Unit 1 Lecture 8: Control of Breathing

Question 1

What determines Palveolar gas?

Answer 1

• Ambient Pgas
• Cell usage (O2) and production (CO2)
• Ventilation Rate (VE)

Question 2

Respiratory centre in the brain is located where?

Answer 2

In the brainstem; it establishes a breathing rhythm

NOTE: Medulla & Pons is where the breathing is regulated

Question 3

What are the dorsal and ventral breathing groups?

Answer 3

• Dorsal consists of inspiratory neurons
• Ventral consists of both inspiratory and expiratory neurons

Question 4

What is the Pre-Botzinger Complex?

Answer 4

Assumption that the packaging of a signal in the medulla and the firing down the nervous system to respiratory muscles to generate ventilation believed to be developed by this complex

Question 5

How does the medulla affect breathing?

Answer 5

It senses signals coming from the body and it will be told when it should send signals to either pick up the breathing or decrease it

Note: Receptors that pick up signals and sends it to medulla

Question 6

What are mechanoreceptors?

Answer 6

Detect changes in pressure, flow or displacement of a structure, and they are practically everywhere (Lung, chest wall, & peripheral muscles)

Doing a bicep curl, mechanoreceptor will sense it.

Question 7

What are metaboreceptors?

Answer 7

Detect changes in Lactic acid and Hydrogen Ions

Essentially changes in metabolic byproduct concentration

REMEMBER: Metabo-reflex is sent to respond to changes in metabolic byproducts (i.e. metabo-reflex to pool blood due to increased metabolites from increased co2 production which will change blood pressure to adapt)

Question 8

What are pulmonary stretch receptors?

Answer 8

Determine how big of a breath should be taken and are always constantly firing

Question 9

What is the Hering-Breuer Reflex?

Answer 9

• Triggered to avoid overinflation of the lungs (mediate tidal volume)
• Activates slow-adapting receptors
• Negative feedback loop

Mediated by the Vagus Nerve

Question 10

Explain what DEMG Activity is and how it works?

Answer 10

• DEMG Activity is an electrode at the level of the diaphragm sensing when medulla sends a burst down phrenic nerve for muscle contraction
• As electrical activity occurs, it generates inspiratory flow and when threshold for inspiration is reached, a signal is sent by stretch receptor to inhibit the DEMG Activity and stop contracting diaphragm

Question 11

How do stretch receptors work in the image below?

Answer 11

When inspiration is occuring, DEMG Activity is on and it allows for contraction of the diaphragm. At the threshold, the stretch receptors activate because the lungs have taken in enough volume and this inhibits the contraction of the diaphragm turning off DEMG Activity. At expiration the stretch receptor slowly turns off as it is no longer needed to deflate the lung

Question 12

What are chemical receptors?

Answer 12

They overlap with metaboreceptors but are fundamentally different as they largely sense fluctuations in O2 and CO2

Question 13

How many groups of chemical chemoreceptors are there and what are they?

Answer 13

Chemical receptors (chemoreceptors) are broken down into peripheral and central medullary receptors

Question 14

Where are the different chemoreceptors located?

Answer 14

Peripheral are found peripheral to the brain (somewhere in blood stream) & central medullary are found in ventral group of medulla

Question 15

What are peripheral chemoreceptors comprised of?

Answer 15

Carotid and Aortic

• Carotid located in the carotid body at the bifurcation of the common carotid artery
• Aortic chemoreceptors are found on the aorta and it senses O2 and CO2 pressure

Carotid body is more sensitive and more influential in maintaining ventilatory responses

Question 16

What happens to VE, when PaO2 decreases?

Answer 16

Ventilation in the peripheral chemoreceptors increases but it is minimal unless PaO2 is critically low (below O2)

• Carotid chemoreceptor senses this and fires to increase arterial O2
• Fires in low arterial O2 situation

Note: Breathing high levels of oxygen inhibit the body

Question 17

Why does a small fluctuation in arterial O2 not cause the carotid body to fire?

Answer 17

If we look at Hb-O2 dissociation curve and look at 80 PO2 of blood we can see that the Hb affinity to bind to oxygen is high. Once it becomes to low and loses the affinity to bind to oxygen which then makes the carotid body fire

Question 18

In terms of peripheral chemoreceptors, changes in H+ does what?

Answer 18

It changes the VE (independent of changes in CO2)

Question 19

What happens when there is excessive loss of fluid from the body? (Production of Non-CO2 acids)

Answer 19

• HCO3- (bicarbonate) is lost which allows for the accumulation of H+ ions/lactic acid which causes blood to become acidic.
• In exercise there is a buildup of lactic acid and hydrogen
• Peripheral chemoreceptors are sensitive to H+ so they will fire to increase ventilation

Question 20

How do central chemoreceptors work?

Answer 20

Senses changes within the brain extracellular fluid

• It responds to changes in pH in the medulla (dorsal part)

NOTE: In the brain there is a blood brain barrier that the CO2 moves in since it is responding so technically it responds to change in CO2

Question 21

What are the central chemoreceptors mainly associated with?

Answer 21

Changes with CO2

• Increase in CO2 will result in more H+ ions and lower pH (acidic)