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Physiology and Pharmacology > Neuro and chemical control of breathing > Flashcards

Neuro and chemical control of breathing Flashcards

1
Q

Describe the involuntary and voluntary input of neural input in breathing

A

Tidal breathing- involuntary

IRV, ERV, breathing frequency- voluntary

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2
Q

What maintains ventilatory homeostasis?

A

Chemo-receptive inputs monitor plasma and cerebral spinal fluid composition

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3
Q

Where are the respiratory centres of the brain?

A

Brain stem under hypathalamus ; pons and medulla

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4
Q

What are the two centres of the control centres in the brains tem called?

A

Pons respiratory center

Medulla respiratory centre

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5
Q

What centres are within the pons respiratory?

A

Pneumotaxic center

Apneustic center

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6
Q

What centres are within the medulla respiratory?

A

Pre-Botzinger complex
Dorsal respiratory complex
Ventral respiratory complex

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7
Q

What groups do inspratory group require?

A

Dorsal and ventral respirator group

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8
Q

What groups do expiratory group require?

A

Mainly from Pre-botzinger complex in ventral respirator group

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9
Q

Describe the dorsal respiratory group (DRG)

A
  • Inspiratory control
  • Located within the nucleus tracts solitaires and is dorsal to VRG
  • Site of sensory info input
  • Site of central chemoreceptor input
  • Some premotor neurons
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10
Q

Describe the ventral respiratory group (VRG) and what 3 regions it spans within the medulla

A

Rostral - Expiration control (Botzzinger complex)
Intermediate- Inspiration control mediated through Pre-botzinger complex - thought to be site of respiratory pattern generator
Caudal- Expiration control

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11
Q

Describe the innervation of the respiratory muscles-nerves

A

Hypoglossal nerve
Laryageal
Carotid sinus- Peripheral chemoreceptor feedback

Vagus nerve- Breathing frequency and volume

Intercostal nerve- Respiratory muscles

Phrenic nerve- Diaphragm inspiration control

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12
Q

Why are expiratory muscles passive during quiet breathing?

A

Elastic recoil pressure is sufficient

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13
Q

What muscles are required during forced expiration?

A

Abdominal wall

Internal intercostals

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14
Q

What is a respiratory rhythm generator?

A

A network of interneurons that produce a predictable and repetitive motor pattern. In the case of breathing, inspiratory neurons must be activated before expiratory neurons

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15
Q

What are properties of RRG?

A
  • Always active even in the absence of concious input (endogenous cyclical oscillation)
  • Transmit in an orderly sequence to respiratory muscles
  • Respond to inputs from other parts of the brain (eg limbic system-emotions as well as sensory afferents(eg pulmonary stretch receptors, peripheral chemoreceptors))
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16
Q

What are the three recognised phases of breathing?

A

Inspiration
Post-inspiration
Late expiration

17
Q

What are the 6 types of neuronal discharge released from phases of breathing?
I (inspiration)
E (expiration)

A 
Pre-I
Early-I
I
Late-I
Early-I
E
18
Q

What happens in Phase 1?

A

Neurons inhibit expiratory neural circuit

Expiratory muscles relax

19
Q

What happens during Early-I?

A

Early-I neurons inhibit output from entire RRG

Refractory period. No breathing movements

20
Q

What happens during I?

A

Neurons ramp fire. As frequency increases so more I neurons contribute. Activate motorneuron circuit to inspiratory muscles and inhibit E and Pre-I neural circuits
Inspiratory muscles contract as intensity of I firing increases Exp muscles relaxed

21
Q

What happens during Late-I?

A

Neurons feedback to suppress I neuronal firing when at peak intensity. May involve stretch receptor input (eg from vagus)
Inspiratory muscles relax and lung begins to deflate due to elastic recoil

22
Q

What happens during Early-E?

A

Neurons repress all I and E neuronal firing. Creates refractory period at peak inhalation
Inspiratory muscles relax and lung begins to deflate by elastic recoil

23
Q

What happens during E?

A

Neurons ramp fire. Activate motoneuron circuit to expiratory muscles. Major point of conscious inout into breathing (eg during exercise)
Expiratory muscles contract as e firing intensity increases Insp muscles relaxed

24
Q

What nerve innervtaes diaphragm?

A

Phrenic nerve

25
Q

What happens if there is an increase in tidal volume?

A

Breathing frequency remains same

Stronger diaphragm contraction and deeper breathing

26
Q

What is involved in the regualtion of involuntary breathing?

A

Controller which recieves sensors that turn into effectors

27
Q

What are central chemoreceptors?

A

Monotor pCO2 in cerebral spinal fluid

28
Q

What are peripheral chemoreceptors?

A 
Carotid body (blood)
Neuroepithelial bodies (airways)
29
Q

Where are central chemoreceptors located and what is their contribution to normal control of breathing?

A

Medulla (surface)

80%

30
Q

Where are peripheral chemoreceptors located and what is their contribution to normal breathing?

A

Arterial vasculature and airway

20%

31
Q

How is CO2 carried in blood?

A

HCO3 bicarbonate

32
Q

What are very sensitive to changing pCO2?

And what makes the response even steeper?

A

Central chemoreceptors

Hypoxia allows for a bigger change in Ve per pACO2-brings cells closer to firing threshold

33
Q

What does hyperventilation do to pACO2? Explain a shallow water blackout

A

Drives it down

Then O2 is consumed during breath hold dive
Low central chemoreceptor sensitivity (caused by breath-holding training) fails to trigger breathing response in time to prevent severe hypoaemia
This causes a loss of consciousness and drowning

34
Q

Peripheral chemoreceptors are located where?

A

Carotid body- carotid sinus

Aortic body- aortic arch

35
Q

What is a peripheral chemoreceptor’s primary response to?

A

Hypoxia

Also hypercapnia and acidosis

36
Q

Is the response to hypoxia linear?

A

No - driven by low low partial pressure of O2

37
Q

Describe the basics of the cellular mechanism of chemoreception

A

O2 DECREASE, pH DECREASE, CO2 INCREASE-Causes depolarisation of O2 or pH sensor

This causes an opening of voltage gated calcium channels where Ca2+ enters the cell

There is then a release of neurotransmitters into the glossopharyngeal nerve and into the brain stem or either DRG or RRG

Brain stem- Hypoxic ventilatory response

DRG RRG- Hypoxic pulmonary vasoconstrictor response (rise in pulmonary artery pressure)

38
Q

What channels regulate chemoreceptor membrane potential?

A

K+ channels

Physiology and Pharmacology (22 decks)

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