Other than holding your breath, what can affect your heart rate? list three variables that can affect heart rate?

High temperatures, exercise, and medications.

Explanation:

Beta blockers can cause a decrease in heart rate while thyroid medications may increase it. Heat can increase your heart rate because your heart plays a big role in keeping you cool. A workload of exercise can also increase the demands on your cardiovascular system, which increases your HR.

i think it would be b. tissue because an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.