The Cardiovascular System
Session 19
Supplemental Instruction
IowaStateUniversity / Leader: / Cody
Course: / AN S 214
Instructor: / Dr. Selsby
Date: / 3/5/13

1.What property of cardiac muscle cells is responsible for the maintenance of cardiac rhythm?

2. What kind of electric coupling is responsible for the uniform contraction of heart muscle?

3. Fill in the diagram at right. And describe the events at each labeled stage.

1.

2.

3.

4. Fill in the diagram at right with the changes in membrane potential exhibited by cells at the SA node.

5. What accounts for the instability of resting membrane potential?

6. What are some of the main differences between action potentials in cardiac and skeletal muscle?

7. Rhythmic depolarization begins in the ______, and results in the contraction of ______. The depolarization can only leave the atria via the ______, due to insulation of the atrial wall by a fat layer. Stimulation is delayed by ______seconds at the ______node in order to ensure atrial emptying. Conveyance of the signal to the ______allows depolarization of the remaining heart tissue. The cardiac action potential travels through the ______fibers, causing contraction of the cardiac muscle from ______(top to bottom/bottom to top).

8. Fill in the table with values describing the decrease in heart rate achieved via inactivation of SA node and ectopic foci.

Functionality status / Rhythm maintained by... / Heart rate
Fully functional heart
Inactive SA
Inactive AV

9. Fill in the three waves and describe what is occurringduring that phase.

______:

______:

______:

10. Match each term with each definition, there may be more than one right answer for each term:

Terms:

  • Systole:
  • Diastole:
  • Stroke volume:
  • Heart rate:
  • Cardiac output:
  • Preload:
  • Contractility:
  • Ejection Fraction:

Definitions:

  1. Stroke Volume/End-Diastolic Volume
  2. Volume of blood pumped from one ventricle of the heart with each beat
  3. Ventricular contraction
  4. Contractile strength at a given muscle length, independent of muscle stretch and EDV
  5. EDV-ESV
  6. Degree of stretch of cardiac muscle cells before they contract (Frank-Starling Law)
  7. Heart Rate (HR) x Stroke Volume (SV)
  8. Volume of blood pumped by each ventricle in one minute
  9. Number of beats per minute
  10. Ventricular relaxation

11. For each event in the heart, not the measures of ventricular volume associated (or the source of the incoming blood), to trace the changes in ventricular filling.

Contractile Event / Measures associated or source of incoming blood / Values Associated
EX: Ventricles complete Contraction / ESV / 60 mL
Atrial Diastole / XXXXXXXXXXXX / +
Atrial Systole / XXXXXXXXXXXX / +
Ventricles filled and ready to contract / =
Ventricles Contract / -
Ventricles complete contraction / =

12. For the figure below, describe the event that is occurring during each of the phases below the figure:

B, C, & D:

E:

F:

G:

H:

13. Describe each of the Electrocardiograms below: