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Respiratory - Week 2 > Respiratory: Physiology - Control of Respiration > Flashcards

Respiratory: Physiology - Control of Respiration Flashcards

1
Q

What is the major rhythm generator of breathing?

A

The Medulla

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2
Q

In brain damage, where would the injury have to be to affect normal ventilation?

A
  • Normal ventilation is retained if the section above the medulla is affected but ventilation ceases if the section below the medulla is affected
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3
Q

What group of neurons in the medulla is responsible for the breathing rhythm?

A

The pre-botzinger complex

These neurons display pacemaker activity; they are located near the upper end of the medullary respiratory centre

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4
Q

Where is the pre-botzinger complex located?

A

Located near the upper end of the medullary respiratory centre

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5
Q

What gives rise to inspiration?

A
  • Dorsal respiratory neurones fire to cause inspiration
  • Fire leads to contraction of inspiratory muscles leading to inspiration
  • When firing stops, the passive process of expiration begins
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6
Q

What occurs during inspiration?

A
  • Diaphragm descends on contraction
  • This increases the verticle dimensions of the thoracic cavity
  • Contraction of the external intercostal muscles elevates the ribs and the sternum
  • This enlarges the thoracic cavity from front to back and from side to side
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7
Q

How does active expiration occur?

A

Increased firing of dorsal neurones which excites a second group of neurones known as the ventral neurones; this excites the internal intercostals, abdominals etc. leading to forceful expiration

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8
Q

What neuron group are considered part of the medullary respiratory center?

A

Dorsal respiratory group
Ventral respiratory group
Pre-botzinger complex

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9
Q

What neuron group are considered part of Pons respiratory center?

A

Pneumotaxic center

Apneustic center

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10
Q

Is expiration a passive or an active process?

A

Passive

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11
Q

When are the ventral neurons of the pons not activated?

A

Not in normal breathing

Activated during hyperventilation

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12
Q

What modifies the rhythm set up by the medulla?

A

The pons respiratory centre

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13
Q

Where is the Pneumotaxic centre located?

A

In the Pons

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14
Q

What does stimulation of the pneumotaxic centre result in?

A

Termination of Inspiration

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15
Q

When is the pneumotaxic centre stimulated?

A

It is stimulated when the dorsal respiratory neurones fire

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16
Q

What occurs if the Pneumotaxic centre is unable to be stimulated?

A 
Breathing is prolonged inspiratory gasps 
Brief expiration (Apneusis)
17
Q

What does apneusis mean?

A

Abnormal breathing - characterised by prolonged breathing

18
Q

What does the Apneustic centre impulses result in?

A
  • Impulses from neurones in the Apneusitc centre excite the inspiratory area of the medulla
  • This results in prolonged inspiration
19
Q

What stimuli affect the respiratory centres?

A
  • Higher brain centres
  • Stretch receptors
  • Juxtapulmonary receptors
  • Joint receptors
  • Barorecptors
  • Central chemoreceptors
20
Q

Describe how pulmonary stretch receptors work?

A

 These are activated during inspiration, afferent discharge inhibits inspiration – Hering-Bruer reflex (guard against hyperinflation)
 They are unlikely to switch off inspiration during the normal respiratory cycle as they are only activated at large volumes, 1L + tidal volumes
 They may be important in new born babies
 They may prevent over-inflation of lungs during hard exercise

21
Q

Describe how joint receptors work?

A

 Impulses from moving limbs reflex increase breathing

 Probably contribute to the increased ventilation during exercise

22
Q

What factors increase ventilation during exercise?

A
  • Reflexes originating from body movement
  • Adrenaline release
  • Impulses from the cerebral cortex
  • Increase in body temperature
  • Later; accumulation of CO2 and H+ generated by active muscles
23
Q

Describe the ventilatory response to exercise, in terms of ventilation over time ?

A
  • Within seconds of starting exercise, ventilation will increase, then level out momentarily (I) before then gradually increasing (II) to reach a plateau (III)
  • As soon as exercise ceases, ventilation will drop a little very suddenly, then gradually decrease over a longer period of time
  • It is thought to be due to a combination of neural and chemical stimuli that we get such a response to exercise
24
Q

Describe how the cough reflex is set up?

A
  • Vital part of body defence mechanisms
  • Activated by irritation of airways or tight airways (e.g. asthma)
  • Centre in the medulla
  • Afferent discharge stimulates: short intake of breath, followed by closure of the larynx, then contraction of abdominal muscles (increases intra-alveolar pressure), and finally opening of the larynx and expulsion of air at a high speed
25
Q

Where are chemoreceptors located?

A

Medulla

Brainstem

26
Q

What do chemoreceptors respond to?

A

H= ions in the cerebrospinal fluid

27
Q

How is the CSF separated form blood?

A

Blood-brain barrier

28
Q

What is the blood-brain permeable to and impermeable to?

A

 This is relatively impermeable to H+ and HCO3

 CO2 diffuses readily

29
Q

What is Hypercapnia?

A

Elevated CO2 levels in the blood.

30
Q

What increases, if the pCO2 levels increase?

A

The Ventilation rate

31
Q

What does Hypoxia mean?

A

Low levels of oxygen, relating to tissues

32
Q

What receptors are stimulated to increase ventilation during hypoxia?

A

Peripheral chemoreceptors

33
Q

When are the central chemoreceptors de-stimulated?

A
  • Hypoxia will not de-stimulate the central chemoreceptor until levels drop to 8.0 kPa (arterial O2); ventilation will be very quickly stimulated thereafter
34
Q

How is Hypoxia caused at high altitudes?

A
  • Hypoxia at high altitudes is caused by decreased partial pressure of inspired oxygen (PiO2)
35
Q

What is the response to hypoxia at high altitude?

A
  • Hyperventilation

- Increased cardiac output

36
Q

What are the acute symptoms of mountain sickness?

A

headache, fatigue, nausea, tachycardia, dizziness, sleep disturbance, exhaustion, shortness of breath, unconsciousness

37
Q

What are the chronic adaptations of high altitude induced hypoxia?

A
  • Increase RBC production
  • Increased 2,3 BPG (2,3-biphosphoglycerate) produced within RBC
  • Increased number of capillaries
  • Increased number of mitochondria
  • Kidneys converse acid
38
Q

What does an increase in 2,3 BPG (2,3-biphosphoglycerate) produced within RBC cause?

A

– this tends to shift the O2 dissociation curve to the right showing that there is an increase of oxygen dissociation into the tissues

39
Q

Describe the H+ drive of respiration?

A
  • Effect is by the chemoreceptors, these play a major role in adjusting acidosis, as they are sensitive to H+
  • Cause an addition of non-carbonic acid to the blood
  • Cause Hyperventilation
    Increases elmination of CO2

Respiratory - Week 2 (8 decks)

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