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38 Cards in this Set
- Front
- Back
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What happens to breathing during muscular exercise?
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It increases - hyperpnea results.
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What is the temporal response pattern of alveolar ventilation at the onset of exercise?
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It sharply increases within seconds of exercise onset, then slowly increases to a steady state.
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How soon after exercise onset does alveolar ventilation reach the steady state?
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90 sec
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So what does that tell us about the signal for hyperpnea?
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It has both a fast and slow component.
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What is the effect of exercise on alveolar and arterial blood gases?
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Homeostasis is maintained until about 60% of maximal exercise capacity.
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So what do we know is NOT the signal for hyperpnea during exercise?
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Increased stimulation of Carotid or intracranial chemoreceptors - they would kick in initially.
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What is observed at about 60% of maximal exercise capacity?
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-Lactic Acidosis
-Hyperventilation |
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What is the relationship between metabolic rate and alveolar ventilation during exercise?
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Because homeostasis is maintained up to 60% max, VA is increasing in proportion to metabolic rate increase. After that, the increase exceeds the increase in metabolic rate.
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How do we know that the ventilatory response is not central command-dependent?
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It is not different when the stimulus is voluntary versus electrically induced.
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Is the ventilatory response to electrically induced exercise different in normal vs paraplegics?
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No; so we see it is also not critically dependent on spinal afferents.
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If oxygen content in room air is increased to 40% will it affect alveolar ventilation?
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No; PaCO2 will remain 40 even though PaO2 doubles (100-200)
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Will the same increase in O2 content affect breathing in a severe COPD patient?
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Yes; PaCO2 will increase from 65 to 70.
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What likely causes the increase in alveolar CO2 in hyperoxic conditions for a COPD patient?
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The increase in alveolar O2, resulting in reduced carotid chemoreceptor activity
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For a resting patient with abnormal ventilation:
PaCO2 = 30 (below normal) PaO2 = 110 (above normal) pH = 7.5 What has happened to alveolar ventilation and CO2 ventilation? |
Both are above normal - indicated by the hypocapnia.
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What is driving the hyperventilation in this patient?
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Emotional stress or brain lesions
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Why does H+ concentration need to be maintained at such a narrow range?
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Because acid affects protein function.
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How does suboptimal protein function affect neurons?
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Excess acid = decreased excitability
Deficient acid = increased excitability |
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What is an acid?
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Compound that donates H
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What is a base?
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Compound that accepts H
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What is Physical-chemical buffering?
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The ability of a compound in solution to minimize the change in H+ in the solution when a strong acid or base are added.
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What are the primary buffers in ECF?
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-Bicarb
-Phosphoric acid -Proteins |
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What are the primary buffers in ICF?
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-Phosphoric acid
-Proteins |
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How can you distinguish whether an acidosis is metabolic or respiratory?
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By looking at the PCO2; if Elevated = respiratory
Decrsed = metabolic |
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What is the isohydric principle?
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The fact that when acid balance is disrupted, all buffers will be altered.
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What are the 2 determinants of the hydrogen ion buffering capacity of a buffer pair within a solution?
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1. Amt of buffer pair in solution
2. pK of buffer pair relative to the pH of the solution |
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What happens when pH = pK?
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There are equal amts of hydrogen ion, acid, and base.
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When are conditions optimal for buffering?
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When pH = pK
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What is physiologic buffering?
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Processes in the body that alter the amount of physical-chemical buffers.
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2 Ways by which plasma [H+] is regulated:
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1. Transmembrane exchange
2. Pulmonary ventilation |
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What is transmembrane exchange?
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Buffering of ECF by moving Na or K from cells in exchange for H.
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2 main sites of bicarb production:
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-Kidney
-Brain |
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When does the brain make lactic acid?
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To buffer a respiratory alkalosis
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How does the kidney respond when tissues produce excess acid?
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it regenerates bicarb by producing ammonia.
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What will increase in urine during a severe metabolic acidosis?
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Ammonium chloride
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What is the role of the BBB in regulating brain [H+]?
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It prevents acid from entering the brain.
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During systemic metabolic acidosis how much does CSF [H+] increase?
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Only 10% of the increase in blood [H+].
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Can the blood brain barrier buffer a respiratory acidosis or alkalosis? Why/why not?
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no; b/c CO2 can easily diffuse across it.
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How does the brain respond to a resp acidosis or alkalosis?
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Acid: increases NH3 production
Alk: increases lactic acid production -Glial cells produce both |
