Neural Control Of Breathing

Question 1

Why do you need to modulate the rate of ventilation?

Answer 1

Efficiency

If you expel too much CO2, alkylysis is caused

Question 2

How are the right balances in blood gases maintained?

Answer 2

By maintaining pressure gradients between alveoli and blood

Question 3

Why does the O2 demand increase in exercise?

Answer 3

Increased ATP production, and increased consumption of O2

Question 4

Ventilation=

Answer 4

Tidal volume x respiratory rate

Question 5

Why does just hyperventilating not have much effect on O2 delivery?

Answer 5

Hb is 98% saturated at rest so hyperventilating won’t change that

Question 6

What provides the contractile signal for the respiratory muscles?

Answer 6

Innervation from motor neurones that synapse from the descending spinal tract

Question 7

What muscles are used in inspiration?

Answer 7

In quiet breathing: diaphragm

Increased/forced inspiration: external intercostals, pectorals, sternomastoid and scalene

Question 8

What muscles are used in expiration?

Answer 8

In quiet breathing: elastic recoil

Increased/forced ventilation: elastic recoil, internal intercostals and abdominals

Question 9

What is the breathing pattern generated by?

Answer 9

Neuronal systems within the brainstem

Question 10

What things do the central pattern generator use to determine the rate and depth of breathing?

Answer 10

• cerebral cortex
• pain and emotional stimuli (hypothalamus)
• peripheral chemoreceptors increase breathing
• central chemoreceptors increase
• receptors in muscles and joints increase
• stretch receptors in lungs inhibit
• irritant receptors inhibit

Question 11

How do central chemoreceptors indirectly respond to changes in arterial pCO2?

Answer 11

They monitor arterial CO2 in the medulla

Question 12

Why do central respiratory chemoreceptors not respond to changes in [H+]?

Answer 12

H+ doesnt cross the blood brain barrier

Question 13

What are peripheral chemoreceptors activated by?

Answer 13

Decreased paO2 and increased paCO2

Question 14

What do peripheral chemoreceptors do when activated?

Answer 14

Signal to respiratory centres in medulla to increase ventilation

Question 15

Where are peripheral chemoreceptors found?

Answer 15

Carotid artery and aortic bodies

Question 16

What happens when you fall asleep (relating to ventilation)?

Answer 16

• decreased metabolic rate (as less respiratory demands)
• postural changes alter the mechanics of breathing
• decreased SNS and increased PNS tone
• decreased heart rate, blood pressure and cardiac output
• decreased tidal volume, breathing frequency and minute volume
• decreased O2 and increased CO2 concs

Question 17

What can cause ventilation disfunction (6)?

Answer 17

• trauma
• stroke
• drugs
• congenital central hypoventilation syndrome
• neonates
• altitude

Question 18

How can trauma cause respiratory malfunction?

Answer 18

Damage to respiratory centres in the brain stem

Question 19

How can a stroke cause respiratory malfunction?

Answer 19

Ischaemia-induced brainstem tissue injury

Question 20

How can drugs (eg opioids) cause respiratory malfunction?

Answer 20

Suppression of neuronal activity

Question 21

Why may neonates suffer from respiratory malfunction?

Answer 21

Incomplete development of respiratory centres prior to birth

Question 22

How can altitude cause respiratory malfunction?

Answer 22

Control systems unable to cope with abnormal atmospheric environment (low O2 and CO2)

Question 23

What is sleep apnoea?

Answer 23

Temporary stopping of breathing during sleep

Question 24

What is the minimum and maximum length and regularity of sleep apnoea periods?

Answer 24

5-160 per hour

10-90 seconds

Question 25

What are the health effects of sleep apnoea?

Answer 25

• Tiredness (poor sleep quality)
• CV complications (stress + increased SNS tone)
• obesity/diabetes (inflammation and metabolic disfunction)

Question 26

What is cheyne-stokes respiration?

Answer 26

Oscillating apnoea and hyperapnoea (stopping breathing then hyperventilating)

Question 27

What are the steps in cheyne-stokes respiration?

Answer 27

(It’s a circle but)
Hypercapnia/hypoxaemia -> compensatory hyperventilation -> hypercapnia+ alkalosis -> decreased respiratory drive -> compensatory hypoventilation -> (back to start)