrium reaction accounts for how much % of the CO2 transport?

Answer 9

60%

Question 10

• • • (summary of CO2 transport 1/2) at the tissue, increased CO2 moves into blood then RBC drives reaction left to right by?

Answer 10

increasing CO2 concentration

Question 11

• • • (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?

Answer 11

decreasing CO2 concentration

Question 12

metabolic rate produces?

Answer 12

CO2

Question 13

breathing is generated at the level of?

Answer 13

the medulla in the brain stem

Question 14

what established arhythmic breathing pattern?

Answer 14

the brain stem

Question 15

what are the two respiratory groups of the medulla?

Answer 15

1. dorsal respiratory group
2. ventral respiratory group

Question 16

both of the medullas respiratory groups have?

Answer 16

inspiratory neurons

Question 17

which of the medullas respiratory groups have expiratory neurons?

Answer 17

ventral respiratory group

Question 18

why do we have more neurons dedicated to inspiration?

Answer 18

because we need muscles to inspire at a resting state than expire which is passive

Question 19

where is the Pre-Botzinger complex?

Answer 19

within the medulla

Question 20

what does the Pre-Botzinger complex generate?

Answer 20

respiratory rhythm (size, frequency, etc.)

Question 21

what does mechanoreceptors do? (not important)

Answer 21

• detect changes in pressure, flow or displacement of a structure and sends it to the medulla
• lung and chest wall
• peripheral muscles

Question 22

what does the metaboreceptors do? (not important)

Answer 22

detect local change in metabolic byproduct concentration like lactate and hydrogen and it can help/send information to control respiratory rhythm as well

Question 23

what does the pulmonary stretch receptors do? (not important)

Answer 23

• 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

Question 24

does chemical factors play a role in determining the magnitude of ventilation?

Answer 24

yes

Question 25

what is O2 and CO2 predominantly sensed by?

Answer 25

chemoreceptors

Question 26

what are the two types of chemoreceptors?

Answer 26

1. peripheral (away from brain, in blood stream) 2. central medullary (in the medulla in the brainstem)

Question 27

what are the two peripheral chemoreceptors?

Answer 27

1. Carotid chemoreceptors (dominates/more active) 2. aortic chemoreceptors

Question 28

where are the carotid chemoreceptors located?

Answer 28

in the carotid body

Question 29

where are the aortic chemoreceptors located?

Answer 29

in the aortic body

Question 30

what does peripheral chemoreceptors respond to?

Answer 30

both respond to changes in the arterial blood gas partial pressures and they send signals up to the medulla

Question 31

which peripheral chemoreceptor is more sensitive and plays a larger role that the other?

Answer 31

carotid is more sensitive and plays a larger role than the aortic body

Question 32

the peripheral carotid chemoreceptor is predominantly a sensor for?

Answer 32

O2 - responds predominantly to fluctuations in oxygen

Question 33

If you increase or decrease resting PO2 (100mmHg) by 20 or 30 mm, what happens to ventilation? why?

Answer 33

almost no change because of oxygen hemoglobin saturation

Question 34

what does the carotid chemoreceptor do if it notices a drop in our arterial PO2?

Answer 34

it sends a signal to the brain to tell it to start hyperventilation to increase our PO2

Question 35

when PaO2 decreases, the receptors _____ their rate of discharge.

Answer 35

increase

Question 36

true or false: increased ventilation is directly proportional to firing rate

Answer 36

true

Question 37

is O2 a strong or weak stimulator of ventilation for the chemoreceptors?

Answer 37

weak because it stimulates only during vast changes in PaO2 which would be 40mmHb below resting (100-40mmHb = 60mmHb)

Question 38

what is another way that ventilation will be stimulated by the chemoreceptor?

Answer 38

if H+ is high (extreme fluid lost, heavy exercise, lactic acid)

Question 39

what does central chemoreceptors located in the medulla do?

Answer 39

they sense changes within the brains extracellular fluid/cerebrospinal fluid (not blood stream) and responds to changes in H+ (pH) in the medulla

Question 40

can hydrogen pass the blood brain barrier?

Answer 40

no

Question 41

can CO2 in the blood pass the blood brain barrier?

Answer 41

yes

Question 42

when CO2 passes the blood brain barrier, some diffuses into the cerebrospinal fluid. what happens?

Answer 42

it goes from left to right in the bicarbonate equilibrium reaction and ultimately dissociates into hydrogen

Question 43

the cerebrospinal fluid (CSF) senses hydrogen (response from central chemoreceptors), but where does this hydrogen come from?

Answer 43

from the arterial CO2 from when it crossed the blood brain barrier and a bit leaked into the CSF

Question 44

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?

Answer 44

- 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

Question 45

what does the central chemoreceptors respond to?

Answer 45

CO2 fluctuations in the arterial blood

Question 46

if O2 decreases, which chemoreceptor regulates it?

Answer 46

carotid peripheral chemoreceptor

Question 47

if CO2 rises, which chemoreceptor regulates it?

Answer 47

central chemoreceptor