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