Explain the role of Calcium in muscle contraction

Action potential that travels down the motor neuron and reaches neuron terminal causes release of Calcium form sarcoplasmic reticulum. This released calcium will reveal binding sites on actin, hence exposing them and prepating to binding with myosin. Myosin heads then bind to the binding sites on actin. This binding allows actin to be pushed inwards, towards the centre of the sarcomere, causing shortening of the sarcomere and consequently muslce contraction.