General rules & guidelinesGeneral rules & guidelines• Punctuality in all classesPunctuality in all classes• 100% attendance100% attendance• No absenteeism in assessmentsNo absenteeism in assessments university rule strictly university rule strictly

appliedapplied• Submission of practical reports within 1 week-delay will Submission of practical reports within 1 week-delay will

invite penalty by the dayinvite penalty by the day• Interaction with lecturer and other studentsInteraction with lecturer and other students

(within time constraints)(within time constraints)• How to studyHow to study

i. Notes in classi. Notes in class

ii. Lecturer’s notesii. Lecturer’s notes

iii. Standard text booksiii. Standard text books

• 1. Be regular in attending classes. Your lecturer has taken a 1. Be regular in attending classes. Your lecturer has taken a lot of pains to prepare the subject. You must draw maximum lot of pains to prepare the subject. You must draw maximum benefit from this. benefit from this.

• 2. If you have doubts, have them clarified2. If you have doubts, have them clarified• 4. Take down points during the lecture/tutorial which you 4. Take down points during the lecture/tutorial which you

feel are important, and also those which you don’t seem to feel are important, and also those which you don’t seem to understand. Compare your notes with the information in the understand. Compare your notes with the information in the book, and make whatever additions you feel are important. book, and make whatever additions you feel are important. Inn this manner you can compile your own information on a Inn this manner you can compile your own information on a given topic and use it for the exams.given topic and use it for the exams.

• 5. You are now studying a clinically oriented syllabus. So 5. You are now studying a clinically oriented syllabus. So don’t be alarmed by clinical terms being htrown at you. don’t be alarmed by clinical terms being htrown at you.

• 6. Read standard prescribed text books regularly6. Read standard prescribed text books regularly

Introduction to Human Physiology

• Course Co-ordinator

• Dr Sami Al Rawas MD PhD

• Consultant, Clinical Physiology

• (Neurophysiology)

• Introduction:• Text Book• i. Principles of Anatomy & Physiology. Tortora

& Grabowsky. Wiley & Sons; 2003

• Reference books• i. . Text Book of Medical Physiology . Guyton &

Hall. 12th edn. Saunders, London. 2011• Ii. Ross ands Wilson. Anatomy and Physiology

in Health and Disease. 10th Edn. Churchill Livingstone. 2006

•

• Homeostasis

• &

• Control Mechanisms - I

Objectives• 1. Explain the meaning of the term internal environment and homeostasis (Giving

examples) and appreciate the importance of constancy of the milieu interior.

• 2. State that homeostasis involves maintaining the internal environment at a constant level or between narrow limits.

• • 3. Explain that homeostasis involves monitoring levels of variables and correcting

changes which may occur under various situations –Physiological or Pathological

• 4. Understand what is meant by controlled variable and set point.

• 5. Explain the feed back mechanisms in control system i.e negative feedback mechanisms.

• 6. List examples of negative feed back systems, and describe 2 such

• 7. Give an example of positive feedback mechanisms e.g. parturition (child birth).

• 8. Understand that disease alters homeostasis of the internal environment and may cause death

• Definition of Physiology

“Is the science of how the body systems work, and the ways in which their integrated cooperation maintains life and health of an individual”

• Pathology is the study ofabnormsalities in body tissues and how they affect body functions and cause illness

• Pathophysiology is how the body function resposnds to Pathology

Atoms

Molecules

Organelles

Cells

Tissues

Organs

SystemsOrganismOrganism

•Integumentary (Skin) Physiology (system)

•Cardiovascular Physiology (system)

•Respiratory Physiology (system)

•Gastrointestinal Physiology (system)

•Renal Physiology (system)

•Reproductive Physiology (system)

•Musculo-skeletal Physiology (system)

•Neurophysiology Nervous system

•Endocrine Physiology (system)

•Immune Physiology (system)

““La fixité du milieu La fixité du milieu intérieur est la condition intérieur est la condition

de la vie libre.”de la vie libre.”

““The fixity of the internal The fixity of the internal

environment is the environment is the

condition for free life.”condition for free life.”

What is the INTERNAL ENVIRONMENT?

• ECF ICF

• 1. Na+ mMol/L 145 15

• 2. K+ 5 150

• 3. HCO3- 28 10

• 4 Cl 105 5

• 5. Anions (proteins) 5 40

• 6. Glucose (mg%) 100 10

• Egs of ECF: plasma; CSF; lymph; aqueous humor

• Examples of constancy of the Internal Environment

1. Body core temperature: 370C

2. Arterial Blood: PaO2 100 mmHg; PaCO2 40 mmHg; pH 7.4

3. Blood sugar (glucose) : 100 mg% (5 mmols)

4. Blood pressure: 120/80 mmHg

5. Electrolytes: Na+ 140 mmol/L; K+ 4 mmol/L pH : stomach= 2-4 , small intestinal pH about 8

urine about 6

All body cells and systems contribute towards this

•

• Homeostasis

&

Control Mechanisms -II

• Definition :

• Claude Bernard’s “Milieu Interieur” or the Internal Environment:

• Maintenance of the constancy of this, which is the EXTRA CELLULAR fluid of the body, is called HOMEOSTASIS

Concept by Walter Canon

Bottom line in Physiology:

Maintain Homeostasis

•Process of maintaining the composition of the internal body compartments within fairly strict limits (ion concentrations, pH, osmolarity, temperature etc).

•Require regulatory mechanisms to defend against changes in external environment and changes due to activity.

•Cellular homeostasis - intracellular fluid composition

•Organismal homeostasis - extracellular fluid composition.

•Control system designed to maintain level of given variable (concentration, temperature, pressure) within defined range following disturbance.

• Feedback loops Negative & Positive egative & Positive

•

• Negative feedback loop requires Negative feedback loop requires

• Sensor (Detector): specific to variable needing to : specific to variable needing to be controlledbe controlled

• Comparator (Control system): reference point reference point for sensor to for sensor to compare againstcompare against

• Effector: if sensor if sensor comparator comparator Error Signal Error Signal restore restore variable to desired levelvariable to desired level

• Biofeedback systems in maintaining homeostasis

•

Controlled condition : eg body temp.

Control centre (COMPARATOR)Sets range of normal

values SET POINT

Receptor(sensor/detector)

stimulus

Effector structure that receives out put from control centre

response

Feed back systems

• Negative feedback of Blood Pressure (BP)• Negative feedback: BP regulation; CO2 regulation of breathing; body

temp. control; ADH & water retention by kidneys

• Controlled condition : eg BP 120/80.

Control centre

receptor

BP

Effector(heart & blood vessels)

disturbance

Negative feedback Control of BP

-Ve Feed back control of body temperature

Properties of negative feed back systems

• 1. They have a GAIN Effectiveness

• 2. Usually fast response

• 3. Incomplete correction leaves behind an ERROR

• Ideal Systolic BP : 120mmHg

• Stimulus(shock) changes BP to 60mmHg

• Coorected BP after feed back mechanism : 90mmHg

• ERROR: 30 mmHg

• Positive feedback system

stimulusreceptor

controller effector

Response +++

+++

• Positive feedback

• Normal labour

• Other examples:

• Action potential

• Coagulation of blood : cascade

• Factors that affect performance of homeostasis mechanisms

• Aging

• Severe environmental conditions beyond control

• Nutrition status

• Disease

• Failure to maintain homeostasis:

disease Symptoms: pts. complaints

Signs: observed by doctor diagnosis

treatment

investigations

homeostasis restored

success

failureHomeostasis not restored

Morbidity/death

Disturbed internal environment

Maintenance of constancy of the Internal Environment

Recapitulate• 1. Internal environment with egs

• 2. Homeostasis

• 3. Feed back loops- -ve and + ve with egs

• 4. What happens when homeostasis is disturbed