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1 LIU Chuan Yong Institute of Physiology Medical School of SDU Tel 88381175 (lab) 88382098 (office) Website:

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Presentation on theme: "1 LIU Chuan Yong Institute of Physiology Medical School of SDU Tel 88381175 (lab) 88382098 (office) Website:"— Presentation transcript:

1 1 LIU Chuan Yong Institute of Physiology Medical School of SDU Tel (lab) (office) Website:

2 2 Chapter 1 Introduction to Physiology

3 3 What is Physiology? Section I What is Physiology? Physiology: biological sciencesPhysiology: biological sciences dealing with the normal life phenomena exhibited by all living organisms.dealing with the normal life phenomena exhibited by all living organisms. Human physiology: basic sciencesHuman physiology: basic sciences dealing with normal life phenomena of the human body.dealing with normal life phenomena of the human body. Goal of physiology:Goal of physiology: explain the physical and chemical factors that are responsible for the origin, development and progression of life.explain the physical and chemical factors that are responsible for the origin, development and progression of life.

4 4 Human Physiology Physiology: (Greek) The study of nature, the involvement of Physics and Chemistry.Physiology: (Greek) The study of nature, the involvement of Physics and Chemistry. The basis forThe basis for –Pathophysiology –Pharmacology –Immunology –Biochemistry –Microbiology

5 5 Why do we study Physiology? Understand the physiologic principle underlie normal function in order to cure the impairments. Understand the physiologic principle underlie normal function in order to cure the impairments.

6 6 Organization of the human body Cells Tissues Organs Organ systems Organisms (Human body) Different Level of Physiological Research

7 7 The integration between systems of the body

8 8 Section II Internal Environment and Homeostasis Interstitial fluid Blood Plasma Intracellular fluid Total body water = 60 % BW = 40 % BW Extracellular fluid 2/3 1/3 1/5 4/5

9 9 Internal environment Extracellular fluid directly baths body cells Internal environment = Extracellular fluid Plasma Plasma Interstitial fluid Interstitial fluid Intracellular fluid

10 10 Extracellular fluids Intracellular fluid 2. Plasma 2. Plasma 1. Interstitial fluid 3. Fluid of special compartments : pericardial fluid, pleural fluid, cerebrospinal fluid

11 11Homeostasis of the internal environment.Maintenance of Relatively Constant Chemical/Physical Conditions of the internal environment. n Claude Bernard__ The father of modern Physiology...The internal environment remains relatively constant though there are changes in the external environment n stable =/= rigidity, can vary within narrow limit (normal physiological range) n The golden goal of every organ : to maintain homeostasis (concept of REGULATION)

12 12 n In fasting blood Arterial pH Bicarbonate24-28 mEq/L O 2 content ml/100 ml Total lipid mg/100 ml Glucose mg/100 ml Normal Physiological ranges

13 13 Homeostasis & Controls Successful compensation Homeostasis reestablished Failure to compensate Pathophysiology Illness Death

14 14 Section 3 Regulation of the Body Functions zRegulation- the ability of an organism to maintain a stable internal conditions in a constantly changing environment y-Three types: x1. Chemical (hormonal) Regulation- a regulatory process performed by hormone or active chemical substance in blood or tissue. -It response slowly, acts extensively and lasts for a long time. x2. Nervous Regulation- a process in which body functions are controlled by nerve system - Pathway: nerve reflex - Types: unconditioned reflex and conditioned reflex

15 15 - Example: baroreceptor reflex of arterial blood pressure - Characteristics: response fast; acts exactly or locally, last for a short time x3. Autoregulation – a tissue or an organ can directly respond to environmental changes that are independent of nervous and hormonal control Characteristics Amplitude of the regulation is smaller than other two types. Extension of the effects is smaller than other two types. In the human body these three regulations have coordinated and acts as one system, feedback control system.

16 16 Section 4 Control System 1.Non-automatic Control Open-loop system 2. Feedback Control The word feedback means a process in which a part of output (feedback signal) from controlled organ returns to affect or modify the action of the control system. Feedback control mechanism consists of two forms: negative and positive feedback control.

17 17 The feedback signals from controlled system produces effect opposite to the action of the control system. The opposite effect is mainly inhibitory action. Negative feedback

18 18 Control Systems (Negative feedback in cardiovascular and endocrine systems) Reference Signal Comparator Controller Effectors Regulated Variable Sensor Feedback Signal Error Signal

19 19 Negative Feedback: Inhibitory. Stimulus triggers response to counteract further change in the same direction. Negative-feedback mechanisms prevent small changes from becoming too large.

20 20 Importance: Maintenance of the homeostasis

21 21 Positive feedback n The feedback signal or output from the controlled system increases the action of the control system Examples: Blood clotting, Micturition, defecation, Na + inflow in genesis of nerve signals, Contraction of the uterus during childbirth (parturition).

22 22 Positive Feedback: Stimulatory. Stimulus trigger mechanisms that amplify the response and reinforces the stimulus.

23 23 Importance: 1) Enhance the action of original stimulus or amplify or reinforce change, promote an activity to finish 2) It is known as a vicious circle because it can lead to instability or even death

24 24 3. Feed-forward control 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

25 25 Significance of Feedback-forward : adaptive feedback control. makes the human body to foresee and adapt the environment promptly and exactly (prepare the body for the change).


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