PPP skeletal muscle

Question 1

What is the muscle contraction cycle?

Answer 1

1 - myosin head bound to actin filament
2 - ATP bind to myosin head and its released from actin
3 - ATP - ADP + Pi (retained); causes myosin head to bend.
4 - Myosin binds to next binding site on actin; Pi released this causes myosin head to straighten up and pull itself over the actin
5 - ADP released

Question 2

How does innervation of the neuromuscular junction cause contraction of a muscle?

Answer 2

Ach released from motor end plate
Na+ voltage gated channels open, Na+ enters the cell
Depolarisation of membrane spreads across T-tubules
Ca2+ released into sarcoplasm this interacts with troponin in the tropomyosin complex which uncovers the actin binding sites.