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

Apneustic cen. - area in the lower pons contain neurons which are tonically active and activate the I neuron (insiparoty ) .activity in these neurin is inhi bited by afferents in the vagus nerve from the airways and lungs.therefore 1. if vagi are intact regular rhythmic respiration continue and .2.if vagi are cut arrest of respiration occurs in inspiration called apneusis.

Section C i.e,transection in the inferior portion of pons i.e, when all pontine tissue are separated from the medulla.respiration continue whether or not the vagi are intact.this respiartion is somewhat irregular and gasping ,but it is rhythmic i.e,inspiration is regularly followed by expiration

complete transection of brain stem .

1.below the medulla ,(sectionD) stops all respiration (apnoea).

2 above pons ,between 2 colliculii.e,decerebratiin (section A ) when bith vagi are also cut regular breathin continue (eupnoea).

Section B transcetion in midpons-1.with vagi cut there occurs arrest of respiration in inspiration (apneusis).

2.if vagi are intacts ,regular rhythmic respiration continues.

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