Exam 4 - Lecture 5

Question 1

What is the pKa of bicarb?

Answer 1

6.1

Question 2

Why does bicarb work so well even though its pKa isnt near body pH?

Answer 2

Because of multiple buffers and proteins in the system that help maintain pH. (Protiens help quite a bit)

Question 3

PPgas equation (again)

Answer 3

PPgas = [concentration of gas] x (Barometric pressure - Water vapor pressure)

PiO₂ = FiO₂ × (PB − PH₂O)

Example: PiO₂ = 0.21 x (760 - 47) = ~150 mmHg

Question 4

Do you include water vapor for expired dead space gas?

Answer 4

No, water vapor was already included during inhalation so if you included it again, it would be doing it twice which is incorrect.

Question 5

What is the FiO2 of expired dead space gas if the patient inhaled 100% FiO2?

A. 94%
B. 100%

Answer 5

Neither (hehe). Taking 713 and dividing it by 760mmHg is underestimating it, and doing 760/760 is overestimating it. he said it gets complicated and its just somewhere in between.

Question 6

How many times can you make an adjustment for water vapor?

Answer 6

Only once, on inhalation.

Question 7

How could you theoretically get expired air samples to not have any water vapor?

Answer 7

Freeze it.

Question 8

Whats a basic way of assessing someones respiratory status? Specific examples?

Answer 8

Simply watching them. Signs like being hunched over, leaning on a wall, a muffled and quiet cough.

Question 9

How much air can a loud cough move?

Answer 9

2L of air

Question 10

Whats the primary site of breathing regulation? Other parts?

Answer 10

Medulla; midbrain and pons

“All the action is basically in the medulla”

Question 11

What are the 3 sections of the brainstem?

Answer 11

Top: Midbrain/Mesencephalon
Middle: Pons (looks like an olive)
Bottom: Medulla (lowest portion before spinal cord)

Question 12

What are respiratory sensors looking at?

Answer 12

pH, PaCO2, PaO2

Also mentioned blood pressure and this is where crossover occurs between CV and respiratory system

Question 13

Main peripheral chemoreceptor and where is it? What do they measure?

Answer 13

Carotid chemoreceptors located at carotid bifurcation. They look for changes in protons, oxygen, and CO2.

Question 14

Secondary peripheral chemoreceptor and location? How do they function?

Answer 14

Aortic bodies located at aortic arch. They monitor blood chemistry coming out of left ventricle.

Question 15

What is “strategic” about peripheral chemoreceptors?

Answer 15

The fact theyre placed in spots so blood can be measured right outside the heart, and headed towards brain.

Question 16

Where are central chemoreceptors located?

Answer 16

In the brainstem, particularly the medulla.

Question 17

What are central chemoreceptors mostly responsive to?

Answer 17

protons (changes in pH)

They can respond to other changes as well (CO2 and O2), but primarily protons.

Question 18

The CNS is covered in ______ and has _____ underneath.

Answer 18

meninges; CSF

Brain tissue is bathed in CSF

Question 19

What is typically the trigger that regulates most breathing? Specifically where?

Answer 19

Changes in pH in the CSF.

Question 20

What has a hard time crossing BBB which results in a slower reaction time in breathing changes? How long is this reaction?

Answer 20

Non-volatile acids such as lactic acid. Book says 3 minutes, but schmidt thinks its faster..

Question 21

What crosses BBB “much easier” than non-volatile acids, resulting in quick breathing changes?

Answer 21

PCO2, almost instantaneous changes.

Question 22

CSF composition is what, per lecture?

Answer 22

clear and should not have alot of proteins

Question 23

What is the pH in CSF?

Answer 23

class says 7.31, levitzky says 7.32

(This was from Notebook LM, can someone confirm this? i dont remember hearing this.)

Question 24

Does CSF have a buffering system? what is it capable of producing?

Answer 24

Yes, can produce bicarb.

Question 25

Can bicarb cross BBB?

Answer 25

Not as itself directly, has to convert to CO2 before crossing

Question 26

CSF bicarb is managed by?

Answer 26

Helper glial cells

Question 27

Is CSF PCO2 higher or lower than arterial PCO2?

Answer 27

Higher

Question 28

What mechanism causes CSF CO2 higher?

Answer 28

Neurons are working and producing CO2, which has to move down a concentration gradient from the cell, through CSF, across the BBB to reach the bloodstream.

Question 29

Whats a healthy CSF PCO2?

Answer 29

50mmHg This pressure gradient difference helps drive CO2 to from brain tissue to blood.

Question 30

If you have to pick one thing that directly activates central chemreceptors, its what?

Answer 30

Protons Historically, there was heated debates about whether it was CO2 or protons

Question 31

Is bicarb a better or worse buffer in the CSF than the blood?

Answer 31

Worse, since CSF doesnt have much proteins. Remember, more buffers around, the more effective each individual buffer is. This is why the CSF pH drops so much with a little bit more CO2

Question 32

higher CO2 results in almost immediate increases in (other than ventilation lol)

Answer 32

brain blood flow. Cerebral blood vessels dilate in response to increased CO2, and the increased flow will help wash out the excess CO2 and return it to normal.

Question 33

Whats the "overall" area in the brainstem thats involved in breathing control? What also happens here?

Answer 33

Lower parts of the reticular formation; where some pain signals terminate.

Question 34

What does the book also call the reticular formation?

Answer 34

Medullary area or medullary respiratory center.

Question 35

What is the reticular formation just a broad term for

Answer 35

Tissue in the lower brainstem with groups of inspiratory and expiratory neurons.

Question 36

What are the two basic groups in the medulla?

Answer 36

DRG and VRG Dorsal Respiratory Group and Ventral Respiratory Group.

Question 37

Dorsal means ___ and ventral means ____

Answer 37

Dorsal: Back (like a dorsal fin) Ventral: Front

Question 38

The DRG is located in an area called? and this area is within?

Answer 38

Nucleus Tractus Solitarius (NTS); located within the reticular formation

Question 39

The DRG probably handles majority of our _____ signals.

Answer 39

inspiratory *Major place where inspiratory signals are generated*

Question 40

The DRG will send projections to other parts of brainstem that control what, and what does it do them?

Answer 40

expiration, inhibiting them when inspiration is active.

Question 41

Signals from DRG are sent to muscles via what kind of nerve(s), with what nerve(s) being the most imporant?

Answer 41

motor nerves; phrenic nerve

Question 42

Motor signals from DRG will crossover at the _____.

Answer 42

Pyramidal Decussation *The left side of DRG will control right respiratory muscles*

Question 43

Another word for crossover is

Answer 43

decussate

Question 44

The DRG is the primary place where what is fed into?

Answer 44

Peripheral gas sensors feed in PaO2, PaCO2, pH.

Question 45

Sensory information from peripheral chemoreceptors feed into the DRG via what nerve(s)?

Answer 45

Vagus nerve (CN X) and the Glossopharyngeal nerve (CN IX)

Question 46

What also feeds into basically the same place as gas sensors (DRG)?

Answer 46

baroreceptors

Question 47

The DRG oddly enough also controls two groups of ____

Answer 47

Forced/labored expiratory muscles, which are the abdominal muscles and internal intercostal muscles.

Question 48

The VRG is located _____ to the DRG

Answer 48

opposite side of brainstem

Question 49

Maybe dont have to know this for final... but: The VRG contains named areas like?

Answer 49

Retrofacial nucleus, nucleus ambiguous/para ambiguous/retro ambiguous

Question 50

The one area within VRG that we need to know is called what?

Answer 50

Botzinger complex or Pre-Botzinger Complex

Question 51

What is the botzinger complex involved in?

Answer 51

Controls the respiratory rate by feeding over to DRG and controlling the pace at which the DRG fires (spacing in between breaths)

Question 52

The botzinger complex is typically thought of as the site of ?

Answer 52

Respiratory Rhythmogenesis (Respiratory rate) *It likely does this by feeding back or doing reciprocal innervation with the DRG?*

Question 53

The VRG is also very important for what?

Answer 53

Motor output for keeping upper airway open.

Question 54

How does the VRG help keep the airway open?

Answer 54

It innervates the muscles around the larynx and pharyngeal constrictor muscles to prevent them from obstructing breathing.

Question 55

In summary, the DRG is responsible for what, and the VRG is responsible for what...

Answer 55

DRG handles most motor output for inspiratory and forced expiratory muscles, and the VRG is responsible for motor output to keep upper airway open while also controling respiratory rate.

Question 56

What is the PRG

Answer 56

Pontine respiratory group

Question 57

Where is the pontine located in relation to the DRG/VRG and in the CNS?

Answer 57

little bit higher up than the DRG/VRG, in the border of the pons and top part of medulla.

Question 58

The PRG is an important place for what sensors to send information?

Answer 58

Irritant receptors

Question 59

Where are irritant receptors located?

Answer 59

in the lungs and airways, especially the trachea.

Question 60

How does irritant receptors send signals? aka what fkn nerve

Answer 60

vagus

Question 61

Information about abnormal conditions in the lungs (e.g. dust) is sent to the ___. This information is then typically passed to the ____.

Answer 61

PRG; DRG

Question 62

The PRG is likely able to do what to inspiration when needed?

Answer 62

limit time spent in inspiration, preventing it from being unnecessarily long

Question 63

the PRG limiting time spent in inspiration is likely based on feedback from what?

Answer 63

Stretch sensors embedded in hte lung tissue, which feed into PRG.

Question 64

If there is a lesion that separates the PRG from medullary respiratory groups, what can happen?

Answer 64

Apneustic breathing The pathway where the PRG tells the DRG to stop inspiration is cut off, now inspiration becomes prolonged and expiration is very short. This is also a death reflex.

Question 65

In summary, the PRG helps ____ inspiratory time from DRG neurons.

Answer 65

fine-tune

Question 66

What nerve controls the diaphragm?

Answer 66

Phrenic (C3 - C5)

Question 67

What is reciprocal inhibition?

Answer 67

When one center activates, it inhibits the other. e.g. when inspiration is active, expiratory is inhibited.

Question 68

What is the first adjustment the respiratory system makes when metabolism/activity increases?

Answer 68

Tidal volume first, then respiratory rate if more is needed.

Question 69

Why is tidal volume adjust preferred over respiratory rate adjustment?

Answer 69

if you only increase rate, dead space increases. But if you increase VT, you get more direct alveolar ventilation.

Question 70

What is the downside to adjusting tidal volume?

Answer 70

Have to adjust inspiratory time

Question 71

What pathological condition would contraindicate raising the tidal volume?

Answer 71

Right sided heart failure, as increased VT will increase workload.

Question 72

What type of fibers are most commonly the motor neurons that control respiratory muscles?

Answer 72

A-alpha

Question 73

Why are the respiratory controlled muscles innervated A-alpha fibers?

Answer 73

Theyre very large and fast. Better to run from a bear when you have fast, quickly activated muscle contraction.

Question 74

Tidal volume is regulated by A-alpha neurons activating progressively ____________.

Answer 74

larger and longer motor neurons.

Question 75

Full activation of respiratory muscles includes all motor units, and once this happens, _____________. (this card sucks, sorry.)

Answer 75

increased forces (like larger VT) come from increasing the firing frequency in the motor neurons.

Question 76

Respiratory rate is governed by ________. (not a structure lol)

Answer 76

the interval of time in between expiratory and inspiratory firing.

Question 77

What fibers carry pain?

Answer 77

C and A-delta fibers.

Question 78

How can a nerve block only block pain but not motor control? Why is this especially helpful for keeping someone alive?

Answer 78

A-alpha fibers are very large, so they are difficult to block, and they carry motor control. Whereas C and A-delta fibers are small, carrying pain which is easy to block. If you block a nerve bundle that includes the phrenic nerve, it can continue to transmit respiration signals. This is a genera rule of thumb and is not absolute.

Question 79

What part of the brain can take over voluntary control of breathing?

Answer 79

"higher parts of the brain" e.g. frontal lobe further example: Frontal lobe thinks it wants to increase breathing, which signals to the motor cortex, which will signal to the brainstem to adjust ventilation.

Question 80

During planned exercise, what tells the brainstem to increase ventilation?

Answer 80

Cerebral cortex, to the degree needed to prevent blood gas changes.

Question 81

How often are the chemoreceptors involved in blood gas regulation for exercise?

Answer 81

Usually arent if the patient is healthy. The autopilot system of cerebral cortex should prevent significant blood gas changes that causes the chemoreceptors to get involved.

Question 82

Can baroreceptors be considered as one of the sensors that affect respiration?

Answer 82

yes, i believe.

Question 83

How does paina affect ventilation'?

Answer 83

It can cause sudden increases in breathing or brief periods of apnea, disrupting normal breathing cycle.

Question 84

What is the "main muscle" for breathing

Answer 84

diaphragm, obviously

Question 85

What are the second most involved respiratory muscles?

Answer 85

Intercostal muscles, particularly external intercostal.

Question 86

After the external intercostal muscles, what are the next most involved muscles for breathing?

Answer 86

Internal intercostals and accessory muscles such as sternocleidomastoid and scalene muscles.

Question 87

What muscles are involved during quiet breathing?

Answer 87

Typically only diaphragm

Question 88

What provides the pattern and timing of breathing?

Answer 88

Brainstem

Question 89

If phrenic nerve is damage how can we keep breathing?

Answer 89

Secondary breathing muscles kick in and have to give a ton of effort. Its exhausting, similar to working out, and you will tire out if you have to sustain this way of breathing.

Question 90

How long could the man in the iron lung survive without it?

Answer 90

He had trained his other respiratory muscles to be strong enough to breathe alone for 30-60 minutes each day but it burns a ton of energy and is not sustainable without rest.

Question 91

____ _____ of the lung is typically adequate for normal breathing.

Answer 91

Elastic recoil

Question 92

What is the order of sensitivity for chemoreceptors?

Answer 92

pH (protons) for both central and peripheral, primarily > PCO2 is secondary > PO2 is tertiary

Question 93

How low do oxygen levels have to drop for peripheral chemoreceptor reflexes to kick in? Why?

Answer 93

70mmHg PO2. Often, hypxia coincides with increased acid reduction and that is what triggers the reflex before the low O2 can.

Question 94

What happens to cardiac output if pH is low or PCO2 is high? Whats the result?

Answer 94

Cardiac output increases, as will blood pressure. This helps get rid of excess CO2 by blowing it off. *Remember, gas exchange is perfusion limited, so if you increase perfusion to alveoli, you can increase diffusion amounts. Also, increased cardiac output will recruit more alveoli*

Question 95

How can you increase or decrease blood pressure for a short time without the use of drugs?

Answer 95

Alter their ventilation. E.g. allowing a patient to by hypercarbic will increase their blood pressure.

Question 96

What patient population do you have to worry about blowing off to much CO2? Why?

Answer 96

Patients with heart problems. Blowing off too much CO2 will result in freed up albumin, which needs positive charges since its negative, so then calcium will bind to the freed sites. this drops ionized calcium in the blood, impairing heart function. dont rob their heart of calcium you fuckin calcemic thief.