Control of ventilation Flashcards Preview

Respiratory System > Control of ventilation > Flashcards

Flashcards in Control of ventilation Deck (20)
Loading flashcards...
1
Q

How does the stimulation of the skeletal muscles of inspiration occur?

A

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

2
Q

Where does ventilatory control reside?

A

Resides within ill defined centres located in the pons and medulla (Respiratory Centres).

3
Q

How do respiratory centres set an automatic rhythm of breathing?

A

through co-coordinating the firing of smooth and repetitive bursts of action potentials in DRG (dorsal respiratory group) - travel to inspiratory muscles.

4
Q

How do respiratory systems have their rhythm modulated?

A
  1. Emotion (via limbic system in the brain)
  2. Voluntary over-ride (via higher centres in the brain)
  3. Mechano-sensory input from the thorax (e.g. stretch reflex).
  4. Chemical composition of the blood (PCO2, PO2 and pH) - detected by chemoreceptors.
5
Q

What is the most significant out of the following inputs:
Emotional

Voluntary

Chemoreceptor

Mechano-sensory receptor

A

Chemoreceptor input is the most significant

6
Q

What are the 2 main chemoreceptors?

A

Central and Peripheral chemoreceptors

7
Q

Features of central chemoreceptors

A
  • Medulla
  • Respond directly to H+ (directly reflects PCO2)
  • Primary ventilatory drive
8
Q

Features of peripheral chemoreceptors

A
  • Carotid and aortic bodies
  • Respond primarily to plasma (H+) and PO2 (less so to PCO2)
  • Second ventilatory drive
9
Q

What is hypercapnia?

A

Raised PCO2
- It is when you have too much carbon dioxide (CO2) in your bloodstream. It usually happens as a result of hypoventilation, or not being able to breathe properly and get oxygen into your lungs

10
Q

How is ventiliation reflexly inhibited?

A

Ventilation is reflexly inhibited by a decrease in arterial PCO2 (reduces CSF [H+])
(hyperventilation)
- It doesn’t respond to changes in plasma (H+).

11
Q

What chemical movement occurs when arterial PCO2 increases?

A

CO2 crosses the blood-brain barrier but H+ does not.

12
Q

What type of chemoreceptors monitor the PCO2 indirectly in the cerebrospinal fluid?

A

Central chemoreceptors

13
Q

How does decreased arterial PCO2 affect ventilation rate?

A

It slows ventilation rate

14
Q

What action do peripheral chemoreceptors carry out following significant fall in arterial PO2 (consider haemoglobin dissociation) or a rise in [H+] ?

A

Cause reflex stimulation of ventilation

15
Q

What occurs to ventilation if plasma pH falls (H+) increases?

A

Ventilation will be stimulated (acidosis)

16
Q

What occurs to ventilation if plasma pH increases (H+) decreases?

A

Ventilation will be inhibited (alkalosis) e.g. vomiting

17
Q

What do Descending neural pathways from cerebral cortex to respiratory motor neurons allow?

A

They allow a large degree of voluntary control over breathing.

18
Q

What mechanism occurs in Hyperventilation?

A

Ventilation is reflexly inhibited by an increase in arterial PO2 or a decrease in arterial PCO2/[H+]

19
Q

Why is respiration inhibited during swallowing?

A

To avoid aspiration of food or fluids into the airways.
Swallowing is followed by an expiration in order that any particles are dislodged outwards from the region of the glottis.

20
Q

Examples of common drugs that affect respiratory centres

A
  • Barbiturates and opioids depress respiratory centre
  • Most gaseous anaesthetic agents increase RR but decrease TV so decrease AV
  • Nitrous oxide