Excitation-Contraction Coupling & Muscle Relaxation

Overview of the Sequence of Events

EXCITATION

1) An electrical signal is transmitted from a motor neuron to a
skeletal muscle fiber

Overview of the Sequence of Events

EXCITATION-CONTRACTION COUPLING

2) Ca2+ is released from the sarcoplasmic reticulum

Overview of the Sequence of Events

CONTRACTION

3) Ca2+ binds to troponin on the thin filament → crossbridges form

Overview of the Sequence of Events

RELAXATION

4) Removal of Ca2+ (resequestered into sarcoplasmic reticulum)

Activation of skeletal muscle is

voluntary

• Requires a signal from the central nervous system (CNS)

CNS signal → electrical impulse is sent along a

motor neuron

The electrical impulse arrives at the

neuromuscular junction (NMJ)

neuromuscular transmission

The electrical impulse will be transmitted from the motor neuron to muscle fibers across the NMJ

Neuromuscular

Junction (NMJ)

Neuromuscular transmission occurs at the NMJ

• Signal is transmitted from neuron to muscle fiber

Motor end plate

a specialized region of sarcolemma

• Has increased surface area for receptors that respond to neurotransmitter