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Chapter 18 Class Notes B BSC2086
Spring 2011
(Slide 2) Depolarization of the Heart is ____________________ and ____________________. About ___% of
Cardiac Cells have automaticity or _____________________, which means they are ____________________.
Autorhythmic Cells initiate Depolarization of __________________ and the _______________________ cells as
well.
(Slide 3) Autorhythmic Cells stimulate and pace the ________________________________ of the Heart. Gap
Junctions between Heart cells ensure the ________________________________________. Depolarization of
the Heart cell has a long ______________________________ period (cannot be excited for _________ ms).
(Slide 4) The bulk of heart muscle (________%) is made of __________________ Muscle Fibers that are
responsible for the Heart’s _________________ activity.
(Slide 5) Similar to skeletal muscle, ________________________ opens voltage-gated __________channels in
the cardiac muscle sarcolemma membrane, which causes a _____________________________________
from_________ mV to __________mV.
(Slide 6) The ____________________wave in _______________________ causes the Sacrcoplasmic Reticulum to
release _________ cations into the cytosol.
Ca2+ provides the signal (via troponin binding) for
_______________________________________. This couples ______________________ to
_____________________________ (i.e., through sliding of myofilaments).
(Slide 7) The Depolarization wave also opens ______________________channels in the Sarcolemma. Ca2+ influx
from slow channels liberates bursts of Ca2+ , and the resulting _________________________ prolongs the
_______________________ phase (causes a plateau).
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Plateau
2
3
1
Tension
development
(contraction)
Tension (g)
Membrane potential (mV)
Action
potential
Absolute
refractory
period
Time (ms)
1 Depolarization is
due to Na+ influx through
fast voltage-gated Na+
channels. A positive
feedback cycle rapidly
opens many Na+
channels, reversing the
membrane potential.
Channel inactivation ends
this phase.
2 Plateau phase is
due to Ca2+ influx through
slow Ca2+ channels. This
keeps the cell depolarized
because few K+ channels
are open.
3 Repolarization is
due to Ca2+ channels
inactivating and K+
channels opening. This
allows K+ efflux, which
brings the membrane
potential back to its
resting voltage.
Figure 18.12
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(Slide 9) ________________________________________ coupling occurs as Ca2+ binds to troponin and sliding of
the filaments begins. Duration of the Action Potential and the Contractile Phase is much ____________in
__________________muscle than in ______________ muscle. _______________________ results from
___________________ of Ca2+ channels and _________________ of voltage-gated K+ channels.
(Slide 10) The _____________________________________________ is a network of
_____________________________ (and non- contractile) cells that initiate and distribute impulses to
coordinate the ____________________________ and _______________________ of the Heart.
(Slide 11) _____________________________ have unstable resting potentials called
_______________________ potentials due to open ____________________ channels. Autorhythmic Cells
__________________________________ towards threshold potential, and at threshold potential,
___________ channels open.
(Slide 12) Explosive ____________ influx produces the rising phase of the
___________________________________.
_______________ , not Na+ is responsible for the Action Potential
of Autorhythmic Cells . Repolarization results from _____________________ of Ca2+ channels and
____________________ of voltage-gated K+ channels.
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(Slide 14) The Autorhythmic Cells form an ________________________ system that distributes the action
potential throughout the heart, and it includes the ____________ and __________________ ______________,
__________________________________ (= Bundle of His), _____ Bundle ___________________, and
_____________________________.
(Slide 15) The ___________________________ (pacemaker) generates impulses about ______________
times/minute (____________________ rhythm), and depolarizes _____________________ than any other part
of the myocardium.
(Slide 16) The ______________________ node, has smaller diameter fibers; fewer gap junctions, and
_____________ impulses approximately 0.1 second; the AV depolarizes _______________ times per minute in
absence of SA node input.
(Slide 17) Atrioventricular (AV) __________________, also called the _________________________ is the
______________ connection between the Atria and Ventricles.
(Slide 18) The ________________ and ___________________ Bundle _________________ are ____________
pathways in the ____________________________ Septum that carry electrical impulses toward the Apex of the
Heart.
(Slide 19) The _____________________ fibers complete the pathway into ________________ and
____________________ walls. The AV ________________ and ________________ fibers depolarize only
__________________ times per minute in absence of AV node input.
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Superior vena cava
Right atrium
1 The Sinoatrial (SA)
node (pacemaker)
generates impulses.
Internodal pathway
2 The impulses
pause (0.1 s) at the
Atrioventricular
(AV) node.
3 The atrioventricular
(AV) bundle
connects the atria
to the ventricles.
4 The bundle branches
conduct the impulses
through the
interventricular septum.
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The Purkinje fibers
depolarize the contractile
cells of both ventricles.
Left atrium
Purkinje
fibers
Interventricular
septum
(a) Anatomy of the intrinsic conduction system showing the
sequence of electrical excitation
Copyright © 2010 Pearson Education, Inc.
Figure 18.14a
Please describe 3 results of defects of the Intrinsic Conduction system (slide #21):
(Slide 22) Defective SA node may result in these 2 things:
(Slide 22) Defective AV node may result in these 2 things:
(Slides 23-24) The heartbeat is modified by the _________________________ nervous system. Cardiac heartbeat
regulation centers are located in the __________________________________. The cardio-acceleratory
(increases heartbeat) center innervates SA and AV nodes, heart muscle, and coronary arteries through
___________________________________. Cardio-inhibitory (decreases heartbeat) center inhibits SA and AV
nodes through ______________________ Fibers in the ___________________ Nerves.
(Slide 26) An electrocardiogram (ECG or EKG): a composite of all the ______________________________
generated by nodal and contractile heart cells at a given time.
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(Slide 27) Please name and describe the 3 major electrical waves of the heart:
Please draw and label the 4 types of EKGs shown in Slide 37:
What are the 2 heart sounds and please describe them (Slide #38).
(Slide 39) What is a heart murmur and when does it occur?
What kind of sound does a stenotic valve make (slide # 40)?
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Please describe the Events of the Cardiac Cycle (slides #42 – 46).
Lub sound
At QRS wave
= Ventricular
Depolarization
Aortic pressure
Increases after
QRS wave
Dup sound
At T wave =
Atrial
Repolarization
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Copyright © 2010 Pearson Education, Inc.
(Slide 49) What is Cardiac Output and how is it calculated?
What is the Cardiac Output at rest?
While maximally exercising?
(Slide 51) Stroke Volume (SV) = End Diastolic Volume (EDV) – End Systolic Volume (ESV). What are 3 main
factors affecting Stroke Volume?
The Frank-Starling law of the heart means that __________________ increases heart efficiency (slide #53, not
52).
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(Slide 54) What 2 general things increase heart contractility?
(Slide #56) The ______________________________ system exerts the most important extrinsic control over
heart. Sympathetic nerves release _______________________ (NE) at Heart synapses. NE binding to B1adrenergic receptor initiates a ________________ second messenger system, that increases ______________
intracellular levels, and increases Ventricular _________________________________ and the Heart’s
__________________________________.
Extracellular fluid
Norepinephrine
Adenylate cyclase
b 1-Adrenergic
receptor
Ca2+
ATP is converted
to cAMP
G protein (Gs)
GDP
Ca2+
channel
Cytoplasm
Phosphorylates
aplasma membrane
Ca2+ channels,
increasing extracellular Ca2+ entry
Inactive protein
Active
kinase A
protein
Phosphorylates SR Ca2+ channels, kinase A
increasing intracellular Ca2+
Phosphorylates SR Ca2+
c
b
release
pumps, speeding Ca2+
Enhanced
2+
removal2+and relaxation
Ca
Ca
actin-myosin Troponin binds
Ca2+ uptake
interaction
to
pump
SR Ca2+
channel
Sarcoplasmic
I Increased Cardiac
reticulum (SR)
muscle
Force and Velocity
Copyright © 2010 Pearson Education, Inc.
Figure 18.21
(Slide 58) Afterload is the ___________________________________ pressure that the ventricles must
overcome to eject blood. ______________________________ increases the Afterload, and results in
____________________ End Systolic Volume and _______________ total Stroke Volume.
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(Slide 59) Positive chronotropic factors ______________________ heart rate. Negative chronotropic factors
__________________ heart rate
(Slide #60) The Sympathetic nervous system is activated by emotional or physical stressors, leading to the
release of _________________________ which causes the pacemaker to fire
_____________________________.
(Slide #61) The ________________________________ Nervous system opposes Sympathetic effects.
______________________________ hyperpolarizes pacemaker cells by opening K+ channels. The Heart at rest
exhibits “______________________” as ______________________ input is dominant, which
____________________ the heart during rest.
(Slide #64) __________________________ from adrenal medulla enhances heart rate and contractility, and
_________________ increases heart rate and enhances the effects of norepinephrine and epinephrine.
____________________________ is abnormally fast heart rate (>____________ bpm), and if persistent, may
lead to ________________________.
(Slide 67) Bradycardia: heart rate slower than __________ bpm.
Name 4 causes of congestive heart failure (slide #68):