DEPARTMENT OF ORTHODONTICS
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.ind...
 Although Bones provide leverage and form the framework of the
body, they cannot move body parts by themselves. Motion re...
CLASSIFICATION OF MUSCLES
• The basis of these classifications is as follows: :
1. DEPENDING UPON THE PRESENCE OR
ABSENCE ...
DEPENDING UPON STRIATIONS
 Under this the muscles are divided into two groups namely
 STRIATED MUSCLE AND
 NON STRIATED...
DEPENDING UPON THE CONTROL
 These are classified into two types namely
 VOLUNTARY MUSCLE AND
 INVOLUNTARY MUSCLE
VOLUNT...
INVOLUNTARY MUSCLE
 These muscles cannot be controlled voluntarily.
 Their action is involuntary either by anatomic nerv...
DEPENDING UPON THE FUNCTION
 They are classified into three types namely
 SKELETAL MUSCLE
 CARDIAC MUSCLE AND
 SMOOTH ...
CARDIAC MUSCLE
 This muscles form the musculature of the heart.
SMOOTH MUSCLE
 These are the muscle, which are in associ...
 Wall of organs of G.IT like oesophagus, stomach and intestine.
 Ducts of digestive glands.
 Trachea, bronchial tube an...
 Through sustained contraction or alternating contraction and
relaxation, muscle tissue has five key functions:
1. Produc...
 Total body movements such as walking and running, and localized
movements such as nodding the head, rely on the integrat...
 Sustained contractions of ring like bands of smooth muscles
(sphincters) may prevents out flow of the contest of a hollo...
 Cardiac muscle contractions pump blood through the blood vessels.
 Skeletal muscle contractions promote flow of lymph a...
 ELECTRICAL EXCITABILITY:
It is a property of both muscle cells and nerve cells, is the ability to
respond to certain sti...
 CONTRACTILITY:
It is the ability of the muscle to shorten and thicken when stimulated by
an action potential.
Thus it ge...
 Each skeletal muscle is a separate organ composed of hundreds to
thousands of cells called fibers because of their elong...
ANATOMY
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 Connective tissue surrounds muscle fibers and whole muscles.
 Fascia sheet or broad band of fibrous connective tissue w...
 DEEP FASCIA is a dense, irregular connective tissue which holds
muscles with similar functions together.
 Allows free m...
 ENDOMYSIUM a thin sheath of areolar connective tissue which
penetrate the interior of each fascicle and separate the ind...
MICROSCOPIC ANATOMY
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 The plasma membrane of the muscle fiber is called as “sarcolemma”
 The multiple nuclei of a skeletal muscle fiber are l...
 SARCOPLASM, the cytoplasm of a muscle fiber is present with in the
sarcolemma.
 Sarcoplasm consists of large amount of ...
 SARCOPLASMIC RETICULUM or the fluid filled system of
membranous sacs encircles each myofibril.
 This is similar to endo...
 When the muscle is in resting position the length of the sarcomeres is
2 m.
 Sarcomeres are separate from one another b...
 The light band contains actin filaments and are called I bands because
they are isotropic to the polarized light.
 The ...
MUSCLE PROTEINS
 Myofibrils are made up of three kinds of proteins.
 Contractile proteins
 Generates force during contr...
CONTRACTILE PROTEINS
Two contractile proteins are namely:
1. Myosin (thick filaments)
2. Actin (thin filaments).
www.india...
 Functions as a motor protein in all the three types of muscles.
 300 molecular of myosin forms – single thick filament....
 These head lie side by side at one end.
 The 4 light chains are also parts of the myosin heads, tow to each
head.
 Par...
ACTIN FILAMENT
 Actin is the main component of the thin filament.
 Actin filament is a double – stranded F-actin each pr...
REGULATORY PROTEINS
 Tropomyosin Is regulatory protein present on the actin filament.
 Its mol.wt is 70,000 length is 40...
 Troponin molecules are attached along the sides of the tropomyosin
molecules.
 Troponin is made up of three subunits
 ...
STRUCTURAL PROTEINS
 These structural proteins helps in alignment, stability, elasticity and
extensibility of myofibrils....
 This forms the M line in the middle of the sarcomeres.
 This binds to titin and also connect adjacent thick filaments t...
 It is a cyto-skeletal protein that links thin filaments of the sarcomeres to
integral membrane proteins of the sarcolemm...
 Skeletal muscles are well supplied by nerves and blood vessels.
 Neurons that stimulate skeletal muscle to contract are...
 In the mid-1950 Jean Hanson and Hurdey had a revolutionary insight
in to the the mechanism of muscle contraction.
 They...
 In the relaxed state, the ends of the action filaments derived from two
successive discs barely begin to overlap one ano...
 At the onset of contraction the sarcoplasmic reticulum releases ca2+
ions which bind to Troponin.
 This moves the Tropo...
 The myosin head induces an ATP binding pocket and an ATP
ase, an enzyme that hydrolyzes ATP into ADP (adenosine
diphosph...
 The release of the phosphate group triggers the power stroke of
contraction.
 During power stroke, the pocket on the my...
 As ATP binds to the ATP - binding pocket on myosin head, the
myosin head detaches from actin.
 Thus the contraction cyc...
 An increase in ca2+ concentration in the cytosol starts muscle
contraction, where as a decrease stops it.
 When a muscl...
 This permits Ca2+ to diffuse across the SR membrane.
 As a result Ca2+ ions flood from the SR into the cytosol around t...
 Ca2+ ions diffuse more rapidly into the cytosol than they are
transported back by the pumps.
 After the last action pot...
MUSCLE METABOLISM
 Contraction of muscle requires a tremendous amount of ATP for
powering the contraction cycle, for pump...
 Muscle fibers have three sources for ATP production.
 They are:
1. Creatine phosphate
2. Anaerobic cellular respiration...
www.indiandentalacademy.com
TYPES OF SKELETAL
MUSCLES:
 Skeletal muscle fibers contract and relax with different
velocities.
 A fiber is categorized...
• Based on these structural and functional characteristics, skeletal
muscle fibers are classified into three main types.
•...
Structural
Characteristic
Slow Oxidative
(SO) Fibers
Fast Oxidative-
Glycolytic (FOG)
Fibers
Fast Glycolytic
(FG) Fibers
F...
Functional
Characteristics
Slow Oxidative (SO)
Fibers
Fast Oxidative-
Glycolytic (FOG) Fibers
Fast Glycolytic (FG)
Fibers
...
 Once an action potential has been elicited at any point on the
membrane of a normal fiber, the depolarization process tr...
ISOTONIC AND ISOMETRIC CONTRACTIONS
 Contraction of a muscle is described as isotonic when a muscle
length is altered dur...
 If a muscle shortens and pulls on another structure, such as a
tendon, to produce movement and reduces the angle at a jo...
ISOMETRIC CONTRACTION
 Contraction of muscle is described as isometric if tension is
generated in the muscle with out any...
 Many hormones that have effects on skeletal muscles are Many
hormones that have effects on skeletal muscles are:
1. GROW...
2. CORTICOSTEROIDS (CORTISOL) administration promote
break down of muscle proteins (endogens proteolysis) and the
extra am...
LENGTH – TENSION RELATIONSHIP
 At a Sarcomere Length of About 2.0 –2.4 µM, the zone of overlap in
each sarcomere is optim...
 When a skeletal muscle fiber is stretched to 170% of its optimal
length, these is no overlap between the actin and myosi...
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ACTIVE AND PASSIVE TENSION
 As thin filaments start to slide past thick filaments, they pull on the Z
discs, which in tur...
 Muscle tension generated by the elastic components is called
passive tension.
 Within limits, the more the elastic comp...
THE NEUROMUSCULAR JUCNTION
 The junction between the terminal branch of the nerve fiber and
muscle fiber is called Neuro ...
 This expands like a bulb called the motor end plate.
 The membrane of the muscle fiber below the end plate is thickened...
www.indiandentalacademy.com
 Synaptic cleft contains basal lamina which is a thin layer of spongy
reticular fiber through which the extra cellular fl...
ACTION POTENTIAL THROUGH MOTOR NERVE FIBER
AXON TERMINAL
Opening of voltage gated calcium channels
Entry of calcium ions f...
POSTSYNAPTIC MEMBRANE
Binding of Ach with receptor and formation of Ach
– Receptor complex
Opening of ligand gated sodium ...
 Involuntary activation of small number of motor units causes
sustained, small contractions that give firmness to a relax...
MUSCLE FATIGUE AND TETANY
 The inability of a muscle to contract forcefully after prolonged activity
is called muscle fat...
 Depletion of creatine phosphate also is associated with fatigue.
 Other factors are
1. In sufficient oxygen
2. Depletio...
TETANY
 With rapidly repeated stimulation, activation of the contractive
mechanism occurs repeatedly before any relaxatio...
ELECTROMYOGRAPHY
 Activation of motor units can be studied by electromyography, the
process of recording the electrical a...
 Used to determine the cause of muscular weakness or paralysis.
 To evaluate involuntary muscle twitching.
 To determin...
MYOTACTIC REFLEX OR STRETCH REFLEX
 The stimulus of the stretch reflex is the stretch of the muscle.
 The stretch reflex...
 If one attempts to flex the spastic limb of a patient forcibly, resistance
is encountered as soon as the muscle is stret...
 The stimulus necessary to elicit this reflex is excessive stretch
and, when elicited, it inhibits muscular contraction, ...
www.indiandentalacademy.com
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CONCLUSION
 The treatment of dento-facial mal-relations requires considerable
insight into the modalities of craniofacial...
ANIMATION
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Muscle /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078

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Muscle /certified fixed orthodontic courses by Indian dental academy

  1. 1. DEPARTMENT OF ORTHODONTICS INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2.  Although Bones provide leverage and form the framework of the body, they cannot move body parts by themselves. Motion result from the alternating contraction and relaxation of muscles.  Muscles constitute 40-50% of total body weight. Muscular strength reflects the prime function of muscle i.e changing chemical energy into mechanical energy to generate force, perform works and produce movement.  In addition, muscle tissue stabilizes the body’s position, regulates organ volume and it also generates heat. INTRODUCTION www.indiandentalacademy.com
  3. 3. CLASSIFICATION OF MUSCLES • The basis of these classifications is as follows: : 1. DEPENDING UPON THE PRESENCE OR ABSENCE OF STRIATIONS. 2. DEPENDING UPON THE CONTROL AND 3. DEPENDING UPON THE FUNCTION. Basis of classification www.indiandentalacademy.com
  4. 4. DEPENDING UPON STRIATIONS  Under this the muscles are divided into two groups namely  STRIATED MUSCLE AND  NON STRIATED MUSCLE STRIATED MUSCLE:  Under light microscope, in each muscle cell, a large number of cross striations (transverse lines) are seen at regular interval.  Skeletal and cardiac muscles are striated. NON-STRIATED MUSCLE  The muscle with out cross striations are called non striated muscle or plain muscle.  Eg. Smooth muscles. www.indiandentalacademy.com
  5. 5. DEPENDING UPON THE CONTROL  These are classified into two types namely  VOLUNTARY MUSCLE AND  INVOLUNTARY MUSCLE VOLUNTARY MUSCLE:  These muscles can be controlled voluntarily.  They are innervated by neurons that are part of the somatic division of the nervous system. E.g. Skeletal muscles. www.indiandentalacademy.com
  6. 6. INVOLUNTARY MUSCLE  These muscles cannot be controlled voluntarily.  Their action is involuntary either by anatomic nervous system or by hormones selected by the endocrine system. E.g. Cardiac and smooth muscles, and some skeletal muscles like muscles, which cause contraction and relaxation of the diaphragm. www.indiandentalacademy.com
  7. 7. DEPENDING UPON THE FUNCTION  They are classified into three types namely  SKELETAL MUSCLE  CARDIAC MUSCLE AND  SMOOTH MUSCLE SKELETAL MUSCLE:  These muscles are in association with bones forming the skeletal system.  They constitute 40% of body mass.  These are about 600 skeletal muscles identified. www.indiandentalacademy.com
  8. 8. CARDIAC MUSCLE  This muscles form the musculature of the heart. SMOOTH MUSCLE  These are the muscle, which are in association with viscera.  So they are also called visceral muscles.  They form the contractile units of wall of the various visceral organs and are present in the following structures like: www.indiandentalacademy.com
  9. 9.  Wall of organs of G.IT like oesophagus, stomach and intestine.  Ducts of digestive glands.  Trachea, bronchial tube and alveolar ducts of respiratory tract.  Ureter, urinary bladder, urethra and genital ducts.  Wall of the blood vessels.  Arrector pilorum of skin  Mammary glands.  Iris and ciliary body of the eye.  Prostate gland. www.indiandentalacademy.com
  10. 10.  Through sustained contraction or alternating contraction and relaxation, muscle tissue has five key functions: 1. Producing Body Movements: 2. Stabilizing body positions 3. Regulating organ volume 4. Producing heat 5. Moving substances with in the body FUNCTIONS OF MUSCLE TISSUE www.indiandentalacademy.com
  11. 11.  Total body movements such as walking and running, and localized movements such as nodding the head, rely on the integrated function of bones, joints and skeletal muscles. PRODUCING BODY MOVEMENTS:  Skeletal muscle contractions stabilize joints and help maintain body positions like standing or sitting.  Postural muscles contract continuously when a person is awake. E.g. Sustained contractions in neck muscles hold the head upright. STABILIZING BODY POSITION: www.indiandentalacademy.com
  12. 12.  Sustained contractions of ring like bands of smooth muscles (sphincters) may prevents out flow of the contest of a hollow organ. E.g. Temporary storage of food in the stomach or urine in the urinary bladder. REGULATING ORGAN VOLUME:  As muscle tissue contracts, it also produces heat.  Much of this heat is used to maintain body temperature. PRODUCING HEAT: www.indiandentalacademy.com
  13. 13.  Cardiac muscle contractions pump blood through the blood vessels.  Skeletal muscle contractions promote flow of lymph and aid the return of blood to the heart.  Smooth muscle contractions moves food and substances such as bile and enzymes through the G.I.T.  Contraction and relaxation of smooth muscle in the walls of blood vessels help adjust this diameter and thus regulate the rate of blood flow. MOVING SUBSTANCES WITH IN THE BODY: www.indiandentalacademy.com
  14. 14.  ELECTRICAL EXCITABILITY: It is a property of both muscle cells and nerve cells, is the ability to respond to certain stimuli by producing electrical signals called action potentials.  CONDUCTIVITY: If is the ability of a cell, especially a muscle cell or neuron, to propagate or conduct action potentials along the plasma membrane. PROPERTIES OF MUSCLE TISSUE www.indiandentalacademy.com
  15. 15.  CONTRACTILITY: It is the ability of the muscle to shorten and thicken when stimulated by an action potential. Thus it generates force to do work.  EXTENSIBILITY: This property of a muscle allows it to contract forcefully even it is already stretched with being damaged.  ELASTICITY: The property helps the muscle tissue to return to its original length and shape after contraction or extension. . www.indiandentalacademy.com
  16. 16.  Each skeletal muscle is a separate organ composed of hundreds to thousands of cells called fibers because of their elongated shapes. SKELETAL MUSCLES: www.indiandentalacademy.com
  17. 17. ANATOMY www.indiandentalacademy.com
  18. 18.  Connective tissue surrounds muscle fibers and whole muscles.  Fascia sheet or broad band of fibrous connective tissue which is deep to the skin and surrounds muscles and other organs.  Superficial fascia or subcutaneous layer – separate muscle from skin.  It is composed of areolar connective tissue and adipose tissue  This provides a pathway for the nerves and blood vessels to enter and exit muscles. CONNECTIVE TISSUE COMPONENTS : www.indiandentalacademy.com
  19. 19.  DEEP FASCIA is a dense, irregular connective tissue which holds muscles with similar functions together.  Allows free movement of muscles at carrier nerves and blood and lymphatic vessels and file the spaces between muscles.  Three layers of connective tissue from deep fascia extend to further protect and strengthen skeletal muscle.  EPIMYSIUM it is the outermost layer encircling the whole muscle.  PERIMYSIUM surrounds groups of 10 to 100 or more individual muscle fibers, separating them into bundles called fascicles. Epimysium and perimysium are dense irregular connective tissue. www.indiandentalacademy.com
  20. 20.  ENDOMYSIUM a thin sheath of areolar connective tissue which penetrate the interior of each fascicle and separate the individual fibers.  All these three connective tissue layers may extend beyond the muscle fibers to form a tendon.  TENDON is a cord of dense regular connective tissue that attaches a muscle to the periosteum of a bone. www.indiandentalacademy.com
  21. 21. MICROSCOPIC ANATOMY www.indiandentalacademy.com
  22. 22.  The plasma membrane of the muscle fiber is called as “sarcolemma”  The multiple nuclei of a skeletal muscle fiber are located just beneath the sarcolemma.  Sarcolemma consists of thousands of tiny invaginations from the surface towards the centre of each muscle fiber. Called as “T (transverse) tubules”.  T tubules are open to the outside the fiber and thus are filled with extra cellular fluid.  Muscle action potentials propagate along the sarcolemma and through the T tubules spreading through out the muscle fiber. www.indiandentalacademy.com
  23. 23.  SARCOPLASM, the cytoplasm of a muscle fiber is present with in the sarcolemma.  Sarcoplasm consists of large amount of glycogen which is used or ATP synthesis. At also contains myoglobin, a red colored oxygen binding protein, found only in muscle fibers.  MITOCHONDRIA lie in rows throughout the muscle fiber.  MYOFIBRILS which are the contractile elements of the skeletal muscle are present in the sarcoplasm and are seen under high magnification.  Myofibrils are about 2 m in diameter and extend the entire length of the muscle fiber.  Prominent striations of these myofibrils gives the muscle its striated appearance. www.indiandentalacademy.com
  24. 24.  SARCOPLASMIC RETICULUM or the fluid filled system of membranous sacs encircles each myofibril.  This is similar to endoplasmic reticulum in non muscle cells.  Dilated end sacs of the sarcoplasmic reticulum are called terminal cisternae butt against T tubule from both sides.  This SR stores the ca2+ ions. Muscle contraction occurs if these ca2+ ions are released from the terminal cisternae.  Within myofibrils are two types of even smaller structures called filaments.  They are only 1-2 m long www.indiandentalacademy.com
  25. 25.  When the muscle is in resting position the length of the sarcomeres is 2 m.  Sarcomeres are separate from one another by a plate shaped regions of dense material called Z –disc.  Actin and myosin filaments are interdigitated partially thus filament causes the myofibril to have alternate dark and light bands. www.indiandentalacademy.com
  26. 26.  The light band contains actin filaments and are called I bands because they are isotropic to the polarized light.  The dark band contains myosin filaments and ends of actin filaments, where they overlap the myosin are called dark bands or A-bands.  This band is anisotropic to polarized light.  A narrow H zone in the centre of the each A band contains thick but not thin filaments.  M. line is present in the centre of the sarcomeres, holds the thick filaments together with the help of supporting proteins. www.indiandentalacademy.com
  27. 27. MUSCLE PROTEINS  Myofibrils are made up of three kinds of proteins.  Contractile proteins  Generates force during contraction.  Regulatory proteins  Regulates the process of contraction.  Structural proteins  Keeps the filaments in alignment, gives the myofibril elasticity and extensibility, link the myofibrils to the sarcolemma and extracellular matrix. www.indiandentalacademy.com
  28. 28. CONTRACTILE PROTEINS Two contractile proteins are namely: 1. Myosin (thick filaments) 2. Actin (thin filaments). www.indiandentalacademy.com
  29. 29.  Functions as a motor protein in all the three types of muscles.  300 molecular of myosin forms – single thick filament.  The myosin molecules is composed of six polypeptide chains, two heavy chains each with a molecular weight of about 200,000 and four light chains with M.W of about 20,000 each.  Two heavy chains wrap spirally around each other to form a double helix, which is called the fail of the myosin molecule.  One end of each of there chains in folded into a globular polypeptide structure called the myosin head. MYOSIN www.indiandentalacademy.com
  30. 30.  These head lie side by side at one end.  The 4 light chains are also parts of the myosin heads, tow to each head.  Part of each myosin molecule hangs to the side along with the head, thus providing an arm that extends the head outward from the body.  The protruding arms and heads together are called cross bridges.  Each cross – bridge is flexible attached to the myosin filament with the help of hinges.  This hinged arm allows the head to be extended for out wards from the body of he myosin filament or to be brought close to the body.  Thus it helps in contraction process. www.indiandentalacademy.com
  31. 31. ACTIN FILAMENT  Actin is the main component of the thin filament.  Actin filament is a double – stranded F-actin each protein molecule. Which is 1 micrometer long.  Each strand of F-actin helix is composed of polymerized G-actin molecules with m.wt of about 42,000.  There are 13 molecules in each revolution of each strand of helix.  One molecule of ADP is attached to one G-actin molecule which is the active site on actin myosin filament where the cross bridges of the myosin filament interact to cause muscle contraction. www.indiandentalacademy.com
  32. 32. REGULATORY PROTEINS  Tropomyosin Is regulatory protein present on the actin filament.  Its mol.wt is 70,000 length is 40nm.  Tropomyosin molecules are wrapped around the side of the F-actin helix.  When the muscle is resting, the tropomyosin molecules lie on top of the active sites of the actin filament, and does not allow the myosin filament to bind with the actin filament and thus not allowing the contraction to occur. Tropomyosin molecules www.indiandentalacademy.com
  33. 33.  Troponin molecules are attached along the sides of the tropomyosin molecules.  Troponin is made up of three subunits  Troponin I – strong affinity for actin  Troponin T – strong affinity for tropomyosin  Troponin c – strong affinity for calcium ions.  This complex helps in attachment of tropomyosin to actin.  The affinity for ca2+ ions initiates the contraction process. TROPONIN www.indiandentalacademy.com
  34. 34. STRUCTURAL PROTEINS  These structural proteins helps in alignment, stability, elasticity and extensibility of myofibrils. TITIN  It is the third most plentiful protein after action and myosin in skeletal muscle  Titin anchors a thick filament to both, Z disc and the M line, and helps in stabilizing the position of the thick filament.  It extends from Z disc to the beginning of thick filaments.  It can stretch atleast 4 times its resting length and then spring back un harmed.  Thus it helps in elasticity and extensibility of myofibrils. www.indiandentalacademy.com
  35. 35.  This forms the M line in the middle of the sarcomeres.  This binds to titin and also connect adjacent thick filaments to one another. MYOMESIN  It is a large but in elastic protein and lies along side the thin filament.  It is also attached to the Z disc.  It helps maintain alignment of thin filaments in the sarcomeres. NEBULIN www.indiandentalacademy.com
  36. 36.  It is a cyto-skeletal protein that links thin filaments of the sarcomeres to integral membrane proteins of the sarcolemma.  Dystrophin reinforce the sarcolemma and help transmit the tension generated by sarcomeres to the tendon. DYSTROPHIN www.indiandentalacademy.com
  37. 37.  Skeletal muscles are well supplied by nerves and blood vessels.  Neurons that stimulate skeletal muscle to contract are the somatic motor neurons.  Blood capillaries bring in oxygen and nutrients and resolve heat and the waste products of muscles metabolism. NERVE AND BLOOD SUPPLY www.indiandentalacademy.com
  38. 38.  In the mid-1950 Jean Hanson and Hurdey had a revolutionary insight in to the the mechanism of muscle contraction.  They examined the first electron micrographs of skeletal muscle and found that the length of the thick and thin filaments were the same in both relaxed and the contracted muscle.  Later on, the researches discovered that skeletal muscle shortens during contraction because the thick and thin filaments slide past one another.  This model, which describes the contraction of muscle, is known as the sliding filament mechanism. CONTRACTION AND RELAXATION OF SKELETAL MUSCLES www.indiandentalacademy.com
  39. 39.  In the relaxed state, the ends of the action filaments derived from two successive discs barely begin to overlap one another, while at the same time lying adjacent to the myosin filaments.  Conversely in the contracted state, actin filaments have been pulled inward among the myosin filaments, so that their ends overlap one another to a major extent.  Z Discs have been pulled by the actin filaments up to the ends of the myosin filaments.  Thus the muscle contractions occurs by the sliding filament mechanism. SLIDING MECHANISM OF CONTRACTION www.indiandentalacademy.com
  40. 40.  At the onset of contraction the sarcoplasmic reticulum releases ca2+ ions which bind to Troponin.  This moves the Troponin, tropomyosin complexes away from the myosin binding sites on actin. When these sites are free, the contraction cycle that causes the filaments to slide.  This contractions cycle occurs in four steps THE CONTRACTION CYCLE www.indiandentalacademy.com
  41. 41.  The myosin head induces an ATP binding pocket and an ATP ase, an enzyme that hydrolyzes ATP into ADP (adenosine diphosphate) and a phosphate group.  This hydrolysis reaction energies the myosin head. ATP HYDROLYSIS  The energized myosin head attaches to the myosin-binding site on actin and then releases the hydrolyzed phosphate group. ATTACHMENT OF MYOSIN TO ACTIN TO FORM CROSS BRIDGES www.indiandentalacademy.com
  42. 42.  The release of the phosphate group triggers the power stroke of contraction.  During power stroke, the pocket on the myosin head where ADP is bound opens, which rotates the myosin head and releases the ADP. The myosin head generates force as it rotates toward the centre of the sarcomere, sliding the thin filament part the thick filament towards the M line. POWER STROKE  At the end of the power stroke, the myosin head remains firmly attached to actin until it binds another molecule of ATP. DETACHMENT OF MYOSIN FROM ACTIN www.indiandentalacademy.com
  43. 43.  As ATP binds to the ATP - binding pocket on myosin head, the myosin head detaches from actin.  Thus the contraction cycle repeats as the myosin ATP-ase again hydrolyses ATP. Contraction cycle repeat over and over, as long as ATP is available and the ca2+ level nears the thin filament is sufficiently high.  600 Myosin heads in one thick filament attach and detach about five times per second.  The continual movement of the myosin head applies the force that draws the discs toward each other, and the sarcomere shortens.  During a maximal muscle contraction, the distance between Z discs can decrease to half the resting length. www.indiandentalacademy.com
  44. 44.  An increase in ca2+ concentration in the cytosol starts muscle contraction, where as a decrease stops it.  When a muscle fiber is relaxed the concentration of ca2+ in its cytosol is very low, only about 0.1 millimole / liter (10-7 M). But where as in the sarcoplasmic reticulum. It is 10,000 times higher that is cytosol.  As muscle action potential propagates.  Along the sarcolemma and into the tubules it causes Ca2+ release channels in the SR membrane to open EXCITATION – CONTRACTION COUPLING www.indiandentalacademy.com
  45. 45.  This permits Ca2+ to diffuse across the SR membrane.  As a result Ca2+ ions flood from the SR into the cytosol around the thick and thin filaments. By this, the Ca2+ ion concentration rises tenfold or more.  This released Ca2+ ions combine with troponin, causing it to change its shape and moves troponin – tropomyosin complex away from the myosin – binding sites on actin.  Once these binding sites are free, myosin heads bind to them, and the contraction cycle begins.  The SR membrane also contains Ca2+ active transport pumps that hydrolyze ATP as they continually move Ca2+ from the cytosol into the SR. Ca2+ ions diffuse more rapidly into the cytosol than they are transported back by the pumps. www.indiandentalacademy.com
  46. 46.  Ca2+ ions diffuse more rapidly into the cytosol than they are transported back by the pumps.  After the last action potential has propagated throughout the T tubules, the Ca2+ release channels close.  As the pumps move Ca2+ back into the SR, the concentration of Ca2+ ions in cytosol quickly decrease.  Inside the SR molecules of a Ca2+ binding protein, called calsequestrin, bind to the Ca2+ to be sequestrated within the SR.  As the Ca2+ level drops in the cytosol, the troponin – tropomyosin complexes slide back over and cover the myosin-binding sites, and the muscle fiber relaxes. www.indiandentalacademy.com
  47. 47. MUSCLE METABOLISM  Contraction of muscle requires a tremendous amount of ATP for powering the contraction cycle, for pumping Ca2+ in to the SR to achieve muscle relaxation, and for other metabolic reactions.  The ATP present inside muscle fibers is enough to power contraction for only a few seconds.  If strenuous exercise is to continue for more than a few seconds, additional ATP must be synthesized. www.indiandentalacademy.com
  48. 48.  Muscle fibers have three sources for ATP production.  They are: 1. Creatine phosphate 2. Anaerobic cellular respiration 3. Aerobic Cellular respiration www.indiandentalacademy.com
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  50. 50. TYPES OF SKELETAL MUSCLES:  Skeletal muscle fibers contract and relax with different velocities.  A fiber is categorized as either slow or fast depending on how rapidly the ATPase in its myosin heads hydrolyzes ATP.  Skeletal muscle fibers vary in the metabolic reactions they use to generate ATP and in how quickly they fatigue. www.indiandentalacademy.com
  51. 51. • Based on these structural and functional characteristics, skeletal muscle fibers are classified into three main types. • They are: 1. Slow oxidative fibers (SO) 2. Fast oxidative glycolytic fibers (FOG) 3. Fast glycolytic fibers (FG)  Most skeletal muscles are a mixture of all these types of muscles, about half of which are so fibers.  Even though they compromise of all the three types of skeletal muscles fibres, the skeletal muscle fibers of any give motor unit are all of same type. www.indiandentalacademy.com
  52. 52. Structural Characteristic Slow Oxidative (SO) Fibers Fast Oxidative- Glycolytic (FOG) Fibers Fast Glycolytic (FG) Fibers Fiber Diameter Smallest Intermediate Largest Myoglobin Content Large Amount Large Amount Small Amount Mitochondria Many Many Few Capillaries Many Many Few Colour Red Red to Pink White (Pale) CHARACTERISTICS OF THE THREE TYPES OF SKELETAL MUSCLE FIBERS www.indiandentalacademy.com
  53. 53. Functional Characteristics Slow Oxidative (SO) Fibers Fast Oxidative- Glycolytic (FOG) Fibers Fast Glycolytic (FG) Fibers Capacity of generating ATP and m,method used High capacity, by aerobic (oxygen – requiring) cellular respiration Intermediate capacity, by both aerobic (oxygen- requiring) cellular respiration and glycolysis (anaerobic) Low capacity, by anaerobic cellular respiration (Glycolysis) Rate of ATP hydrolysis by myosin ATPase Slow Fast Fast Contraction velocity Slow Fast Fast Fatigue resistance High Intermediate Low Glycogen stores Low Intermediate High Order of recruitment First Second Third Location where fibers are abundant Postural muscles such as those of the neck Leg muscles Arm muscles Primary functions of fibers Maintaining posture and endurance – type – activities Walking, sprinting Rapid, intense movements of short duration CHARACTERISTICS OF THE THREE TYPES OF SKELETAL MUSCLE FIBERS Contn… www.indiandentalacademy.com
  54. 54.  Once an action potential has been elicited at any point on the membrane of a normal fiber, the depolarization process travels over the entire membrane if conditions are right, or it might not.  It applies to all normal excitable tissues. ALL OR NONE LAW www.indiandentalacademy.com
  55. 55. ISOTONIC AND ISOMETRIC CONTRACTIONS  Contraction of a muscle is described as isotonic when a muscle length is altered during contraction with the tension on the muscle remaining constant.  Isotonic contractions are of two types: 1. Concentric isotonic contraction. 2. Eccentric isotonic contraction. www.indiandentalacademy.com
  56. 56.  If a muscle shortens and pulls on another structure, such as a tendon, to produce movement and reduces the angle at a joint then it is said to be concentric contraction. E.g. Picking a book up off a table involves concentric isotonic contractions of the biceps brachial muscle in the arm. CONCENTRIC ISOTONIC CONTRACTION  When the overall length of a muscle increases during a contraction, it is called as an eccentric contraction. E.g. While placing the book back on the table, the previously shortened biceps gradually lengthens while it continuous to contract. ECCENTRIC ISOTONIC CONTRACTION www.indiandentalacademy.com
  57. 57. ISOMETRIC CONTRACTION  Contraction of muscle is described as isometric if tension is generated in the muscle with out any change in the length of the muscle. E.g: Holding a book steady using an out starched arm.  Contraction and stretching applied in opposite directions create the tension. www.indiandentalacademy.com
  58. 58.  Many hormones that have effects on skeletal muscles are Many hormones that have effects on skeletal muscles are: 1. GROWTH HORMONE: is administrate to a person if causes increase in the bulk of the But this increase in bulk is not due to the increment in contractile element but increments of non- contractile proteins of the muscle cells. Here the muscles become voluminous but are weak. ROLE OF HORMONES IN MUSCLE CONTRACTION www.indiandentalacademy.com
  59. 59. 2. CORTICOSTEROIDS (CORTISOL) administration promote break down of muscle proteins (endogens proteolysis) and the extra amino acid thus available are utilize to form glucose. (Glyconeogenesis). 2. ANDROGEN administration to a person increase the contractile elements of protein and thus the strength of the muscle is increased. 2. INSULIN lack as in untreated diabetes mellitus, can cause muscle wasting due to endogenous proteolysis – gluconeogenesis. www.indiandentalacademy.com
  60. 60. LENGTH – TENSION RELATIONSHIP  At a Sarcomere Length of About 2.0 –2.4 µM, the zone of overlap in each sarcomere is optimal, and the muscle fiber can develop maximum tension.  Maximum tension occurs when the zone of overlap between a thick and thin filament extends from the edge of the H zone to one end of a thick filament.  As the sarcomeres of a muscle fiber are stretched to longer length, the zone of overlap is shorter. Fewer myosin heads can make contact with thin filament.  Consequently, the tension, the fiber can produce decrease. www.indiandentalacademy.com
  61. 61.  When a skeletal muscle fiber is stretched to 170% of its optimal length, these is no overlap between the actin and myosin filaments. And the tension generated is zero.  As the sarcomeres length becomes increasingly shorter than the optimum, the tension that can develop again decreases.  This is because thick filament crumple as they are compressed by Z discs, resulting in fewer myosin heads making contact with thin filaments.  But the resting muscle length is held very close to the optimum by firm attachments of skeletal muscles to bones and to other in elastic tissues, so that overstretching does not occur. www.indiandentalacademy.com
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  63. 63. ACTIVE AND PASSIVE TENSION  As thin filaments start to slide past thick filaments, they pull on the Z discs, which in turn pull on neighboring sarcomeres. Eventually, whole muscle cells pull on their surrounding connective tissue layers.  The elastic components of a muscle are titin molecules, endomysium, perimysium, epimysium and tendons.  These elastic components stretch slightly before they transfer the tension generated by the sliding filaments.  Muscle tension that is generated by the contractile components i.e thin end thick filaments is called active tension. www.indiandentalacademy.com
  64. 64.  Muscle tension generated by the elastic components is called passive tension.  Within limits, the more the elastic component of a muscle are stretched, the greater the passive tension.  As a skeletal muscle start to shorten, it first pulls on its connective tissue covering and tendons.  The covering and tendons stretch and then become taut, and the tension Passed through the tendons pulls on the bone to which they are attached.  Thus the movement of a part of a body occurs. www.indiandentalacademy.com
  65. 65. THE NEUROMUSCULAR JUCNTION  The junction between the terminal branch of the nerve fiber and muscle fiber is called Neuro Muscular Junction (NMJ).  All the muscle fibers innervated by a single motor nerve fiber are called a motor unit.  A muscle fiber contracts in response to action potentials.  These action potentials arise at the neuromuscular junction, the synapse between a motor neuron and a skeletal muscle fiber.  The terminal branch of the nerve fiber is called axon terminal.  While approaching close to the muscle fiber, the axon loses the myelin sheath and the axis cylinder is exposed. www.indiandentalacademy.com
  66. 66.  This expands like a bulb called the motor end plate.  The membrane of the muscle fiber below the end plate is thickened, and invaginates inside the muscle fiber forming a depression known as synaptic trough or synaptic gutter into which the motor end plate fits.  The membrane of the nerve ending is called the pre synaptic membrane.  The membrane of the muscle fiber is called post synaptic membrane.  The space between these two is called synaptic cleft.  Axon terminal contains synaptic vesicles in the which the neurotransmitter substance acetylcholine present.  The Ach is synthesized by mitochondria present in the axon terminal and stored in the vesicles.www.indiandentalacademy.com
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  68. 68.  Synaptic cleft contains basal lamina which is a thin layer of spongy reticular fiber through which the extra cellular fluid diffuses  Large quantity of the enzyme, acetyl cholinesterase is attached to the matrix of basal lamina.  The postsynaptic membrane is thrown into numerous folds called sub neural clefts.  The post synaptic membrane contains the receptor proteins called nicotinic acetylcholine receptors to which the Ach binds forming Ach- receptor complex. www.indiandentalacademy.com
  69. 69. ACTION POTENTIAL THROUGH MOTOR NERVE FIBER AXON TERMINAL Opening of voltage gated calcium channels Entry of calcium ions from ECF Opening of vesicles and release of Ach SYNAPTIC CLEFT Passage of Ach www.indiandentalacademy.com
  70. 70. POSTSYNAPTIC MEMBRANE Binding of Ach with receptor and formation of Ach – Receptor complex Opening of ligand gated sodium channels and entry of sodium ions from ECF Development of end plate potential MUSCLE FIBER Generation of action potential Excitation contraction coupling Muscular contraction www.indiandentalacademy.com
  71. 71.  Involuntary activation of small number of motor units causes sustained, small contractions that give firmness to a relaxed skeletal muscle.  This firmness is known as muscle tone. MUSCLE TONE www.indiandentalacademy.com
  72. 72. MUSCLE FATIGUE AND TETANY  The inability of a muscle to contract forcefully after prolonged activity is called muscle fatigue.  Fatigue results mainly from changes within muscle fibers.  Several factors are thought to contribute for muscle fatigue.  The one important factor is inadequate release of Ca2+ ions from the SR, resulting in a decline of Ca2+ concentration in the sarcoplasm. www.indiandentalacademy.com
  73. 73.  Depletion of creatine phosphate also is associated with fatigue.  Other factors are 1. In sufficient oxygen 2. Depletion of glycogen and other nutrients build up of lactic acid and ADP and failure of action potentials in the motor neuron to release enough acetylcholine. www.indiandentalacademy.com
  74. 74. TETANY  With rapidly repeated stimulation, activation of the contractive mechanism occurs repeatedly before any relaxation has occurred.  The individual responses fuse into one continuous contraction. Such a response is called a tetanus (tetanic contraction).  It is a complete tetanus when there is no relaxation between stimuli.  When there are periods of incomplete relaxation between the summated stimuli it is called incomplete tetanus.  During a complete tetanus, the tension developed is about four times that of the individual twitch contraction. www.indiandentalacademy.com
  75. 75. ELECTROMYOGRAPHY  Activation of motor units can be studied by electromyography, the process of recording the electrical activity of muscle on a cathode- ray oscilloscope.  This may be done in un-anaesthetized humans by using small metal discs on the skin overlying the muscle as the pick-up electrodes.  It can also be done by using hypodermic needle electrodes.  The record obtained with such electrodes is the electromyogram www.indiandentalacademy.com
  76. 76.  Used to determine the cause of muscular weakness or paralysis.  To evaluate involuntary muscle twitching.  To determine the abnormal levels of muscles enzymes that appear in blood. www.indiandentalacademy.com
  77. 77. MYOTACTIC REFLEX OR STRETCH REFLEX  The stimulus of the stretch reflex is the stretch of the muscle.  The stretch reflex when elicited causes sustained contraction of the stretched muscle.  Functional significance of this reflex is that it serves as a mechanism for upright posture or standing.  The same stretch reflex is also useful in functional appliance therapy as the forces elicited by this reflex results in tooth movement and bone remodeling and may prevent further forward adaptation of the maxillary dentoalveolar process. www.indiandentalacademy.com
  78. 78.  If one attempts to flex the spastic limb of a patient forcibly, resistance is encountered as soon as the muscle is stretched throughout the initial part of the bending.  This resistance is due to hyperactive reflex contraction of the muscle in response to stretch reflex.  If the flexion is forcibly carried further a point is reached at which all resistance to additional flexion seems to melt, and the previously rigid limb collapses readily.  Thus the muscle first resists and then relaxes.  This is called clasp-knife reflex. CLASP – KNIFE REFLEX www.indiandentalacademy.com
  79. 79.  The stimulus necessary to elicit this reflex is excessive stretch and, when elicited, it inhibits muscular contraction, thus causing the muscle to relax.  The functional significance of the clasp-knife reflex is, it protects the overloaded muscle by preventing damaging contraction against strong stretching forces. www.indiandentalacademy.com
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  82. 82. CONCLUSION  The treatment of dento-facial mal-relations requires considerable insight into the modalities of craniofacial growth and muscle physiology.  The goal of modern orthodontics is to make the appliances subservient to the achievable goals.  So, it is necessary for an orthodontist to know the mechanism of muscle physiology as the success of the functional appliance therapy depends on the neuromuscular response. www.indiandentalacademy.com
  83. 83. ANIMATION www.indiandentalacademy.com
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