Fisiologia

La meta de la fisiología es explicar los factores físicos y químicos que son responsables del origen y progresión de la vida

Hambre Frio

Miedo Reproduccion

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CélulaLa unidad viva basica

del cuerpo

Cada organo es un agregado de celulas

Cada celula esta adaptada

para funciones diferentes

Extra - Intracelular

Extracelular: variable

Intracelular: Ambiente Interior

Homeostasis

Son los mecanismos que nos permiten mantener casi constante el ambiente interno

Transporte de fluidos extracelular: sistema circulatorio

"Homeostatic" Mechanisms of the Major Functional Systems

Homeostasis

The term homeostasis is used by physiologists to mean maintenance of nearly constant conditions inthe internal environment. Essentially all organs and tissues of the body perform functions that help

maintain these relatively constant conditions. For instance, the lungs provide oxygen to theextracellular fluid to replenish the oxygen used by the cells, the kidneys maintain constant ionconcentrations, and the gastrointestinal system provides nutrients.

A large segment of this text is concerned with the manner in which each organ or tissue contributes tohomeostasis. To begin this discussion, the different functional systems of the body and theircontributions to homeostasis are outlined in this chapter; then we briefly outline the basic theory of thebody's control systems that allow the functional systems to operate in support of one another.

Extracellular Fluid Transport and Mixing System-The Blood Circulatory System

Extracellular fluid is transported through all parts of the body in two stages. The first stage is movementof blood through the body in the blood vessels, and the second is movement of fluid between the bloodcapillaries and the intercellular spaces between the tissue cells.

Figure 1-1 shows the overall circulation of blood. All the blood in the circulation traverses the entirecirculatory circuit an average of once each minute when the body is at rest and as many as six timeseach minute when a person is extremely active.

Figure 1-1 General organization of the circulatory system.

Guyton & Hall: Textbook of Medical Physiology, 12e [Vishal]'Homeostatic' Mechanisms of the Major Functional Systems

5 / 1921

Figure 1-2 Diffusion of fluid and dissolved constituents through the capillary walls and through theinterstitial spaces.

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As blood passes through the blood capillaries, continual exchange of extracellular fluid also occursbetween the plasma portion of the blood and the interstitial fluid that fills the intercellular spaces. Thisprocess is shown in Figure 1-2. The walls of the capillaries are permeable to most molecules in theplasma of the blood, with the exception of plasma protein molecules, which are too large to readilypass through the capillaries. Therefore, large amounts of fluid and its dissolved constituents diffuseback and forth between the blood and the tissue spaces, as shown by the arrows. This process ofdiffusion is caused by kinetic motion of the molecules in both the plasma and the interstitial fluid. Thatis, the fluid and dissolved molecules are continually moving and bouncing in all directions within theplasma and the fluid in the intercellular spaces, as well as through the capillary pores. Few cells arelocated more than 50 micrometers from a capillary, which ensures diffusion of almost any substancefrom the capillary to the cell within a few seconds. Thus, the extracellular fluid everywhere in the body-both that of the plasma and that of the interstitial fluid-is continually being mixed, thereby maintaininghomogeneity of the extracellular fluid throughout the body.

Origin of Nutrients in the Extracellular Fluid

Respiratory System

Figure 1-1 shows that each time the blood passes through the body, it also flows through the lungs.The blood picks up oxygen in the alveoli, thus acquiring the oxygen needed by the cells. The

membrane between the alveoli and the lumen of the pulmonary capillaries, the alveolar membrane, is

only 0.4 to 2.0 micrometers thick, and oxygen rapidly diffuses by molecular motion through thismembrane into the blood.

Gastrointestinal Tract

A large portion of the blood pumped by the heart also passes through the walls of the gastrointestinaltract. Here different dissolved nutrients, including carbohydrates, fatty acids, and amino acids, are

absorbed from the ingested food into the extracellular fluid of the blood.

Guyton & Hall: Textbook of Medical Physiology, 12e [Vishal]'Homeostatic' Mechanisms of the Major Functional Systems

6 / 1921

Origen de los nutrientes

Funciones metabólicas

Higado transforma productos en formas mas

“usables”

Sistema Urinario

Sistema nervioso

Sistema endocrino

Sistema Inmune

Sistema Tegumentario

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