Question

question 6
1 pts
an electrical charge called an ______ causes the muscle walls of the heart to contract.

question 7
1 pts
which of the following is not a component of the respiratory system:
veins
trachea
respiratory airways (e.g., bronchioles)
lungs

question 8
1 pts
the primary role of the cardiovascular system is

Explanation:

For Question 6, an electrical charge called an action - potential causes the heart muscle walls to contract. In Question 7, veins are part of the circulatory system, not the respiratory system which includes trachea, respiratory airways, and lungs. For Question 8, the primary role of the cardiovascular system is to supply tissues with oxygen and nutrients.

Answer:

Question 6: action - potential
Question 7: veins
Question 8: supplying tissues with oxygen and nutrients