BC Biomedical NIBP-1010 Manual de usuario descargar pdf (Pagina 18)

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Heartfunctions‐physiology

A healthy heart works as a pump, which makes the blood circulate in the body. Blood

is brought from the organs by veins, leading via the upper and the lower vena cava into the

right atrium. By a contraction of the right atrium, the blood is ejected into the right ventricle.

From the right ventricle, the blood is transported via the pulmonary arteries into the lungs,

where it gets rid of carbon dioxide and arterializes. The blood returns from the lungs into the

left atrium via a pulmonary vein, it passes through the valve into the left ventricle, from where

it spreads via the aorta and other arteries throughout the body to supply the tissues with

oxygen and nutrients, and to remove waste materials.

In one minute of a resting state, the heart ejects approximately five litres of blood. If

the heart is in stress, this volume can increase temporarily up to three times. This quantity is

called the cardiac output - CO. For the correct function of the heart it is necessary that the

contractions of the heart muscles are strong enough and synchronized. The contractions are

initialized via electric incitement of the heart muscles; see the chapter below [2.3], [2.4],

[2.5].

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Theheart’sconductionsystem‐electrophysiology

The heart muscle’s cells are excitable, just like all the others, which means, that an

adequate stimulus on a membrane induces a response in the form of an action potential.

However, in case of the heart cells, this potential lasts much longer and its course differs in

the working myocardium as well as in different parts of the conduction system - the set of

specific cells, which are capable of

independent generation of electrical impulses

(automatia), thus controlling the heart’s

functioning. The structure, which generates

pulses with the highest frequency, is called the

pacemaker. Via its activity, it determines the

heart rate - HR. In healthy heart, this is the

sinoatrial (SA) node in the right atrium. From

this node, the pulses spread spokewise via the

atriums all the way to the septum between the

atriums and the ventricles, which is made of

valves. The valves function not only as a

Fig. 2.3: The heart’s transmission

(conduction) system [2.6].

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BC Biomedical NIBP-1010 Manual de usuario Pagina 18