module 5 - 13.10 the sliding filament model Flashcards
What is me sliding filament theory?
When skeletal muscles contract longitudinally by the actin filaments and myosin filaments in each myofibril slide past each other
What is the result of a sarcomere contracting?
- Lighter band becomes narrower
- The z-lines move closer
- The h-zone becomes narrower
What is me darker area or an election micrograph of related and connected sarcomere?
The darker area is myosin and actin overlapping
What is the structure of myosin molecules?
- Have flexible and globular head and long tail
- made of many myosin molecules arranged in a bundle
- heads of myosin molecules have binding site for ATP and separate binding site for actin (actin-myosin birding site)
- myosin heads prodded along length of me myosin filament.
What is the structure or actin filaments and actin molecules?
- Made of 2 actin molecules twisted around each other forming a loose double helix
- actin-myosin binding sites are blocked by tropomyosin
- tropomyosin is held in place by a globular protein called troponin
What is a neuromuscular junction?
- The synapses between a motor neurone and muscle fibres
- found in motor end plates
- many neuromuscular junctions along a muscle to ensure au muscle fibres contract simultaneously
- a single motor neurone will connect all muscle fibres in a motor unit
When is a strong muscle contraction achieved?
When motor units are stimulated
What happens when an action potential arrives at the neuromuscular junctions?
It causes voltage gated calcium ion channel proteins to open
How do calcium ions diffuse through the synaptic knob? And what does mis cause?
- Through facilitated diffusion
- causes synaptic vesicles to fuse with presynaptic membrane by exocytosis
Where do acetylcholine molecules diffuse across?
Synaptic cleft
Where are the receptor proteins that acetylcholine birds to? And what does this cause?
- The sarcoma
- causes sodium ion channels in the receptor protein to open and sodium ions diffuse into the sarcoplasm
- depolarisation of the sarcolemma occurs
Where does the depolarisation of the sacolemma travel?
Travels deep into the muscle fibre by travelling along t-tubules
What does depolarisation of t-tubules cause?
Causes sarcoplasmic reticulum to release calcium ions that diffuse down their concentration gradient
What does calcium binding to troponin cause?
Causes conformational change which stops tropomyosin from blocking myosin binding sites on actin filaments.
Where is ADP bound to?
Myosin head
