Chapter 1 Flashcards
Homeostasis
The maintenance of the near constant conditions of the internal environment.
Negative feedback system
The feedback system that reduces the output of a given system. Ex, the hormonal secretion.
Positive feedback system
The feedback system that increases the output of another system. For example, the clotting enzyme cascade theory.
Physiology
The science that seeks to explain the physical and chemical mechanics that are responsible for the origin, development and progression of life. Each type of life has its own functional characteristics.
Human Physiology
The science of human physiology attempts to explain the specific characteristics and mechanisms of the human body that makes it a living body.
Cells
The basic living unit of the body is the cell. Each organ is an aggregate of different cells held together by intercellular supporting structures.
First characteristic of cells
Each type of cell is specially adapted to perform one or a few particular functions.
How many red blood cells are there in the body? How many cells are there in the body?
There are 25 trillion red blood cells in the body. There are 75 trillion other cells in the body. There are a total of 100 trillion cells in the body.
Second characteristic of cells
Cells often differ markedly from one another, all of them have certain basic characteristics that are alike.
Give an example of the second characteristic of cells
Oxygen reacts with carbohydrates, proteins and fat to release energy needed to function. All cells deliver the products of their chemical reactions into the surrounding fluids.
Intracellular fluid
The fluid present inside the cells is called intracellular fluid. 2/3rds of the total fluid in body is present as intracellular fluid
Extracellular fluid
Fluid present outside the cells is called extracellular fluid. This fluid contains the ions needed to maintain life. It is 1/3rd of the total body fluid.
The diffusion of the extracellular fluid
The extracellular fluid is in constant motion throughout the body. It is transported rapidly in the circulating blood and then mixed between the blood and the tissue fluids by diffusion through the capillary walls.
Who discovered the extracellular fluid?
A french physiologist Claude Bernard gave the term milieu intérieur, which means extracellular fluid which is also called internal environment.
Difference between extracellular and intracellular fluid
Extracellular fluid contains more sodium, chloride and bicarbonate ions along with nutrients like oxygen, glucose, fatty acids and amino acids as well as carbon dioxide.
Intracellular fluid contains large amounts of potassium, magnesium and phosphate ions.
Who invented the term Homeostasis?
In 1929, Walter Cannon invented the term Homestasis.
Disease and homeostasis
Disease is considered to be a state of disrupted homeostasis. However homeostasis continues to operate and maintain vital functions through several compensations even during disease. Pathophysiology explains how various physiological processes are altered in injury or disease.
Stages of ECF movement
The first stage is movement of blood through the body in the blood vessels and the second stage is movement of fluid between the blood capillaries and the intercellular spaces between tissue cells. As blood passes through the blood capillaries continual exchange of ECF also occurs between plasma portion of blood and the interstitial fluid.
How long does it take for blood to traverse the body?
All blood circulates throughout the body in an average of 6 minutes. During active moments, it takes about 1 minute.
Explain the kinetic flow of body fluid
The process of diffusion is caused by the kinetic movement of the molecules in both the plasma and the interstitial fluid. That is, the molecules of the fluid and plasma constantly moving and bouncing in all directions in the fluid and plasma within the intercellular spaces, as well as through the capillary pores. Few cells are located more than 50 micrometer from a capillary, which ensures diffusion of almost any substance from the capillary. Thus the fluid in the extracellular spaces and the fluid in the interstitial region constantly mixes together and maintains homogenity.
Examples of how little changes in values can cause great adverse effects
An increase of even 7 degree celsius in the body can lead to a vicious cycle which leads to an increase in cellular metabolism causing cell death on large scale. If potassium ion concentration is reduced to less than one third of the normal then person is likey to get paralyzed as nerves cant carry signals. If that concentration increases two to three times then heart muscle will be severely depressed. If calcium falls below one half of the normal then sponataneous generation of excessive nerve impulses will happen causing tetani. When glucose concentration falls to less than one half of normal then this can lead to extreme mental irratibility and sometimes even convulsions.
How does negative feedback relate to homeostasis? Give an example of negative feedback
If some factor in the body becomes excessive or deficient, a control of system initiates negative feedback which consists of a series of changes that return the factor toward a certain mean value, thus maintaining homeostasis. For example, in the arterial pressure- regulating mechanisms a high pressure causes a series of reactions that promote a lowered pressure.
Gain of control system
Degree of effectiveness with which a control system maintains constant conditions is determined by gain of the negative feedback. Gain = correction/error. Correction = value to which something rises - value to which it would have risen without negative feedback. Error, the amount the thing rose after negative feedback. The more the absolute value of gain, the better the system. For example, the gain of temperature regulation system is -33 whereas for baroreceptor it is -2. So temperature regulation system is much more effecient.
Positive feedback and its example.
Positive feedback is also known as ‘vicious cycle’ because it can increase a negative attribute further thus leading to a vicious cycle causing death of the person. For example, when a person loses blood, their heart weakens as less blood goes to the coronary vessels, this in turn leads to pumping of less blood. Thus at the end the heart becomes so weak that it cannot pump out any more blood anymore.
