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5 out of 9

Transection at mid-pons lead to. (AIIMS NOV 2009)

A Rapid, shallow breathing
B Apneusis

C Hyperventilation
D Deep breathing

Ans. D Deep breathing

MEDULLA – has pre botzinger complex Q(betweennucleus ambiguous and lateral rectal nucleus) which acts as pacemaker for spontaneous respiration, also contains DRG & VRG(DORSAL &VENTRAL RESPIRATORY GROUP OF NEURONS)

a. DRG - contains inspiratory neurons which supply inspiratory muscles

b. VRG - both inspiratory & expiratory neurons

PONS – contain 2 centres

a. Apneusticcentre (in lower pons) : stimulates inspiratory neurons. If not inhibited by vagus and pneumotaxiccentre will cause apneusis Q.

b. Pneumotaxiccentre(in upper pons) : inhibit apneusticcentre Q. Near Parabranchial Nucleus (NPBL) Q

I. Effect of Lesion/ Transection of brainstem on respiration

a. Section A: Above pons : Normal tidal respiration but voluntary control is lost. If vagus also cut then slow & deep breathing because vagus inhibits apneusticcentre Q.

b. Section B: At Mid pons : loss of inhibitory action of pneumotaxiccentre on apneusticcentre there is stimulation of inspiratory neurons by apneustic resulting in slow and deep breathing. If vagus also cut then APNEUSIS Q.

c. Section C: Between Pons & Medulla: Spontaneous respiration continues, although somewhat- irregular and gasping Q because respiration is produced by medulla but made rhythmic & regular by pontinecentres Q.

d. Section D: Below medulla: No respiration. Q