Physiology

1. Physiology • Considers the operation of specific organ systems • Renal – kidney function • Neurophysiology – workings of the nervous system • Cardiovascular – operation of the heart and blood vessels • Focuses on the functions of the body, often at the cellular or molecular level

2. Physiology • Understanding physiology also requires a knowledge of physics, which explains electrical currents, blood pressure, and the way muscle uses bone for movement

3. Principle of Complementarity • Function always reflects structure • What a structure can do depends on its specific form

4. Levels of Structural Organization • Chemical – atoms combined to form molecules • Cellular – cells are made of molecules • Tissue – consists of similar types of cells • Organ – made up of different types of tissues • Organ system – consists of different organs that work closely together • Organismal – made up of the organ systems

5. Levels of Structural Organization Smooth muscle cell Molecules Cellular levelCells are made up of molecules 2 Atoms Chemical levelAtoms combine to form molecules 1 Smooth muscle tissue Heart Tissue levelTissues consist of similar types of cells 3 Cardiovascular system Blood vessels Epithelial tissue Smooth muscle tissue Blood vessel (organ) Organismal levelThe human organism is made up of many organ systems 6 Connective tissue Organ levelOrgans are made up of different types of tissues 4 Organ system levelOrgan systems consist of different organs that work together closely 5 Figure 1.1

6. HOME0/STATIS => SAME STAY => SAME STATE • DEFINED AS “DYNAMIC CONSTANCY OF THE INTERNAL ENVIRONMENT” • Claude Bernard — “mileu interieur” = internal environment remains fairly constant with changing external or internal conditions • 1893 — experiment with dogs • Question: How is food broken down to supply energy? • It was thought that food (sugar) was completely used up in the body for energy

7. DEFINED AS “DYNAMIC CONSTANCY OF THE INTERNAL ENVIRONMENT” • Claude Bernard — “mileu interieur” = internal environment remains fairly constant with changing external or internal conditions • EXPERIMENT: • Sugar-fed dog • Meat-fed dog • Sacrificed both – found both had sugar in blood • Bernard later went on through series of experiments to show that sugar was stored in the liver in the form of glycogen • Glucose (in the blood) actually INHIBITS glycogen breakdown • Led to the concept of feedback • From 1929-1932 Walter cannon described and coined the term (term) homeostasis

8. Logic: • 1) All organisms (living systems) are open systems • 2) Open systems are subject to disturbances • 3) Disturbances are kept within narrow limits • 4) By automatic adjustments (feedback) • 5) System is NOT in equilibrium • 6) But steady state • Organisms are open systems, which are kept in a steady state (homeostasis) by feedback mechanisms • What is a feedback mechanism? • Process or event that causes another event which has an effect on the initial or subsequent event • Simplest: A —— B —— A • Common: A —— B —— C —— A • Two types: positive or negative

9. Homeostasis • Homeostasis is the ability to maintain a relatively stable internal environment in an ever-changing outside world • The internal environment of the body is in a dynamic state of equilibrium • Chemical, thermal, and neural factors interact to maintain homeostasis

10. Homeostatic Control Mechanisms • The variable produces a change in the body • The three interdependent components of control mechanisms are: • Receptor – monitors the environments and responds to changes (stimuli) • Control center – determines the set point at which the variable is maintained • Effector – provides the means to respond to the stimulus

11. Homeostatic Control Mechanisms Controlcenter Input:Informationsent alongafferentpathway to 3 Output:Information sentalong efferentpathway to 4 Effector Receptor (sensor) Changedetectedby receptor 2 Response ofeffector feedsback to influencemagnitude of stimulus andreturnsvariable tohomeostasis 5 Stimulus:Produceschangein variable 1 Imbalance Variable (in homeostasis) Imbalance Figure 1.4

12. Negative Feedback • In negative feedback systems, the output shuts off the original stimulus • Example: Regulation of blood glucose levels

13. Negative Feedback Figure 1.5

14. Positive Feedback • In positive feedback systems, the output enhances or exaggerates the original stimulus • Example: Regulation of blood clotting Figure 1.6

15. Homeostatic Imbalance • Disturbance of homeostasis or the body’s normal equilibrium • Overwhelming of negative feedback mechanisms allowing destructive positive feedback mechanisms to take over

16. Organ Systems Interrelationships • Nutrients and oxygen are distributed by the blood • Metabolic wastes are eliminated by the urinary and respiratory systems Figure 1.2

17. Necessary Life Functions I • Maintaining boundaries – the internal environment remains distinct from the external • Cellular level – accomplished by plasma membranes • Organismal level – accomplished by the skin • Movement – locomotion, propulsion (peristalsis), and contractility • Responsiveness – ability to sense changes in the environment and respond to them • Digestion – breakdown of ingested foodstuffs

18. Necessary Life Functions II • Metabolism – all the chemical reactions that occur in the body • Excretion – removal of wastes from the body • Reproduction – cellular and organismal levels • Cellular – an original cell divides and produces two identical daughter cells • Organismal – sperm and egg unite to make a whole new person • Growth – increase in size of a body part or of the organism

19. Survival Needs • Nutrients – chemical substances used for energy and cell building • Oxygen – needed for metabolic reactions • Water – provides the necessary environment for chemical reactions • Maintaining normal body temperature – necessary for chemical reactions to occur at life-sustaining rates • Atmospheric pressure – required for proper breathing and gas exchange in the lungs