Regulation of Respiration- Control of respiration

Control of respiration

1. Regulation of Respiration
1Dr.Krithika Pai

2. INTRODUCTION
Normally, quiet regular breathing occur because
of two regulatory mechanisms:
1. Nervous or neural mechanism
2. Chemical mechanism
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3. NERVOUS MECHANISM
1. Respiratory centers
2. Afferent nerves
3. Efferent nerves.
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4. 1.RESPIRATORY CENTERS
•Respiratory centers are group of neurons,
which control the rate, rhythm and force of
respiration
•centers are bilaterally situated in reticular
formation of the brainstem (medulla
oblongata and pons )
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5. Medullary centers
•1. Dorsal
respiratory
group of neurons
•2. Ventral
respiratory
group of neurons
Pontine centers
•1.Apneustic
center
•2.Pneumotaxic
center
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7. Centers Situation Function
MEDULLARY
CENTERS
1. Dorsal Respiratory
Group of Neurons
•nucleus of tractus
solitarius which is
in the upper part of the
medulla oblongata
•inspiratory center
•responsible for basic
rhythm of respiration
•mainly causes
inspiration
•Generate inspiratory
ramp
2. Ventral Respiratory
Group of Neurons
•nucleus ambiguous
and nucleus
retroambiguous
of medulla oblongata
•expiratory center
•ventral group neurons
are inactive during
quiet breathing and
become active during
forced breathing.
•During forced
breathing, these
neurons stimulate
both inspiratory muscles
and expiratory muscles
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8. Note
Inspiratory ramp
•Inspiratory ramp is the pattern of impulse
discharge from dorsal respiratory group of
neurons.
•These impulses are characterized by steady
increase in amplitude of the action potential.
•Impulse discharge from these neurons is not
sudden and it is also not uniform
•Significance: there is a slow and steady
inspiration, so that the filling of lungs with air is
also steady
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9. Centers Situation Function
PONTINE CENTERS
Apneustic Center
reticular formation of
lower pons
increases depth of
inspiration by
acting directly on dorsal
group neurons.
Pneumotaxic Center dorsolateral part
of reticular formation in
upper pons.
•control
the medullary
respiratory centers,
particularly the
dorsal group neurons
•inhibits the apneustic
center so that the dorsal
group neurons are
inhibited. Because
of this, inspiration stops
and expiration starts
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10. Pre-Bötzinger Complex
•It is an additional respiratory center found in
animals.
•It is formed by a group of neurons called
pacemaker neurons, located in the
ventrolateral part of medulla.
•Pacemaker neurons generate the rhythmic
respiratory impulses.
•Medullary centers send nerve fibers into this
complex
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11. 2.Efferent Pathway
1. Phrenic nerve fibers (C3 to C5), which supply
the diaphragm
2. Intercostal nerve fibers (T1 to T11), which
supply the external intercostal muscles
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13. 3.Afferent Pathway
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.
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14. CHEMICAL MECHANISM
•operated through the chemoreceptors.
Chemoreceptors are the sensory nerve
endings,
•which give response to changes in chemical
constituents of blood.
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15. Changes in Chemical Constituents of Blood
which Stimulate Chemoreceptors
1. Hypoxia (decreased pO2)
2. Hypercapnea (increased pCO2)
3. Increased hydrogen ion concentration
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16. Types of Chemoreceptors
1. Central chemoreceptors
2. Peripheral chemoreceptors
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17. CENTRAL CHEMORECEPTORS
•Situation- deeper part of medulla oblongata,
close to the dorsal respiratory group of
neurons
•Chemo receptors are in close contact with
blood and cerebrospinal fluid.
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18. Mechanism of Action
Main stimulant : increased hydrogen ion concentration
in brain
When CO₂ levels rise in the blood, it diffuses
into the CSF, forming carbonic acid (H₂CO₃),
which dissociates into hydrogen ions (H⁺) and
bicarbonate ions (HCO₃⁻).
The increase in H⁺ lowers the pH,
stimulating the central chemoreceptors to
send signals to the respiratory centers in
the brain to increase the rate and depth of
breathing,
thus expelling more CO₂.
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19. PERIPHERAL CHEMORECEPTORS
•Situation -present in carotid and aortic region
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21. Mechanism of Action
•Main stimulant : Hypoxia
•It is because of the presence of oxygen
sensitive potassium channels in the glomus
cells of peripheral chemoreceptors.
•Hypoxia causes closure of oxygen sensitive
potassium channels and prevents potassium
efflux
•This leads to depolarization of glomus cells and
generation of action potentials in nerve ending
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22. •These impulses excite the dorsal group of
neurons
•Dorsal group of neurons in turn, send
excitatory impulses to respiratory muscles,
resulting in increased ventilation.
•This provides enough oxygen and rectifies the
lack of oxygen.
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