Control of Ventilation

Question 1

what is the role of the respiratory chemosensors?

Answer 1

they monitor CO2, O2 gas levels in the system and they send a signal up to the central controller- which then tells our respiratory muscles to increase or decrease activity - the respiratory control system is based on a negative feedback system

Question 2

what is the main region of the brain in control of respiration?

Answer 2

the Medulla of the brain stem - contains a cluster of neurons which control respiration-

• medullary respiratory center
• pons respiratory center

Question 3

what are the two main clusters of neurons in the medullar respiratory center?

Answer 3

the dorsal respiratory group and the ventral respiratory group.

Question 4

when inspiratory neuron fibers fire- what occurs?

Answer 4

it induces muscle contraction and therefore inspiration - but their inhibition then induces exhalation

*so you can think of them as controlling both inspiration and exhalation - where exhalation is passive*

Question 5

during what action are inspiratory and expiratory ventral respiratory group neurons inactive?

Answer 5

they are both inactive during quiet breathing

• they are utilized when damad for ventilation is increased beyond normal (active expiration)

Question 6

which respiratory group is most often quiet?

Answer 6

the ventral respiratory group

Question 7

describe the generation of respiratory rhythm?

Answer 7

the neurons in the pre-botzinger complex- constantly fire and activate inspiratory neurons in the dorsal group which then activate muscles

so this pre-botzinger complex sets the pace of breathing

Question 8

the role of the pons respiratory center is what?

Answer 8

composed of two clusters of neurons ( the pneumotaxic center and the apneustic center) - it fine tunes our breathing

Question 9

what is the pneumotaxic center’s role?

Answer 9

•Pneumotaxic centre sends signals to the DRG that help silence/inhibit the inspiratory neurons.- prevents overinspiration

Question 10

What is the role of the apneustic center?

Answer 10

•Apneustic centre conversely prevents the inspiratory neurons from being switched off.

Question 11

what occurs if the pneumotaxic center is damaged?

Answer 11

you get really long isnpiration and really short exhalation

Question 12

what other regions of the brain can affect respiration?

Answer 12

cortex = can exert voluntary control of our breathing-

limbic system and hypothalamus = emotional states - ‘sobbing’

Question 13

main effectors of the inspiration/exhalation

Answer 13

•1. Diaphragm- phrenic nerve

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•2. Intercostal muscles- intercostal nerves

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•3. Abdominal Muscles-

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•4. Accessory muscles- neck muscles - activated in patients extremely short of breath

Question 14

what are the different sensors of the respiratory control system?

Answer 14

chemoreceptors

lung receptors

other receptors

Question 15

what are the two main types of chemoreceptors?

Answer 15

central and peripheral chemoreceptors

Question 16

what is a chemoreceptor?

Answer 16

•Specialised tissue that respond to changes in the chemical composition of the blood or other fluid.

Question 17

where are the central chemoreceptors found?

Answer 17

in the central nervous system

Question 18

what is the most important regulator of ventilation?

Answer 18

the central chemoreceptors - they respond to a chnage in pH of the cerebrospinal fluid or the blood

Question 19

does cerebrospinal fluid have a greater or lesser buffereing copacity than plasma?

Answer 19

cerebrospinal fluid has a lesser buffereing ability than plasma - so a small change in pH is detected very quickly

Question 20

someone who hyperventilates often - what prevents them from having consisently lowered pH of the cerebrospinal fluid?

Answer 20

the ependymal cells - which act as a ‘kidney’ for the cerebrospinal fluid - therefore even if your plasma pH has dropped quite substantially, this regulates your pH around the brain so there is no lasting damage

Question 21

were are peripheral chemorectors found?

Answer 21

carotid bodies

and aortic bodies

Question 22

where are the carotid bodies found?

Answer 22

where the carotid divides into external and internal -

Question 23

how do the aortic bodies communicate with the brian?

Answer 23

through the vagus nerve

Question 24

what type of cells make up the carotid body receptor?

Answer 24

gloma cells

Question 25

peripheral chemoreceptors are more or less sensitive to arterial oxygen than carbon dioxide?

Answer 25

they are most sensitive to changes in oxygen

Question 26

although the peripheral chemorecptors are sensitive to changes in oxygen - how low does the oxygen have to be to induce a response?

Answer 26

it would have to be at about 60 mmHg O2 before a response is elicited

Question 27

why are chemoreceptors not activated in carbon monoxide poisoning?

Answer 27

because the arterial O2 content is not changed - the chemoreceptors observe ‘total’ oxygen levels in blood

Question 28

why are the carotid chemoreceptors placed where they are?

Answer 28

they are strategically placed in an area of the body with an extremly high blood flow

Question 29

what are the lung receptors of the boody?

Answer 29

•1. Pulmonary stretch receptors (slowly-adapting pulmonary stretch receptors) Hering-Breuer reflex

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•2. Irritant receptors (rapidly-adapting pulmonary stretch receptors)

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•3. Juxta-capillary receptors (J-receptors)

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•4. Bronchial C fibers

Question 30

what is the Hering-Breuer reflex?

Answer 30

it is a stretch reflex -they prevent overinflation of the lungs-

Question 31

what are the irritant receptors of the lungs?

Answer 31

they are activated by breathing in irritants - like cold air, smoke, fog, toxins etc - when activated they are associated with broncho restriction

Question 32

Juxta capillary receptors induce what?

Answer 32

they induce rapid shallow breating classical of pulmonary oedema

Question 33

response to CO2 is altered by what ?

Answer 33

response is altered by sleep, age (our CO2 levels are higher with age) and genetics

Question 34

what molecule is the main driver of ventilation? oxygen or carbon dioxide?

Answer 34

carbond dioxide-

Question 35

what is the response to a reduced pH?

Answer 35

•Sensed by peripheral chemoreceptors

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•Important in metabolic acidosis

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•If reduction is severe carotid chemoreceptor may be stimulated

Question 36

what are the two types of sleep apnea?

Answer 36

obstructive- very common - often associated with obesity and can lead to further sleep deprivation and associated cognitive issues

central = respiratory depression during sleep - recognized by the absense of respiratory effects