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Introduction. Instructor: Li Li. Department of Physiology. Jining medical college. Office: 0850 physiological sciences. Email: [email protected] Introduction. ⑴ Definition and Scope of Physiology. ⑵ Structure and Fundamental Characteristics of Living Organism.

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Instructor: Li Li

Department of Physiology

Jining medical college

Office: 0850 physiological sciences

Email: [email protected]


⑴ Definition and Scope of Physiology.

⑵ Structure and Fundamental Characteristics of Living Organism.

⑶ Internal Environment, Homeostasis and Biorhythm.

⑷ Regulation of Body Function.

Definition and Scope of Physiology


Physiology is the study of how living organisms work. It is a study of the normal functions of organs and organ systems of the body, the conditions under which these functions are carried out and the mechanisms by which they are achieved.


① whole organism (interplay of many separate organs).

② organs and organ systems.

③ Molecule and cell.

Salty food

Excretion of sodium in the urine

gone wrong - disease

Definition and Scope of Physiology


① Many areas of function are still poorly understood.

② The integration of molecular biology with physiology will provide an ever-sharper view of how our bodies work.

③ Physiology is essential for the study and practice of medicine.

normal function - physiology

⑵ Structure and Fundamental Characteristics of Living Organism

Structure of Living Organism.

The definition and multiplication and differentiation and classification of cell.

Fundamental Characteristics of Living Organism.

Three characteristics.

Structure of living organism Organism


The basic units of Living Organisms. The simplest structural units into which a complex multicellular organism can be divided and still retain the functions characteristic of life are called cells.


A single cell divides to create two cell.


①Definition: The process of transforming an unspecialized cell into a specialized cell.

②Effect:The formation of tissues and organs and organ systems.

Structure of living organism Organism


Classification (according to the function they perform)

⑴ Muscle cells .

①generate the mechanical forces that produce movement.

②Be classified into skeletal, cardiac, smooth muscle cells.

③form muscle tissue.

⑵Nerve cells.

①initiate and conduct electrical signals.

②control the activities of other cells .

③form nerve tissue.

⑶ Epithelial cells.

⑷ Connective tissue cells.

Structure of Living Organism Organism



⑶ Epithelial cells.

① For selective secretion and absorption of ions and organic molecules and for protection.

②form epithelial tissue .

⑷ Connective tissue cells.

① Connect, anchor, and support the structures of the body.

②form connective tissue .


Figure Classification of muscle cell.

① skeletal muscle; ② cardiac muscle; ③ smooth muscle.

multiplication Organism

fertilized egg

two cells

four cells

Spherical mass



epithelial tissue

muscle tissue

nerve tissue

connective tissue



organs and organ systems

Unspecialized cell

Specialized cell

organ and organ system

Fundamental Characteristics of Living Organism Organism

⑴ Metabolism .

① All the chemical reactions in all the cells of the body.

② It include the energy and material metabolism.


Definition: The property of living organisms that permits them to react to stimuli.

Manifestation: Action Potential.

Assessment: Intensity and time period of stimulus.

⑶ Reproduction.

Help to maintain static conditions and the automaticity and continuity of life.

⑶ Internal Environment, Homeostasis and Biorhythm. Organism

Body Fluid Compartments and Internal Environment

① The composition of body fluid.

② The definition of internal environment.


① The definition and characteristics of homeostasis.


① The definition of biorhythm and circadian rhythm.

② The effect of biorhythm on homeostasis.

③ The characteristics of biorhythm.

Internal environment Organism

Extracellular fluid

Intracellular fluid


Interstitial fluid

Figure Body fluid.

Intracellular fluid (2/3) Organism

body fluid

plasma (20%)

extracellular fluid (1/3)

interstitial fluid (80%)

Body Fluid Compartments and Internal Environment


internal environment

Internal environment

The extracellular fluid are the ions and nutrients needed by the cells for maintenance of cellular life, and all cells live in the environment, so extracellular fluid is called internal environment.

Intracellular fluid Organism


Extracellular fluid

Figure Significance of concentration difference.

Homeostasis Organism


A state of reasonably stable balance between physiological variables (a stable state of internal environment).

① Homeostasis is a dynamic, not a static process.

② It can be quantified by Time-Averaged Means.

③ The maintenance of homeostasis rely on a wide variety of control system.

④Nonhomeostatic state can have life-threatening consequences.

Biological Rhythms Organism


A characteristic of many body functions changesrhythmically.

Circadian rhythm

Circadian rhythm is the most common type, which cycles approximately once every 24 h.

① waking and sleeping.

② body temperature.

③ hormone concentrations in the blood.

④ the excretion of ions into urine and so on.

Biological Rhythms Organism

Effect on homeostasis

They add an anticipatory component to homeostatic control system, in effect a feedforward system.


① They are internally driven, and they are free-running rhythms( the biological rhythms persisted in the complete absence of environmental cues).

② Environmental time cues can entrain a circadian rhythm to 24h, and they also function to phase-shift rhythms( rest the internal clock).

③ The suprachiasmatic nucleus in the hypothalamus functions as the principal pacemaker for circadian rhythms.

suprachiasmatic nucleus Organism

optic chiasma

Figure The neural basis of body rhythms.

⑷ Regulation of Body Function. Organism

General Characteristics of Homeostatic Control System.

Feedback System.

Resetting of Set Points.

Feedforward Regulation.

Components of Homeostatic Control System.

Processes Related to Homeostasis.

General Characteristics of Homeostatic Control System Organism

① Homeostatic control systems include nerve system and hormonal system.

②The nerve system is composed of three major parts: the sensory input portion, the central nervous system and the motor output portion.

③The hormonal system include eight major endocrine glands that secret chemical substances called hormones.

④The regulation of internal environment include nervous regulation and hormonal regulation and auto-regulation.

⑤ Hormonal system and nerve systems complement each other to maintain homeostasis.

The sensory input portion Organism

The motor output portion

The central nervous system

Figure The nerve control system.

Figure OrganismEndocrine system

1 Hypothalamus; 2 Pituitary gland; 3 Thyroid gland; 4 Pancreas; 5 Adrenal gland; 6 Testicle (male only); 7 Ovary (female only) ; 8 Parathyroid glands .

Feedback System Organism


① Negative feedback system.

② Positive feedback system.

Negative feedback system

A change in the variable being regulated brings about responses that tend to push the variable in the direction opposite to the original change, Homeostatic control operates mainly on negative feedback.

Example: the thermoregulatory system; enzymatic processes and so on.

Positive feedback system

An initial disturbance in the system sets off a train of events that increase the disturbance even further, less frequently seen in biological systems.

Example: the process of parturition and micturition and the blood coagulation and so on.

Effector Organism


Figure Negative feedback system.

Negative feedback Organism






Figure Example of Negative feedback.

Figure Effect of OrganismNegative feedback system.

Figure OrganismPositive feedback system.

posterior pituitary gland Organism





Figure Process of parturition.

Resetting of Set Points Organism

Set point

The values that the homeostatic control system are trying maintain.

Characteristics of Set point

① The set point for many regulated variables can bephysiologically altered or reset.

② The set point can be reset in response to external stimuli such as bacteria, and it also occur on a rhythmical basis every day.

③ It is often possible to keep one property relatively constant only by moving others away from their usual set point, so it is not possible for everything to be held relatively constant by homeostatic systems.

Homeostatic control system Organism

Homeostatic control system

Set point


Set point




Chills and shivering

Create heat


( Inhibits proliferation of pathogens)


Feedforward Regulation Organism


Feedforward regulation anticipates changes in a regulated variable, improves the speed of the body’s homeostatic responses, and minimizes fluctuations in the level of the variable being regulated.


① when it becomes cold, you will wear more clothes.

② When you see the picture of delicious food, you salivate.

③Your heart beats faster before you start running.

Components of Homeostatic Control System Organism


A reflex is a specific involuntary, unpremeditated, unlearned “built-in’’ response to a particular stimulus.

Many of homeostatic control system belong to the general category of stimulus-response sequences known as reflexes.

Reflex arc ( the pathway mediating a reflex)

① receptor

② afferent pathway

③ integrating center

④ efferent pathway

⑤ effector

Integrating center Organism

Efferent pathway

Afferent pathway

Smooth muscle



Skeletal muscle


Body temperature


Heat loss


Heat production

Negative feedback

Specific neurons in the brain

Endocrine gland

Nerve endings


Figure General components of reflex arc.

The present usage of reflex was not restricted to the nervous system!

Components of Homeostatic Control System Organism

Local Homeostatic Responses

Like a reflex, a local response is the result of a sequence of events proceeding from a stimulus.

Unlike a reflex, the entire sequence occurs only in the area of the stimulus.

The significance of local responses is that they provide individual areas of the body with mechanisms for local self-regulation.

Intercellular Chemical Messengers

① Hormones

② Neurotransmitters

③ Paracrine agents

④ Others.

Day 1 Organism

Heat chamber

Heat chamber

Temperature and the volume of sweat are measured.


Day 2-9

Temperature and the volume of sweat are measured.


Results: on day 10, he sweat earlier and much more profusely than he did on day 1, and his body temperature does not rise to nearly the same degree.

Conclusion: he become acclimatized to the heat.

Processes Related to Homeostasis Organism

Adaptation and Acclimatization


A characteristic that favors survival in specific environments. Homeostatic control systems are inherited biological adaptations.


An improved ability to respond to an environmental stress, it is a type of adaptation.

The representation of acclimatization is varied. Some are reversible, some are irreversible.

GI tract Organism







Synthesis in the body

Storage depots

Reversible incorporation into other molecules




Figure Balance diagram for a chemical substance.

Processes Related to Homeostasis Organism

Balance in the homeostasis of chemicals

① The balance of substances in the body is achieved by matching inputs and outputs.

② Total body balance of a substance may be negative, positive, or stable.

Summary Organism

⑴ Definition and Scope of Physiology.

⑵ Structure and Fundamental Characteristics of Living Organism.

⑶ Internal Environment, Homeostasis and Biorhythm.

⑷ Regulation of Body Function.