Term
| What happens if you cut both vagus nerves? |
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Definition
- Tidal volume increases
- Respiratory rate decreases
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Term
| What does the vagus nerve do to respiration? |
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Definition
- Periodically sends inhibitory signals to say stop inspiration & start expiration & vice versa
- Functionally keeps tidal volume down & rate up
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Term
| What is the effect of decreasing the amount of oxygen inspired? |
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Definition
- Not very sensitive
- You won't see a change in minute volume with small-medium changes in O2
- Eventually you'll get a hypoxic drive if you keep decreasing inspired O2
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Term
| Where are the peripheral chemoreceptors located, and what nerves serve them? |
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Definition
- Cartoid body & scattered along the aorta
- Served by cranial nerves 9 & 10 (glossopharyngeal & vagus)
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Term
| How do the peripheral chemoreceptors work? |
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Definition
- Get a large blood flow but don't use much O2, just "taste it"
- When O2 begins to drop significantly, you get a change in neural activity
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Term
| Why can you have a period of apnea when a hypoxic animal is given 100% oxygen? |
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Definition
- The animal blew off CO2 during hyperventilation
- Now, with 100% oxygen, there is plenty of O2 in the blood and not too much CO2 and so there is no drive for respiration
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Term
| What happens if you increase CO2 and decrease O2? |
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Definition
- You get a large ventilatory drive
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Term
| What stimulates peripheral chemoreceptors? |
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Definition
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Term
| What do hydrogen ions do to neural sensitivity? |
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Definition
- H+ increases neural sensitivity
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Term
| What causes hypoxic drive? |
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Definition
- As pO2 decreases, impulses from the chemoreceptors increase
- Those signals go to the CNS to cause hypoxic drive
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Term
| What affect does CO2 have on minute ventilation? |
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Definition
- Increase in CO2 has a much steeper & more rapid effect on ventilation than O2
- Causes immediate effect on ventilatory drive
- Causes an increase in minute ventilation
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Term
| What chemoreceptor does CO2 affect and how? |
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Definition
- High CO2 reaches the brain and changes the cerebral spinal fluid (CSF)
- In the 4th ventrical of the medulla, there are chemoreceptors that are sensitive to changes pf pCO2 in the CSF
- Temporarily excites inspiratory & expiratory neurons but not for long because they will be quickly destroyed
- Excitation causes increased minute ventilation
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Term
| What controls respiration centrally? |
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Definition
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Term
| What two areas are very sensitive to hypoxia? |
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Definition
- Retina & choclea
- That's why if you screw up anesthesia, they can go blind & deaf
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Term
| What happens if you put the neurons under a depressant like demerol? |
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Definition
- They become more sluggish in their reaction times
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Term
| What happens if an animal is breathing very high levels of CO2? |
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Definition
- Minute ventilation will increase
- Once you return it back to normal air, there won't be apnea because its still trying to blow off CO2
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Term
| What is the most powerful stimulant of respiratory response? |
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Definition
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Term
| Why is it good that there is a lag time for changes in the CSF so the medullary chemoreceptors can respond? |
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Definition
- Prevents a minute-to-minute change in respiration
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Term
| What is the Herring-Brewer reflex? |
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Definition
- When the thorax is stretched by inspiration, there is an increase in neural activity in the vagus nerves that decreases inspiratory activity in the brain
- Eventually the signals accumulate and stop inspiration by inhibiting activity on the inspiratory neurons
- This stops the inhibition of the inspiratory neurons on expiratory neurons to allow expiration to occur
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Term
| What happens if you overventilate an animal? |
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Definition
- Cause a period of apnea by over squeezing the bag
- Signals scream up the vagus nerve to the brainstem to say STOP INSPIRATION so much that you'll have a period of brief apnea
- You can also cause hypocapnia, which will cause apnea
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Term
| Why does tidal volume increase if you cut both vagus nerves? |
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Definition
- Vagus nerves are inhibitory to inspiration
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Term
| What is apneustic breathing? |
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Definition
- Expiration usually takes longer than inspiration, but with apneustic breathing the animal will expire faster than it inspires
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Term
| What happens to the cardiac rate during inspiration and expiration? |
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Definition
- During late inspiration, cardiac rate increases as the heart goes faster & stronger
- During expiration, it settles back down
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Term
| Why can you cause breathing by raking your knuckles across a dog's ribs? |
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Definition
- Spinothalamic pathway is pain pathway
- If you cause minimal pain, collaterals to the medulla are excited and cause inspiration
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