PULMONARY 08: CONTROL OF RESPIRATION

Question 1

What are the two main tasks that must happen for there to be control of respiration

Answer 1

1. ) Establishment of automatic rhythmic breathing (via inspiratory muscles)
2. ) Accomodation for changing demand, whether this be metabolic, postural/mechanical, or nonventilatory actions (like talking, coughing, etc where you would need to overcome autonomy to do them)

Question 2

What is the order of control of respiration

Answer 2

A central controller leads to outputs in the driving muscles of inspiration, whose effects are interpreted by sensors that feed back to the CNS

Question 3

Four major automatic sites of respiratory control

Answer 3

1. Respiratory control center (ex. medulla)
2. Central chemoreceptors (in CNS)
3. Peripheral chemoreceptors (aortic arch, carotid sinus)
4. pulmonary mechanoreceptors/sensory nerves

Question 4

How does voluntary respiration take place?

Answer 4

Via routing though the motor cortex and corticospinal tracts

Question 5

Control of respiration in the brainstem happens in what major areas

Answer 5

Medulla
DRG (dorsal respiratory group)
VRG (ventral respiratory group)

Pons also does play a role , DRG and VRG are by this

Question 6

DRG controls (inspiration, expiration?) and VRG controls (inspiration, expiration)?

Answer 6

DRG: Inspiration
VRG: Inspiration, expiration

Question 7

Define eupnea

Answer 7

Normal, rhythmic breathing

Question 8

Define dyspnea

Answer 8

Difficulty breathing/respiratory distress

Question 9

What nerve controls the diaphragm?

Answer 9

Phrenic nerve

Question 10

Under normal tidal breathing, do many/any neurons fire during expiration?

Answer 10

No

Question 11

Where are the central chemoreceptors

Answer 11

Ventrolateral surface of medulla oblongata

Question 12

What do central chemoreceptors sense? HOW is it sensing this?

Answer 12

Changes in pH of CSF

Because of the blood brain barrier, hydrogen ions can’t really pass through. However CO2 is highly diffusible. It will cross the BBB and be converted to bicarb and hydrogen ions , and this is what is detected. Thus, they are detecting CO2 in blood indirectly by measuring pH locally

Question 13

What do peripheral chemoreceptors respond to? What is the main component that responds to the gaseous elements?

Answer 13

Decreases in partial pressure of oxygen, pH, or increases in pCO2.

Glomus cells respond to ppCO2/O2 changes

Question 14

What exactly are glomus cells?

Answer 14

Neuron-like cells in clusters that contain many potassium ion channels which respond to changes in gas content. THey then release neurotransmitters and signal to medulla/DRG

Question 15

How much of chemoreception is done by periphery, vs central chemoreceptors?

Answer 15

It’s mostly central chemoreceptors (2/3), the other 1/3 is done by peripheral chemoreceptors

Question 16

Purpose of pulmonary mechanoreceptors . Where are they located?

Answer 16

Prevent overinflation of the lungs (don’t allow for overstretching). They are located in the smooth muscle cells of airways (thus are very sensitive to mechanical changes locally in inspiration)

Question 17

Hering Breur reflexes

Answer 17

Inflation: Inflation of lung inhibits inspiratory muscle activity via vagus nerve
Deflation: Deflation of lung initiates respiratory activity

Question 18

Pulmonary irritant receptors – where are they, what do they respond to?

Answer 18

They are located between airway epithelial cells and can respond to a number of large stimuli (ex. cigarette smoke particles). They may play a role in asthma

Question 19

J (juxtacapillary) receptors and bronchial C fibers - what are they, what do they respond to?

Answer 19

Respond to chemicals in pulmonary and bronchial circulation (J and C respectively). They are located in alveoli and conducting airways and are mechanically stimulated.

Question 20

Nose/upper airway irritant receptors - how are they stimulated and what do tehy do?

Answer 20

Activated duringn diving, aspiration, sneeze refle, whenever something goes down the wrong pipe.

Question 21

What is the prevailing theory as to why we yawn and sigh so much?

Answer 21

It rescues collapsed airways and alveoli by forcing more into that space. This forces them open.

THe action of air moving through also stimulates surfactant release.

Also: As you yawn or sigh, this mechanically breaks up cytoskeleton of SM cell and fluidizes it. As we get to higher generation of airways, SM is the dominant component that regulates the radii of systems. So if they squeeze down, they would hold airway at reduced radius

Question 22

What’s going on when we cough or sneeze?

Answer 22

You create a massive expiratory force against a closed block (glottis). Then the pressure builds up - you have a massive gradient between lower and upper airways. This, followed by tracheal constriction via muscles and a transmural pressure difference leads to a VERY high velocity of flow of air out of the system

Question 23

At any given CO2 level, ventilation is ___ due to peripheral chemoreceptors

Answer 23

Elevated, higher

Question 24

At lower PaO2, ventilation at a given CO2 pressure is ____

Answer 24

Higher

Question 25

Ventilation responses is more sensitive to O2, or CO2?

Answer 25

Co2

Question 26

Slope of CO2 response curve can change in use of ____ , which is clinically important because of…?

Answer 26

Drugs, which is clinically important when you consider surgeries. – patients may not be properly maintaining ventilation rate themselves

Question 27

What is a caveat to the “CO2 affects ventilation rate more than O2” rule

Answer 27

In patients with severe lung disease and chronic CO2 retention, hypoxic stimulus becomes the main stimulus for ventlation

Question 28

Two types of sleep apnea

Answer 28

1. Obstructive sleep apnea (tongue falls to base of throat, epiglottis falls, etc).
2. Central sleep apnea (problem with CNS)

Question 29

What is going on in obstructive sleep apnea

Answer 29

Something is physically obstructing the airway - pleural pressure is going in rhythimc motions, which eventually pulls on system hard enough to wake person up or pull things through system. But because of that block, this isn’t always happening.

Question 30

What is going on in central sleep apnea

Answer 30

Due to a reduction of central feedback system (usually genetic) - loss of airflow, but this is because you’re just not getting the signal from you rbrain to breathe. Tends to only manifest at night.

Question 31

Kussmaul breathing

Answer 31

deep breathing, normal frequency

Question 32

apneustic breathing

Answer 32

Sustained periods of inspiration, quick expiration

Question 33

cheyne-stokes breathing

Answer 33

Rapid hyperventilation followed by breaks

Question 34

Biot’s respiration

Answer 34

Periods of kussmault breathing followed by rest