Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Medicine 1 - Physiology > Control of Ventilation: Chemoreceptors & Acid-Base Balance > Flashcards

Control of Ventilation: Chemoreceptors & Acid-Base Balance Flashcards

1
Q

What does ventilatory control require?

A

Stimulation of the skeletal muscles during inspiration.

This occurs via the phrenic (to diaphragm) and intercostal nerves (to external intercostal muscles).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Is neural input required at rest?

A

At rest, expiration is passive so no neural input is required.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What part of the brain is responsible for ventilatory control?

A

Pons and medulla (respiratory centres)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is ventilatory control entirely dependent on?

A

Signals from the brain (severe spinal cord above the origin of the phrenic nerve) (C3-5) breathing ceases)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What modulates the rhythm of the respiratory centre?

A

Emotion (via limbic system in the brain)

Voluntary control (via higher centres in the brain)

Mechano-sensory input from the thorax (eg stretch reflex)

Chemical composition of the blood (PCO2, PO2, and pH) - detected by chemoreceptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does emotion modulate the rhythm of the respiratory centre?

A

There are pathways that connect the limbic system to the respiratory centres in the brain stem.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does DRG stand for?

A

Dorsal respiratory group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does PRG stand for?

A

Pontine respiratory group - pneumotaxic area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does VRG stand for?

A

Ventral respiratory group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does NTS stand for?

A

Nucleus tractis soolitaris

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which respiratory centre is located in the pons?

A

PRG

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does the VRG supply?

Ventral respiratory group

A

Tongue, pharnyx, larynx, expiratory muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does the DRG supply?

A

Inspiratory muscles via phrenic nerve and intercostal nerve.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the most significant input over modulation of the rhythm of the respiratory system?

A

Chemoreceptor input

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are chemoreceptors?

A

Sensors that detect changes in CO2, O2, and pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the two types of chemoreceptors?

A

Peripheral
Central

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Where are central chemoreceptors found?

A

Found in CNS - located in the medulla

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What do central chemoreceptors respond to?

A

Respond directly to hydrogen ions (H+) - the central chemoreceptors are responding to carbon dioxide, but they do so by directly binding hydrogen ions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

When changes are detected what do central chemoreceptors do?

A

When changes are detected, the receptors send impulses to the respiratory centres in the brainstem that initiate changes in ventilation to restore normal pCO2.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How do central chemoreceptors respond to a rise in pCO2?

A

Increase in ventilation.

More CO2 is exhaled, the pCO2 decreases and returns to normal.

21
Q

How do central chemoreceptors respond to a decrease in pCO2?

A

Decrease in ventilation.

Less CO2 is retained in the lungs, the pCO2 increases and returns to normal.

22
Q

Where are peripheral chemoreceptors found?

A

Found in the carotid and aortic bodies

23
Q

What do peripheral chemoreceptors respond to?

A

Respond primarily to large changes in PO2 and changes in plasma hydrogen ion concentration (h+)

24
Q

What do peripheral chemoreceptors provide?

A

Secondary ventilatory drive

25
Q

What is hypercapnea?

A

Raised PCO2

26
Q

What responses are coordinated to restore pO2?

A

The respiratory rate and tidal volume are increased to allow more oxygen to enter the lungs and subsequently diffuse into the blood

Blood flow is directed towards the kidneys and the brain (as these organs are the most sensitive to hypoxia)

Cardiac Output is increased to maintain blood flow, and therefore oxygen supply to the body’s tissues

27
Q

How do central chemo receptors detect change in arterial pCO2?

A

Via changes in the pH of the Cerebral Spinal Fluid (CSF)

28
Q

How is the pH of the CSF is established?

A

Ratio of pCO2 : [HCO3–].

The HCO3– levels remain relatively constant.

29
Q

How do central chemoreceptors respond when there are changes in the hydrogen ion concentration of cerebrospinal fluid?

A

Increasing rate and depth of breathing.

30
Q

What causes an increase in H+ ions of the cerebrospinal fluid?

A

Raised PCO2 = hypercapnea

31
Q

What change in the cerebrospinal fluid causes ventilation to be inhibited?

A

Decrease in arterial PO2 (reduces CSF (H+)) (hyperventilation)

32
Q

What is the blood brain barrier (BBB)>

A

A specialized system of brain microvascular endothelial cells (BMVEC) thatshields the brain from toxic substances in the blood

33
Q

What crosses the blood brain barrier, CO2 or H+?

A

CO2

34
Q

How the pH of the CSF is inversely proportional to the arterial pCO2?

A

CO2 reacts with H2O, producing carbonic acid, which lowers the pH.

35
Q

What does a small decrease in pCO2 lead to?

A

Increase in the pH of the CSF, which stimulates the respiratory centres to decrease ventilation.

36
Q

What does a small increase in pCO2 lead to?

A

Decease in the pH of the CSF, which stimulates the respiratory centres to increase ventilation.

37
Q

What do those with chronically elevated PCO2 (eg those with COPD) rely on to stimulate ventilation?

A

Changes in PaO2 to stimulate ventilation.

Breathing pattern set by hypoxia so their tissues become hypoxic, as the partial pressure of oxygen in the tissues reduces.

On hypoxic drive

37
Q

What happens if pCO2 levels stay abnormal for an extended period of time?

A

Choroid plexus cells within the blood brain barrier allow HCO3– ions to enter the CSF.

Movement of HCO3– ions alters the pH which in turn resets the pCO2 to a different value.

This can be relevant in certain diseases, such as Chronic Obstructive Pulmonary Disease (COPD).

38
Q

What do those on hypoxic drive rely on?

A

Peripheral chemoreceptors are the ones that are providing secondary ventilatory drive for most of us, but which become much more important in individuals with chronic lung disease who are on ‘hypoxic drive’.

They are then fully reliant on these peripheral chemoreceptors.

39
Q

What is considered a significant fall in arterial PO2?

A

<60mmHm - consider haemoglobin disassociation curve

40
Q

What does an increase in H+ accompany?

A

A rise in arterial PCO2- mainly do that through hydrogen ions that are generated as a result of an increase in PCO2.

41
Q

Why do peripheral chemoreceptors not do much until arterial PO2 falls below 60?

A

Because stimulating ventilation when the partial pressure of oxygen in plasma is more than 60, would add very little oxygen onto the haemoglobin because it’s already more than 90 percent saturated.

However, when our PO2 falls below 60, we then start going into the deep part of the oxygen-haemoglobin curve. And at this point here, small changes in PO2 will have a much more significant effect on the saturation of haemoglobin.

42
Q

What happens if plasma pH falls?

A

If plasma pH falls ([H+] increases) ventilation will be stimulated (acidosis)

43
Q

What happens if plasma pH increases?

A

If plasma pH increases ([H+] falls) e.g. vomiting (alkalosis), ventilation will be inhibited.

44
Q

What chemical equation regulates acid/base balance in the body?

A

CO2 + H20 ⇌ H2CO3 ⇌ H+ + HCO3-

45
Q

What can alter plasma pCO2?

A

Hypo/hyperventilation

46
Q

What does hypoventilation cause?

A

Hypoventilation, causing CO2 retention, leads to increases [H+] bringinabout respiratory acidosis.

47
Q

What does hyperventilation cause?

A

Hyperventilation, blowing off more CO2, leads to decreased [H+] bringing about respiratory alkalosis.

48
Q

What happens to ventilation during moderate exercise?

A

Ventilation increases in exact proportion to metabolism, but the signals causing this are not known.

The arterial PO2 and PCO2 to remain unchanged and thus do not drive the increased ventilation.

Medicine 1 - Physiology (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions