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

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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)

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
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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

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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

• 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
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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
  axon
• Types 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 fiber
• Velocity 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 gt 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.
• 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

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• 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

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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

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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 junction
• It is the junction between motor neuron muscle
  fiber (motor end plate MEP)

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• 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

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• 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

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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 tension
• 4- relaxation
  
  

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