BIO 202 STUDENT LECTURE NOTES
Lecture: Heart ll
Cardiac muscle fibers
Describe shape of cells, number of nuclei, striated?, voluntary? ______________________________________________
__________________________________________________________________________________________________
Describe intercalated discs ____________________________________________________________________________
- in essence, cells act like one giant muscle cell – this is referred to as a _____________________ __________________
Discuss some of the other structures/organelles found in cardiac muscle cells and how they are similar or differ from
skeletal muscle fibers ________________________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
Now label these on this image
Action Potential and Contraction of Cardiac Muscle Cells (first label the AP and the contraction on the graph below:
ACTION POTENTIAL– name and describe what is
happening at each step:
1. ________________________ :
______________________________________
______________________________________
2. _________________________:
T ______________________________________
E ______________________________________
N 3. _________________________:
S ______________________________________
I ______________________________________
O
N CONTRACTION
Length of contraction compared to skeletal
muscle? _______________________________
Some of Ca⁺⁺ needed for contraction is from
“2” above. But where does most of it come
from? _________________________________
Why is the plateau phase/ long AP/ long
contraction important?___________________
______________________________________
Label the absolute refractory period. Why is it
important?______________________________
_______________________________________
Discuss the difference in how an AP starts in cardiac muscle and how it contracts as a unit versus motor units in skeletal
muscle ____________________________________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
Why do cardiac cells have lots of mitochondria? __________________________________________________________
They also have myoglobin. What does myoglobin do? _____________________________________________________
Intrinsic Conduction System
Specialized cardiac muscle cells that do not ______________________ but can initiate and distribute _______________
What does autorhythmic mean? _______________________________________________________________________
How does an unstable resting potential relate to autorhythmic cells? __________________________________________
__________________________________________________________________________________________________
What are five types of these cells found in the intrinsic conduction system and indicate which is the fastest (which one
sets the pace?) 1. _______________________________ 2. _______________________________
3. _____________________________ 4. __________________________________ 5. ___________________________
The depolarization wave of the action potential spreads throughout the heart by the intrinsic conduction system and
then by spreading through gap junctions between cells in the atrium and between cells in the ventricle. Why do the
atrial cells not spread the AP through gap junctions to the ventricular cells? __________________________________
________________________________________________________________________________________________
Then how does the AP go from the atrium to the ventricles? _______________________________________________
In going through this structure, there is a delay of about 0.1 sec. – why is this important? ________________________
_________________________________________________________________________________________________
Label the different “parts” of the intrinsic conduction system and
indicate the direction of the action potential on the image to the right:
What is an ECG (=EKG)? _____________________________________
_________________________________________________________
How many “leads”(tracings) are there? ________________________
Below, draw a normal ECG of a single heart contraction. Label
the different waves and intervals and then with each, briefly
indicate what is occurring electrically in the heart.
Extrinsic control of heart rate:
ANS can change the rate and force of contraction:
The overall cardiac center in the ________________
of the brainstem is composed of three component
centers, two of which are:
1. cardioaccelatory center
What division of ANS? ____________________
What three areas does it innervate, and what are its
effects?
1. _______________________________________
_______________________________________
2. _______________________________________
_______________________________________
3. _______________________________________
_______________________________________
2. cardioinhibitory center
What division of ANS? ____________________
What two areas does it innervate, and what are its
effects?
1. _______________________________________
_______________________________________
2. _______________________________________
_______________________________________
Heart Sounds:
What causes the first heart sound (“Lub”) _______________________________________________________________
What causes the second heart sound (“Dup”) ____________________________________________________________
What is a heart murmur? ____________________________________________________________________________
What is often the cause of murmurs in adults? ___________________________________________________________