A normal, healthy animal never contracts the flexor muscles and the extensor muscles of the same leg at the same time. Why not?
A) When the interneuron sends excitatory messages to one, inhibitory messages go to the other.
B) They are mechanically connected in a way that makes it impossible for both to contract at the same time.
C) Such coordination is learned through prenatal movement.
D) Both muscles are controlled by branches of the same axon.

Question

Quizplus · Accepted Answer

When the interneuron sends excitatory messages to one muscle, inhibitory messages go to the other muscle to prevent both from contracting at the same time. This is known as reciprocal inhibition and is controlled by the spinal cord.

A Normal, Healthy Animal Never Contracts the Flexor Muscles and the Extensor