The Muscles of the Back Contract to Straighten So That

Multiple Choice

The muscles of the back contract to straighten so that you sit at a more erect posture and subsequently the muscles are suddenly stretched as you nod off. Which of the following best represents the sequence of events when you start to nod off?
(1) Muscles of the back are stretched.
(2) The muscle spindle is stretched.
(3) Action potentials in sensory neurons of the muscle spindles increase.
(4) Action potentials in alpha motor neurons of skeletal muscle fibers increase.
(5) Skeletal muscle of the back contract.

A) 1, 2, 3, 4, 5
B) 1, 5, 2, 3, 4
C) 1, 5, 3, 2, 4
D) 5, 2, 3, 4, 1
E) 4, 5, 3, 2, 1