1.1. A condition known as sinus node dysfunction can result when a specific type of tissue in the heart is replaced by fibrous connective tissue.  Suggest how this could cause problems for impulse initiation and transmission within the heart.

1.2. One symptom of sinus node dysfunction is bradycardia, or a slow heart rate.  One treatment for bradycardia is to take a drug called atropine.  The effects of atropine, along with some other chemicals, on the heart rate of frogs is shown in Figure 1 below.

Figure 1

Describe the effect that atropine has when administered alongside acetylcholine.  Suggest an explanation for this.

1.3. A student concluded from the graph that epinephrine would be a better treatment for bradycardia in humans than atropine. Evaluate their conclusion.

1.4. Epinephrine is also known as adrenaline.  

Explain the role played by adrenaline in the control of heart rate.