8/2/2019 21. Muscles Contraction
1/21
1
Muscle Muscles
Highly vascularised
Muscle fibers elongated cells
3 types of vert. Muscle
Skeletal muscle
Smooth muscle
Cardiac muslce
8/2/2019 21. Muscles Contraction
2/21
2
Smooth Muscle
Smooth muscle
Spindle shaped Central nucleus
Tubular organs
Circular + longitudinal
Digestive system autonomic nervous system
Contracts slowly
Fatigues slowly
8/2/2019 21. Muscles Contraction
3/21
3
Cardiac Muscle Cardiac muscle
Found in heart
Does not fatigue autonomic nervous system
8/2/2019 21. Muscles Contraction
4/21
4
Skeletal muscle
Skeletal muscle
Attached to bones Locomotion
Striated
Btn 0.01 to 0.1 mm
multinucleatedvoluntary
nervous system
fatigues quickly
8/2/2019 21. Muscles Contraction
5/21
5
Tendons
Skeletal muscle attached to
skeleton bytendons
Cartilage
Continuous w/ muscle
Fuses with periosteum At least two muscle
involved in moment
Antagonistic muscles
8/2/2019 21. Muscles Contraction
6/21
6
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
8/2/2019 21. Muscles Contraction
7/21
7
Skeletal Muscle Muscle fibres (MF)
cylindrical
parallel MF surrounded by
Collagen Tendons
Muscle Fibres
Sarcolemma
Myofibrils
Sarcomere Myofilaments MyosinActin
8/2/2019 21. Muscles Contraction
8/21
8
Sarcoplasmic reticulum
8/2/2019 21. Muscles Contraction
9/21
9
Muscle striation Light and dark bands
I band light
A bands dark Arrangement of myofilaments
8/2/2019 21. Muscles Contraction
10/21
10
Myofilaments
8/2/2019 21. Muscles Contraction
11/21
11
Actin Thin filament Fibrous actin (F Actin) Tropomyosin
Rod shaped 2 F Actin
Troponin complex
Troponin T Troponin C Troponin I
8/2/2019 21. Muscles Contraction
12/21
12
Myosin Thick filament 2 regions
Rod myosin heads Project from the rod ATPase activity
Heads hooks Actin
8/2/2019 21. Muscles Contraction
13/21
13
Sarcomere filament arrangement
A f fil
8/2/2019 21. Muscles Contraction
14/21
14
Arrangement of myofilaments
C t ti lidi fil t th
8/2/2019 21. Muscles Contraction
15/21
15
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
8/2/2019 21. Muscles Contraction
16/21
16
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 '
8/2/2019 21. Muscles Contraction
17/21
17
'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
8/2/2019 21. Muscles Contraction
18/21
18
Action potential arrival
8/2/2019 21. Muscles Contraction
19/21
19
Muscle contraction
M fil t A ti
8/2/2019 21. Muscles Contraction
20/21
20
Myofilaments - Actin
8/2/2019 21. Muscles Contraction
21/21
21
Muscle contraction