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

Question

Quizplus · Accepted Answer

When you nod off, the sequence starts with the muscles of the back being stretched (1), which stretches the muscle spindle (2). This leads to an increase in action potentials in sensory neurons of the muscle spindles (3), followed by an increase in action potentials in alpha motor neurons of skeletal muscle fibers (4), causing the skeletal muscles of the back to contract (5).

The Muscles of the Back Contract to Straighten So That