Introduction to Human Physiology XIA Qiang（夏强）, MD & PhD Department of Physiology Room 518, Block C, Research Building School of Medicine, Zijingang Campus Email: xiaqiang@zju.edu.cn Tel: ☆88206417 (Undergraduate School), 88208252 (Medical School)

Graduate Attributes and Capabilities Attitudes Knowledge Skills

Learning Philosophy I hear and I forget, I see and I remember, I do and I understand.

Handheld device software Epocrates: drugs manual >3300 drugs More than 45% medical doctors used DynaMed: evidence based medicine database

https://www.medsch.ucla.edu/mobile/requirement/req-2014.htm

http://guides.library.harvard.edu/hms/mobileApps

Course Structure Lectures: 80 academic hours Practicals: 64 a.h. 5 a.h./week 2 a.h. on Mon., 3 a.h. on Wed. Practicals: 64 a.h. 4 a.h./week Begin from second week

Evaluation Participation: 5% Practical reports: 15% Weekly assessments (from Summer Week 2 on), mini-tests at lecture & midterm exam: 30% Final examination: 50% “Double pass” policy: Total >= 60 Final examination >= 60 Weekly assessments & midterm exam >= 60

Recommended textbook Widmaier EP, Raff H, Strang KT (2010 or later) Vander’s Human Physiology: The Mechanisms of Body Function, McGraw-Hill.

Course website Course website: http://m-learning.zju.edu.cn Demo

Human Physiology Specific characteristics, functions and mechanisms of the human body that make it a living being What ? How ?

Body Components Differentiated Cells - specialized function Tissues - groups of cells with related function (muscle, nervous, connective, & epithelium) Organ- functional unit Organ system – several organs act together to perform specific function skin = barrier entry = respiratory & GI transport = CV & diffusion exit = renal & GI

Fluid Compartments ICF ISF plasma organs external environment internal environment

Body Fluid = 60% of Body Weight (BW) Internal environment Body Fluid = 60% of Body Weight (BW) Intracellular Fluid 2/3, 40% of BW Extracellular Fluid 1/3, 20% of BW Plasma 5% of BW Interstitial Fluid 15% of BW 70 kg Male, 42 L

Extracellular Fluid= Internal Environment

Homeostasis Homeostasis (from the Greek words for “same” and “steady”): maintenance of static or constant conditions in the internal environment Central theme of physiology Walter B. Cannon

Components of Homeostasis: Concentration of O2 and CO2 pH of the internal environment Concentration of nutrients and waste products Concentration of salt and other electrolytes Volume and pressure of extracellular fluid

How is homeostasis achieved? ----Regulation Body's systems operate together to maintain homeostasis: Skin system Skeletal and muscular system Circulatory system Respiratory system Digestive system Urinary system Nervous system Endocrine system Lymphatic system Reproductive system

Homeostasis and Illness

Regulation of body functions Nervous Regulation Humoral Regulation Autoregulation

Nervous regulation Reflex Knee jerk reflex

Reflex Arc Receptor Afferent (sensory) nerve Reflex center (brain or spinal cord) Efferent (motor) nerve Effector

Humoral regulation Endocrine cells Hormone Traditional description of humoral regulation by hormone Receptor

Endocrine action: the hormone is distributed in blood and binds to distant target cells Paracrine action: the hormone acts locally by diffusing from its source to target cells in the neighborhood Autocrine action: the hormone acts on the same cell that produced it

Neuroendocrine (Neurosecretion) Vasopressin Oxytocin

Autoregulation Definition: Intrinsic (independent of any neural or humoral influences) ability of an organ to maintain a constant blood flow despite changes in perfusion pressure Mechanism: Stretch-activated constriction of vessels Significance: Maintenance of near-constant cerebral, renal and coronary blood flow

80~180 mmHg

Control systems of the body CYBERNETICS or Control and Communication in the Animal and the Machine (MIT Press 1948) Norbert Wiener (1894-1964) Originator of Cybernetics

1. Non-automatic Control System Open-loop system Seldom seen under physiological conditions Stress Control Center Effectors Stimulus Response

2. Feedback Control System Control Center Effectors Stimulus Response Closed-loop system Automatic control Negative feedback Positive feedback

Negative feedback: common A change in a condition leads to responses from the effectors which counteracts that change

Examples: Regulation of blood pressure, Regulation of body temperature, Regulation of hormone release…

Gain of the negative feedback: The degree of effectiveness with which a control system maintains conditions Correction Error Gain=

Positive feedback: uncommon A change in a condition leads to responses from the effectors which amplifies that change +

Examples: Child birth Micturition Blood coagulation Vicious circle under pathophysiological conditions…

3. Feed-forward Control Often seen in nervous system Rapid Adaptive control Examples: some muscle contraction, conditioned reflex Control Center Effectors Stimulus Response Monitor Disturbance

Summary Terms: Regulation of body functions Internal environment Homeostasis Negative feedback Positive feedback Regulation of body functions

THANK YOU FOR YOUR ATTENTION!