This presentation is about muscle fibers, muscle contraction, tetanus, motor unit, summation.......

1. Physiology of the cell
by
H. Khorrami Ph.D.
http://khorrami1962.spaces.live.com
http://www.scribd.com/khorrami4
khorrami4@yahoo.com

2. Muscle types
• Cardiac Muscle
– Striated muscle found only in the heart
– Under involuntary control
– Only rests between contractions
• Smooth Muscle
– Lack striations
– Usually under involuntary control
– Contraction is slow and rhythmic
– Muscles of internal organs
• Skeletal Muscle
– Striated muscle fibers with no clear separation
between cells
– Under voluntary control

3. Muscles

4. • Synapse
• Motor unit
Neuro-muscular junction

5. Synaptic cleft

7. (Plasma membrane)
Mammalian muscle
Note alignment
of T-tubules

12. Myofibril arrangement in muscle

18. • http://www.youtube.com/watch?v=CepeYFvq
mk4
• https://www.youtube.com/watch?v=hr1M4Sa
F1D4

19. Titin
• Largest protein with 34,350 AA
• Mutation:
– familial hypertrophic cardiomyopathy
– Tibial muscular dystrophy

20. Synaptic transmission steps
• Na-K conductance
• Depolarization of presynaptic membrane
• Motor end-plate potential
• Increase Ca++ entrance
• Ca2+-calmadulin
• Synapsin-1
• Vesicle fusion
• NT release

25. T-tubules are NOT
positioned at M lines.

27. This gap is
actually only
~10 nm.
Ca2+
-ATPase

29. Molecular mechanisms of crossbridge action

30. This causes a conformational
shift in the myosin head.

31. Actin filament components and Ca2+
activation
F
Troponin is a complex of three
proteins including troponin C, a
Ca2+
-binding protein closely
related to calmodulin.

32. Binding of myosin to actin
leads to release of Pi.
After death, as ATP runs out,
cytosolic [Ca2+
] slowly rises,
actin binding sites are opened,
crossbridges are formed and
become locked in the "rigor"
position without ATP to bind.

34. Rigor Mortis

36. Single twitch

38. Summation of skeletal muscle tension; tetanus

39. Tetanus

40. Length-tension curve for skeletal muscle
Full overlap between
thick and thin filaments
Decreasing overlap limits
maximum tension
No overlap
(Muscles are not naturally
stretched to this point)
Actin poking
through M line;
myosin bumping
into Z disk.
Contraction range with
normal skeletal movements

41. Lmax

42. Tension in muscle

43. Elastic elements
• PEE
• SEE
• TEE

44. Contraction
• Isometric
• Isotonic
– Concentric
– Eccentric

45. Time is required for maximal twitch force to develop, because some
shortening of sarcomeres must occur to stretch elastic elements of
muscle before force can be transmitted through tendons
By the time this maximal force is developed, [Ca2+
] and number of
active crossbridges have greatly decreased, so an individual twitch
reaches much less than the maximum force the muscle can develop

48. Muscle Metabolism

50. Mitochondria generate ~32 ATP from one glucose
(slow, but efficient).
Glycolysis generates 2 ATP from one glucose
(fast, but inefficient; lactate accumulates).
Creatine kinase reaction: (fastest)
ADP + creatine-P  ATP + creatine
Adenylate kinase reaction (fast; used when ATP
levels are very low):
ADP + MgADP  AMP + MgATP

51. Muscle fiber types

52.  Central: involving central nervous system
may involve such factors as dehydration, osmolarity, low
blood sugar, and may precede physiological
fatigue of actual muscles
 Peripheral: in or near muscles, accumulation of lactate
and pH, especially in fast-twitch fibers
 inorganic phosphate may increasingly inhibit
cleavage of ATP in the crossbridge cycle or in
the sequestering of Ca2+
Muscle Fatigue

53. Muscle Spindle, Intrafusal Fibers
• Motor
• Sensory
– Dynamic
– Static

56. Nuclear Bag & Nuclear Chain

57. Muscle Control, Proprioception

58. Golgi tendon organ

59. Gamma Motoneuron

61. Motor unit
• Small motor unit: 1-to-1 e.g. in EOM
• Large motor unit: 1-to-2000 e.g.
gastrocnemius muscle

64. Motor Unit: Fibers Innervated from
1 neuron
• "All or none" within
each motor unit
• Fine touch
– 1:1 nerve to fiber
– Finger tips
• Big muscles
– 1: 2000
– Leg, postural muscles
PLAY
Animation: Muscular System:
Contraction of Motor Units

65. Contractile force
can also be
regulated through
activation of
more, or fewer,
motor units.

66. • Weak stimulus
– Lowest threshold fibers
– Slow twitch typically
• Moderate: adds fast
oxidative
• High stimulus: all fibers
• Asynchronous:
– Units take turns
– Prevents fatigue
Recruitment of Fibers: Produce
Graduated Force

67. Hypokalemia, Causes
• Kidney disease
• Diabetes
• Cirrhosis(chronic alcoholism)
• Laxative abuse(loose weight)
• Diuretics
• Steroids,…
– steroid psychosis, mood changes, agitation, and
irrational behavior
• Corticosteroids( organ transplant, Cushing
disease,…)
• Hypervitaminosis B12

68. Hypokalemia,
• Proximal muscle weakness
• Myopathies
• Cardiac arrhythmia
• Hypokalemic periodic quadriparesis
– Autosomal dominant disorder
– Areflexic paresis
– Irregular attacks
– Large carbohydrate meals often precipitate attacks

69. Hyponatremia
• Compulsive water intake
• Adrenal insufficiency
• Kidney disease
• Hi ADH
• Medications

70. Hyponatremia
• Osmosis, cell swelling, cerebral edema,..
• Confusion, agitation, stupor
• Nausea and vomiting
• Headache, confusion
• Loss of energy, drowsiness and fatigue
• Restlessness and irritability
• Muscle weakness, spasms or cramps
• Seizures
• Coma

71. Proprioceptors
• Specialised sensory receptors within joints, muscles,
and tendons
• Sensitive to both tension and pressure
• Play a role in relaying information concerning muscle
dynamics to the conscious and subconscious parts of
the CNS
• They provide the brain with information concerning
kinesthetic sense, or conscious appreciation of the
position of body parts with respect to gravity
• Mostly at subconscious level,
• GTO located in tendons near the myotendinous
junction and are in series

72. Techniques to Increase ROM
• MET
• PNF( Proprioceptive Neuromuscular
Facilitation)

73. PNF Theories
• Autogenic inhibition
• Reciprocal inhibition
• Stress relaxation
• Gate control theory

74. PNF Techniques
• Contract-Relax (CR) method
• Contract-Relax-Antagonist-Contract (CRAC)
Method
• **PNF before exercise decrease the muscle
performance
• ** PNF after exercise increase the muscle
performance

76. Ach Agonist
• Stimulate Ach receptor but not destroyed by
AchE:
– Nicotine, carbacol & methacoline
– Produce spasm

77. Skeletal Muscle Attachment
• Tendon Attachments
– Origin
• Attachment to the bone that doesn’t move
– Insertion
• Attachment to the bone that does move
• Antagonistic Pairs
– Flexor
• Flexes the joint (moves toward the body)
– Extensor
• Extends the joint (away from the body)

78. Rheobase & chronaxie

80. Trigger points
• Is a hyperirritable spot, a palpable nodule
in the taut bands of the skeletal muscles'
fascia
• Direct compression or muscle contraction
can elicit jump sign, local tenderness, local
twitch response and referred pain which
usually responds with a pain pattern
distant from the spot

81. Classification of Triger Point
• Primary
– Muscle belly, severe pain(jump sign) with pressure
and radiate according to referred pain map
• Secondary(satellite) or as cluster
– Usually disappear when central trigger point heal
• Active/Inactive(can increase stiffness)
• Tendon, can develop degenerative process of
the joint if not treated
• Ligamentous, i.g. ant longitudinal,
Ligamentum patellae, fibular collateral

82. Causes of Trigger Point
• Injury sustained by a fall, by stress or birth trauma
• Lack of exercise, commonly in sedentary persons, 45% are
men
• Aging
• Bad posture, upper and lower crossed pattern, swayback
posture, telephone posture, cross-legged sitting,
• Muscle overuse and respective micro trauma,
weightlifting, ..
• Chronic stress condition, anxiety, depression,
psychological stress trauma,
• Vitamin deficiencies, vitamin C, D, B; folic acid; iron;
• Sleep disturbance,
• Joint problems and hypermobility

84. Pathophysiology
• Overactive
• Local inflammation
• Loss of oxygen & nutrients
• Involuntary muscle contraction
• Higher demand to oxygen
• Higher concentration of Ach, NAd, 5HT
• Low PH

85. Muscle Cramp
• If you’ve ever had a “charley horse” that odd
pain in your calf, you’ve had a cramp
• But they can happen anywhere in your body
at any time, even when you’re asleep
• No matter where you get them, what’s going
on inside is the same: Your muscles suddenly
tighten up when you don’t want them to
• Several things can bring on cramps, but you
can do some things to keep them from
happening

86. Possible Cause: Not Enough Water
• Cramps may be your body’s way of telling you
that you need some, you’re dehydrated
• Other signs include dizziness, headache, and
constipation. So keep water with you and sip it
throughout the day, especially if you’re
outside in hot weather

87. High Temperatures
• Your body loses fluids when you work or
exercise in the heat, and that can make you
more likely to cramp. This may be partly
because your muscles need water, but it’s also
because you sweat out important minerals
called electrolytes, sodium, potassium, and
calcium

88. Medications
• Statins, which are used to control cholesterol,
and diuretics, which help your body get rid of
fluid, are just two of the drugs that can bring
on cramping as a side effect

89. Poor Circulation
• If your cramps get worse when you walk, your
muscles may not be getting enough blood.
That can happen as you get older or if you’re
not very active. It also can be caused by a
condition called claudication, when arteries
are narrower than they should be and blood
can’t get through easily

90. Monthly Cycle
• Some women get cramps during their periods.
That happens because a woman’s body makes
certain hormones that make the muscles in
her uterus tighten up. This helps push out
blood and tissue, but it can also cause
cramping

91. Growth
• Kids often get cramps when they go through a
growth spurt. These are sometimes called
“growing pains,” but they may actually be
caused by too much activity, or kids may just
be more sensitive to pain. The cramps happen
most often in the legs and can wake a child
out of a sound sleep. It may help to stretch
the muscle or put a heating pad on the area
for a short time

92. Exercise
• It’s important to stay active, but if you do too
much all at once or your body’s not used to it,
your muscles can cramp. Instead, pace
yourself: Regular exercise can make your
muscles stronger and harder to tire out, so
they won’t cramp as easily. Be sure to warm
up first, and do plenty of stretching before and
after

93. How to Feel Better
• Cramps usually go away on their own fairly
quickly, but you can do some things to help
them along. If an activity like running
triggered one, stop right away. Then gently
stretch or massage the muscle or use a
heating pad or hot bath to bring blood to the
area and relax it. Ice and over-the-counter
anti-inflammatories, like ibuprofen, can help if
you have pain and swelling, too

94. Why Stretching Helps
• Muscles are bunches of fibers that quickly get
smaller or bigger when you move your body
to do something -- from grabbing something
off a shelf to running a race. When you stretch
those fibers regularly, they can do their job
more easily, and that helps you cramp less

95. Why Your Diet Matters
• Colorful fruits and vegetables have minerals
called electrolytes that help keep your
muscles in good shape and can help you avoid
cramps. Leafy greens and bananas are good
choices

96. Smooth muscle