INTRODUCTION TO PHYSIOLOGY

INTRODUCTION TO PHYSIOLOGY

LECTURE--------1

DR ZAHOOR ALI SHAIKH

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What is Physiology ?

• Physiology deals with functions of the body.• Central aim is to keep the HOMEOSTASIS that

is to keep the INTERNAL- ENVIORNMENT of the cell constant, so that cells can work.

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Levels of organization in the Body

• Cells are basic units of life.• Cell is the smallest unit which is capable of

carrying out the processes associated with life.

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Basic Cell Function

• Obtaining food and O2from the surrounding.

• Perform chemical reaction to use food and O2 Food + Oxygen = CO2+ H2O+Energy• Eliminate CO2 and other waste products.• Synthesize protein.• Exchange of material through cell membrane.

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Specialized Function of cells

• Digestive System - secrete digestive enzymes• Muscle Cells - Muscle contraction• Nerve Cell - send electrical impulses

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• Cells are organized in Tissues, Organs, Systems and finally Body.

• Cells of similar structure and function are organized in Tissues .

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TYPES OF TISSUE

• There are FOUR types of Tissue 1- Muscle Tissue 2- Nervous Tissue 3- Epithelial Tissue 4- Connective Tissue

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1. Muscle Tissue

• Muscle Tissue - for contraction• THREE types of Muscles : 1– Skeletal Muscle 2– Cardiac Muscle 3– Smooth Muscle

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2. NERVOUS TISSUE

• Nervous Tissue – Specialized cells for initiation and transmission of Electrical impulses

• Brain• Spinal cord• Nerves

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3. Epithelial Tissue• Two types 1. Epithelial lining e.g. Skin, Digestive

system 2. Secretary glands e.g. Salivary glands

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Glands – Two types

• Exocrine - Having duct e.g. salivary gland• Endocrine - Ductless e.g. Thyroid gland

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4. Connective Tissue

• Connective tissue connects, supports the body• e.g. Tendon - attach skeletal muscle to bone Elastin - helps in stretching and recoil of

the lungs

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ORGANS

• Organs are composed of tissues (Two or more types ) to perform a particular function.

• E.g. stomach has all four primary tissues i.e. Epithelial, Muscle, Nervous and connective tissue.

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BODY SYSTEMS

• Organs make the body system.• Each system works to perform related

functions and is essential for survival of body.• E.g. – Digestive system works for digestion and

absorption.

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TOTAL BODY

• Composed of organ systems linked together structurally and functionally.

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CONCEPT OF HOMEOSTASIS• Body cells work in INTERNAL ENVIRONMENT

that surrounds the body.What is Internal Environment ?• It is aqueous(watery) Extracellular Fluid

(Interstitial fluid ) with which body cells are in direct contact it is outside the cell but not inside the cell.

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Components of the extra celluar fluid ( internal environment)

Extracellular Fluid (ECF)

What is Extracellular Fluid (ECF) ?• ECF consists of -Plasma (fluid portion of blood) and Interstitial fluid (which surrounds the cells)• Materials are exchanged between the plasma and

interstitial fluid across the capillary membrane e.g. O2 and nutrition go from plasma to interstitial fluid than to cell

• Same way waste products go from cell to Interstitial fluid to plasma.

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HOMEOSTASIS (continued)• Homeo = Same• Stasis = Stay• Cells can only work when Internal

environment (cell surrounding) physical and chemical state is within narrow physiological limits.

• Homeostasis is essential for survival of each cell.

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HOMEOSTASIS (continued)• All body system work for Homeostasis so that

body can function.• How body keeps Internal environment constant.• E.g.- If CO2 increases – it affects

respiration(increased) to get rid of increased CO2 -when cold outside, our body temperature

decreases than shivering occurs to increase the body temperature.

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HOMEOSTASIS (continued)• For Homeostasis, Following factors are to be

maintained constant: -supply of nutrient -concentration of O2 and CO2 -waste product concentration -pH as acidity affects enzyme activity -concentration of water and electrolytes - Temperature, narrow limit 35-38c - plasma volume and Blood pressure

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Homeostasis

Body Systems

• ELEVEN Body Systems work for Homeostasis : 1. Circulatory system 2. Digestive system 3. Respiratory system 4. Urinary system 5. Skeletal system 6. Muscular system

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Body Systems (CONT)

7. Integumentary system- skin, hair, nails, sweat glands, temperature regulation

8. Immune system 9. Nervous system 10. Endocrine system 11. Reproductive system

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Body Systems

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Body Systems

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FEEDBACK MECHANISM

• Feedback refers to responses made after a change has been detected [response has taken place].

• There are two types of feedback mechanism: 1. Negative Feedback 2. Positive Feedback

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NEGATIVE FEEDBACK

• In Negative Feedback, response occurs to restore to the normal (by moving the factors in the opposite direction of its initial change).

• Example: 1. If CO2 increases in the body, there will be

respiratory stimulation which will try to wash out CO2 and bring it back to the normal. It is Negative Feedback mechanism.

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NEGATIVE FEEDBACK

• Example ( cont )2. If blood sugar decreases, body will try to

increase blood sugar. It is Negative Feedback mechanism.

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POSITIVE FEEDBACK

• Positive Feedback mechanism amplifies (increases) the initial change, so that initial change is increased.

• Example: If temperature increases, Positive Feedback will

increase it more.• In body Positive Feedback is not common, but

Positive Feedback does occur in our body under certain circumstances.

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POSITIVE FEEDBACK

• Positive Feedback birth of baby: Here hormone Oxytocin causes

powerful contraction of uterus. As contraction push the baby against cervix (exit of the uterus), the resultant stretching of the cervix sends message to brain(posterior pituitary) and causes release of more Oxytocin, which causes even stronger uterine contractions. Positive Feedback does not stop until baby is born.

What you should know from this Lecture

• What is Physiology ?• What is Homeostasis?• What is Internal Environment of the cell?• What are the functions of cell? - General - Specialized• Organization of the body Cell – Tissue – Organs – System – Body• Feedback Mechanism - Negative and Positive

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