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Washburn University- BI 255 Lab Final Exam; Questions with Detailed Solutions
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Washburn University- BI 255 Lab Final Exam; Questions with Detailed Solutions
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Washburn University- BI 255 Lab Final Exam; Questionswith Detailed Solutions
Frog Heart experiments CORRECT ANS-Mechanical, affects of temperature and various
drugs
What are the autonomic neurotransmitters CORRECT ANS-Acetylcholine, norepinephrine
(epinephrine used in lab)
What does acetylcholine do to the heart CORRECT ANS-Parasympathetic, decreases
pacemaker rate by increasing K+ and decreasing Ca2+ and Na+ movement. As the pacemaker
slows, so does the heart.
What does norepinephrine do? CORRECT ANS-Sympathetic. Increases heart rate and
magnitude of contraction, increased blood pressure, triggers release of glucose from energy
stores. It alters the permeability of the membrane and increases depolarization. (Allows more
Ca2+ to enter from an extracellular fluid)
How does temperature effect heart rate CORRECT ANS-Increased temperature increases
heart rate and decreased temperature decreases heart rate. Temp changes the rate in which
ions move in and out of heart cells and thereby affect the rate of depolarization and
repolarization. Thus, a change in heart rate and force of contraction.
, Washburn University- BI 255 Lab Final Exam; Questions
with Detailed Solutions
Absolute refractory period CORRECT ANS-Following each depolarization and subsequent
contraction of the heart muscle, there is a time period the muscle cannot be re-stimulated.
This allows time to move the blood through the heart efficiently and prevent the heart from
ever reaching a state of fatigue.
Difference between cardiac and skeletal muscle refractory periods CORRECT ANS-The
refractory period in cardiac muscle is much longer than in skeletal muscle and the heart fully
relaxes between action potentials.
How was the refractory period tested in lab? CORRECT ANS-Use of the iWorx stimulator
box, the stimulation frequency was set to consistently stimulate the heart and create action
potentials. Even with frequent stimulation, action potentials only occurred after the refractory
period ended.
Define extra systole CORRECT ANS-The absolute refractory period is followed by a relative
refractory period during which a strong electrical stimulus can elicit an early extra systole. A
heartbeat outside the normal rhythm.
, Washburn University- BI 255 Lab Final Exam; Questions
with Detailed Solutions
Compensatory pause CORRECT ANS-After an extra systole, the next naturally occurring
depolarization will fall into the absolute refractory period generated by a new contraction, the
long pause that follows is the compensatory pause.
How was extra systole created in lab CORRECT ANS-The heart was stimulated every
second, eventually the stimulation occurred during a relative refractory period causing an
extra systole
Compare cardiac action potential to skeletal muscle action potential CORRECT ANS-Cardiac
has NA+ going in , Ca2+ going in, and K+ going out. Where as Skeletal just has Na+ in and K+
out. The cardiac muscle has a much longer absolute refractory period (200 - 400ms compared
to 1-3ms in skeletal muscle). Calcium increases the action potential resulting in the plateau
phase.
What do you mean when you use the term heart block? CORRECT ANS-A condition in
which impulses fail to pass normally through the conducting system of the heart to the
ventricular muscle. If some, but not all impulses from the pacemaker reach the ventricles, the
block is partial. Usually have a consistent ratio (2:1, 3:1)
, Washburn University- BI 255 Lab Final Exam; Questions
with Detailed Solutions
Complete block CORRECT ANS-No impulses from the pacemaker reach the ventricular
muscle, the atria and ventricles beat independently of one another (mammals) and no
consistent ratio between their rates of beating is seen. (Frogs - usually results in no ventricular
activity)
What happened when we squeezed the heart with forceps? CORRECT ANS-The tissue
between the atria and ventricle were damaged. This resulted in AV node damage altering
signaling between the atria and ventricles.
How does KCl act as a euthanizing agent? CORRECT ANS-The addition of KCl to the outside
of the heart cells prevents diffusion of K+ out of the cell, thus the cell doesn't repolarize and
the heart can't fire again. Keeps the heart cells from repolarizing, if it can't repolarize, it can't
fire again.
Skeletal muscle uses motor unit recruitment and summation to increase the strength of a
contraction. How does the heart increase the strength of its contractions? CORRECT ANS-It
increases the amount of extracellular and intracellular calcium. (If I remember correctly, the
more calcium the more myosin - actin crossbridges)
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