This PPT covers the entire concepts in Muscular System. It includes details of 3 types of muscular tissue like Skeletal, cardiac and smooth muscle. Concepts of contraction cycle, sliding filament mechanism, neuromuscular junction, muscle metabolism, muscle tone and Different types of contraction.

1. MUSCULAR SYSTEM
PREPARED BY: JEGAN.S.NADAR

2. TYPES OF MUSCULAR TISSUE
The three types of muscular tissue
Skeletal
Cardiac
Smooth
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3. FUNCTIONS OF MUSCULAR TISSUE
Producing Body Movements
Walking and running
 Stabilizing Body Positions
Posture
 Moving Substances Within the Body
Heart muscle pumping blood
Moving substances in the digestive tract
 Generating heat
Contracting muscle produces heat
Shivering increases heat production
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4. PROPERTIES OF MUSCULAR TISSUE
Extensibility
Ability to stretch without being damaged
Elasticity
Ability to return to an original length
Excitability
Ability to respond to stimuli and to produce action potential
Contractility
Ability to contract forcefully when stimulated
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5. SKELETAL MUSCLE TISSUE
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6. SKELETAL MUSCLE TISSUE
 Skeletal muscle tissue is so named because most skeletal muscles move bones of the
skeleton.
 Skeletal muscle tissue is striated: Alternating light and dark protein bands are seen.
 Skeletal muscle tissue works mainly in a voluntary manner.
 Most skeletal muscles also are controlled subconsciously to some extent.
 For example, your diaphragm continues to alternately contract and relax without conscious
control so that you don’t stop breathing
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8. SKELETAL MUSCLE TISSUE ANATOMY
The various components of skeletal muscle tissue are:
1. Connective tissue component
2. Muscle fiber
3. Nerve and blood supply
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10. STRUCTURE OF SKELETAL MUSCLE
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11. CONNECTIVE TISSUE COMPONENTS
Connective tissue components are:
 Fascia
 Tendon
 Epimysium
 Perimysium
 Endomysium
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12.  Fascia
 Dense sheet or broad band of irregular connective tissue that surrounds muscles
 Tendon
 Cord that attach a muscle to a bone
 Epimysium
 The outermost layer
 10-100 muscle fibers into bundles called fascicles
 Perimysium
 Surrounds numerous bundles of fascicles
 Endomysium
 Separates individual muscle fibers from one another
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13. SKELETAL MUSCLE FIBER
• The diameter of a mature skeletal muscle fiber ranges from 10 to 100 µm.
• The typical length of a mature skeletal muscle fiber is about 10 cm to30 cm
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14.  Various components of skeletal muscle fiber are
1.Sarcolemma
2.Transverse tubule
3.Sarcoplasm
4.Myofibril
5.Sarcoplasmic reticulum
6.Filaments
7.Sarcomere
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15. 1. Sarcolemma
 The plasma membrane of a muscle cell
2. Transverse (T tubules)
 Tunnel in from the plasma membrane
 Muscle action potentials travel through the T tubules
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17. 3. Sarcoplasm:
 It lies within sarcolemma
 The cytoplasm of a muscle fiber
 Sarcoplasm contains
Glycogen: used for synthesis of ATP
Myoglobin: red-colored protein which binds oxygen molecules and it releases
oxygen when it is needed for ATP production
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18. 4. Myofibrils
 Thread like structures which have a contractile function
 (Length: 2μm)
5. Sarcoplasmic reticulum (SR)
 Membranous sacs which encircles each myofibril
 Stores calcium ions (Ca++)
 Release of Ca++ triggers muscle contraction
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19. 6. Filaments
 Filaments are smaller structure present inside myofibril
 Function in the contractile process
 Two types of filaments :
 Thick (16nm diameter and Length: 1-2μm) and
 Thin (8nm diameter and Length: 1-2μm)
 There are two thin filaments for every thick filament
7. Sarcomeres
 Compartments of arranged filaments
 Basic functional unit of a myofibril
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20. Sarcomere:
 Z discs
• Separate one sarcomere from the next
• Thick and thin filaments overlap one another
 A band
• Darker middle part of the sarcomere
• Thick and thin filaments overlap (zone of overlap)
 I band
• Lighter, contains thin filaments but no thick filaments
 H zone
• Center of each A band which contains thick but no thin filaments
 M line
• Supporting proteins that hold the thick filaments together in the H zone
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23. MUSCLE PROTEINS
Myofibrils are built from three kinds of proteins
1) Contractile proteins
• Generate force during contraction eg: Actin and Myosin
2) Regulatory proteins
• Switch the contraction process on and off eg: Troponin and tropomyosin
3) Structural proteins
• Align the thick and thin filaments properly
• Provide elasticity and extensibility
• Link the myofibrils to the sarcolemma
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24. Contractile Proteins
 Myosin
 Thick filaments
 Functions as a motor protein which can achieve motion
 Convert chemical energy in ATP to mechanical energy of motion
 It is shaped like 2 golf club twisted together
 Myosin head and myosin tail
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26. Actin
 Thin filaments
 Each Actin has myosin binding site where a myosin head can attach
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27. Regulatory Proteins
Tropomyosin and troponin
 In relaxed muscle- Myosin is blocked from binding to actin because
strands of tropomyosin cover the myosin-binding sites on actin
 The tropomyosin strands in turn are held in place by troponin molecule
 Calcium ion binding to troponin moves tropomyosin away from myosin-
binding sites
 Allows muscle contraction to begin as myosin binds to actin
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30. Structural Proteins
Several structural proteins are titin, α-actinin, nebulin and dystrophin
Titin
• Stabilize the position of myosin
• accounts for much of the elasticity and extensibility of myofibrils
Dystrophin
• Links thin filaments to the sarcolemma
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31. NERVES AND BLOOD SUPPLY
 Skeletal muscles are well supplied with nerves and blood vessels
 The neurons that stimulate skeletal muscle to contract are somatic motor
neurons
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32. CONTRACTION AND RELAXATION OF
SKELETAL MUSCLE- PHYSIOLOGY
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33. The Sliding Filament Mechanism
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35. THE CONTRACTION CYCLE
The onset of contraction begins with the SR releasing calcium ions into the
muscle cell
Where they bind to actin opening the myosin binding sites
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36. The contraction cycle consists of 4 steps
1) ATP hydrolysis
• Hydrolysis of ATP reorients and energizes the myosin head
2) Formation of cross-bridges
• Myosin head attaches to the myosin-binding site on actin
3) Power stroke
• During the power stroke the crossbridge rotates, sliding the filaments
4) Detachment of myosin from actin
• As the next ATP binds to the myosin head, the myosin head detaches from actin
• The contraction cycle repeats as long as ATP is available and the Ca++ level is
sufficiently high
• Continuing cycles applies the force that shortens the sarcomere Jegan

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38. Excitation–Contraction Coupling
 An increase in Ca++ concentration in the muscle starts contraction
 A decrease in Ca++ stops it
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41. THE NEUROMUSCULAR JUNCTION
 The neurons that stimulate skeletal muscle fibers to contract are called somatic motor neurons.
 Each somatic motor neuron has a threadlike axon that extends from the brain or spinal cord to a
group of skeletal muscle fibers
 A muscle fiber contracts in response to one or more action potentials propagating along its
sarcolemma and through its system of T tubules
 Acts as Synapse
Where communication occurs between a somatic motor neuron and a muscle fiber
 Neurotransmitter
Chemical released by the initial cell communicating with the second cell
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42.  Synaptic end bulb: axon terminals dividing into clusters (at the end of NMJ)
 Synaptic vesicles
• Sacs suspended within the synaptic end bulb containing molecules of the
neurotransmitter acetylcholine (Ach)
• Synaptic cleft: space between synaptic end bulb and motor end plate
 Motor end plate
• The region of the muscle cell membrane opposite the synaptic end bulbs
• Contain acetylcholine receptors
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45.  A nerve impulse (nerve action potential) elicits a muscle action potential in
the following way
1) Release of acetylcholine
 Nerve impulse arriving at the synaptic end bulbs causes many synaptic vesicles to
release ACh into the synaptic cleft
2) Activation of ACh receptors
 Binding of ACh to the receptor on the motor end plate opens an ion channel
 Allows flow of Na+ to the inside of the muscle cell
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46. 3) Production of muscle action potential
 The inflow of Na+ makes the inside of the muscle fiber more positively charged
triggering a muscle action potential
 The muscle action potential then propagates to the SR to release its stored Ca++
4) Termination of ACh activity
 Ach effects last only briefly because it is rapidly broken down by
acetylcholinesterase (AChE)
Release of
acetylcholine
Activation of
ACh
receptors
Production of
muscle action
potential
Termination
of ACh
activity
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49. MUSCLE METABOLISM
 ATP is required for contraction and relaxation of skeletal muscle
 A huge amount of ATP is needed to
 Power the contraction cycle,
 To pump Ca2 into the sarcoplasmic reticulum, and
 For other metabolic reactions involved in muscle contraction.
 The ATP present inside muscle fibers is enough to power contraction for only a few
seconds.
 If muscle contractions continue past that time, the muscle fibers must make more ATP
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50. Muscle fibers have three ways to produce ATP
1) From creatine phosphate
2) By anaerobic cellular respiration
3) By aerobic cellular respiration
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51. 1. CREATINE PHOSPHATE
Creatine-
amino acid
Synthesized in liver,
kidney and pancreas and
transferred to muscles
In relaxed muscles--
Excess ATP is used to
synthesize creatine
phosphate- Energy-rich
molecule
Creatine phosphate
transfers its high energy
phosphate group to ADP
regenerating new ATP
Creatine phosphate and ATP provide
enough energy for contraction for
about 15 seconds
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53. 2. ANAEROBIC RESPIRATION
 Anaerobic cellular respiration is a series of ATP-producing reactions that do not
require oxygen.
 When muscle activity continues and the supply of creatine phosphate within the
muscle fibers is depleted, glucose is catabolized to generate ATP.
 Anaerobic cellular respiration can provide enough energy for about 30 to 40
seconds of maximal muscle activity.
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55. 3. AEROBIC RESPIRATION
 Muscular activity that lasts longer than half a minute depends majorly on
aerobic respiration
 Each molecule of glucose yields about 36 molecules of ATP
 A fatty acid molecule yields more than 100 molecules of ATP
 In Aerobic respiration muscle tissue has 2 source of oxygen
 Directly from blood
 Oxygen released from myoglobin
 Although aerobic respiration is slower it yields more ATP
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57. Copyright 2009, John Wiley & Sons, Inc. Jegan

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59. MUSCLE TONE
 A small amount of tension (tautness) in the muscle due to weak contractions of
motor units
 Small groups of motor units are alternatively active and inactive in a constantly
shifting pattern to sustain muscle tone
 Muscle tone keeps skeletal muscles firm
 Keep the head from slumping forward on the chest
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60. Copyright 2009, John Wiley & Sons, Inc. Jegan

61. TYPES OF CONTRACTIONS
 Isotonic contraction
 Concentric isotonic contraction
 Eccentric isotonic contraction
 Isometric contraction
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62. 1. ISOTONIC CONTRACTION (EQUAL TENSION)
 The tension developed remains constant while the muscle changes its length
 Used for body movements and for moving objects
 Picking a book up off a table
 The two types of isotonic contractions are there
 Concentric isotonic contractions
 Eccentric isotonic contractions
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63.  In a concentric isotonic contraction (muscle shortening process), if the tension
generated is great enough to overcome the resistance of the object to be moved,
the muscle shortens and pulls on another structure.
 When the length of a muscle increases during a contraction, the contraction is an
eccentric isotonic contraction (muscle lengthening process). During an eccentric
contraction, the tension exerted by the myosin cross-bridges resists movement of a
load (the book, in this case) and slows the lengthening process.
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64. 2. Isometric contraction (equal length)
 The tension generated is not enough for the object to be moved and the muscle
does not change its length
 Holding a book steady using an outstretched arm
 These contractions are important for maintaining posture and for supporting objects in a
fixed position.
 Although isometric contractions do not result in body movement, energy is still expended
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66. COMPARISON BETWEEN ISOTONIC AND ISOMETRIC
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67. SMOOTH MUSCLE
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68. LOCATION
Smooth muscle is found in the
Walls of hollow organs such as the Stomach, Oesophagus, Bronchi.
Iris of eye
In the walls of blood vessels.
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69. ANATOMY
 A single relaxed smooth muscle fiber is 30–200 µm long.
 It is thickest in the middle (3–8 µm) and tapers (reduces its thickness) at each end.
 Within each fiber is a single, oval, centrally located nucleus.
 The sarcoplasm (cytoplasm of striated muscle cells) of smooth muscle fibers contains
both thick filaments and thin filaments but they are not arranged in orderly
sarcomeres (a structural unit in muscle) as in striated muscle
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70.  The various filaments have no regular pattern of overlap and thus smooth muscle
fibers do not exhibit striations and has a smooth appearance.
 Smooth muscle fibers also lack transverse tubules and have only a small amount
of sarcoplasmic reticulum for storage of Ca2+ .
 Although there are no transverse tubules in smooth muscle tissue, there are small
pouch like invaginations of the plasma membrane called caveolae that contain
extracellular Calcium that can be used for muscular contraction
 In smooth muscle fibers, the thin filaments attach to structures called dense bodies.
These dense bodies are similar to Z- disc in skeletal muscle fibers
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71. Anatomy of Smooth Muscle
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72. TYPES OF SMOOTH MUSCLES
1. Visceral (single-unit) smooth muscle tissue.
2. Multiunit smooth muscle tissue
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73. 1.Visceral (single-unit) smooth muscle tissue.
 It is found in tubular arrangements that form part of the walls of small arteries and
veins and of hollow organs such as the stomach, intestines, uterus, and urinary bladder.
 The fibers connect to one another by gap junctions, forming a network through which
muscle action potentials can spread.
 When a neurotransmitter, hormone, or autorhythmic signal stimulates one fiber, the
muscle action potential is transmitted to neighbouring fibers, which then contract with
unity, as a single unit.
 Eg. in walls of stomach, intestine
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75. 2. Multiunit smooth muscle tissue
 Multiunit smooth muscle tissue is found in the walls of large arteries, in airways to
the lungs, in the muscles of the iris that adjust pupil diameter
 It consists of individual fibers, each with its own neuron terminals and with few
gap junctions between neighbouring fibers.
 Stimulation of one visceral muscle fiber causes contraction of many adjacent
fibers, but stimulation of one multiunit fiber causes contraction of that fiber only.
 Eg: in iris of eye, walls of blood vessels.
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76. 09/01/15
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77. PHYSIOLOGY OF SMOOTH MUSCLES
 Contraction in a smooth muscle fibre starts more slowly and lasts much longer than
skeletal muscle fibre contraction.
 Another difference is that smooth muscle can both shorten and stretch to a greater
extent than the other muscle types.
 Sarcoplasmic reticulum (the reservoir for Ca2+ in striated muscle) is found in small amounts
in smooth muscle. Calcium ions flow into smooth muscle cytosol from both the interstitial
fluid and sarcoplasmic reticulum.
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78. MECHANISM OF SMOOTH MUSCLE CONTRACTION
 Several mechanisms regulate contraction and relaxation of smooth muscle cells.
 A regulatory protein called calmodulin binds to Ca2+ in the cytosol
 After binding to Ca2+, calmodulin activates an enzyme called myosin light chain
kinase (MLCK)
 This MLCK uses ATP to phosphorylates the myosin head (i.e energizes the myosin
head) thereby causing contraction of smooth muscles. (unphosphorylated myosin
leads to relaxation).
 Once the myosin head is energized then the same steps as studied in the contraction cycle
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82. • Relaxation of smooth muscles will occur when there is less concentration of
calcium ions in cytoplasm.
• The phosphorylation by MLCK is countered by a myosin-light chain
phosphatase (MLCP) which dephosphorylates the myosin head and thereby
inhibits contraction.
MLCK
Phosphorylates myosin head
thereby causing contraction
MLCP
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83. CHARACTERISTIC SKELETAL MUSCLE SMOOTH MUSCLE
Microscopic
appearance
Long cylindrical fiber many
peripherally located one
centrally located nuclei;
unbranched; striated.
Fiber thickest in middle, tapered at
each end, and with one centrally
positioned nucleus; not striated.
Location Tendons of bones
Most commonly attached by Walls of
hollow viscera, airways, blood
vessels, iris and ciliary body of eye..
Fiber diameter Very large (10–100 µm). Small (3–8 μm).
COMPARE AND CONTRAST BETWEEN
SMOOTH MUSCLE AND SKELETAL MUSCLE
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84. CHARACTERISTIC SKELETAL MUSCLE SMOOTH MUSCLE
Fiber length Very large (10-100 cm) Intermediate (30-200 μm)
Sarcoplasmic reticulum Abundant. Very little.
Transverse tubules present Yes No
Junctions between fibers no
Gap junctions in visceral smooth
muscle; none or very few in
multiunit smooth muscle.
Source of Ca2+ for
contraction
Sarcoplasmic reticulum
Sarcoplasmic reticulum and
interstitial fluid (caveolae)
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85. CHARACTERISTIC SKELETAL MUSCLE SMOOTH MUSCLE
Nervous control
Voluntary (somatic nervous
system).
Involuntary (autonomic
nervous system).
Speed of contraction Fast. Slow.
Regulator proteins Troponin and tropomyosin
Calmodulin and myosin light
chain kinase
Autorhythmicity No.. Yes, in visceral smooth muscle
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86. CARDIAC MUSCLE
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87. CARDIAC MUSCLE
Compared with skeletal muscle fibers, cardiac muscle fibers are shorter in length and
less circular in transverse section
They exhibit branching, which gives individual cardiac muscle fibers a “stair-step”
appearance
LENGTH: 50–100 µm long
DIAMETER : 14 µm.
Usually one centrally located nucleus is present, although an occasional cell may have two
nuclei.
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88. Structure of Cardiac Muscle Fibers
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89. Adjacent cardiac cells are joined end to end by specialized structures known as
intercalated discs
Within intercalated discs there are two types of junctions
 Desmosomes: Holds adjacent cells together
 Gap junctions: allow action potential to spread from one cell to adjacent cells.
When one cardiac cell undergoes an action potential, the electrical impulse spreads
to all other cells that are joined by gap junctions so they become excited and
contract as a single functional unit
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92.  Mitochondria are larger and more numerous in cardiac muscle fibers than in
skeletal muscle fibers.
 They have the same arrangement of actin and myosin, and the same bands, zones,
and Z discs, as skeletal muscle fibers.
 The transverse tubules of cardiac muscle are wider but less abundant than those of
skeletal muscle; the one transverse tubule per sarcomere is located at the Z disc.
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94.  The sarcoplasmic reticulum of cardiac muscle fibers is somewhat smaller than
the SR of skeletal muscle fibers. As a result, cardiac muscle has a smaller
intracellular reserve of Calcium ions
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95. PHYSIOLOGY OF
CARDIAC
CONTRACTILE CELLS
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96. PROPERTIES OF CARDIAC MUSCLE FIBERS
AUTORHYTHMICITY
EXCITABILITY
CONDUCTIVITY
CONTRACTILITY
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97. 1. AUTORHYTHMICITY :
 The ability of the heart to initiate its beat continuously and regularly without
external stimulation
 Cardiac muscle fibers are myogenic (independent of nerve supply) due to
the specialized excitatory & conductive system of the heart.
 They have intrinsic ability of self-excitation.
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98. Autorythmic fibers
 Forms 1% of the cardiac muscle fibers
 Have two important functions
1. Act as a pacemaker (set the rhythm of electrical excitation)
2. Form the conductive system (network of specialized cardiac muscle fibers that
provide a path for each cycle of cardiac excitation to progress through the
heart)
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100. 2. EXCITABILITY :
 The ability of cardiac muscle to respond to a stimulus of adequate strength
& duration by generating an AP.
AP initiated by SA node
travels along conductive pathway
excites atrial & ventricular muscle fibres
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101. 3. CONTRACTILITY
 Ability of cardiac muscle to contract in response to stimulation
4. CONDUCTIVITY
 Property by which excitation is conducted through the cardiac tissue
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102. CHARACTERISTIC SKELETAL MUSCLE CARDIAC MUSCLE
Microscopic
appearance
Long cylindrical fiber
many peripherally located one
centrally located nuclei; unbranched;
striated.
Branched cylindrical fiber with
one or more centrally located
nucleus intercalated discs join
neighboring fibers, striated
Location
Tendons of bones Heart.
Fiber diameter Very large (10–100 µm). Large (10–20 µm).
Connective tissue
Endomysium, perimysium, and
epimysium
Endomysium and perimysium.
Fiber length Very large (10-100 cm) Large (50–100 µm).
Sarcoplasmic
reticulum
Abundant. Some.
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103. CHARACTERISTIC SKELETAL MUSCLE CARDIAC MUSCLE
Transverse tubules
present
Yes Yes, aligned with each Z disc.
Junctions between
fibers
no Intercalated discs contain gap
junctions and desmosomes.
Source of Ca2+ for
contraction for
contraction
Sarcoplasmic reticulum Sarcoplasmic reticulum and
interstitial fluid
Nervous control Voluntary (somatic nervous
system).
Involuntary (autonomic nervous
system).
Speed of contraction Fast. Moderate.
Regulator proteins Troponin and tropomyosin . Troponin and tropomyosin.
Autorhythmicity No.. Yes Jegan

104. THANK
YOU