From today we are going to study a new course of medical science, that is, Human physiology. I am very glad to have this chance to study with you. I come from the department of Physiology, My name is Gao DM. My English is not very good but I will make my best to help you to master the general knowledge of physiology. Pay attention, I speak English often with French Accent. In order to familiar each other can you introduce yourself simply to me? What your name and where you come from?
In order to help yourself to review, I think it is a good idea to take some note of what we learn in class, because I think what I present in class is important contents of physiology. Besides, as physiology is a science about human function, I think when you learn or review the knowledge of physiology, you should ask some questions, three www, such as what is the function of heart or lung? How it functions? Why is can function like this?
Today , we are going to study chapter one: Introduction. In this chapter, we will study some general information about physiology.
Definition of physiology. In your opinion, what is physiology? Physiology is one of the biological sciences which deals with the mechanisms of the normal functions of the living organism. Pay attention! You can see clearly the Object of physiology research : normal functions of living organism (perhaps the organism is virus, or bacteria, plant, animal, or human being) You can simply say that physiology is the science about how the living organism works. Goal of physiology is to explain the physical and chemical factors that are responsible for the origin, development, and progression of life.
Each type of life, from the very simple virus to the largest tree or to the complicated human being, has its own functional characteristics. Therefore, physiology can be divided into viral Physiology, bacterial Physiology, plant Physiology, and human Physiology. In human physiology, we are concerned with the specific characteristics and mechanisms of the human body that make it a living being. For example, you may often ask: (next slide)
Why does a medical student must study physiology?. The relationship between physiology and clinical medicine The Simple answer Physiology is the basis of your next medical courses, such as pathology, pathophysiology, pharmacology and clinical medicines As a medical student, you will be a doctor. And as a doctor, what is your duty? I think the duty of the doctor is to prevent, to diagnose and to cure the disease, thereby to keep persons health. But before to treat a patient, you should know what disease the patient suffer from. For instance, there is a common disease called “hypertension” . To determine if a person suffer from hypertension, you must know what is blood pressure, its normal value, how BP is formed and why BP can change. And all these questions will be answered in our study of physiology. So we say that Physiology is the basis of clinical medicine. It is a very important course in medicine. If you want to become a good doctor, you must learn the knowledge of physiology well.
As introduction of human physiology, I would like to talk simply with you about the history of Physiology. Generally speaking, human physiology is developing in the process of the struggle of human being to diseases. Some persons make them great contributions in the developing of physiology. That are: ……….. Especially, William Harvey.
Before 1628, physiology was still not an independent science. It is Harvey who make the physiology a independent science.
William Harvey was a famous English physician and physiologist. He studied at Cambridge University and at the University of Padua, Italy. As a young student and a doctor, Harvey was very interested in anatomy especially in the blood flow in the human body. Do you know how the blood circulate in our body? Answer… heart→ artery → capillaries →vein →heart . The heart pumps the blood to the artery. Then blood flow from the artery, capillaries and returns the heat by vein. Now , it is clear about the blood circulation. But at that time, one didn’t know that blood is circulated in our body. Because one didn’t know capillary. Most doctors of the time felt that the lungs moved the blood around the body. And blood was consumed, that is to say : the blood is not circulate, once blood flows from a organ, such as the heart or lung, it dose not return. Of course, it is not right.
Harvey questioned these beliefs and investigated them scientifically. Harvey carried out many experiments, both dissections and physiological experiments on animals. He dissected hearts and found that the valves in the heart allowed blood to flow in only one direction. Atrioventricular valve→ ventricle ; aortic valve → artery 2. the heartbeat of living animals showed that the left and the right ventricles contracted together. 3. Harvey removed the heart from a living animal, it continued to beat, thus acting as a pump. 4. Harvey also used mathematical data to prove that the blood was not being consumed. He removed the blood from human cadavers (dead bodies) and found that the heart could hold roughly two ounces of blood. By calculating the number of heartbeats in a day and multiplying this by two ounces, he showed that the amount of blood pumped was far greater than the amount that the body could possibly make. 30*2*75*24=108,000 He also estimated how much food and liquids a person could eat during a day. To Harvey, this showed that the teaching by Galen that the blood was being consumed by the organs of the body was false. Blood had to be flowing through a 'closed circuit' . Even though he lacked a microscope, Harvey theorized that the arteries and veins were connected to each other by capillaries, which would later be discovered some years after Harvey's death. He proved that the heart was a pump which forced the blood around the body through arteries and that the blood was returned to the heart through the veins. In 1628 Harvey formally presented his findings in his publication - the Motion of the Heart and Blood in Animals,
The living organism has some common fundamental characteristics, for example, Metabolism, Growth, Development, Reproduction and Excitability Here, we discuss the metabolism and excitability.
What is metabolism? The complex of physical and chemical processes occurring within a living cell or organism that are necessary for the maintenance of life. In metabolism some substances are broken down to yield energy for vital processes while other substances, necessary for life, are synthesized.
In metabolism some substances are broken down to produce energy for vital processes while other substances, necessary for life, are synthesized. Metabolism can be divided into to classes: Anabolism and catabolism: Obviously, Catabolism and anabolism are two opposing activities taking place simultaneously in the cell. Both are necessary for maintaining the life. In one hand, we take the energy by catabolism. On the other hand, we store the energy by anabolism for the future use. If the metabolism stops the life will end.
An other important Fundamental characteristics is excitability. The environment in which we live varies all the time. For example, The weather varies from day to day. the temperature can change between 50 and -50 ℃…mechanical, chemical and electrical changes In order to live when environmental changes act on the body, the body functions must to modify to adapt to the environment change. This is the fundamental property of a living cell, even a living organism or a person. When stimulus is given to a skeletal muscle, the muscle will contract. This is the excitability. Here the definition of stimulus and response
By electrophysiological research, it is found that in a excitable cell, for example, in a skeletal muscle cell, if a proper stimulus is given, the muscle cell will contract, but before the muscle cell contracts, an electrical change across the cell membrane can be recorded. That is an action potential. In all excitable cells, the Primary response to the stimulation is the action potential. So in modern physiology, physiology is the property that living cells can elicit an action potential to react to stimuli.
Almost all of cell in our body represent the excitability; While the muscles, neurons and glandular cells are more sensitive to the stimulation and they can elicit an action potential. So they are called excitable cells. The response of excitable cell to the stimulation can be classified into two types:
What is the relationship of excitability with the threshold ? The excitability is inverse proportional to the threshold. That is, the higher the threshold needed, the lower the excitability, vice versa. For example, If the threshold intensity is 1V, and the other is 0.5 V, Whose excitability is higher?
The environment we live in is called external environment.
About 60 per cent of the adult human body is fluid, mainly a water solution of ions and other substances. Although most of this fluid is inside the cells and is called intracellular fluid, about one third is in the spaces outside the cells and is called extracellular fluid. This 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.
Thus, all cells live in the extracellular fluid. In the extracellular fluid are the ions and nutrients needed by the cells to maintain cell life. For this reason, the extracellular fluid is also called the internal environment of the body, a term introduced by the great French physiologist Claude Bernard more than 100 years ago.
The term homeostasis is the maintenance of nearly constant conditions in the internal environment.
Essentially all organs and tissues of the body perform functions that help maintain these constant conditions.
Examples of Control Mechanisms For instance , Because oxygen is required for chemical reactions in all cells, the oxygen concentration in the tissue fluid is low, Carbon dioxide is a major end product of the oxidative reactions in cells, carbon dioxide concentration in the blood is higher than normal. On the other hand, the expiratory movement of the lungs take oxygen to the extracellular fluid to replenish the oxygen and remove excess carbon dioxide from the blood and tissue fluids. This process continues until the concentration returns to normal. If a person suffers from some respiratory diseases, the homeostasis of oxygen and carbon dioxide will disappear, even die.
Regulation- the ability of an organism to maintain a stable internal conditions in a constantly changing environment
The regulation of the body functions is achieved by three types: Nervous regulation Chemical Regulation 3. Autoregulation
So called nervous regulation is the regulation achieved by the activity of nervous system How does the nervous system regulate the body function? but what is the basic manner of nervous system? That is reflex. Can you tell me what is the reflex. the regular responses of the organism to the stimulation under the mediation of the central nervous system. The reflex is a kind of response, but is a regular response. The reflex is reached in the participation of the central nerve system. I think you have learned some reflex in the study of anatomy, can you give me some example of reflex.
The stretch reflex of skeletal muscle. Structural basis of reflex: Receptor: to detect the environmental change or to receive stimulus; Afferent nerve: to carry the stimulation information to the center; Reflex center: to analyse the input information and decide the response to the stimulation; Efferent nerve: to carry the central information to the effector; Effector: to complete the reflex. In order to achieve of the reflex activity, the reflex arc must keep the structural and functional integrality. If the afferent or efferent nerve is cut, the reflex stops or not induced. If the center is injured, the reflex can not appear.
Acid 杨梅 waxberry
nervous regulation : rapid in onset, accurate in response, shorter in duration humoral regulation : slow in onset, diffuse in nature, longer in duration.
The very fact that we remain alive is almost beyond our own control, for example, hunger makes us seek food. Sensations of cold make us provide warmth. Thus, the human being is actually a robot. If we investigate the control system of the body functions using the theory of cybernetics (The theoretical study of communication and control processes in biological, mechanical, and electronic systems, especially the comparison of these processes in biological and artificial systems.), we can find that the human body is an integrate autocontrol system.
The control system of our body has three types: I. Non-autocontrol system Feedback control system (autocontrol system) Feed-forward control system
According to the theory of cybernetics, a control system is composed of two parts: One is the control system or control part, another is the controlled system or controlled part.
In non-autocontrol system, the control system control the activity of the controlled system, the result of the activity of controlled system is called output variables. In our body, the non-autocontrol system is rare. So, we do not discuss it in detail.
In the living organism, the most important control system is autocontrol system or the feedback control system. At first, let’s look at the structure of the autocontrol system.
Autocontrol system is also composed of the Control system and the controlled system two parts, but there exists a closed loop. In one hand, the control system control the activity of the controlled system on the other hand, the activity of controlled system, the output variables, was sent back by a monitor to the control system to modify the activity of the control system. This called feedback. Is the effect of the controlled system on the control system . The feedback is the key point of autocontrol.
In modern familiar life, we often use a heater or cooler to keep the room in a proper temperature and so on . For example: 空调 Air-condition, Electric cooker, Refrigeratory 冰箱. They are working in a same mechanism. In this example, it is a heater as the controlled system. The switch (of course, it is autoswitch or a computer system) is the control system. The thermometer is the temperature monitor. The set point mean the point where the room temperature should be kept. The set point can be set artificailly.
For example, there is a air-condition in a room. If you want to make the room temperature in 37℃, you can set it yourself. The control system may start up the heater, the heater (controlled part) begins to heat the room according to the command of the control system. The room temperature increases. If the room temperature can keep in 37directly. No! Because the atmosphere temperature must influence the room temperature. For example, if the atmosphere temperature is higher, the room temperature may be higher than the set point. This higher temperature is monitored By the thermometer and send back to a comparator (feedback). The system found that the room temperature is three 3℃ higher than the set point. The control system sends the command to low the heater or stop it. Thereby, the room temperature is reduced below the set point, again the monitor send back the information to the comparator. The control system sends the command to intensify the heater. The temperature rises. So the room temperature keeps in 37.
Most control systems of the body act by negative feedback
Therefore, in general, if some factor becomes excessive or deficient, a control system initiates negative feedback, which consists of a series of changes that return the factor toward a certain mean value, thus maintaining homeostasis.
For instance, some movements of the body occur so rapidly that there is not enough time for nerve signals to travel from the peripheral parts of the body all the way to the brain and then back to the periphery again to control the movement. Therefore, the brain uses a principle called feed-forward control to cause required muscle contractions. That is, sensory nerve signals from the moving parts apprise the brain whether the movement is performed correctly. If not, the brain corrects the feed-forward signals that it sends to the muscles the next time the movement is required. Then, if still further correction is needed, this will be done again for subsequent movements. This is called adaptive control. Adaptive control, in a sense, is delayed negative feedback. Thus, one can see how complex the feedback control systems of the body can be. A person’s life depends on all of them. Therefore, a major share of this text is devoted to discussing these life-giving mechanisms.
How to study physiology?
1. Take note :
2. Ask: what
I. Definition of physiology
Physiology is one of the biological
sciences which deals with the
mechanisms of the normal
functions of the living organism.
Goal of physiology :
to explain the physical and chemical factors
that are responsible for the origin,
development, and progression of life
In human physiology, we are concerned with the
specific characteristics and mechanisms of the
human body that make it a living being.
How is the food digested and
absorbed in the digestive system ?
How are all bodily functions
regulated by our nervous
system and endocrine system?
II. The relationship between
physiology and clinical medicine
Physiology is the basis of clinical medicine.
Duty of doctor: to prevent, diagnose and cure
diseases , to keep health
For example : Hypertension
BP: concept, normal value, formation and
its influencing factor
III. History of Physiology
The Greek philosopher Aristotle (384–322 B.C.)
speculated on the function of the human body.
Galen (A.D. 130–201) wrote widely on the subject
and was considered the authority until the advent
of the Renaissance.
Physiology became a fully experimental science
with the revolutionary work of the English
physician William Harvey (1578–1657), who
demonstrated that the heart pumps blood through
a closed system of vessels.
However, the father of modern physiology is the
French physiologist Claude Bernard (1813–1878),
III. Foundation of Physiology
Famous physician and
the Motion of the Heart and Blood in
1. The valves in the heart allowed blood to flow in
only one direction.
2. The left and the right ventricles contracted
3. Harvey removed the heart from a living animal, it
continued to beat : pump.
4. Harvey also used mathematical data to prove that
the blood was not being consumed:
the heart could hold two ounces of blood.
the amount of blood pumped was far greater
than the amount that the body could make.
He also estimated how much food and liquids a
person could eat during a day.
Blood had to be flowing through a 'closed circuit' . 16
IV. Fundamental characteristics
of living organism
The complex of physical and chemical
processes occurring within a living cell or
organism that are necessary for the
maintenance of life.
the synthesis of complex molecules
from simpler ones
the breakdown of larger, more complex
molecules into smaller, simpler
molecules, during which energy is
released for the activity of the body.
Stimulus: the environmental change that
can induce a change of the body
(1) Definition of excitability
The property that living organisms can
react to stimuli is defined as excitability .
The property that living cells can elicit an
action potential to react to stimuli.
(Action potential is the index of
(2) EXCITABLE CELL
The cells that can elicit an action potential
i.e. Muscle cell , neurons and glandular cell
（ 3 ） The types of response :
1) Excitation (excitatory response):
-- an increase in activity
inhibition (inhibitory response):
-- a decrease in activity
(Threshold ， threshold of stimulus)
the smallest intensity of stimulus needed to
elicit a minimal response or an action
The higher the threshold needed, the lower
the excitability, vice versa.
The golden goal of every organ : to
Organism in homeostasis
Change results in loss of homeostasis
Organism attempts to compensate
the ability of an organism to maintain
a stable internal conditions in a
constantly changing environment
Types of regulation
I. Nervous regulation
II. Humoral regulation
I. Nervous regulation:
１ . the basic manner of nervous
(1) definition of reflex :
-- the regular responses of the organism to
the stimulation under the mediation of the
central nervous system.
(2) Structural basis of reflex:
2. the types of reflex ：
unconditioned and conditioned reflex
II. Humoral regulation
Definition: Regulation of carried
special chemicals produced by
tissues through body fluid.
Types of humoral regulation
(1) telecrine ：
Endocrine glands → hormones→ blood→ tissues or
Neurons secrete hormones →tissues or cells
(3) Paracrine （ local humoral regulation ）
Local chemicals →surrounding tissues or cells
Chemicals by cells→to itself
The characteristics of nervous
and humoral regulation
A tissue or organ can respond directly to
the environmental change, depending
neither on nervous nor on humoral
Significance of negative
2) Positive feedback
The feedback signal or output from the
controlled system increases the action
of the control system
significance ： accelerate the
completion of a physiological
For example ：
Blood clotting, Micturition, defecation,
Positive Feedback: Stimulatory.
Stimulus trigger mechanisms that amplify the
response and reinforces the stimulus.
III. Feed-forward control
The direct effect of interfere signal on
the control system
Concept: a direct effect of stimulus on
the control system before the action of
feedback signal occurs.
Here the direct effect of the stimulus is
termed disturb signal or interfere signal.
Example: Shivering before diving into
the cold water