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Muscle Muscles

Highly vascularised

Muscle fibers elongated cells

3 types of vert. Muscle

Skeletal muscle

Smooth muscle

Cardiac muslce

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Smooth Muscle

Smooth muscle

Spindle shaped Central nucleus

Tubular organs

Circular + longitudinal

Digestive system autonomic nervous system

Contracts slowly

Fatigues slowly

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Cardiac Muscle Cardiac muscle

Found in heart

Does not fatigue autonomic nervous system

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Skeletal muscle

Skeletal muscle

Attached to bones Locomotion

Striated

Btn 0.01 to 0.1 mm

multinucleatedvoluntary

nervous system

fatigues quickly

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Tendons

Skeletal muscle attached to

skeleton bytendons

Cartilage

Continuous w/ muscle

Fuses with periosteum At least two muscle

involved in moment

Antagonistic muscles

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Lever systems

Flexor decreases angle btn 2 skeletal elements

Extensor increases angle btn 2 skeletalelements

Adductor limbs away from body axis

Abductor limbs towards body axis

Rotator allows for rotation of part or all of limb

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Skeletal Muscle Muscle fibres (MF)

cylindrical

parallel MF surrounded by

Collagen Tendons

Muscle Fibres

Sarcolemma

Myofibrils

Sarcomere Myofilaments MyosinActin

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Sarcoplasmic reticulum

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Muscle striation Light and dark bands

I band light

A bands dark Arrangement of myofilaments

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Myofilaments

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Actin Thin filament Fibrous actin (F Actin) Tropomyosin

Rod shaped 2 F Actin

Troponin complex

Troponin T Troponin C Troponin I

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Myosin Thick filament 2 regions

Rod myosin heads Project from the rod ATPase activity

Heads hooks Actin

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Sarcomere filament arrangement

A f fil

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Arrangement of myofilaments

C t ti lidi fil t th

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Contraction sliding filament theory Hugh Huxley, Andrew Huxley

Not related

Papers published same month Sarcomere shortened during

contraction

A band?

H zone and I band?

Filaments slide past each other

Actin filaments move inwards

Sarcomere contract 30% of length

M l t ti

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Muscle contraction Initiated by action

potential from motorneurons Neuromuscular junction Axons highly branched

100s muscle fibres Motor unit Musclefibres

Activated by 1 motorneuron

Simultaneouscontraction

' ll thi '

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'all-or-nothing' response Muscle fibre stimulated by

impulse

Contraction occurs ifstimulus = or above

threshold level

Response is maximal

After contraction Absolute refractory

no contraction Relative refractory

period

A ti t ti l i l

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Action potential arrival

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Muscle contraction

M fil t A ti

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Myofilaments - Actin

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Muscle contraction