pengaturan sistem respirasi
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dr.Zulkarnain, M.ScBagian Fisiologi
Fakultas Kedokteran Unsyiah
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Basic elements of the respiratory control
system
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1. The medullary rhythmicity area (the medulla oblongata)
to control the basic rhythm of respiration.
Dorsal Respiratory Group (Inspiratory area)
Ventral Respiratory Group (Expiratory area)
2. The pneumotaxic area (the Pons)to promotes inspiration
3. The apneustic area (the Pons)to inhibits inspiration
To help coordinate the transition
between inhalation and
exhalation.
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Respiratory ControlCenters
Respiratory centers in
the brain stem establish
a rhythmic breathingpattern
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1. Dorsal Respiratory Group
The impulses propagate to theexternal intercostal muscles via
intercostal nerves and to the
diaphragm via the phrenic nerves
The muscles contract and
inhalation occurs (2 seconds). With no impulses arriving, the
diaphragm and external intercostal
muscles relax for about 3 seconds
allowing passive elastic recoil of
the lungs and thoracic wall.
2. Ventral Respiratory Group
The neurons of the expiratory area inactive during quiet breathing
Impulses from the expiratory area cause contraction of the internal
intercostaland abdominal muscleswhich decreases the size of the
thoracic cavity and causes forceful exhalation.
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Roles of the medullary rhythmicity area in controlling (a) the
basic rhythm of respiration and
(b) forceful breathing.
During forceful breathing, the inspiratory area
activates the expiratory area.
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This area sends stimulatory impulses to
the inspiratory area that activate it and
prolong inhalation. The result is a long,
deep inhalation when the
pneumotaxic area is active, it overrides
signals from the apneustic area.
Transmits inhibitory impulses to the
inspiratory area. The impulses shorten the duration
of inhalation when the
pneumotaxic area is more active,
breathing rate is more rapid.
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Cortical Influences on Respiration Chemoreceptor Regulation of Respiration
Proprioceptor Stimulation of Respiration
The Inflation Reflex
Other Influences on Respiration Limbic system stimulation
Temperature
Pain
Stretching the anal sphincter muscle
Irritation of airways
Blood pressure
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Chemoreceptorssensory neurons that respond to
changes in the levels of certain chemicals in the body. Central chemoreceptors (in or near the medulla
oblongatain the central nervous system ) respond to
changes in H concentration or PCO2, or both in
cerebrospinal fluid.
Peripheral chemoreceptors (in the aortic bodies and in
the carotid bodies)
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Normally, the PCO2 in arterial blood is 40 mmHg.
If even a slight increase in PCO2 occurs hypercapniaor hypercarbia
The central chemoreceptors are stimulated and respond vigorously to the resulting
increase in H level.
The peripheral chemoreceptors also are stimulated by both the high PCO2 and the rise
in H.
In addition, the peripheral chemoreceptors (but not the central chemoreceptors)
respond to a deficiency of O2.
If arterial PCO2 is lower than 40 mmHg hypocapniaor hypocarbia
The central and peripheral chemoreceptors are not stimulated, and stimulatory impulses
are not sent to the inspiratory area.
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Regulation of breathing in
response to changes
in blood PCO, PO, and pH(H concentration) via
negativefeedback control.
An increase in arterial blood
PCO stimulates theinspiratory center
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Increased
Arterial PCOon Ventilation
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Cortical Influences on Respiration
The cerebral cortex has connections with the respiratory center can voluntarily alterour pattern of breathing.
We can even refuse to breathe at all for a short time limited by the buildup of CO2
and H in the body.
PCO2 and H concentrations increase to a certain levelthe inspiratory area is strongly
stimulated, nerve impulses are sent along the phrenic and intercostal nerves to
inspiratory muscles Proprioceptor Stimulation of Respiration
Nerve impulses from the proprioceptors stimulate the inspiratory area of the medulla
oblongata.
Axon collaterals (branches) of upper motor neurons that originate in the primary motor
cortex (precentral gyrus) also feed excitatory impulses into the inspiratory area.
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Other Influences on Respiration
Limbic system stimulation Emotional anxiety may stimulate the limbic system, which then sends
excitatory input to the inspiratory area, increasing the rate and depth ofventilation.
Temperature An increase in body temperature, as occurs during a fever or vigorous
muscular exercise, increases the rate of respiration. A decrease in bodytemperature decreases respiratory rate.
Pain prolonged somatic pain increases respiratory rate. Visceral pain may slow
the rate of respiration
Stretching the anal sphincter muscle This action increases the respiratory rate and is sometimes used to
stimulate respiration in a newborn baby or a person who has stoppedbreathing.
Irritation of airways Physical or chemical irritation of the pharynx or larynx brings about an
immediate cessation of breathing followed by coughing or sneezing.
Blood pressure A sudden rise in blood pressure decreases the rate of respiration, and a
drop in blood pressure increases the respiratory rate.
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Referensi
Tortora GJ & Derrickson B. Principles of Anatomy and Physiology. 12thed. USA: John
Wiley and Sons. 2009. p.905-10
Guyton A.C., Hall J.E. Regulation of Respiration. In: Textbook of Medical Physiology;
11th edition. Pennsylvania: W.B. Saunder. 2006. p.514-23
Sherwood L. Human Physiology : From Cells to Systems. 7th ed. USA : Thomson-
Brooks/Cole. 2010.
West JB. Respiratory physiology the essentials. 9thedition. Philadelphia: Lippincott
William & Wilkins; 2012.
dr.Zul 2013
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