Total body water (60% body weight)

1. IntroductionPhysiology is the study of the living things.(from Greek physis = nature; logos= studyHuman physiology is concerned with the way the human body works. It is the study of the functions of systems and organs. Organs consist of tissues which are formed of cells

2. Homeostasismaintenance of constant conditions in the internal environment.The functions of all organs & systems of the body help to maintain these constant conditions.

3. Body fluidsthe body of a normal male is composed of about:- 18% proteins- 15% fats - 7% minerals - 60 % water

4. Total body water (60% body weight) 20% outside the cells -Extracellular fluid ( ECF) -Main cation is Na + -Main anion is Cl - & HCO3 40 % inside the cells -Intracellular fluid (ICF) -Main cation is K+ -Main anion protein & phosphate 4% plasma 16% interstitial fluid

6. The cell • It is the structural unit of various tissues & organs • It consists of • cell membrane • Protoplasm → cytoplasm, cell organelles & nucleus The mechanisms that control the transport through the cell membrane are so important to maintain the differences between ICF & ECF

7. Transport through cell membrane • Diffusion • Passive- no energy • Occurs through lipid bilayer or protein channels • 2 types • -Simple • -Facilitated- needs carrier • Active transort • Occurs against electrochemical gradiant • Needs carrier, energy ATP, ATPase • 2 types • -Primary active e.g • Na + - K + pump • -Secondary active Endocytosis The membrane engulf particulate matter Pinocytosis phagocytosis Osmosis Diffusion of water from high concentration to low concentration of water

10. Endocytosis & exocytosis

11. Physiology of the nerve The neuron - the basic structure unite of the nervous system - it is formed of cell body, dendrites & the axon Types of nerve fibers - myelinated nerve fibers - unmyelinated nerve fibers

13. Electric properties of the neuron 1- Nerve excitability the ability to respond to a stimulus ( a stimulus is a change in the environment) 2- nerve conductivity conduction of action potential along the length of nerve fiber Velocity of conduction is increased by increasing the diameter of nerve fiber & it is faster in myelinated nerve fibers

14. Nerve excitability • The ability to respond to a stimulus • Threshold stimulus is the minimal stimulus needed to excite the nerve & produces action potential • Types of membrane potential - resting membrane potential - action potential

15. Resting membrane potential (RMP) • It is membrane potential during rest • = - 90 mV in large nerve & skeletal muscle fiber • It is recorded by 2 microelectrodes, one inside and the other on the surface of nerve fiber. • Causes of RMP 1- selective permeability of the membrane permeability to K+ > Na + responsible of -86 mV of RMP 2- sodium – potassium pump (protein, ATP, ATPase) - Active transport of 3 Na + outside & 2 K + inside the cells - responsible for – 4 mV of RMP

17. Action potential • It is the rapid change in membrane potential following stimulation of the nerve by threshold stimulus. • Phases& shap latent period is the interval between stimulus application & start of action potential. Depolarization Membrane potential decreases slowly from – 90 mV to – 65mv ( firing level) then become rapid until it overshoots the isopotential and reach + 35mV Repolarization membrane potential returns to resting level It starts rapidly then slows down and overshoots in opposite direction to form small prolonged hyperpolarization then RMP is reached gradually

20. Ionic basis of action potential Depolarization is produced by Na + inflow through voltage gated Na + channels Electric stimulation opens some voltage gated Na + channels, flow of Na + causes more depolarization & more opening of Na channels till membrane potential reach -65 mv ( firing level) ,then all Na channels are opened Repolarization is caused by K + outflow through voltage gated K + channels Hyperpolaization is caused by slow closure of K + channels Re-establishing of Na + & K + gradient after action potential by Na + - K + pump

21. Physiology of muscle Muscles are divided into two types Striated muscles skeletal& cardiac muscles Smooth muscles no striations 40% of the body is skeletal muscles, 10% is smooth and cardiac muscles

22. Skeletal muscles • Attached to bones • Striated muscle • 40% of the body • Functions locomotion, breathing, posture, heat production, venous drainage

23. Physiologic anatomy of skeletal muscles Muscle muscle fibers myofibrils myofibrils myosin filaments myosin molecules consisted of 2 heavy chains & 4 light chains forming helix & heads ( cross bridges) . Heads contains actin binding sites, ATP binding sites & a catalytic site that hydrolyses ATP. Actin filaments F- actin moleculesforming helix & have active sites which combine with cross bridges of myosin (ADP). tropomyosin molecules strands cover the active sites of actin under resting condition. troponin troponin I for actin - troponin T for tropomycin tropnonin C for calcium Titin framework lining up the actin & myosin filaments

26. Physiologic anatomy of skeletal muscles

27. Changes following skeletal muscle stimulation • Electrical changes • Excitability changes • Mechanical changes • Metabolic changes

28. Electrical changes -Resting membrane potential ….. -90 mV -Action potential….. 2- 4 msec depolarization & repolarization precedes contraction by 2 msec -Action potential in muscle results from nerve impulse arriving at neuromuscular junction

29. Neuromuscular junction It is the junction between motor neuron & muscle fiber (motor end plate MEP)

30. Steps of neuromuscular transmission NMT 1- action potential is propagated to nerve terminal & increases membrane permeability to Ca 2+ which causes rupture of acetyl choline (Ach) vesicles Acetylcholine increases entry of Na+ inside muscle fiber 2- This causes depolarization of membrane of muscle fiber ( end plate potential EPP) 3- EPP is graded, non propagated, depolarize muscle membrane to firing level leading to action potential. 4- Action potential is conducted in both direction along muscle fiber and initiates muscle contraction 5- Acetyl choline is degraded rapidly by acetylcholine esterase preventing multiple muscle contraction

32. Properties of neuromuscular transmission NMT 1- unidirectional i.e. in one direction from nerve to muscle 2- delay- 0.5 msec 3-Fatigue- from repeated stimulation & exhaustion of acetylcholine vesicles 4-Effect of ions ------ Ca 2+inceases Mg 2+ decreases 5- Effect of drugs Drug that stimulate NMT -by Ach like action e.g.. Methacholine -by inactivating acetyl choline esterase e.g.. Neostigmin Drugs that block NMT Curare which compete with Ach for its receptors on muscle fiber

33. Myasthenia gravis - Autoimmune disease • antibodies against Ach receptors • weakness of skeletal muscles

34. Mechanical changes (Excitation contraction coupling) it is the process by which an action potential initiates the contractile process. It involves 4 steps: 1- calcium release from sarcoplasmic reticulum. 2-activation of muscle proteins and sliding of actin over myosin 3- generation of tension 4- relaxation