Introduction to MEDICAL PHYSIOLOGY

BYDr. Arnold B. Fonollera, D.D.M.

Associate ProfessorBiological Sciences Department

Medical Physiology defined• The study of the various systems of the

body, from a molecular level through integrated functioning as it relates to the whole being.

• Generally, the term medical physiology applies to human beings.

• What is understood about cellular metabolism in any kind of plant or animal can be extrapolated to human physiology.

• Therefore, the science of physiology applies to all living things.

• Unlike branches of science focused on form and structure, such as anatomy, medical physiology is clearly concerned with function.

DR. Walter Bradford Canon1871-1945

• As a solo area of study, medical physiology stems from the work of the early 20th century physiologist, Walter Cannon, who presented his theory of homeostasis, or body wisdom.

• Inspired by the earlier concept of milieu interieur, Cannon proposed homeostasis as a state of internal stability maintained by the body through deliberate communication and regulation between body systems.

The Basis of Medical Physiology• If one were to think of the human body

as a home heating system, it makes perfect sense.

• When a heating thermostat, which has been previously programmed, detects that the ambient temperature has fallen below an acceptable level, it sends an electronic signal to the furnace to produce more heat.

• The human body is equipped with similar devices to trigger the appropriate response to maintain stability.

• However, the systems of the body are not limited to electrical impulses and use chemical messengers as well.

Course Objectives

• The objective of this course is to help students learn and comprehend functions of the human body that are essential for clinical medicine.

• Assist in acquiring a balanced foundation in cellular and systemic physiology in preparation for advanced study in other basic sciences and in clinical medicine.

• Emphasis is on understanding general physiological principles and on how cellular and organ system functions are integrated within the organism.

• In this regard, physiology may be distinguished from other basic biomedical sciences because it deals with the function of the whole organism and emphasizes those processes that regulate and control entire organ systems.

• A systems approach will be used in concentrating on each of the major organ systems individually.

• Examine the interrelationships and interdependencies that exist among these various functional components.

• Illustrate the relevance of knowledge to the practice of medicine. • A good working knowledge of physiology is a prerequisite for the

student and practitioner who must ultimately interpret and evaluate disorders of function and provide rational treatment plans.

Physiology is Different Than Histology or Anatomy

Concepts vs Memorization

like physics there are things to memorize

but it is the concepts that are essential

you must put in the intellectual effort to

understand the concepts

you must think about the ideas to become

comfortable with them

do not expect that you will learn

physiology by cramming for exams

Dynamic vs Static subject

new discoveries

new insights

so what you learn today may need to be

revised in the future

What is Physiology?

Focuses on homeostasis, the maintenance of important properties of living organisms in a narrow range in the face of significant environmental fluctuations

Examples of propertiesblood pressureionic composition of bloodosmolarity of bloodoxygen and carbon dioxide content of bloodacid-base balance of bloodglucose concentration of bloodbody temperature

Goals are to identify the processes that control and regulate the important properties of living systems

sensors – afferent pathwaysintegrating centers - set pointseffectors – efferent pathways

• How do these systems respond to perturbations in order to return to normal?

• How does the body measure physiological parameters?

molecular mechanismscellular mechanisms

SENSE

RESPOND

Steady State vs Equilibrium:The difference between Life and Death

equilibrium – no net change and no dissipation of energysteady state – no net change but continuous dissipation of energy or matter

Life is a steady state process. We continuously dissipate energy to keep away from equilibrium.

equilibriumno net change

steady staterate of inflowmatchesrate of effluxbut flux throughthe system

What is Physiology?Focuses on homeostasis, the maintenance of important parameters in living organisms in a narrow range (in the steady state) in the face of significant environmental fluctuations

normalrange

elevated

decreased

Example: body temperature

Shivering

Sweating

Core Body Temperature Sensors

CNS Integrating Center

Sweat Ducts

Skeletal Muscle, Brown Fat

EFFECTORS

SENSORSINFORMATION INTEGRATIONFeedback control system

normalrange

elevated

decreased

EFFECTORS

Components of a Physiological System

Blood Pressure

blood volume distribution arterial vs venous

cardiac output heart rate stroke volume contractility

vascular capacity arterial vs venous elasticity of vascular wall

tissue perfusion substrate delivery waste removal

stretch receptorsmetabolic demands

DETERMINANTS

FUNCTIONS

Example: Factors Effecting a Physiological Parameter

SENSORS

INTEGRATINGCENTERS

Physiology is the Basis of Medicine

many diseases cause organ dysfunctionmedicine

tries to correct dysfunctionor minimize its effects

trying to restore system towards normal homeostatic setpointneed to understand physiological parameters that can be manipulated

Example – Congestive Heart Failure (CHF)leads to pump failure – inability to maintain adequate level of circulationneed to know causes of failure

some may be reversible others irreversibleif irreversible what else can be done to

maximize pumpingminimize symptomschanges in blood volume, arterial or venous blood pressure

at molecular level need to know potential targets that can be modulated

1) What are the major determinants of blood pressure?

2) Why do people develop hypertension (HTN)?

3) How does knowledge of the physiology of blood pressure regulation guide options for the treatment of HTN?

4) What are the major determinants of cardiac output and heart function?

5) How do people in heart failure compensate for pump failure in order to maintain output?

6) How does a knowledge of cardiac physiology guide options for treatment of heart failure?

7) How does the kidney regulate composition and volume of body fluids?

8) How is acid-base balance maintained?9) How does the respiratory system conduct

and regulate gas exchange?

Major Clinical Issues Related to the Course

STUDY WELL!