OF THE HEART
Understanding the concepts presented in this chapter will enable the student to:
Describe how changing the concentrations of sodium, potassium, and calcium ions
inside and outside the cell affect the resting membrane potential in cardiac cells.
Explain why the resting potential is near the equilibrium potential for potassium
and the peak of an action potential approaches the equilibrium potential for
Describe the mechanisms that maintain ion concentration gradients across the
cardiac cell membrane.
Describe the role of voltage-gated Na+, K+, and Ca++ channels in the generation
of action potentials in pacemaker and nonpacemaker cells of the heart.
Describe how autonomic nerves, circulating catecholamines, extracellular
potassium concentrations, thyroid hormone, and hypoxia alter pacemaker activity.
Describe the role of afterdepolarizations and reentry in the generation of
Describe the normal pathways for action potential conduction within the heart
and how autonomic nerves, circulating catecholamines, and cellular hypoxia
alter conduction velocity within the heart.
Describe what each of the waves, intervals, and segments of a normal
electrocardiogram (ECG) tracing represents.
Recognize the following from an ECG rhythm strip:
Normal sinus rhythm
Sinus bradycardia and tachycardia
Atrial flutter and fibrillation
Atrioventricular (AV) blocks: first, second, and third degree
Premature ventricular complex
Ventricular tachycardia and fibrillation
10. Describe the location for placement of electrodes for each of the following
leads: I, II, III, aVR
, aVL, and aVF, and precordial V, to V6.
Draw the axial reference system and show the position (in degrees) for the
positive electrode for each of the six limb leads.
12. Describe, in terms of vectors, how the QRS complex is generated and why the
QRS appears differently when recorded by different electrode leads.
13. Estimate the mean electrical axis for ventricular depolarization from the six