Regulation of Respiration

1. Respiratory system
(Regulation of respiration)
Mr N.JEGAN
Associate Professor
K.M.COLLEGE OF PHARMACY.
MADURAI.

2. Respiration
 Respiration is a reflex process
 But it can be controlled voluntarily for a short period of
about 40 seconds.
 Normal respiratory rate is 12–15 respirations per minute

3. Respiration-Regulation mechanism
There are two mechanism to regulate respiration
1. Nervous or neural mechanism
2. Chemical mechanism

4. Nervous mechanism
In brain stem the following part is responsible to
control or regulation of respiration.
Medulla oblongata
Pons

5. NERVOUS MECHANISM
Nervous mechanism that regulates the respiration
through following centre(Group of neuron) and Nerves
1. Respiratory centers
2. Afferent nerves
3. Efferent nerves

7. RESPIRATORY CENTERS
Respiratory centers are group of neurons, which
control the rate, rhythm and force of respiration. It
contain following centre.
Modullarly centers
Dorsal respiratory group of neurons Ventral group of neurons
Pontine centers
Apneustic Center Pneumotaxic Center

8. MEDULLARY CENTERS
Medullary centers contain following group of neurone.
1. Dorsal respiratory group of neurons
2. Ventral respiratory group of neurons
1.Dorsal respiratory group of neurons:
It is inspiratory neurons and generate inspiratory response.
It is responsible for normal inspiration.

9. MEDULLARY CENTERS
2. Ventral respiratory group of neurons
It have both inspiratory and expiratory neurons.
Normally, ventral group neurons are inactive during
quiet breathing and become active during forced
breathing.
It control respiratory muscles
1.Diaphragm
2.Intercostal muscles

10. PONTINE CENTERS
It contain two types of center
Apneustic Center
Apneustic center increases depth of inspiration by
acting directly on dorsal group neurons.
Pneumotaxic Center
Primary function of pneumotaxic center is to control
the medullary respiratory centers, particularly the
dorsal group neurons.
It acts through apneustic center.

11. Afferent Nerves
Respiratory centers receive afferent impulses from:
1. Peripheral chemoreceptors and baroreceptors via
branches of glossopharyngeal and vagus nerves
2. Stretch receptors of lungs via vagus nerve.
By receiving afferent impulses from these receptors,
respiratory centers modulate the movements of thoracic
cage and lungs through efferent nerve fibers.

12. Efferent Nerves
Nerve fibers from respiratory centers leave the
brainstem ,spinal cord and terminate on motor neurons.
Motor neurons divide two sets of nerve fibers arise:
1. Phrenic nerve fibers - which supply the
diaphragm
2. Intercostal nerve fibers -which supply the external
intercostal muscle
Both muscles regulate the respiration.

14. Respiration-Mechanism
Pontine respiratory centers regulate the medullary
centers.
Pontine center- Apneustic center
Stimulate the activity of dorsal group of neurons in
medullary centers by discharging impulses
Impulses are transmitted by
phrenic and intercostal nerves.
It contract the Intercostal and Diaphragm muscles
Inspiration

15.  Pneumotaxic center inhibits the apneustic center
and restricts the duration of inspiration.
 Normally, during inspiration, dorsal respiratory
group neurons inhibit expiratory neurons of ventral
group.
During expiration
The expiratory neurons inhibit the dorsal group
neurons. Thus, the medullary respiratory centers control
each other.

16. Solid green line = Stimulation,
Dotted red line = Inhibition.
Respiratory centers in Brain stem

17. CHEMICAL MECHANISM
 Chemical mechanism of regulation of respiration is
operated through the chemoreceptors.
Chemoreceptors are the sensory nerve endings,
which give response to changes in chemical constituents
of blood.
 Changes in Chemical Constituents of Blood which
Stimulate Chemoreceptors
1. Hypoxia (decreased pO2)
2. Hypercapnea (increased pCO2)
3. Increased hydrogen ion concentration

18. Types of Chemoreceptors
Chemoreceptors are classified into two groups:
1. Central chemoreceptors
2. Peripheral chemoreceptors

19. CENTRAL CHEMORECEPTORS
 Central chemoreceptors are the chemoreceptors
present in the brain.
 CO2 combines with water to from carbonic acid, which in
turn, releases H+ ions in CSF of brain.
CO2 + H2O → H2CO3 → H+ + HCO3–
Hydrogen ions stimulate the central chemoreceptors
for inspiration.

20. PERIPHERAL CHEMORECEPTORS
 Peripheral chemoreceptors are the chemoreceptors
present in carotid and aortic region of Aorta in Heart.
 These chemoreceptors sense low O2 concentration.
when O2 concentration is low, alveolar ventilation
increases respiratory centers in brain stem.

23. Next Topic
Lungs volume and Lungs
capacities