Recitation
and Lab # 04
The goal of this recitations / labs is to review material related to the
heart for the second test of this course. Info on the heart as a pump
has been referred to in lectures and is presented in labs as
computer simulations related to the frog model and heart functions
(4 expts) and to the ECG and heart function (6 expts). Although no
additional info is presented in the lab section, its content allows for a
better discussion of the material presented in the lecture / recitation
course.
12
Question and answers related to the heart lecture:
•
Ranking of most important items for recitation / lab # 04
–  Name the main four differences between cardiocytes and skeletal
muscle cells. Please see figures for lecture on heart as a pump.
–  For each of these 4 differences answer in an “a, b, c, and d” format.
Please notice that this question is equivalent to 4 “regular” recitations.
–  In order to answer this recitation question you need to understand all
material tested in your first exam plus the material presented in the
lecture on the heart as a pump and summarized in the lab # 04.
Recitation question # 04
The fourth recitation question attempted to “force” you to practice on the
(a,b,c,d) sub-questions for four specific characteristics presented in a lecture."
If you can not write an idea into a single sentence,"
you probably have not yet understood the material.
1
Recitation question # 04
The fourth recitation question attempted to “force” you to practice on the
(a,b,c,d) sub-questions for four specific characteristics presented in a lecture."
If you can not write an idea into a single sentence,"
you probably have not yet understood the material.
Recitation question # 04
Characteristics of cardiocytes not present in
skeletal muscles
the heart is an electrical syncitium!
intercalated disks!
the heart does not tetanize!
delay K gate opening due to increase
intracellular calcium!
the heart has automaticity!
delay K gate opening cause Na leakage to
reach threhold!
the heart has a variable force of
contraction under extrinsic and intrinsic
control!
Na / Ca channels and Ca channels!
2
Recitation question # 04
Characteristics of cardiocytes not present in
skeletal muscles!
Structure / Function Relationships !
Electrical syncitium!
a)
b)
c)
d)
Gap junctions
…….!
……..!
………!
/
Intercellular Na diffusion!
Does not tetanize!
a)
b)
c)
d)
L-Type Ca channels / Long absolute refractory period!
………!
……….!
………..!
Automaticity!
a)
b)
c)
d)
Funny channels / Automatic depolarization to threshold!
………….!
…………!
…………. !
Intrinsic control!
a)
b)
c)
d)
Stretch receptors / Extra L-Type Ca channels open!
……………!
…………..!
…………..!
Virtual Lab # 04
12
The goal of this recitations / labs is to review material
related to the heart for the second test of this course. Info
on the heart as a pump has been referred to in lectures
and is presented in labs as computer simulations related
to the frog model and heart functions (4 expts) and to the
ECG and heart function (6 expts). Although no additional
info is presented in the lab section, its content allows for a
better discussion of the material presented in the lecture /
recitation course.
Physiology Interactive Lab Simulation
(PhILS)
Students should review all simulated experimental labs
available in the software package used for this course.
Students should perform the different labs following the
instructions and time schedule defined for each lab.
3
Physiology Interactive Lab Simulations
(PhILS version 2.0 has fewer labs than PhILS version 3.0)
Osmosis and diffusion
01 varying ECF concentration
Metabolism
02 size and basal metabolic rate
03 cyanide and electron transfer
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
Skeletal muscle function
04 stimulus dependent force generation
05 the length - tension relationship
06 principles of summation and tetanus
07 EMG and twitch amplitude
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Resting potential
08 resting potential and external K
09 resting potential and external Na
Circulation
Action potentials
10 the compound action potential
11 conduction velocity and temperature
12 refractory period
13 measuring ion currents
Blood
Synaptic potential
14 facilitation and depression
15 temporal summation of EPSPs
16 spatial summation of EPSPs
Endocrine function
17 thyroid gland and metabolic rate
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
PhILS - Frog Heart Function
(thermal and chemical effects)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
At the completion of this simulation you will be able to:
1)  Describe steps in exposing the frog heart
2)  Use virtual recording instruments to monitor the movement of
the exposed heart by recording a deflection of a line tracing
3)  Measure the amplitude of the line deflection
4)  Measure time between deflections and convert it into a rate, bpm
5)  Apply cold Ringer, adrenaline, and acetylcholine and monitor the
effects on heart contractions as an indication of stroke volume
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
4
PhILS - Frog Heart Function
(thermal and chemical effects)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
PhILS - Frog Heart Function
(thermal and chemical effects)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Cooling and Ach slow heart rate (HR) and decreases cardiac
output (CO). Cooling slows the rate at which channels open
and close, whereas Ach hyperpolarize the membranes of the
pacemaker cells, which slows the rate of depolarization and
increases the difference between membrane potential and
threshold.
Adrenaline (also known as epinephrine or Epi across the
Atlantic ocean) increases HR by depolarizing the membrane
and increasing the rate of depolarization. In addition,
adrenaline is secreted onto the cardiac muscle, which
produces stronger contractions and a larger stroke volume
(SV). These two factors, a fast HR and increased SV, increase
the CO.
Digestion
37 Glucose transport
5
PhILS - Frog Heart Function
(refractory period of the heart)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
At the completion of this simulation you will be able to:
1)  Describe steps in exposing the frog heart
2)  Use virtual recording instruments to monitor the movement of
the exposed heart by recording a deflection of a line tracing
3)  Apply brief electrical shocks to the ventricle
4)  Determine when an electrical shock can produce a contraction
during the cardiac cycle
5)  Describe the refractory period in terms of time when a contraction can not be produced by ventricular electrical stimulation
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
PhILS - Frog Heart Function
(refractory period of the heart)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
The cardiac cycle consist of a contraction of the atria followed
by a ventricular contraction. In this lab, electrical shocks were
applied to the exposed frog heart to produce second contractions of the ventricle. The extra ventricular contractions were
produced only when the ventricle was relaxing. These data
suggest that there is a prolonged refractory period following the
AP, which prevents the ventricle from fibrillation. This feature
insures that the muscle has time to relax so that the heart can
filled with blood before contracting once more.
6
PhILS - Frog Heart Function
(Starling’s law of the heart)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
At the completion of this simulation you will be able to:
1)  Describe steps in exposing the frog heart
2)  Use virtual recording instruments to monitor the movement of
the exposed heart by recording a deflection of a line tracing
3)  Measure the amplitude of the line deflection and use it as a
measure of heart contraction
4)  Adjust the length of the heart in a stand and correlate the
amplitude of the line deflection with the length of the heart
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
PhILS - Frog Heart Function
(Starling’s law of the heart)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
The amount of tension produced by a contracting heart depends
upon the length of the muscle fibers. Stretching the sarcomeres
optimizes the amount of overlap between thick and thin filaments
with the result that the number of cross-bridges increases.
Beyond a certain limit, however, stretching cardiac muscle fibers
decreases both filament overlap and tension. Increasing venous
return increases end diastolic volume (EDV). Stretched
cardiocytes produced more tension and the stronger contraction
ejects more blood from the ventricle (Sterling law of the heart).
7
PhILS - Frog Heart Function
(heart block)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
At the completion of this simulation you will be able to:
1)  Describe steps in exposing the frog heart
2)  Use virtual recording instruments to monitor the movement of
the exposed heart by recording a deflection of a line tracing
3)  Determine which components of the line tracing are produced by
a contraction of the atria and the ventricle
4)  Interrupt communication through AV node to simulate a block
5)  Observe synchronous beating of the atria and the ventricle
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
PhILS - Frog Heart Function
(heart block)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
control
atria
ventricle
sulcus
The heart pacemaker is in the sinoatrial (SA) node and APs are
conducted from theree directly to the atria and ventricles through
muscle cells that make-up a heart connection system. The cells
that conduct APs to the ventricles are also pacemaker cells, but
their rhythm is much slower than those in the SA node, and its
effect is never seen in the normal heart. In this lab, a thread was
tied around the frog heart to prevent communication between the
SA node and the conducting system. The atria contracted at its
normal rate, but the ventricle showed a slower rate, as it was
driven by the AV node (a slower pacemaker).
8
PhILS - ECG and Heart Function
(ECG and exercise)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
At the completion of this simulation you will be able to:
1)  Connect patch electrodes to the volunteer’s wrist and left ankle
2)  Use virtual instruments to display the ECG on the screen
3)  Identify the different components of the human ECG
4)  Determine HR by measuring time between adjacent R-waves
5)  Measure timefor the P-R, R-T, and T-P segments
6)  Determine which of these three segments account for the
exercise – induced changes in the R-R interval
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
PhILS - ECG and Heart Function
(ECG and exercise)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
Exercise increase HR, which is seen as a decrease in the time
interval between adjacent R waves in the ECG. Exercise does not
change the P-R and R-T segments suggesting that the cardiac
cycle is not substantially influenced by exercise. However, R-P
segments is decreased by a time that is comparable to that seen
in the R-R interval. This observation indicates that exercise –
induced increases in HR can be accounted for by a decrease in
the time interval between cardiac cycles, the time when coronary
blood flow occurs.
9
PhILS - ECG and Heart Function
(the meaning of heart sounds)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
At the completion of this simulation you will be able to:
1)  Connect patch electrodes to the volunteer’s wrist and left ankle
2)  Use virtual instruments to display the ECG on the screen
3)  Use virtual event marker to indicate heart sounds on the screen
4)  Correlate the heart sounds to the different ECG components
5)  Describe how the ECG relates to heart valve function
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
PhILS - ECG and Heart Function
(the meaning of heart sounds)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
Depolarization of the ventricle muscle fibers is a significant component of the QRS complex of the ECG and initiates contraction.
The resulting increase in ventricular blood pressure closes atrioventricular valves and produces the “lub” heart sound (up). As a
result the “lub” heart sound occurs around the QRS wave.
Ventricular repolarization evokes the T-wave and relaxation of the
ventricle. The resulting drop in ventricular blood pressure closes
semilunar valves and produces the “dup” heart sound (down).
The “dup” sound, thus, is heard around the T-wave of the ECG.
10
PhILS - ECG and Heart Function
(ECG and finger pulse)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
At the completion of this simulation you will be able to:
1)  Connect patch electrodes to the volunteer’s wrist and left ankle
2)  Use virtual instruments to display the ECG and the finger pulse,
on the screen of a virtual computer
3)  Identify the different components of the human ECG
4)  Measure the time interval between the P-wave and the peak of
the finger pulse, and describe the events that take place in the
circulatory system
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
PhILS - ECG and Heart Function
(ECG and finger pulse)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
An AP in the ventricles produces a contraction which increases
blood pressure and closes the atrioventricular (AV) valves. The
contraction continues and when the blood pressure in the left
ventricle is greater than that in the aorta, the semilunar valves
open, and blood flows from the left ventricle into the aorta. The
resulting increase in blood pressure maintains blood flow around
the circulatory system. This lab shows that increase in arterial
blood pressure is detected in the finger about 0.25 seconds after
the AP in the ventricles.
11
PhILS - ECG and Heart Function
(electrical axis of the heart)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
At the completion of this simulation you will be able to:
1)  Connect patch electrodes to the volunteer’s wrist and left ankle
2)  Use virtual instrument to display the ECG on a computer screen
3)  Identify and describe the different components of human ECG
4)  Measure the amplitude of the QRS-wave with the electrodes at
two different orientations
5)  Use the data to calculate the electrical axis of the heart
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
PhILS - ECG and Heart Function
(electrical axis of the heart)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
The heart lies at an angle in the chest with the tip pointing to the
left side. This lab measures the amplitude of the QRS complex
with the recording electrodes in two orientations. The data are
used to construct a graph and draw a line that represents the
angle of the heart. The volunteer in this lab had a heart that was
about 70 degrees from the horizontal axis.
12
PhILS - ECG and Heart Function
(ECG and heart block)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
At the completion of this simulation you will be able to:
1)  Connect patch electrodes to the volunteer’s wrist and left ankle
2)  Use virtual instrument to display the ECG on a computer screen
3)  Analyze the ECG from a volunteer with a normal ECG and from
four students with different levels of heart block
4)  Determine the severity of the heart block and explain the
underlying mechanism
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
PhILS - ECG and Heart Function
(ECG and heart block)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
Problems with communication through the AV node can delay or
prevent excitation of the ventricles. The degree of heart or AV
block is categorize at 3 levels. A 1st degree AV block occurs when
the AP moves slowly through the AV node and the P-R interval is
greater than 0.2 sec. A 2nd degree block occurs when the P-R
interval slowly increases over time until the QRS is skipped. A 3rd
degree block occurs when there is no communication through
the AV node. Under these conditions atria and ventricle beat
independently, and the slower ventricular pacemaker is usually
in the AV node, the AV bundle, or the Purkinje fiber.
13
PhILS - ECG and Heart Function
(abnormal ECG)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
At the completion of this simulation you will be able to:
1)  Connect patch electrodes to the volunteer’s wrist and left ankle
2)  Use virtual instrument to display the ECG on a computer screen
3)  Analyze the ECG from a volunteer with a normal ECG and from
three students with abnormal ECGs
4)  Explain the physiological problems in the hearts of students with
abnormal ECGs
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
PhILS - ECG and Heart Function
(abnormal ECG)
Frog heart function
18 thermal and chemical effects
19 refractory period of the heart
20 Starling’s law of the heart
21 heart block
Amy
Bryan
ECG and heart function
22 ECG and exercise
23 the meaning of heart sounds
24 ECG and finger pulse
25 electrical axis of the heart
26 ECG and heart block
27 abnormal ECG
Circulation
28 cooling and peripheral blood flow
29 blood pressure and gravity
30 blood pressure and body position
Blood
31 pH and Hb - O2 binding
32 DPG and Hb - O2 binding
Respiration
33 altering body position
34 altering airway volume
35 exercise - induced changes
36 deep breathing and cardiac function
Digestion
37 Glucose transport
Chris
Deb
Amy’s ECG is normal but Brian’s QRS-waves have two peaks.
This probably indicates a problem in conduction of APs from AV
node to ventricle myocardium, and may be due to differences in
conduction velocity along the two AV bundles. Chris has an
ectopic beat every 3 cycles, indicative of extra beats coming
from the AV node, AV bundle, or a Purkinje fiber. Deb has atrial
fibrillation, where the atria contract at a very high frequency.
14