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Flashcards in Ventilatory Control Deck (41):
1

Breathing Pattern - Inspiration

Progressive increases in diaphragm activation
Lungs fill a constant rate until end of tidal volume
Activation of inspiratory muscles ceases

2

Breathing Pattern - Expiration

Relaxation of Inspiratory muscles (dia relaxes)
Elastic recoil allows for passive expiration
Activation of inspiratory muscles controls rate of expiration

3

Feedforward Control

Ventilation adjustment based on exercise (muscle contraction) or motor activity
Apparent particularly at onset of exercise
Doesnt require much, it just does it...but with exercise the feedforward sys stimulates ventilatory response proportional to amount of muscle you have contracting

4

Feedback Control

Allows for matching of response to some control value
Requires a sensor, and a comparator (sensor, controller, and effector)

5

Pre-Botzinger Complex

Rhythmic inspiration initiated by pacemakeer cells in the PBC
Located in the medulla
Stimulates ventilation and inhalation to occur
Between lateral reticular nucleus and nucleus ambiguous

6

Respiratory Centers

1. Medullary respiratory center - the rhythm generator
2. Pntine (pneumotaxic) respiratory group: fine tuning

7

Medullary Respiratory Center

PBC - initiates inspiration
Dorsal Respiratory Group - Stimulates to diaphragm - activates phrenic and allows for continuous inspiration
Ventral Respiratory Group - Stimualtes the intercostal and abdominal muscles - When respiratory drive inc (exercise) VRG is recruited, contributes to inhalation and exhalation, sends powerful signal for forceful exhalation

8

Pontine Respiratory Group

Transmits signal to the inspiratory area to limit inspiration
Controls the switch off point of the inspiratory ramp
Causes the shut off of inspiration - so shuts down DRG

9

Normal Breathing Pattern Firing

PBC - initiate inhale
DRG - inhale
PRG - shut down DRG and leads to passive exhale

10

What are the things that we are sensing and what is the effector response

Chemoreceptors
Mechanoreceptors
Input from working muscle (spindles)
Response - phrenic and other muscles for respiration

11

Reflex - Pulmonary Stretch Receptors

Mechanoreceptors
Located in smooth muscle airways
Slowly adapting receptors - they will fire anytime there is a stretch and say when need to shut down inspiration so can stop to exhale and can have another inhale (inhibits the DRG)
Increases resp rate
Prolongs expiration

12

Reflex - Chest Wall Proprioceptors

Muscle spindle and GTOs

13

Reflex - Irritant Receptors

Located btw airway epithelial cells in larger airways
Rapidly adapting receptor - firing is proportional to lung volume amount and rate of change
Responds to chemical and mechanical stimuli
Cough reflex. sneezing, bronchoconstriction, rapid breathing

14

Reflex - Juxtacapillary Receptors (C fiber endings)

Unmyelinated and serve protective function
Give feeling of dyspnea
Two groups
1. Pulmonary C fibers - located next to alveoli and are sensitive to mechanical events (edema)
2. Bronchial C fibers - located in airways, responsive to inflammatory events

15

Reflex - Central Chemoreceptors

Located in medulla and are sensitive to H+ in the ISF
H+ can't cross, so CO2 crosses, binds with water, and then is converted into H+ and HCO3-
HCO3- is buffer in CSF

16

Reflex - Peripheral Chemoreceptors

Located in carotid and aortic bodies
Unlike central, they are sensitive to PaO2

17

More sensitive driver for ventilation

CO2
If hold breath, inc response from CO2
People hyperventialte before holding breath so that CO2 gets low so that then you dont get a sens of needing to breathe for longer period of time

18

As you inc arterial PCO2

(normally at 40)
As inc, sensed by central chemoreceptors

19

PO2, as you drop ventilation...

100, as drop ventilation, not much of anything is happening until at hypoxic level of like 60 or so and this is sensed by the peripheral chemoreceptors

20

Kidneys vs. Lungs

Kidneys = Bicarbonate Control
Lungs = pCO2 control
Acid/base balance - kidneys and lungs play role in keeping this balance

21

Acid Base Chemistry - Acid

Proton Donor
H+ - molecule that can liberate H+ ions

22

Acid Base Chemistry - Base

Proton Acceptor
Molecule that is capable of combining with H+
Bicarbonate --> Carbonic Acid

23

Buffer

Minimizes pH changes but doesn't add or remove acid from the body
Bicarbonate is Ex

24

pH

Measure of H+ ion concentration
The more acid = the lower the pH

25

Normal pH

7.4

26

Abnormal pH

Inhibit ATP production
Interfere with muscle contraction

27

Acid Base balance is maintained by

buffers
- Release H+ ions when pH is high
- Accept H+ ions when pH is low

28

Tolerable limits for pH
Muscle
Urine

6.9 - 7.5
Muscle with normal breathing = 7-7.1
Urine = 4.5-8

29

Acidosis

A lot of H+
1. Resp. Acidosis (Inc pCO2)
2. Metabolic Acidosis (dec HCO3-)

30

Alkalosis

1. Resp Alkalosis (dec PCO2)
2. Metablic Alkalosis (inc. HCO3-)

31

Respiratory

Issue with CO2
Acidosis = high pCO2 (comp with raise bicarb)
Alkalosis = low pCO2 (comp with low bicarb)

32

Metabolic

Issue with Bicarbonate
Acidosis = low bicarb (comp with low pCO2)
Alkalosis = high bicarb (comp with raise pCO2)

33

1st line of defense against acid-base status

Intra and Extracellular buffers
Immediate
Ex = Buffers

34

2nd line of defense against acid base status

respiratory compensations
1 to 15 minutes
Ex: blowing out more CO2

35

3rd line of defense against acid base status

kidney compensations
Most powerful
hours to days
kidney can alter how much acid or base we have

36

Buffers

Combine with acid or base to buffer
Intracellular = bicarbonate and proteins
Extracellular = bicarbonate and phosphates

37

Bicarbonate Buffering System

Can go either way
Eqn to the right = to the tissues, more acid produced and buffer with bicarb
Eqn to the left = go to lungs, excrete CO2 by blowing out

38

Respiratory Compensations

2nd line of defense
Inc Ventilation, exhale more CO2
Stimulated by inc H+ (acidic) --> so this reduces H+ and blood pCO2
CO2 exhalation has to match CO2 production though
Need carbonic anahydrase

39

Renal Compensation

3rd line of defense
Urinary excretion of H+ (acid) and sometime bicarb
Kidneys dont excrete free H+ - 2/3 of it is excreted with ammonia
Most bicarb filtered in kidneys is reabsorbed back into the bloodstream

40

What is decreased at altitude

Decreased O2 diffusion
Decreased pO2 in the air as go to altitude

41

Hyperventialtion shifts the curve...

Left - pH going up
Hypoxemia --> paO2 is low --> peripheral chemo --> hyperventilate --> Inc PaO2 and dec PaCO2 --> resp alkalosis --> Inc pH