Human Body and its Control System
Physiology attempts to describe the chemical and physical elements that account for the mechanism of life. Each form of life, from the smallest virus up to the largest mammal has its own unique characteristics. Therefore the subject of physiology is divided into many subdivisions.
Human Physiology
Human physiology is the study of the functioning of the normal body, and is responsible for describing how various systems of the human body work. It attempts to expain the specific mechanisms happening inside the humand body. The fact that that how we strive to survive is beyond our conscious control, for hunger drives us to find and eat food, thirst motvicates us to drink, sensations of cold makes us seek warmth, and fear makes us seek ashelter and protection. Thus the human body is automated, and the fact that we are knowledgeable beings, this special characteristic allows us to adapt under widely varying conditions.
Cells: Living Units of the Body
The cell is the basic living unit of the body, and when grouped together focus into tissues of our organs held together by other supporting structures. Each cell specifically performs one or a few particular function. One example, the read blood cell numbering to 25 trillion in one human body, transport oxygen from the lungs to tissue ,although they are the most abundant among cells, there are still about 75 trillion cells of other types that perform specific function different from red blood cells. All in all, the body contains approximately about 100 trillion cells.
Although many cell types differ markedly from one another, all of them have certain characteristics that are similar. Cells also have the ability to reproduce additional cells of their own type, in case when cells of a particular type are destroyed from one cause or another.
“Internal” Environment – The Extracellular Fluid
The human body consist of approximately 60 percent of fluid mainly a water solution of ions and other substances. Although most of this fluid is inside the cells, only about one third is in the spaces outside the cells called extracellular fluid wherein ions and nutrients are stored needed by cells to maintain cell life. Essentially all cells live in the same environment. For this reason, the extracellular fluid is called the “internal” environment of the body. Cells can perfom their special function as long as the porper conditions are available in the internal environment.
The extracellular fluid is filled with large amounts of sodium, chloride and bicarbonate ions plus nutrients for the cells, such as oxygen, glucose, lipids and amino acids. It also contains carbon dioxide as an end product of cellular respiration plus other waste products transported to the kidneys for excretion.
Conversely, the intracellular fluid contains large amounts of potassium, magnesium, and phosphate ions instead of sodium and chloride ions.
Conversely, the intracellular fluid contains large amounts of potassium, magnesium, and phosphate ions instead of sodium and chloride ions.
“Homeostatic” Mechanisms of the Body Systems
Homeostasis
The human body consists of trillions of cells all working together for the maintenance of the entire organism. While cells may perform very different functions, all the cells are quite similar in their metabolic requirements. Maintaining a constant internal environment with all that the cells need to survive (oxygen, glucose, mineral ions, waste removal, and so forth) is necessary for the well-being of individual cells and the well-being of the entire body. The varied processes by which the body regulates its internal environment are collectively referred to as homeostasis. The term homeostasis is used by physiologists to mean maintenance of nearly constant conditions in the inernal environment. Essentially all organs and tissues of the body perfom functions that help maintain these constant conditions.
Extracellular Fluid Transcport
Extracellular fluid is transported throughout the body in two stages. In stage one, blood moves through the body in blood vessels, and in stage two, extracellular fluid moves between blood capillaries and intercellular spaces between tissue cells.
When blood is passing though the blood capillaries, continual exchange of extracellular fuid also occur between the plasma portion of blood and interstitial fluid that fill the intercellular spaces. The capillary walls are permeable to most molecules of the blood with large plasma proteins being excluded. That is, fluid and dissolved molecules are continually moving in and out of the capillary walls and intercellular fluid which ensures almost complete homogeneity of the extracellular fluid throughout the body.
