How do nerves enter a muscle?

[Realitycheck]

Do they enter the muscle through the origin and spread from there, or maybe somewhere near the musculotendinous junction?

[lucaspa]

Do they enter the muscle through the origin and spread from there, or maybe somewhere near the musculotendinous junction?

 

Neither. Nerves enter muscles at multiple points along the body of the muscle, where the muscle cells are.

 

Both the origin and insertion (and both are "musculotendinous junctions") are mostly fibroblasts, not myofibers (muscle cells). Any decent anatomy book will show this.