muscle physiology Flashcards
1
Q
muscle types under involuntary control
A
- cardiac muscle, contains short striated cells and intercalated discs
- smooth muscle (in organ systems and blood vessels)
2
Q
myogenic muscle
A
- contract spontaneously, not from excitation from neurons
- specialised muscle cells produce electric potential
- e.g. autorhythmic fibres in vertebrate hearts
3
Q
skeletal muscles
A
- under voluntary control
- attached to skeleton, causes movement
- made from bundles of long striated muscle fibres
4
Q
properties of skeletal muscle fibres
A
- irritability
- conductivity
- contractability
- extensibility
5
Q
skeletal muscle fibres structure
A
- fibres are single cells with multiple nuclei arranged around outside
- each muscle fibre contains myofibrils that contain microfilaments arranged in repeating units called sarcomeres
6
Q
sarcolemma
A
muscle cell membrane
7
Q
sarcoplasm
A
- muscle cell cytoplasm
- contains sarcoplasmic reticulum
8
Q
sarcomere
A
- repeating units of microfilaments actin and myosin
- actin = thin filaments, binding site for myosin
- myosin = thick filaments, myosin heads extend towards actin
- contains regulatory proteins troponin and tropomyosin
- elastic filaments composed of titin
- non-elastic filament nebulin
9
Q
titin
A
- elastic filament
- anchors and stabilises myosin
- helps recover sarcomere length after contraction
10
Q
nebulin
A
- non-elastic filament
- stabilises actin
11
Q
sliding filament theory
A
- myosin head hydrolyses ATP
- converts to high energy form that can bind to actin, creating cross bridges
- pull actin towards centre of sarcomere each time ATP is hydrolysed (if more ATP and calcium provided in high levels)
12
Q
ATP sources for muscle contraction
A
- small amounts stored in cytoplasm (about 10s of contraction)
- stored creatine phosphate can convert ADP to ATP (30s contraction)
- stored glycogen
- aerobic respiration
13
Q
arrangement of sarcomeres in muscle fibres
A
- lots in parallel increases force generation
- lots in series increases degree of shortening
- optimal balance is mix of both, but depends on muscle type
14
Q
relationship between length of sarcomere and tension
A
- large overlap, little length means low tensions, as nowhere to pull actin filament
- optimal overlap has most tension
- little overlap, large length means low tension as lack of myosin heads available to form cross bridges
15
Q
neurogenic muscles
A
- stimulated by action of neurons across a neuromuscular junction (NMJ)
- e.g. vertebrate skeletal muscles
