The contractile unit of a muscle:

Thick filaments within a myofibril are:

Thin filaments in a myofibril are

The energy needed to perform a muscle contraction comes directly from

The neurotransmitter stored in the axon terminal identified as #3

The neuron that transmits an impulse from the central nervous system to the muscle is called a:

Do the lengths of the thick and thin filaments change during contraction?

___ and ___ are the two proteins bound to actin.

According to the sliding filament theory, a muscle fiber contracts when myosin filaments pull actin filaments closer together and thus shorten sarcomeres within a fiber. When all the sarcomeres in a muscle fiber shorten, the fiber contracts.