L18

Question 1

The Bohr effect is characterised by a right shift in the lungs

BECAUSE

Hb has a high affinity for
oxygen at low PCO2.

Answer 1

In the lungs there is a left shift because O2 should be higher than CO2. therefore if the statement said left shift the first statement would be true

right = release 
left = loading

Question 2

• Why do we need to maintain normal levels of O2 and CO2

Answer 2

for metabolic and biochemical stability (e.g pH)

Question 3

O2 usage and CO2 production quite variable. Despite this, O2 and CO2 are normally kept within
close limits.

HOW???

Answer 3

By tight control of ventilation

Question 4

what is the central control

Answer 4

the pons, medulla and other parts of the brain

Question 5

what is the role of the central control

Answer 5

Sets pattern /rhythm of breathing
coordinates sensors and effectors to
maintain respiratory homeostasis

Question 6

what are the sensors that send signals to the central control

Answer 6

chemoreceptors, lungs and other receptors

Question 7

that is the role of the sensors

Answer 7

Receives a variety of neural and chemical inputs from central and
peripheral receptors

Question 8

what are the effectors of the central control

Answer 8

respiratory muscles

Question 9

what is the role of the effectors of the central control (respiratory muscles)

Answer 9

to adjust ventilation

Question 10

what is the role of the respiratory rhythmic centers

Answer 10

Generate cycles of contraction and
relaxation in the diaphragm, establishing
pace of respiration

modify activity in response to chemical and pressure signals

Question 11

what is the Pre-Botzinger complex

Answer 11

• Respiratory rhythm generator

Question 12

what does Inspiratory
center of the dorsal
respiratory group (DRG) do

Answer 12

DRG sends signals to diaphragm and external intercostals for inspiration (just diaphragm at rest and external when you need more) they have no effect on expiratory muscles

Question 13

which of DRG or VRG function at rest

Answer 13

DRG

Question 14

when does Ventral respiratory group (VRG) function

Answer 14

when exercising

Question 15

what is the role of VRG

Answer 15

it controls both expiratory and inspiratory neurons therefore when exercising it signals both to inspiratory and expiratory muscles

Question 16

what is the role of Pre-Botzinger complex (PBC)

Answer 16

PBC is the base generatory of the respiratory system (like the SA node in the heart)

It generates the cyclic contraction and relaxation of the diaphragm and maintains/establishes the normal rate of respiration

Question 17

what respiratory structures are located in the medulla

Answer 17

DRG, VRG, PBC

these are the respiratory rhythmicity centers

Question 18

what is the role of the Apneustic and Pneumotaxic

Centers in the Pons

Answer 18

they Adjust the output of the respiratory

rhythmicity centers

Question 19

what is the Pneumotaxic center also known as

Answer 19

pontine respiratory group (PRG)

Question 20

what is the role of the Apneustic centres

Answer 20

they stimulate DRG

Question 21

what is the role of the Pneumotaxic

Center

Answer 21

to inhibit the Apneustic centres

Question 22

when and why would the Pneumotaxic Center want to inhibit the Apneustic centre

Answer 22

By doing this it stops the inspiratory signals and activates the active exhalation. This happens when you want to push lots of CO2 out of your system as it stops inhalation and cativates expiration

Question 23

what are the higher centres of the respiratory control

Answer 23

• Cerebral cortex
• Limbic system
• Hypothalamus

Question 24

what is the role of the higher centres of respiratory control

Answer 24

Higher Centers
Can alter the activity of
the pneumotaxic centers

The higher centres can override the respiratory system to take control

Question 25

what do chemoreceptors respond to

Answer 25

Respond to a change in the chemical composition of blood or other fluid surrounding it

Question 26

what chemicals are in respiratory system

Answer 26

CO2 + H2O ↔ H2CO3 ↔ H+ and HCO3- and O2

Question 27

where do the different chemicals act

Answer 27

CO2 and H+ acts mainly on respiratory centre | O2 acts mainly through peripheral chemoreceptor

Question 28

what are the 2 types of chemoreceptors

Answer 28

- Central chemoreceptors | - Peripheral chemoreceptors

Question 29

describe the central chemoreceptors

Answer 29

Specialized cells on the ventrolateral surface of the medulla. Sensitive to the PCO2 but not PO2 of blood * Insensitive to hypoxia * Very sensitive to hypercapnia and hypocapnia (as CO2 is easily diffusible across blood brain barrier) * Sensitive to pH of the surrounding extracellular fluid * Insensitive to arterial acidity

Question 30

central chemoreceptors cause what % of the increase in ventilation in response to hypercapnia

Answer 30

~70%

Question 31

where are the peripheral chemoreceptors located

Answer 31

in the carotid and aortic bodies

Question 32

describe peripheral chemoreceptors

Answer 32

• Quite close to but distinct from arterial baroreceptors • Stimulated mainly by decrease in PO2 and an increase in arterial H+ concentration. (note H+ could increase for a number of reasons not just from CO2)

Question 33

which is the predominant peripheral chemoreceptor

Answer 33

• Carotid body input is the predominant peripheral chemoreceptor

Question 34

what are the peripheral chemoreceptors stimulated by

Answer 34

1. hypoxia (decreased O2) 2. metabolic acidosis (increased H+) 3. respiratory acidosis (increased CO2)

Question 35

what is the central chemoreceptors stimulated by

Answer 35

H+

Question 36

explain how central chemoreceptors are stimulated

Answer 36

CO2 diffused across the BBB (H+ is not very good at getting across) in the CSF there is carbonic anhydrase which breaks down CO2 into H+ and bicarbonate H+ acts on the central chemoreceptors

Question 37

Which one of the following is NOT correct regarding the respiratory control centre? A. It is located in the medulla. B. Dorsal respiratory group (DRG) consists of only inspiratory neurons and produce only inspiratory stimulus C.Pre-Botzinger complex is the respiratory rhythm generator. D.Sectioning the brain stem at the level of low medulla leads to respiratory arrest. E. Ventral respiratory group (VRG) neurons produce inspiratory and expiratory stimulus at rest.

Answer 37

E because it says at rest. if it said when exercising then it would be correct

Question 38

Breathing Responses to...

Answer 38

- Hypoxia (decrease in O2) - Hypercapnia (increase in CO2) - Arterial acidity (increase in H+) concentration – not due to changes in CO2

Question 39

what could lead to a decrease in PO2

Answer 39

This decrease in O2 won't usually happen at sea level (might happen if you go up in altitude) therefore a decrease in O2 usually is because of disease like emphysema

Question 40

what happens when PO2 decreases

Answer 40

less O2 is going to diffuse across into the arteries which will be sensed by the peripheral chemoreceptors Any change in PO2 is sensed by the peripheral chemoreceptors which will send signals to the main peripheral chemoreceptors sensor (carotid bodies) which sends signals to the central controller --> DRG which will increase contraction to bring in more O2 When it goes back to normal then the chemoreceptors will stop sending signals

Question 41

when will we get an increase in ventilation (in terms of O2) why

Answer 41

• Total oxygen transport by the blood is not reduced very much until the 𝑃𝑎𝑂2 falls below 60mmHg. • Increased ventilation would not result in more oxygen added to the blood until that point is reached. This has to do with the O2-disassociationion curve . This is because the top part of the curve gives us some flexibility as above 60, Hb is pretty much saturated anyway so there is no point in bringing more in Below 60 has an immediate response to increase O2

Question 42

at what pressure of O2 will we see an increase in ventilation

Answer 42

below 60mmHg

Question 43

what happens when we live in at a higher altitude short term

Answer 43

as you go up the pressure decreases therefore the O2 decreases ↓ inspired O2 ↓ PAO2 ↓PaO2 peripheral chemoreceptors fire, increase in respiratory muscle contraction, increase in ventilation

Question 44

what happens when we live in at a higher altitude long term

Answer 44

the peripheral chemoreceptors stimulate ventilation EPO which is a hormone is secreted by the kidneys which stimulates erythrocyte synthesis resulting in increased Hb conc therefore increasing O2 carrying capacity you also get an increase in skeletal muscle capillary density (from the hypoxia), more mitochondria, and myoglobin which all increase O2 transfer plasma volume can also be decreased to make the blood more concentrated with Hb

Question 45

explain the breathing response to hypercapnia

Answer 45

• Central and peripheral chemoreceptors detect this • Reflex mechanisms controlling ventilation prevent even small increase in arterial PCO2 Any change in CO2 is going to have an effect on out pH Even a small change in Co2 causes a huge change in venterlation (which does not happen with O2 because of the reserve)

Question 46

• Reflex mechanisms controlling ventilation prevent even small increase in arterial PCO2 what diseases is this reflex commonly seen in

Answer 46

• This reflex is commonly seen in emphysema – retention of CO2 – respiratory acidosis • Reduced CO2 – respiratory alkalosis – psychiatric disorders (eg excessive breath holding)

Question 47

CO2 has an immediate effect on breathing as it acts on the central chemoreceptors. This is responsible for 70% of the increase in venterlation what % is peripheral chemoreceptors responsible for

Answer 47

30%

Question 48

what is Metabolic acidosis

Answer 48

– increased lactic acid | during exercise

Question 49

what is Metabolic alkalosis

Answer 49

– loss of H+ by vomiting

Question 50

is metabolic acidosis/alkalosis sensed by peripheral or central chemoreceptors

Answer 50

peripheral as H+ cant get across the BBB

Question 51

describe the Control of ventilation during exercise

Answer 51

When we exercise we are consuming more O2 therefore we are producing more CO2 This is detected by our receptors which cause signals to out muscles to increase ventilation CO2 is not the only reason why we increase ventilation during exercise

Question 52

Exercise can increase alveolar ventilation by how much

Answer 52

• Exercise can increase alveolar ventilation 20-fold

Question 53

what is the main stimulis for ventilation

Answer 53

* The major stimuli for the increased ventilation at moderate exercise is not only due to increased CO2 production * Exercising muscles produce more CO2

Question 54

what is exercises effect on PACO2

Answer 54

• As the alveolar ventilation also increases in exact proportion to the CO2 increase, there is no change. Aleveolar PCO2 = CO2 production / Alveolar ventilation

Question 55

exercise increases venous PCO2 but not arterial PCO2 why is this

Answer 55

This is because... a. the level of arterial PCO2 is determined by alveolar PCO2 b. Alveolar PCO2 is determined by the ratio of CO2 production to alveolar ventilation