total body water (60% body weight)
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Introduction Physiology is the study of the living things . (from Greek physis = nature; logos = study Human 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. - PowerPoint PPT PresentationTRANSCRIPT
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IntroductionPhysiology is the study of the living things.
(from Greek physis = nature; logos= study Human 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
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Homeostasismaintenance of constant conditions in the internal environment.The functions of all organs & systems of the body help to maintain these constant conditions.
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Body fluidsthe body of a normal male is composed of about:- 18% proteins- 15% fats - 7% minerals - 60 % water
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Total body water (60% body weight)
40 % inside the cells-Intracellular fluid (ICF)-Main cation is K+ -Main anion protein & phosphate
20% outside the cells-Extracellular fluid ( ECF)-Main cation is Na +
-Main anion is Cl - & HCO3
16% interstitial fluid 4% plasma
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The cell
• It is the structural unit of various tissues & organs• It consists of o cell membrane o 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
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Transport through cell membrane
Diffusion• Passive- no energy• Occurs through lipid bilayer or protein channels• 2 types -Simple -Facilitated- needs carrier
OsmosisDiffusion of water from high concentration to low concentration of water
Active transort• Occurs against electrochemical gradiant• Needs carrier, energy ATP, ATPase• 2 types -Primary active e.g Na + - K + pump -Secondary active
EndocytosisThe membrane engulf particulate matterPinocytosisphagocytosis
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Endocytosis & exocytosis
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Physiology of the nerve
The neuron - the basic structure unite of the nervous
system - it is formed of cell body, dendrites & the
axonTypes of nerve fibers - myelinated nerve fibers - unmyelinated nerve fibers
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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 fiberVelocity of conduction is increased by increasing
the diameter of nerve fiber & it is faster in myelinated nerve fibers
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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
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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
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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.DepolarizationMembrane 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 levelIt starts rapidly then slows down and overshoots in opposite direction
to form small prolonged hyperpolarization then RMP is reached gradually
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Ionic basis of action potentialDepolarization is produced by Na + inflow through
voltage gated Na + channelsElectric 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 +
channelsRe-establishing of Na + & K + gradient after action
potential by Na + - K + pump
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Physiology of muscleMuscles are divided into two typesStriated muscles skeletal& cardiac musclesSmooth muscles no striations40% of the body is skeletal muscles, 10% is smooth and cardiac muscles
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Skeletal muscles
• Attached to bones• Striated muscle• 40% of the body• Functions locomotion, breathing,
posture, heat production, venous drainage
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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 molecules forming 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
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Physiologic anatomy of skeletal muscles
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Changes following skeletal muscle stimulation
• Electrical changes• Excitability changes• Mechanical changes• Metabolic changes
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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
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Neuromuscular junctionIt is the junction between motor neuron & muscle fiber (motor
end plate MEP)
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Steps of neuromuscular transmission NMT1- 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 contraction5- Acetyl choline is degraded rapidly by acetylcholine
esterase preventing multiple muscle contraction
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Properties of neuromuscular transmission NMT1- unidirectional i.e. in one direction from nerve to muscle2- delay- 0.5 msec3-Fatigue- from repeated stimulation & exhaustion of
acetylcholine vesicles4-Effect of ions ------ Ca 2+ inceases Mg 2+ decreases5- Effect of drugsDrug that stimulate NMT -by Ach like action e.g.. Methacholine -by inactivating acetyl choline esterase e.g.. NeostigminDrugs that block NMTCurare which compete with Ach for its receptors on muscle
fiber
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Myasthenia gravis- Autoimmune disease- antibodies against Ach receptors - weakness of skeletal muscles
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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 tension4- relaxation
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