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19 Cards in this Set
- Front
- Back
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what controls breathing |
a) metaboliccontroller in medulla b) behavioral controller in the cortex c)reflex control |
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frequency of inspiration |
with nothing 14.9 min-1 with noseclip 12.2 |
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tidal volume |
normal 0.4 with noseclip 0.49 |
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what are the CVS determinants of breathing |
Voluntary/behavioural centre Involuntary/Metabolic centre |
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what is the Voluntary/behaviouralcentre |
in the BRAIN STEM o Always overrides the behavioural centre. o Responds to metabolic demands for and production of CO2 and determines in part the “set point” for CO2 (monitored as PaCO2). o The Limbic System (survival responses), frontal cortex (emotions), sensory inputs (pain, startle) and sleep (reticular formation) may influence the metabolic centre. |
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what is the Voluntary/behavioural centre |
In the motor cortex can control breathing |
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what feedbacks in the metabolic controller? |
1. Chemoreceptors in the carotid bodies sense hydrogen ion levels DOMINANT influence 2. The stretch and irritant receptors on the lungs 3. (less important) there is a chemoreceptor in the metabolic controller |
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breathing pacemaker |
multiples neurones in the medulla One group, the pre-Botzinger complex, essential for generating the respiratory rhythm and is known as the ‘gasping centre’ |
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6 GROUPS OF NEURONES |
Early inspiratory – initiates inspiratory flow via respiratory muscles. Inspiratory augmenting – may dilate pharynx, larynx and airways. Late inspiratory – signals the end of inspiration. Expiratory decrementing – may brake passive expiration by abducting larynx and pharynx. Expiratory augmenting – activate expiratory muscles when ventilation increases UPON EXERCISE. Late expiratory – signal the end of expiration, may dilate the pharynx in preparation for inspiration. |
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Reflex Control of Breathing |
♣ 5th (V) nerve – afferents from NOSE and FACE (IRRITANT - defensive). ♣ 9th (IX) nerve – afferents from pharynx and larynx (IRRITANT - defensive). ♣ 10th (X) nerve – afferents from bronchi and bronchioles (IRRITANT and STRETCH). o Hering-Breuer reflex from pulmonary stretch receptors in the lungs, terminates inspiration/expiration but this is weak in humans. |
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the 2 parts of the metabolic controller |
o The central part – medulla – responds to hydrogen ion concentration in the extra-cellular fluid. (Slow response: ECM) o The peripheral part – carotid body – responds to hydrogen ion concentration in the blood. (quick response: blood) |
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PaO2 and receptors |
low PaO2 causes the receptors to be more sensitive |
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respiratory acidosis |
* Rapid response (acute hypoventilation) all in ventilation leads to a rise in PCO2 and [H+] which stimulates the metabolic controllers to increase Ventilation * slower system (chonic hypoventilation): renal excretion of weak acids to maintain homeostasis |
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Metabolic acidosis |
When the source of excess H+ comes from metabolism rather than inadequate ventilation. |
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The breathlessness can be scored |
The breathlessness can be scored on a 10-point BORG scale or by doing a breath holding time test (BHT) |
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metabolic acidosis causes |
o Renal problems o Diabetes o Acid poisoning |
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metabolic acidosis compensation |
Compensatory Mechanisms: o Ventilatory stimulation lowers PaCO2 and H+ o Renal excretion of weak (lactate and keto) acids o Renal retention of chloride to reduce strong ion difference |
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Metabolic Alkalosis causes |
o Vomiting o Diuretics o Dehydration |
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Metabolic Alkalosis compensation |
o Hypoventilation raises PaCO2 and H+ o Renal retention of weak (lactate and keto) acids o Renal excretion of chloride to increase strong ion difference |
