The _______, or Pacemaker of the Heart, Is a Small

Q38: The cardiac muscle becomes _, or lacking

Q39: _ increases heart rate.<br>A) Relaxation<br>B) Norepinephrine<br>C) Acetylcholine<br>D)

Q40: The _ valve guards the passageway between

Q41: Fill in the correct labels for the

Q42: Based on what you have learned about

Q44: Fill in the correct labels for the

Q45: According to _ law of the heart,

Q46: Sensory receptors in blood vessels and in

Q47: The valve between the right ventricle and

Q48: Cardiac output is the volume of blood