The document provides a detailed overview of the regulation of respiration, emphasizing the roles of various respiratory centers in the brain, including the dorsal respiratory group, ventral respiratory group, pneumotaxic center, and apneustic center. It describes the physiological mechanisms of nervous and chemical control of respiration, highlighting the impacts of carbon dioxide, hydrogen ions, and oxygen levels on respiratory function. Additionally, it discusses the changes in respiratory regulation during exercise, including increased ventilation and oxygen consumption.

1. UNIVERSITY OF THE ZANZIBAR
SCHOOL OF HEALTH & MEDICAL
SCIENCES
ACADEMIC COURSE 2022 - 2023

2. PHYSIOLOGY

3. Pr.Diane Millo Martin.
Ferst Degree Specialist in
Physiology and Pathophysiology
Associate Professor
Visiting Lecturer

4. LECTURE:
REGULATION OF RESPIRATION

5. SUMMARY:
1. Nervous control of respiration.
Respiratory center.
2. Chemical control of respiration
a) Central chemoreceptor.
b) Peripheral chemoreceptor.
3. Regulation of respiration during
exercise.
4. Others factors.

6. BIBLIOGRAPHY
Textbook of Medical Physiology
Guyton & Hall.
13 edition.
Chapter 41
pages: 514 to 522.

7. Regulation of ventilation
According to body needs
paO2 y paCO2 normal
Normal ventilation

8. REGULATION OF RESPIRATION
VOLUNTARY INVOLUNTARY
RC

9. RESPIRATORY CENTER
Concept: Respiratory center is composed of
several group of neurons located bilaterally
in the medulla oblongata and pons of the
brain stem.
Organization:
– Dorsal respiratory group of neurons.
– Ventral respiratory group of neurons.
– Pneumataxic center.
– Apneustic center.
– Chemosensitive area.

10. RESPIRATORY CENTER
Dorsal respiratory
group (inspiration)
Ventral respiratory group
(expiration and inspiration)
Apneustic center
Pneumotaxic center

11. RESPIRATORY CENTER
DORSAL RESPIRATORY GROUP:
• Location: Nucleus of the Tractus Solitarius and
adjacent reticular substance neurons of the
medulla. (N. Solitarius is the sensory
termination of vagus and glossopharyngeal
nerves).
• Functions:
- Generate the basic rhythm of respiration. The
neurons of this area are excited by themselves
during a period of time. Nervous signal
transmitted to the inspiratory muscles is not an
instantaneous burst of action potentials. In
normal respiration, it begins weakly and
increase steadily in a ramp manner for about 2
second and it ceases abruptly for 3 second.
Next, inspiratory signal begins another cycle.

12. RESPIRATORY CENTER
DORSAL RESPIRATORY GROUP:
• Functions:
The inspiratory signal is a RAMP SIGNAL.
There are two qualities of inspiratory ramp:
- Control of the rate of increase of the ramp
signal.
Ex: Heavy respiration the ramp increase
rapidly.
- Control of limiting point at which the ramp
suddenly ceases. Ex: Method for controlling
the rate of respiration.

13. RESPIRATORY CENTER
VENTRAL RESPIRATORY GROUP
• Location: In each side of the medulla about 5 mm
anterior and lateral to the dorsal respiratory group of
neurons (Nucleus ambigus and nucleus retroambigus).
• Functions:
- It is inactive during normal respiration.
- This group is activated from basic oscillatory
mechanism of the dorsal respiratory area when
increased pulmonary ventilation.
- During the electrical stimulation of the few of the
neurons in the ventral group causes inspiration, while the
stimulation of others causes expiration, therefore theses
neurons contribute to both inspiration and expiration.
They are important in providing the powerful expiratory
signals to the abdominal muscles during heavy
expiration.

14. RESPIRATORY CENTER
PNEUMOTAXIC CENTER
• Location: Dorsally in the nucleus parabrachialis
on the upper pons.
• Functions: Transmits inhibitory signals to
dorsal respiratory group that produce:
- Control the SWITCH-OFF point of the
inspiratory ramp (control the duration of the
filling phase of the lung cycle). Pneumotaxic
center limits the duration of the inspiration.
- A secondary effect is the regulation of
respiratory rate.

15. RESPIRATORY CENTER
APNEUSTIC CENTER
• Location: Low portion of the pons.
• Function: Transmits excitatory
signal to dorsal respiratory group
that avoid the end of inspiration. (If
pneumotaxic center is damaged).

16. RESPIRATORY CENTER
Chemosensitive Area
Location: Bilaterally in the
ventral surface of the
medulla (high sensitive to
changes of either blood
pCO2 or H+ concentration)

17. HERING – BREUER INFLATION REFLEX
Help to control of respiration, because stops the
inspiration when the lungs become overly inflated.
Stopping
inspiration
Distention
receptors
Vagus N
e
r
v
e
Dorsal
respiratory
group

18. HUMORAL REGULATION OF THE
VENTILATION
H+
CO2 O2
Chemical factors
Respiratory
Center Chemoreceptors

19. HUMORAL REGULATION OF THE
VENTILATION
• HYDROGEN ION:
H+ is the most potent stimulus for
the neurons of chemosensitive
area, but it do not easily cross the
blood-brain barrier.

20. RESPIRATORY CENTER
Chemosensitive Area
H+
CO2 + H2O H2CO3
H+
HCO3
-

21. HUMORAL REGULATION OF THE
VENTILATION
• CARBON DIOXIDE: The most important
humoral factor. It has two effects:
- Direct effect with the neurons in the
chemosensitive area. (Weak effect).
- Indirect effect (Formation of hydrogen
ions).
Blood-brain barrier is not very permeable
to H+, but CO2 passes through this
barrier with facility.

22. EFFECTS OF THE CARBON DIOXIDE
CO2
CO2 + H2O H2CO3
H+
HCO3
-

23. HUMORAL REGULATION OF THE
VENTILATION
• OXYGEN: Changes O2 concentration don’t
have direct effect on the respiratory center. It
has an indirect effect acting through the
peripheral chemoreceptors.
• Location of chemoreceptors:
- Carotid bodies (Hering’s nerves to
glossopharyngeal).
- Aortic bodies (Vagus nerve).
• Stimuli: Decrease of O2, increase CO2 and H+
concentration.

24. REGULATION OF RESPIRATION
DURING EXERCISE
• In exercise oxygen consumption and
CO2 increases as 20-fold.
• Alveolar ventilation increases.

25. REGULATION OF RESPIRATION
DURING EXERCISE
WHAT CAUSES INTENSE VENTILATION
DURING EXERCISE?
The cerebral motor cortex transmits
motor impulses to the exercising
muscles and the same time transmits
collateral impulses into the brain stem to
excite the respiratory center that
increase the rate of ventilation.