Control of respiration

1. Ms.Anu Sebastian: B.Pharm; M.Pharm
Assistant Professor,
Dept. Of Pharmacology
Nirmala College Of Pharmacy
Muvattupuzha,Ernakulam,Kerala

2.  The basic rhythm of respiration is controlled by
respiratory centres located in the medulla and pons of
the brain stem.
 Medullary rhythmicity area: In medulla oblongata
 Pneumotaxic area: In the upper pons
 Apneustic area: In the lower pons
 MEDULLARY RHYTHMICITY AREA
 Its function is to control the basic rhythm of
respiration.
 It contains Inspiratory area & Expiratory area.

3. INSPIRATORYAREA
 The inspiratory center sends nerve impulses along the phrenic
nerve to the diaphragm and along the intercostal nerves to the
external intercostals muscles.
 The nerve impulses to the diaphragm and the external intercostal
muscles continue for a period of about 2 seconds. This stimulates
the inspiratory muscles to contract, initiating inspiration.
 The neurons stop firing or about 3 seconds, which allows the
muscles to relax. The elastic recoil of the lungs and chest wall
leads to expiration.
 This automatic, rhythmic firing produces the normal resting
breathing rate ranging between 12-15 breaths per minute.

4. EXPIRATORYAREA
 The expiratory area appears to function mainly during forced
expiration, stimulating the internal intercostals and abdominal
muscles to contract.
 In addition, other respiratory centers within the pons modify
inspiration and allow for smooth transitions between inspiration
and expiration.

6.  PNEUMOTAXIC AREA
 In the upper pons
 Transmit inhibitory impulses to the inspiratory area, turn of the
inspiratory area before the lungs become too full of air.
 Shortens the duration of inhalation
 When the pneumotaxic area is more active, breathing rate is more rapid.
 APNEUSTIC AREA
 In the lower pons
 Sends stimulatory impulses to the inspiratory area that activate it & prolong
inhalation.
 The result is a long deep inhalation
 When the pneumotaxic area is active, it overrides signals from the apneustic area.

7. REGULATION OF RESPIRATORY CENTRE
 The basic rhythm set by inspiratory area is modified by
other brain centers, receptors in PNS and other factors.
1. Cortical influences on respiration
 Cerebral cortex has neuronal connections with
respiratory center, so we can voluntarily alter the
breathing pattern.
 This voluntary control is protective as it prevent the
entry of irritating gases or water entering the lungs.

8. Increase in PCO2 & H+
↓
Stimulate inspiratory area
↓
Activate phrenic and intercostals
muscles
↓
Contraction of diaphragm & external
intercostals muscles
↓
Breathing
Emotional stimuli
↓
Activate hypothalamus & limbic
↓
Stimulate respiratory center
↓
Alter breathing

9. 2. Chemoreceptor regulation
 The sensory neurons that respond to changes in chemicals are
called chemo receptors.
 These are located centrally and peripherally to monitor the levels
of O2 & CO2
 The central chemoreceptors are located near to medulla oblongata
in CNS. They respond to changes in H+/PCO2 or both in CSF.
 Peripheral chemoreeptors are located in :
 Aortic bodies: Located in the wall of arch of aorta
 Carotid bodies: Located in the all of right and left common
carotid artery, where they divide into external and internal carotid
arteries.

10. 3. Proprioceptor regulation
Proprioceptor monitor movements of joints and muscles.
During exercise
↓
Changes in movements of
Joints & muscles motor neuron
↓
Activation of proprioceptors
↓
Sending input to inspiratory
area in medulla
↓
Alter breathing

11. 4. Inflation reflex / Hering Breuer reflex
Over inflation of lungs
Activation of baro/ stretch receptors on the walls of bronchioles
Activation of vagus nerve
Send impulses to inspiratory area & apneustic area
Inhibition of apneustic area & inspiratory area
Exhalation
As air leaves the lungs, it deflates
Inactivation of stretch receptors
Activation of Inspiratory area & apneustic area
Inhalation begins

12.  5. Other influences on respiration
 Limbic system: Emotions/anxiety etc stimulate limbic system, activate
inspiratory are & increase rate & depth of Respiration.
 Temperature: Increase in body temperature, increase rate of respiration
& vice versa.
 Pain: Prolonged somatic pain, increase rate of respiration & visceral pain
decreases rate of respiration.
 Stretching of anal sphincture muscle: Increases respiratory rate.
 Irritation of airways: Irritation in the airways causes immediate
cessation of breathing followed by coughing & sneezing.
 Blood pressure: sudden rise in B.P, decrease rate of respiration and fall
in BP increases respiratory rate.

13. THANK YOU