Neural Mechanism Of Breathing Regulation

NEURAL MECHANISM OF BREATHING REGULATION

Q. 1

The components of the respiratory control pattern generator is responsible for automatic respiration. Pacemaker regulating the rate of respiration is:

 A

Pneumotaxic centre

 B

Dorsal group of nucleus

 C

Apneustic centre

 D

Pre-Botzinger Complex

Q. 1

The components of the respiratory control pattern generator is responsible for automatic respiration. Pacemaker regulating the rate of respiration is:

 A

Pneumotaxic centre

 B

Dorsal group of nucleus

 C

Apneustic centre

 D

Pre-Botzinger Complex

Ans. D

Explanation:

Rhythmic respiration is initiated by a small group of synaptically coupled pacemaker cells in the pre-Bötzinger complex (pre-BÖTC) on either side of the medulla between the nucleus ambiguus and the lateral reticular nucleus. 

These neurons discharge rhythmically, and they produce rhythmic discharges in phrenic motor neurons that are abolished by sections between the pre-Bötzinger complex and these motor neurons. They also contact the hypoglossal nuclei, and the tongue is involved in the regulation of airway resistance.
 
Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 36. Regulation of Respiration. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong’s Review of Medical Physiology, 24e.

 


Q. 2

The main components of the respiratory control pattern generator is responsible for automatic respiration. Pacemaker of respiration is:

 A

J-center

 B

DRG

 C

Pneumotaxic centre

 D

Pre-BÖTC

Q. 2

The main components of the respiratory control pattern generator is responsible for automatic respiration. Pacemaker of respiration is:

 A

J-center

 B

DRG

 C

Pneumotaxic centre

 D

Pre-BÖTC

Ans. D

Explanation:

Rhythmic respiration is initiated by a small group of synaptically coupled pacemaker cells in the pre-Bötzinger complex (pre-BÖTC) on either side of the medulla between the nucleus ambiguus and the lateral reticular nucleus.

These neurons discharge rhythmically, and they produce rhythmic discharges in phrenic motor neurons that are abolished by sections between the pre-Bötzinger complex and these motor neurons.

Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 36. Regulation of Respiration. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong’s Review of Medical Physiology, 24e.


Q. 3

Spontaneous rhythmic respiration initiated in

 A

Pre-Botzinger complex

 B

Dorsal respiratory group

 C

Pneumataxic centre

 D

Apneusic centre

Q. 3

Spontaneous rhythmic respiration initiated in

 A

Pre-Botzinger complex

 B

Dorsal respiratory group

 C

Pneumataxic centre

 D

Apneusic centre

Ans. A

Explanation:

A i.e. Pre-Botzinger complex


Q. 4

Which of the following are inactive during normal respiration ‑

 A

Pre-Botzinger complex

 B

Dorsal group of neurons

 C

Ventral VRG group of neurons

 D

Pneumotaxic center

Q. 4

Which of the following are inactive during normal respiration ‑

 A

Pre-Botzinger complex

 B

Dorsal group of neurons

 C

Ventral VRG group of neurons

 D

Pneumotaxic center

Ans. C

Explanation:

Ans. is ‘c’ i.e., Ventral group of neurons

Medullary respiratory centers

  • The principal areas in the medulla oblongata concerned with regulation of respiration are : ‑

1) Dorsal respiratory group (DRG) : – The dorsal respiratory group of neurons are mainly concerned with inspiration. They descend and terminate on spinal motor neurons innervating the primary muscles of inspiration, i.e., the diaphragm and the external intercostal muscles.

2) Ventral respiratory group (VRG) : – The ventral respiratory group of neurons is mainly concerned with forceful expiration but also shows some activity during inspiration. Therefore, these neurons contribute to both expiration and inspiration. These neurons are divided into : ‑

i)      The rostral VRG neurons : – These neurons show activity primarily synchronous with inspiration and therefore be called inspiratory (I) neurons. They terminate on spinal motor neurons supplying the accessory muscles of inspiration, i.e., sternocleidomastoid, scalenes and anterior serrati.

ii)     The ventral VRG neurons : – These are mostly expiratory (E) neurons. But since the expiration is generally a passive process, E neurons are silent most of the time. However, these neurons show activity when expiration is forceful, as during exercise. These neurons terminate on spinal motor neurons supply the muscles of expiration, i.e., internal intercostal and abdominal muscles.

3) Pre-Botzinger complex : – These neurons are responsible for generation of respiratory rhythm, i.e., the pacemaker cells which regulate the rate of respiration are located in Pre-Botzinger complex.

Pontine respiratory centers

  • The important pontine areas concerned with respiration are : ‑

1)   Pneumotoxic center (nucleus parabrachialis medialis) : – It is located in upper part of pons and transmits signals to the inspiratory area. The function of the pneumotaxic center is primarily to limit inspiration, i.e., the primary effect of this center is to control the “switch-off” point of the inspiratory ramp thus controlling the depth of inspiration, i.e., the duration of the filling phase of the lung cycle. Pneumotaxic center also inhibits apneustic center further inhibiting inspiration. Therefore strong stimulation of this center results in an early termination of inspiratory ramp and hence, inspiration is shortened and the tidal volume decreases. Conversely, in the absence of inputs from this center, inspiratory ramp continues much longer and hence inspiration is prolonged and the tidal volume increases.

2) Apneustic center : – This center located in the lower (caudal) part of pons. The apneustic center excites inspiratory center (DRG) and produce a prolonged inspiratory drive which delays the onset of expiration. Thus, though the respiratory rhythm is established in the medulla, this rhythm is spoilt by a strong inspira­tory drive orginating in the apneustic centers. However, two influences seems to keep the apneustic center in check : (i) Pneumotaxic center of upper pons and (ii) Influence from stretch receptors in lung via vagus. Both of these influence inhibit inspiratory activity.


Q. 5

Respiratory rhythm is generated in ‑

 A

Pneumotaxic centre

 B

Dorsal group of nucleus

 C

Apneustic centre

 D

Pre-Botzinger Complex

Q. 5

Respiratory rhythm is generated in ‑

 A

Pneumotaxic centre

 B

Dorsal group of nucleus

 C

Apneustic centre

 D

Pre-Botzinger Complex

Ans. D

Explanation:

Ans. is ‘d’ i.e., Pre-Botzinger Complex


Q. 6

Pacemaker regulating the rate of respiration ‑

 A

Pneumotaxic centre

 B

Dorsal group of nucleus

 C

Apneustic centre

 D

Pre-Botzinger Complex

Q. 6

Pacemaker regulating the rate of respiration ‑

 A

Pneumotaxic centre

 B

Dorsal group of nucleus

 C

Apneustic centre

 D

Pre-Botzinger Complex

Ans. D

Explanation:

Ans. is ‘d’ i.e., Pre-Botzinger Complex

“The main components of the respiratory control pattern generator responsible for automatic respiration are located in the medulla. Rhythmic respiration is initiated by a small group of synaptically coupled pacemaker cells in the pre-Botzinger complex on either side of the medulla between the nucleus ambiguus and the lateral reticular nucleus”.



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