Regulaion of Respiration (presentation)

PRESENTED BY
ROSHAN TIMILSINA
B.PHARMACY 2ND SEMISTER
REGULATION OF
RESPIRATION
PHARMACEUTICAL SEMINAR 1ST

CONTENTS
Introduction
Types of Regulation Mechanism
Types of Respiratory Centers
Nervous Connections of Respiratory Centers
Factor Affecting Respiratory Centers
Conclusion
References
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Friday, July 13, 2018Pharmaceutical Seminar Ist
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Regulation of Respiration
Maintain normal level of PO2 and PCO2 in arterial blood.
Reflex process but it can be controlled voluntarily for short
period.
Variation, even under normal physiological condition.
Normally, quite regular breathing occurs of two regulatory
mechanisms i.e
1) Nervous or neural mechanism
2) Chemical mechanism
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Nervous Mechanism
Nervous mechanism that regulates the respiration includes:
1) Respiratory Centers
2) Afferent nerves
3) Efferent nerves
Respiratory centers: The centres in the medulla oblongata and pons
that collects sensory information about the level of oxygen and
carbon dioxide in the blood and determines the signals to be sent
to the respiratory muscles.
Stimulation of these respiratory muscles provide respiratory
movements which leads to alveolar ventilation.
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Respiratory centers are situated in the
reticular formation of the brainstem and
depending upon the situation in
brainstem, the respiratory centers are
classified into two groups:
1) Medullary centers
a) Dorsal Neurons (Inspiratory Centre)
b) Ventral Neurons (Expiratory Centre)
2) Pontine centers
a) Apneustic Centre
b) Pneumotaxic Centre
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Dorsal Neurons (Inspiratory center) :
It is formed by nucleus of tractus solitarius
Which is situated in upper part of medulla oblongata these neurons
collectively called inspiratory centre.
Function:
It is concerned with inspiration which generates the inspiratory
ramp by the virtue of their autorhythmic property.
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Ventral Neurons (Expiratory Centre) :
It is situated in medulla oblongata anterior and lateral to the
inspiratory center
It is also called Expiratory Centre of respiratory neurons
It is formed by neurons of nucleus ambiguous and nucleus
retroambiguous
Function:
This center is inactive during quiet breathing and inspiratory
center is the active center, but during forced breathing or when
the inspiratory center is inhibited it becomes active.
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It is the nerve centre
in the brainstem controlling normal respiration.
It is situated in the reticular formation of lower Pons.
Function:
This center increases depth of inspiration by acting directly on
the dorsal neurons or inspiratory center.
8Apneustic Centre :

Pneumotaxic Centre :
It is situated in dorsolateral part of reticular formation in upper
pons.
It is formed by the neurons parabrachial and subparabrachial
nuclei.
Function:
 It controls medullary respiratory centers, it inhibits the apneustic
centre so that dorsal group neurons are inhibited because of this,
inspiration stops and expiration starts.
 It increases respiratory rate by reducing the duration of inspiration
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Connection of Respiratory Centre
Efferent pathway
• Nerve fiber from respiratory center leaves the brain and descend in
anterior part of lateral column of spinal cord.
• These nerve fibers terminate in the motor neurons in the anterior
horn cells of the cervical and thoracic segments of spinal cord.
• From motor neurons two sets of nerve fiber arise which supplies
particular muscle:
• Phrenic nerve fibers (C3 to C5), which supplies diaphragm
• The intercostal nerve fibers (T1 to T11) supplies intercostal
muscles.
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Afferent pathway
• Respiratory center receive afferent impulses from:
different parts of the body according to movements of thoracic
cage and lungs.
peripheral chemoreceptor and baroreceptor impulses are carried
by glossopharyngeal and vagus nerves.

Factors affecting respiratory centers:
Impulses from higher centers: impulses from higher center can
stimulate or inhibit respiratory centers directly.
Impulses from stretch receptors of lung:
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Impulses from ‘J’ receptors of lungs:
 ‘J’ receptors are juxtacapillary receptors which are present in wall
of the alveoli and have close contact with the pulmonary capillaries.
 These receptors get stimulated during conditions like pulmonary
edema, pulmonary congestion, pneumonia as well as due to
exposure of exogenous and endogenous chemicals.
 Stimulation of ‘J’ receptor produces a reflex response called apnea.
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Impulses from irritant receptors of lungs:
 Irritant receptors are situated on the wall of bronchi and
bronchioles of lungs.
 They got stimulated by harmful chemicals like ammonia and
sulfur dioxide.
 Stimulation of irritant receptors produces reflex
hyperventilation along with bronchospasm which prevents
entry of harmful chemicals into the alveoli.
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Impulses from Thermoreceptors:
 Thermoreceptors give response to change in the body temperature.
 They are cutaneous receptors namely cold and warmth
 When this receptors get stimulated they send signals to cerebral cortex
 Cerebral cortex in turn stimulates respiratory centres and causes hyperventilation.
Impulses from pain receptors:
 Pain receptors give response to pain stimulus.
 Like other receptors this receptors also send impulses to the cerebral cortex.
 Cerebral cortex in turn stimulates the respiratory centers and causes
hyperventilation.
Friday, July 13, 2018
Pharmaceutical Seminar Ist
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Cough reflex:
 This is a protective reflex caused by irritation of parts of the respiratory
tract beyond nose like larynx, trachea and bronchi.
 Irritation of any of this part causes stimulation of vagus nerve and cough
occurs.
 Cough begins with deep inspiration followed by forceful expiration with
closed glottis.
 So the intrapleural pressure rises above 100 mm Hg.
 Then, glottis is suddenly opened with explosive outflow of air at a higher
velocity. So the irritants may be expelled out of the respiratory tract.
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Chemical Mechanism:
The chemical mechanism of the respiration is operated through
the chemoreceptors.
Chemoreceptors are the sensory nerve endings, which give
response to change in chemical constituents of blood like:
 Hypoxia (decreased pO2)
 Hypercapnea (increased pCO2)
 Increased hydrogen ions coancentration (decreased blood pH)
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Chemoreceptors are classified into two groups:
Friday, July 13, 2018
Pharmaceutical Seminar Ist
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1) Central chemoreceptors
They are present in the brain and situated in deeper part of medulla oblongata, close to
the dorsal respiratory group of neurons.
Responsible for 70% to 80% of increased ventilation through chemical regulatory
mechanism
• They are very sensitive to increase in hydrogen ion concentration.
• Hydrogen ion cannot cross the blood brain barrier and blood cerebrospinal fluid barrier.
• On the other hand if carbon dioxide increases in the blood as it is a gas it can cross
both the barrier easily and after entering the brain it combines with water to form
carbonic acid. As carbonic acid is unstable, it immediately dissociates into hydrogen
and bicarbonate ions.
The hydrogen ion now stimulates the central chemoreceptors which stimulates dorsal
group of respiratory center (inspiratory group) and increase rate and force of breathing.
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2) Peripheral chemoreceptors
The receptors are present in peripheral portions of the body that’s
why called as peripheral chemoreceptors.
They are very sensitive to reduction in partial pressure of oxygen.
• Whenever, the partial pressure of oxygen decreases these
chemoreceptors become activated and send impulses to
inspiratory center and stimulate them.
• Thereby increases rate and force of respiration and rectifies the
lack of oxygen.
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CONCLUSION
• Respiratory centers in the medulla oblongata of the brain controls
breathing. Respiratory centers send impulses through the phrenic nerve
to the diaphragm and through the intercostal muscles to either contract
or relax. Respiratory center receives afferent impulses from different
parts of the body according to movements of thoracic cage and lungs.
From peripheral chemoreceptor and baroreceptor impulses are carried
by glossopharyngeal and vagus nerves to respiratory center. Nerve fiber
from respiratory center leaves the brain and descend in anterior part of
lateral column of spinal cord. These nerve fibers terminate in the motor
neurons in the anterior horn cells of the cervical and thoracic segments
of spinal cord. The peripheral chemoreceptors that detect changes in
the levels of oxygen and carbon dioxide.

References
1. Tortora GJ and Derrickson BH (2009), Principles of Anatomy
and Physiology (12th Ed.), Danvers and Wiley India Pvt. Ltd, 332-
336.
2. KC Tulza and Gautam R (2014), Essential Text Book of
Anatomy and Physiology (1st Ed.), Samiksha Publication Pvt. Ltd,
191-194.
3.URL1:https://en.wikipedia.org/wiki/Respiratory_center
(Assessed on June 24th 2018).

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Regulaion of Respiration (presentation)

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