sistem pernafasan (respiration system)

8/2/2019 Sistem Pernafasan (Respiration System)

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Respiration


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Control of breathing


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Breathing is controlled by:

1. the Central Control ( the brain )2. the Chemical Control.


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The Brain controls the breathingmechanism through the Medulla or theRespiratory Center.

The Chemical control is by the chemicalreceptors or Chemoreceptors.


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Respiratory Centers in the Brain


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The 3 Medullary Centers Controlling

Respiration:

1) Bilaterally, on either side of the

reticular formation are the medullaryrespiratory centers; an inspiration centerand an expiration center send nerve

impulses to the diaphragm andintercostal muscles.
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2) The next center up in the pons is theapneustic center. The apneustic centerfacilitates inspiration. Generally, theapneustic center kicks the inspiratory

center into gear if you go too long withoutbreathing (for example, if you were verytired).
http://faculty.etsu.edu/currie/images/resp10.jpghttp://faculty.etsu.edu/currie/images/resp10.jpg


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3) The pneumotaxic center is located inthe cranial part of the pons. This areacontrols the other 2 centers and cuts off

inspiration at a certain point to make surethat inspiration does not continue toolong. In other words it is a timer for

duration of inspiration.


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The Chemical control is done through

receptors in the body which is sensitive toCO2 and O2. . These receptors are knownas Chemoreceptors.

They are found in the:

1. Carotid Bodies

2. Aortic Bodies.


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Respiratory Chemoreceptors

1)Central Chemoreceptors are located onboth sides of the medulla in thebrain. These chemoreceptors are

primarily sensitive to pCO2 and the pH ofblood. As pH falls (gets more acidic) andpCO2 levels rise, these chemoreceptorsprovide stimulatory inputs to the

inspiratory center; this increasesventilation or breathing in an attempt toreduce H+ and CO2 in the blood.


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3) Peripheral Chemoreceptors known as the Aortic Bodiesinthe aortic arch and the Carotid Bodiesat the junction of the

carotid arteries in the neck.

Carotid and Aortic bodies are sensitive to:

Decreasing O2 ( HYPOXIA ) Increasing CO2 ( HYPERCAPNIA)

Deceasing pH ( more acidic)

When there is hypoxiaor hypercapniaor when the bloodbecomes more acidic, nerve impulse are sent to therespiratory centersin the medulla in the brain whichstimulates us to breathe more.


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Summary:

BREATHING IS CONTROLLED by:

1. Respiratory centers in the Brain.

2. Chemoreceptors:

a. Peripheral chemorecetpors ( Carotid and Aortic Bodies)

b. Central chemoreceptors ( on surface of medulla of brain )


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Mechanics of Breathing


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Physiology of Respiration

Measurement of gases

1. Gases in atmosphere 78% N2, 21% O2, 0.04% CO2 2.Pressure developed by gas is % x total pressure(760mm Hg) (i.e., partial pressure)

78% x 760 = 600 mm Hg = PN221% x 760 = 160 mm Hg = PO20.04% x 760 = .3mm Hg = PCO2

pressures in alveoli and blood differentpartial pressures are independent so gases can diffusein opposite directions


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Atmospheric Pressure (Patm) - pressure exertedby the air surrounding the body. At sea level its

equal to 760mmHg. For our purposes, we'llassume it to be constant and assign it a value of0mmHg.

Intrapulmonary Pressure (Palv) - pressure exertedby the air within the alveoli. It rises and fallsduring inspiration and expiration, but it alwaysequalizes with atmospheric pressure.

Intrapleural Pressure (Pip) - pressure within thepleural cavity. It is always lower than bothatmopsheric pressure and intrapulmonarypressure.


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FRC = Functional Residual Capacity

TV = Tidal Volume VC = Vital Capacity

RV = Residual Volume TLC = Total Lung Capacity

ERV = Expiratory Reserve Volume

IRV = Inspiratory Reserve Volume


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Normal pulmonary function tests:


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Pulmonary function tests (values shown as

% of expected value):

FEV1 61%

Vital Capacity 73% FEV1/VC 0.61 (normally >0.72)

Residual volume 175%

Total lung capacity 105% Diffusion Cap. CO 13%


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Pulmonary function tests in COPD (emphysema):


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sistem pernafasan (respiration system)

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