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Introduction to Physiology

Lecture 1By

Dr: Nassar Ayoub

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Section I What is Physiology?What is Physiology?

• PhysiologyPhysiology: biological sciences : biological sciences • dealing with the normal life phenomena dealing with the normal life phenomena

exhibited by all living organisms.exhibited by all living organisms.• Human physiologyHuman physiology: basic sciences : basic sciences

• dealing with normal life phenomena of the dealing with normal life phenomena of the human body. human body.

• Goal of physiologyGoal of physiology::• explain the physical and chemical factors explain the physical and chemical factors

that are responsible for the origin, that are responsible for the origin, development and progression of life.development and progression of life.

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Human Physiology–Physiology: Physiology: (Greek) The study of nature, the (Greek) The study of nature, the

involvement of Physics and Chemistryinvolvement of Physics and Chemistry..

The basis forThe basis for

PathophysiologyPathophysiology

PharmacologyPharmacology

ImmunologyImmunology

BiochemistryBiochemistry

MicrobiologyMicrobiology

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Why do we study Why do we study PhysiologyPhysiology??

� Understand the physiologic principle Understand the physiologic principle underlie normal function in order to underlie normal function in order to cure the impairmentscure the impairments ( ( ((خللخلل..

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Organization of the human body

CellsTissues

Organs

Organ systems

Organisms(Human body)

Different Level of Physiological Research

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The integration between systems of the body

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Section II Internal Environment and Homeostasis

Interstitial fluidInterstitial fluid

Blood PlasmaBlood Plasma

Intracellular fluidIntracellular fluid

Total body water = 60 %Total body water = 60 % BWBW

= 40 % BW= 40 % BW

Extracellular fluidExtracellular fluid

2/32/3

1/1/

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1/51/5

4/54/5

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Internal environment

Extracellular fluid directly baths body cells

Internal environment = Extracellular fluid

PlasmaPlasma

Interstitial fluidInterstitial fluid

Intracellularfluid

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Extracellular fluids

Intracellularfluid

2. Plasma2. Plasma

1. Interstitial fluid1. Interstitial fluid3. Fluid of special compartments3. Fluid of special compartments: : pericardial fluid, pleural fluid, cerebrospinal flupericardial fluid, pleural fluid, cerebrospinal fluid id

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HomeostasisHomeostasis• Maintenance of Relatively Constant Chemical/Physical

Conditions of the internal environment. of the internal environment.

� Claude BernardClaude Bernard__ The father of modern Physiology__ The father of modern Physiology

...The internal environment remains relatively constant ...The internal environment remains relatively constant though there are changes in the external environmentthough there are changes in the external environment

� stable =/= rigidity, can vary within narrow limitstable =/= rigidity, can vary within narrow limit (normal physiological range)(normal physiological range)

� The golden goal of every organ : to maintain The golden goal of every organ : to maintain homeostasishomeostasis (concept of REGULATION) (concept of REGULATION)

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� In fasting blood In fasting blood

Arterial pHArterial pH 7.35-7.457.35-7.45

BicarbonateBicarbonate 24-28 mEq/L24-28 mEq/L

OO22 content content 17.2-22.0 ml/100 ml17.2-22.0 ml/100 ml

Total lipidTotal lipid 400-800 mg/100 ml400-800 mg/100 ml

GlucoseGlucose 75-110 mg/100 ml75-110 mg/100 ml

Normal Normal Physiological rangesPhysiological ranges

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Homeostasis & Controls

•Successful compensation

•Homeostasis reestablished

•Failure to compensate

•Pathophysiology

•Illness

•Death

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Section 3 Regulation of the Body Functions

� Regulation- the ability of an organism to maintain a stable internal conditions in a constantly changing environment

�-Three types:

�1. 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.

�2. Nervous Regulation- a process in which body functions are controlled by nerve system

- Pathway: nerve reflex

- Types: unconditioned reflex and conditioned reflex

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- Example: baroreceptor reflex of arterial blood pressure

- Characteristics: response fast; acts exactly or locally, last for a short time

�3. 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”.

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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.

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The feedback signals from controlled The feedback signals from controlled system produces effect opposite to the system produces effect opposite to the action of the control system.action of the control system.

The opposite effect is mainly The opposite effect is mainly “inhibitory action”.“inhibitory action”.

Negative feedbackNegative feedback

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

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Importance:

Maintenance of the homeostasis

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Positive feedbackPositive feedback� The feedback signal or output from the The feedback signal or output from the controlled system increases the action of controlled system increases the action of the control systemthe control system

Examples: Blood clotting, Micturition, Examples: Blood clotting, Micturition, defecation, Nadefecation, Na++ inflow in genesis of nerve inflow in genesis of nerve signals, Contraction of the uterus during signals, Contraction of the uterus during childbirth (parturition).childbirth (parturition).

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

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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 (viSHəs ) circle because it can lead to instability or even death

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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

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Significance of Feedback-forward :

adaptive feedback control.

makes the human body to foresee and adapt the environment promptly(prämptlē) and exactly

(prepare the body for the change).