Arrange the events in the stimulation of heart muscle in order from earliest (1) to latest (5). note that this question does not list every step in the pathway, but the steps presented should be arranged in order.

1) Pacemaker impulse generation.

2)AV node impulse conduction

3) AV bundle impulse conduction.

4) Bundle branches conduction.

5) Purkinjie fibres impulse conduction.

Explanation:

The cardiac conduction has following components.

1)SA node is the heart pacemaker in the right upper quadrant of heart. It generates electrical impulses and these impulses then move through atria and AV node to the Purkinjie fibres.

2) The impulses reach AV node. It controls heart rate. It serves as electrical relay station which slows the electrical current sent by SA node before the signals has passed to ventricles.

3) AV bundle is continuation is AV node and it transmits impulse from AV node to the Purkinjie fibres.

4) Electricle impulses from bundle of his passes through bundle branches (right and left ) to Purkinjie fibres.

5)Purkinjie fibres take the impulses from the bundle branches to the myocardium of ventricles.

4.) metal

"-the movement of carbon from the nonliving environment into living things and back to the environment

-carbon is the essential component of proteins, fats, and carbohydrates (which make up all organisms)

-carbon exists in air, water, and living organisms

-producers convert carbon dioxide in the atmosphere into carbohydrates during photosynthesis

-bacteria in the atmosphere cycles through the system in filtration units

-in cellular respiration, carbon is released back into the atmosphere as carbon dioxide

-some carbon is stored in limestone (forming one of the largest "carbon sinks" on earth)

-largest carbon reservoir on earth= limestone

-carbon stored in the bodies of organisms as fat, oils, or other molecules may be released into the soil or air when the organism dies

-this may form deposits of coal, oil, or natural gas (fossil fuels, which increased the atmospheric carbon dioxide)

-fossil fuels store carbon left over from bodies of organisms that died millions of years ago

-they are located in the surface of earth, deep within the earth and beneath the ocean floor."    

b. lithosphere, asthenosphere, mesosphere   is the answer most likely