Introduction to MEDICAL PHYSIOLOGY BY Dr. Arnold B. Fonollera, D.D.M. Associate Professor Biological 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 Canon 1871-1945 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.

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. Course Objectives

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 properties blood pressure ionic composition of blood osmolarity of blood oxygen and carbon dioxide content of blood acid-base balance of blood glucose concentration of blood body temperature Goals are to identify the processes that control and regulate the important properties of living systems sensors – afferent pathways integrating centers - set points effectors – efferent pathways

SENSE How do these systems respond to perturbations in order to return to normal? How does the body measure physiological parameters? molecular mechanisms cellular mechanisms RESPOND

Steady State vs Equilibrium: The difference between Life and Death equilibrium – no net change and no dissipation of energy steady 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. steady state rate of inflow matches rate of efflux but flux through the system equilibrium no net change

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 Example: body temperature Sweat Ducts elevated Sweating Core Body Temperature Sensors CNS Integrating Center normal range Skeletal Muscle, Brown Fat Shivering decreased

INFORMATION INTEGRATION Feedback control system Components of a Physiological System EFFECTORS elevated INFORMATION INTEGRATION Feedback control system SENSORS normal range EFFECTORS decreased

Example: Factors Effecting a Physiological Parameter INTEGRATING CENTERS SENSORS stretch receptors metabolic demands DETERMINANTS cardiac output heart rate stroke volume contractility FUNCTIONS tissue perfusion substrate delivery waste removal Blood Pressure vascular capacity arterial vs venous elasticity of vascular wall blood volume distribution arterial vs venous

Physiology is the Basis of Medicine many diseases cause organ dysfunction medicine tries to correct dysfunction or minimize its effects trying to restore system towards normal homeostatic setpoint need to understand physiological parameters that can be manipulated Example – Congestive Heart Failure (CHF) leads to pump failure – inability to maintain adequate level of circulation need to know causes of failure some may be reversible others irreversible if irreversible what else can be done to maximize pumping minimize symptoms changes in blood volume, arterial or venous blood pressure at molecular level need to know potential targets that can be modulated

Major Clinical Issues Related to the Course What are the major determinants of blood pressure? Why do people develop hypertension (HTN)? How does knowledge of the physiology of blood pressure regulation guide options for the treatment of HTN? What are the major determinants of cardiac output and heart function? How do people in heart failure compensate for pump failure in order to maintain output? How does a knowledge of cardiac physiology guide options for treatment of heart failure? How does the kidney regulate composition and volume of body fluids? How is acid-base balance maintained? How does the respiratory system conduct and regulate gas exchange?

STUDY WELL!