Muscles Flashcards
Neuromuscular junction
Ap arrives her which triggers release of Ca triggering Ach release which binds to receptors on sarcolemma opening Na+ channels
Depolarisation of sarcolemma
Depol travels down t tubule in contact w sarcoplasmic reticulum
Sr contains Ca+ which open Ca binds to troponin
Contract muscle
Ca+ binds to troponin which pulls tropomyosin away from the site
Stage 1
Cocked myosin hydrolyses atp
Ready to bind in cocked position
Stage 2
Attach
Myosin heads bind to actin forming cross bridge
Stage 3
Power stroke
Myosin head flexes pulling actin along
Adp and p dissociate
Stage 4
Release
Cross bridge still in place
Atp bind to myosin detach from actin
Energy for contraction
Aerobic respiration
Anaerobic respiration
Creatine phosphate store if phosphate used up rapidly
Types of muscle
Skeletal
Cardiac
Involuntary
Skeletal muscle
Striated
Voluntary
Regularly arranged - unidirectional contraction
Rapid contraction
Short contraction
Tubular and multinucleated fibres
Cardiac
Specialised striated
Involuntary
Branch and interconnected strands simultaneously contract
Intermediate contraction speed and length
Branched uninucleate fibres
Involuntary
Non striated
Involuntary
No regular arrangement contract different directions
Slow contractions
Can be contracted for long time
Spindle shaped and uninucleate
Sarcolemma
Plasma membrane which encloses bundles of muscle fibres
Sarcoplasm
Shared cytoplasm within a muscle fibre
T tubules
Parts of sarcolemma that fold inwards to help spread electrical impulses ensures whole of fibre receives impulse
Sarcoplasmic reticulum
Modified version of endo plastic reticulum
Extends through fibre and contains calcium ions required for muscle contraction
Myofibrils
Long cylindrical organelles made of protein lined up in parallel
Made up of actin and myosin
Actin
Thinner filament 2 twisted strands
Myosin
Thicker filament
Rod shaped fibres w bulbous heads
Light bands
Appear light as region where actin and myosin do not overlap ( only actin present)
Dark bands
Presence of thick myosin as well as overlapping actin
Z line & H zone
Z line - centre of each z line ( distance between 2 = sarcomere)
H zone - lighter coloured region in middle only myosin ( reduce when muscle contracts)
Slow twitch
Fatigue resistant
Lots of aerobic resp
Lots of mitochondria
Slower contraction
Good blood supply high amounts of myoglobin
Appear darker
Fast twitch
Rapid contraction large amount of calcium ions required
Anaerobic resp
Fewer blood vessels than slow twitch
Eg human eyelids
Low myoglobin
