Figure 6 (below) shows tidal volume tracings (the peaks on the right) obtained f

Question

Figure 6 (below) shows tidal volume tracings (the peaks on the right) obtained from animals with various brain areas severed. The tracings illustrate the role each of the centres of the brain has in controlling breathing. WARNING: This is a difficult exercise and you will have to think about what happens with each cut (in answering the questions below with reference to Fig 5 and the associated text). BOTH VAGUS NERVES INTACT FIRST CUT SC SUIPER LICULI NERVES CUT SECOND CUT INFER LLICULI NBUMOTAX CENTRE 2 PNBUSTIC CENTRE THIRD CUT DRG VRG FOURTH CUT SPINAL CORD Figure 6: Tidal volume tracings with sectioning of the nervous system

Explanation / Answer

If cut severs the pneumotaxic center then the person would have slow and deep breath under intact vagus nerve. If vagus nerves cut, then the person would undergo apneusis; in which deep full inspiration occurs but with short release. It causes the tidal volume to increase.

In intact vagus nerve, it occurs due to apneusitc center response, this sends signal to medulla to increase breath rate. In cut vagus nerve, the response occurs due to no control of breathing because vagus nerves innervate lungs and hence control it through parasympathetic process.

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