Question

question 11
maintenance of muscle tone in the walls of the blood vessels is an example of voluntary muscle contractions.
true
false
question 12
since contraction of the hamstrings causes the knee to bend and contraction of the quadricep causes the knee to extend, these muscles are said to be antagonistic.
true
false

Explanation:

For Question 11: The muscle - tone in blood vessel walls is maintained by smooth muscles, which are involuntary muscles. So it's not a voluntary muscle contraction.
For Question 12: Hamstrings and quadriceps have opposite actions on the knee joint (flexion and extension respectively), which is the definition of antagonistic muscles.

Answer:

Question 11: B. False
Question 12: A. True