During exercise, sensory receptors detect changes in oxygen and carbon dioxide levels in the blood. This information is then sent to the brain's medulla, which causes the heart to beat faster and increases the rate of breathing. Exercising also causes the nervous system to signal the pancreas and thyroid gland to release hormones which regulate metabolism.

One statements is an example of a scientific observation. another statement is an example of a scientific explanation. identify the correct statement for each category to illustrate how scientific explanations are inferred from scientific observations.

Match the following terms describing electrical events with the correct phases of the cardiac cycle. the ventricular muscle cells depolarize at the start of this phase. during this phase, na+ entry through the funny channels causes the pacemaker potential of sa nodal cells to gradually become less negative until it reaches threshold. the ventricular muscle cells repolarize right before this phase. the cytosolic concentration of calcium in the contractile cells of the ventricle is highest during this phase. a. isovolumetric relaxation b. ventricular ejection c. isovolumetric contraction d. ventricular filling

The following hormone had their receptors in the cell membrane except a-insulin b-tsh c-gh d- cortisol