Multiple ChoiceMore than one choice may apply.Using the figure, identify the most external part of the pericardium. a. b. c. d. e.

Cardiac muscle cells are joined by structures called:

a. T-tubules.

b. tight junctions.

c. sarcoplasmic reticulum.

d. intercalated discs.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

e. The heart plays a role in the regulation of blood pressure and secretes the hormone atrial natriuretic peptide.

The ______is the primary pacemaker of the heart.

a. atrioventricular node

b. sinoatrial node

c. Purkinje fiber system

d. atrioventricular bundle