Control Of Lung Function Flashcards
What nuclei in the medulla oblongata and pons control breathing? DIVE AP
- Dorsal respiratory group- what does it do? (+what does it inhibit)
- Inspiratory centre
- Main controller of respiration
- Sets the ‘rate’
- Ventral respiratory group- what does it do? (+what does it inhibit)
- Expiratory centre
- Inactive during quiet breathing
- Inhibits DRG & apneustic centre
- Apneustic centre- what does it do? (+what does it inhibit)
- Associated with inspiration
- Stimulates activity in DRG
- Inhibited by pulmonary afferents
- doesn’t inhibit anything
- Pneumotaxic centre- what does it do? (+what does it inhibit)
- Associated with expiration- is the ‘inspiratory off switch’, inhibits DRG
- Regulates depth and frequency of breathing
What nuclei sets the rate
DRG
Which nuclei regulates depth & frequency?
Pneuomotaxic center
Graph of respiratory pacemaker during quiet breathing- explain it
APs increase in frequency until pneumotaxic centre is activated which stops inspiration- called ramp potential pattern
After period of latency, apneustic centre helps program rhythm into dorsal respiratory group
normal circulation, what are the capillaries like in terms of gaps between the cells?
They have H2O filled gap junctions but capillaries are thought to be continuous
How does this differ to blood-brain barrier (BBB)?
BBB has tight junctions due to nerve cells which help even more tightly pack endothelial cells together which restricts what can cross it
What does CO2 and H2O do to affect our drive to breathe?
In capillary, they react to form carbonic acid which dissociates into H+ and bicarbonate
The H+ and bicarbonate can’t cross lipid bilayer of endothelial cells (and therefore BBB) as they are charged but CO2 can so it crosses into CSF where it reacts with H2O (same reaction) to form carbonic acid which dissociates into H+ and bicarbonate
The H+ interact with afferent fibres in medulla which sends signals to dorsal respiratory group to determine rate and rhythm of breathing
What are the 3 types of receptors in the airways that affect ventilation?
- Irritant receptors- what do they do?
- Afferent receptors embedded within and beneath airway epithelium
- Detect foreign matter- solid, liquid, gas- and lead to cough to get rid of it
- Cough involves forceful expiration against a closed glottis with sudden glottal opening and high velocity expulsion of air
- Stretch receptors- what do they do?
- Are further down airways down secondary bronchi in tubes that can change size depending on how much pressure is in them
- Excessive inflation of lungs activates pulmonary stretch receptors
- Afferent signals to respiratory centres inhibit DRG and apneustic centre and stimulate pneumotaxic & VRG
- This inhibits inspiration and stimulates expiration
- J receptors- what do they do?
- Located next to alveoli
- Are sensitive to oedema and pulmonary capillary engorgement (leads to high pressure)
- They increase breathing frequency after this as the above impede ability of lungs to ventilate and exchange gas e.g. oedema is thick
Graph of volitional apnoea- describe what is happening
When ventilating, arterial oxygen and CO2 remain stable
When holding breath, arterial oxygen decreases and CO2 increases- accumulation of H+ beyond BBB stimulates medulla to breathe in
Green CO2 threshold for breathing- once CO2 level passes that we start struggling for breath
Purple O2 threshold for blackout- once O2 level passes below, we blackout
What is happening in the right part of the gra
- Increasing ventilation increases arterial O2 and decreases CO2
- Once breath is held, struggle phase is now much closer to O2 threshold for blackout so once he starts struggling he may blackout soon after
Describe the emotional change to ventilation
- Special senses (taste/smell/hear/sight) + higher brain centres like limbic system elicit emotional response
- This can affect the respiratory control centre in brainstem
- How are nerves distributed so that exercise can affect breathing?
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- A branch of the efferents from the primary motor cortex that go to gross skeletal musculature also innervate medulla (to tell brain to start breathing since we’re exercising)
- Also, proprioceptive afferents from muscle spindles and golgi tendon organs innervate medulla on the way to the brain- can be shown by cycling someone else’s legs → will change their ventilation
What is the cold shock ventilatory response? (i.e. what does immersion in cold water result in?)
Immersion in cold water (<10oC) results in inspiratory gasp and hyperventilation due to superficial sensory nerve endings in skin
Alkeamia
Acidaemia
Alkalosis
Acidoses
- AlkaemiaHigher than normal blood pH
- AcidaemiaLower than normal blood pH
- AlkalosisCircumstances that decrease H+ conc and increase pH
- AcidosisCircumstances that increase H+ conc and decrease pH
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How is alkalaemia and acidaemia corrected by bo
- An acidosis causes acidaemia and will require alkalosis to correct
- An alkalosis causes alkalaemia and will require acidosis to correct
- Changes in ventilation can stimulate a rapid compensatory response to change CO2 elimination and alter pH
- Changes in HCO3- and H+ retention/secretion in kidneys can stimulate a slow compensatory response to alter pH
