Control of Respiration

Question 1

Ventilation vs respiration

Answer 1

Ventilation- process of moving air in and out the lungs (mainly regulated by CO2)

Respiration- the process involved in the exchange of gases between the cells

Question 2

SEnsor, effectors and controllers

Answer 2

Sensors- chemoreceptors, stretch receptors

Effectors- respiratory muscles

Controller- respiratory centers

Question 3

Where is central control of breathing?

What does it regulate?

Answer 3

ANS at the medulla and pons (brain stem) as well as cerebral cortex.

Depth of ventilation and frequency

Question 4

How can you increase frequency and contract/breath size?

Answer 4

Frequency- more AP/minute

Depth- more AP/burst

Generally both of these increase together to increase ventilation

Question 5

What happens at the respiratory center?

Answer 5

This is the rhythm generator. Burst of AP originate here and conduct down the phrenic nerve stimulating the diaphragm

Question 6

What happens in the expiratory center?

Answer 6

Normally expiratory is passive process which relies on elastic recoil of lungs and chest wall.

During exercise these neurons fire when inspiration muscles are silent stimulating expiratory muscles

Question 7

What does the pons control in breathing>

Answer 7

They control the apeustic center which does prolonged inspiration by quick expiration.

this breathing is seen by directly stimulating the apeustic center.or when the connection between the apneustic and pnemotaxic (inhibitory) is severed

Question 8

What does the pneumotaxic center control

Answer 8

It inhibits apneustic center by terminating inspiration and controls the depth of breathing

The pneumotaxic center can be overridden by temp, emotion and voluntary (breath holding, hyperventilation, speech)

Question 9

Four things that stimulate ventilation

Answer 9

1. Exercise (linear)
2. CO2 (linear)
3. pH
4. O2 (non linear)

Question 10

List all receptors for breathing

Answer 10

1 Stretch receptors
2Irritant receptors
3 Joint and muscle receptors
4 Juxtacapillary receptors (in alveolar walls and sense engorgement)
5. Chemoreceptors (in medulla)
6. Peripheral receptors (in carotid and aortic)

Question 11

How do stretch receptors work?

Answer 11

Located in airway walls and they respond to mechanical stretch. When lungs are inflated more than 50% above resting volume further inflation is prohibited

Question 12

Irritant receptors function and location?

Answer 12

Location- airway epithelium and send afferent signals to vagus nerve.

Stimulated by irritants like smoke, dust, hisamine (released in asthma) and reponses like coughing sneezing and bronchoconstriction

Question 13

What directly stimulates the central chemorecptors?

Answer 13

H+ in the CSF. H+ isn’t permable to the BBB but CO2 is.

1. CO2 diffuses into the CSF where it spontaneously forms carbonic acid which disscoaites into the H+ and HCO3-

Question 14

Explain the buffer response when H+ is in the CSF

Answer 14

There isn’t really one. Most times protein acts as a buffer, but the lack protein in CSF means any changes in PaCO2 translate to changes in CSF pH

Question 15

When would we expect increased ventilation

Answer 15

When CO2 increases (so HCO2 and H+ increase) and pH decreases because we want to blow of fthe CO2.

The central chemoreceptors are responding to the increase in H+

Question 16

Direct and indirect to chemoreceptors

Answer 16

Direct- H+

Indirect- Parteral of CO2 (because of how it crosses BBB and becomes H= and HCO3-)

Question 17

SHape of central chemorecptors response

Answer 17

Linear- 1 torr increase leads to 4 L.min increase
Very sensitive to small changes in Alveolar

Slope is steeper if hypoxic

Question 18

Do central chemorecptors adapt? Explain

Answer 18

Yes! After days of sustained change (increase or decrease) in PCO2 Alveolar (edema, COPD or high altitude (low CO2) a non respiratory response regulates CSF and restores H+ back to normal .

Question 19

When are the central chemocrecptors response lowered? (4)

Answer 19

1 Sleep

2. Old ppl.
3. Trained athletes
4. Drugs (anesthesia)

Question 20

Important factors about peripheral chemoreceptors

1. What do they respond to? 
Where?
Shape of graph? 
Adaptation abilities?
precentage of ventilation that they are responsible for? 

Fast or slow response

Answer 20

1 .Hypoxia- to PP of O2 not the content- so no response in anemia (also respond to hypercapnia (high PCO2 and acidosis(low pH) - overall response elevated when are three are effected

2. Carotid!! and aortic arch
3. Non linear- small changes in PaO2 only show small change but when PaO2 is below 60 the response is great
4. No adaptation
5. 20% importance in normal breathing
6. Fast response

Question 21

What happens when the glomes cells in the carotid body are anoxic for 2 mins?

Answer 21

Inhibits K+ channels
Leads to a burst of AP
Leads to influx of Ca2+
Release of NT
More EPSPs
Increase info to medullary respiration response

Question 22

Why does exercise increase ventilation so efficiently?

best guess?

Answer 22

We don’t know! there is no change in PaO2, PaCO2 or pHa.

The response to increase ventilation is almost immediate before blood gases level cans change so it is believed that the response is neurally mediated. The more gradual changes in between may be due to hormonal or blood borne.

Question 23

Differnece in arterial/venous saturation in

1. Normal patient
2. Patient that starts with subnormal values

Answer 23

1. Arterial should remain fairly constant even with exercise,while venous saturation decreases with exercise but returns to normal almost immediatley
2. With dysfunction venous Hb saturation decrease dramatically with exercise because the patient can’t increase CO and muscles only get what the heart delivers. Arterial Hb saturation should remain the same during exercise even if they have heart failure.

** remember PO2 doesn’t change during exercise so can’t increase ventilation***

Question 24

Effectors

Answer 24

Respiratory receptors get message from medulla and send AP through phrenic to the diaphragm. Diaphrgam gets help from inspiration intercostals, scalene muscles when needed.