muscles Flashcards
what are the 3 types of muscle
- skeletal
- cardiac
- smooth
what are muscles made up of
tiny muscle fibres called myofobrils
how do myofibrils make up muscles
grouped into a single muscle fibre which are further grouped into bundles of muscle fibres which are grouped into muscle tissue
what makes up a muscle fibre
- sarcolemma
- nucleus
- sarcomeres (make up a myofibril)
- mitochondria
what’s the membrane called in a muscle fibre
sarcomere
what’s the ER called in a muscle fibre
sarcoplasmic reticulum
what filaments make up a scaromere
myosin & actin
main neurotransmitter in muscles
acetylcholine
what does acetylcholine do
• acts as an excitatory neurotransmitter at neuromuscular junctions connecting motor neurones with skeletal muscle
what acts as the post synaptic membrane when talking about muscles
the sarcolemma (muscle fibre membrane)
how is a muscle fibre contracted
same stages as chokinergic synapses - neurotransmitter and sodium ions lead to depolarisation of the sarcolemma
what type of neurotransmitters do u find in the neuromuscular junction
only excitatory
what neurones are involved
only motor neurones
does the action potential carry on at the sarcolemma?
no
what does acetylcholine do in neuromuscular junctions
binds to receptors on membrane of muscle fibres
structure of myosin filament
- thick
- long rod shaped tails
- bulbous heads
structure of actin filaments
- thin
- consists of 2 strands twisted around one another
- binding sites
what does tropomyosin do
wrap around actin, covering up its binding sites
what wraps around actin
tropomyosin
what do calcium ions do
cause tropomyosin to change shape and pull away from the binding sites on actin
how is a muscle contracted
- calcium moves tropomyosin
- myosin head attaches to actin binding sites
- myosin changes angle pulling actin filament along
- ADP is released & ATP fixes to myosin head, moving it away from actin binding site
- ATP hydrolysed back to ADP by ATPase provides energy to move myosin head back to its normal position
the 3 ways ATP is supplied to a skeletal muscle
- aerobic respiration in mitochondria by slow twitch fibres
- anaerobic respiration by fast twitch fibres
- creatine phosphate - enzyme converts this to ADP v quickly
what are fast twitch muscle fibres
fibres with many mitochondria, often found in muscles requiring endurance
what are slow twitch muscle fibres
few mitochondria, rich in glycogen
