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Electrophysiology of Cardiac Cells
Physiology Test 3
90
Physiology
Graduate
10/24/2011

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Term
the basic types of activites required by the heart to impart potential and kinetic energy to blood
Definition
excitation, condiction, & contraction
Term
T/F in a normal heart excitation, conduction, & contraction are inseperately linked
Definition
T
Term
Heart tissue that express excitability
Definition
atrial m., ventricular m., conductive tissue, and pacemaker cells
Term
specialize in contracting (doing work)
Definition
atrial and ventricular muscle
Term
capable of spontaneous depolarization
Definition
pacemaker cells
Term
specialize in propagqating impulses from one area of the heart to another and can also depolarize spontanteously at a slower rate
Definition
conductive tissue
Term
pacemaker, transitional cells, purkinje cells, atrial and ventricular muscle cells are able to work together because...
Definition
they display slightly different physiologic properties that alow them to preform cyclic activities
Term
initiate pulses
Definition
P cells
Term
purkinje cells
Definition
transmit impulses throught the heart
Term
the bigger the animal
Definition
the larger the cardiac cell size
Term
P Cells occur
Definition
SA and AV nodes
Term
P cells contain
Definition

few myofibrils or mitochondria and a little glycogen

Have no intercalated disks

Term
P cells are the macemakes cells that conduct at a velocity of
Definition
0.05m/sec
Term
transmit impulses from P cells to other cells in the heart
Definition
transitional cells
Term
Containnumerous myofibrils and mitochondria but lack well adaptive T-tubules. 20-30 microns long & make side to side (end to end) contacts via intercalated disks
Definition
atrial muscle cells
Term
ventricular muscle cells
Definition
have a well developed sarcoplasmice reticulum and t tubles. 100 microns in length. abundant myofibrils and mitochondria. COnduct at a velocity of 1m/sec
Term
Cardiac cells are excited by cells that have
Definition
inherent cyclic discharge rhythems
Term
Cardiac cells form a network called __ because they can receive electrical impulses directly from other cells
Definition
syncytium
Term
Cardiac cells have what kind of syncytium?
Definition
electrical & mechanical
Term
intercalated disks are located at...
Definition
Z line
Term
the functional specializations of intercalated disks
Definition

desmosomes

fascia adherens

nexuses

Term
These are sparce in sinoatrial & atrioventricular nodal cells but plentiful in Perkinje cells where conduction is rapid
Definition
nexuses
Term
The type of action potential produced in the SAN & the AVN
Definition
Slow
Term
The tyoe of action potential that occurs in the atrial muscle cells, ventricular muscle cells & the purkinje system
Definition
fast
Term
Functions as the pacemaker of the heart by virtue of its high rate of spontaneous depolarization
Definition
SAN
Term
Spontaneous discharges of the pacemaker does not alter what in other cells?
Definition
inherent rate of discharge
Term
Transmembrane poteneials (TMP) of SAN have no __ but do have ___
Definition
stable resting membrane potential; MRP
Term
Maximum repolarization potential (MRP)
Definition
most polarized condition
Term
When __ is reached, the cells begin to hypopolarize & will eventually give rise to anothr action potential
Definition
MRP
Term
___ has a long refractory periods which prevent the ventricles from being restimulated prematurely
Definition
AV nodal cells
Term
The AV nodes properties are helpful in cases of..
Definition
atrial defibrillation
Term
AVN
Definition
backup pacemaker
Term
AV node provides pacing at about __ of the SAN
Definition
one-half
Term
The __ of the spontaneous change during pacemaer potential is one of the determinates of heart rate.
Definition
slope
Term
The slow decrease in TMP is brought about by ___
Definition
a decline in the outward potassium current
Term
__ increases towards the end of the pacemaker potential
Definition
Calcium
Term
What increases during the rising phase of the action potential?
Definition
potassium & calcium
Term
There is an absence of fast __ channels but a presence of __ __ chennels.
Definition
sodium; pacemaker sodium
Term
T/F The rising phase is caused promarily by calcium?
Definition
T
Term
Increases potassium and thus will slow the heart rate
Definition
acetylcholine
Term
increases intracellules concentrations of calcium and sodium thus increasing the heart rate
Definition
Epinephrine
Term
The resting potential of fast action potentials is much more __ than slow action potentials
Definition
negative
Term
Phase 0
Definition
rapid initial depolarization characterized by a reversal potential
Term
The reversal potential is almost soel caused by
Definition
sodium influx through voltage-gated fast sodium channels
Term
Phase 1
Definition
initial rapid repolarization that begins to return the potential towards zero
Term
Phase 1 is caused by
Definition
rapid decrease in conductance of the membrane to sodium and increase towards potassium
Term
Phase 2
Definition
slow phase of repolarzation resulting in a plateau caused by slow influx of calcium and sodium
Term
During the Phase 2 plateau, the cell membrane is more permeable to __
Definition
calcium than sodium
Term
Because of the Phase 2 shorter plateau, what can beat faster than the ventricles
Definition
atria
Term
Phase 3
Definition
a final rapid repolarization which returns the membrane to its resting potential
Term
Phase 3 is caused by
Definition
decrease influx of calcuim and an increase in outward flow of potassium
Term
During what phase is calcium pumped back into the sarcoplasmic retculum or out into the extracellular fluid?
Definition
Phase 3
Term
Phase 4
Definition
The diastolic or RPM
Term
During what phase is the excess sodium pumped out of the cell?
Definition
Phase 4
Term
Phase 0 is prominate in
Definition
atrial & ventricular muscle cells & Purkinje fibers
Term
__ eliminates the fast responses of muscle cells and Purkinje fibers and converts them to the slow type of action potential
Definition
Tetrodotoxin
Term
Tetrodotxin blocks __
Definition
fast sodium channels
Term
___ are calcuim antagonists and partially block the slow enterance of calcium. Can stabelize the heart in cases of arrythmias
Definition
Verapamil
Term
True or False: The calcium that influxes during the AP is enough for contraction
Definition
False; some must be brought in fromt he S.R.
Term
Ways the rate of discharge in a pacemaker cells can change
Definition

slope of diastic depolarization

threshold potential

resting potential

Term
tachycardia is a possibe effect of__
Definition
postive chronotrophe
Term
Stimulating __ will result in bradycardia, a negative chronotropic response.
Definition
vagus nerve
Term
ACh would exhibit ___
Definition
negative chronotropic effect
Term

Which statent about the features of cardiac cells is false?

A. the full polarity of the resting potential is not as great as other cells

B. The oversoot of the action potential is more

C. The time course of the action potential is slower

Definition
B
Term
The transmission velocity in the atrial muscle, bundle of His & ventricular muscle is about...
Definition
0.8-1.0m/sec
Term
Conduction velocity in the AV node is about (not in the Perkinje systern)...
Definition
0.03-0.05m/sec
Term
In the Purkije systern the AV conduction velocity is about...
Definition
5.0m/sec
Term

Conducton velocity depends on all of the following except:

A. Fiber diameter

B. Rapidity of depolarization

C. Rapidity of repolarization

D. Amplitude of the action potential

Definition
C
Term
There is no wave for __ in the ECG due to this being simultaneous with another depolarization
Definition
atrial repolarization
Term
cardiac muscle is different than skeletal muscle physiologically because....
Definition
cardiac action potentials are longer
Term
The peak force of the muscle twitch in cardiac muscle is reached simultaneous with...
Definition
the AP is reaching the end of repolarization
Term
What, in cardiac muscle, not only initiates but modulates a mechanical event?
Definition
AP
Term
Because electrical & mechanical events are very near the same duration in cardiac cells, cardiac muscles cannot __
Definition
tetanize
Term
___ strengthens the contractile process in the heart by interfering with the sodium-potasium movement in the cell-membrane
Definition
digatalis glycosides
Term
Tension and length are very hard to measure in cardiac muscle, so they may be replaced with
Definition
cardiac output & end-diastolic volume
Term
Frank Starling law
Definition
the ability of the heart to self-regulate in response to changing loads of inflowing blood
Term
inotrope
Definition
any agent which alters the force of contraction without changing the degree of strech on cardiac fibers
Term
__ regulation occurs when filling of the heart increases cardiac metabolism & hence the force of contraction
Definition
homeometric
Term
__ regulation areises from a changing fiber length
Definition
heterometric
Term
True/False The heteromteric means expresses the Frank-Starling Law
Definition
True
Term
__ of the energy requiremements of the heart are derived from non-esterfied fatty acids & the remainder by glucose
Definition
70%
Term
The heart does not need neural input to finction, but it is innervated by nerve terminals of the __
Definition
ANS (both sympathetic and parasympathetic)
Term

These nerve terminals of the ANS contain:

A. granular vesicles = adrenergic

B. agranular vesicles = cholinergic

Definition
A & B
Term
Sympathectomy will
Definition
decrease the heart rate
Term

__ innervation to hte heart increases te rate & force of contraction

A. sympathetic

B. parasympathetic

Definition
A
Term
The phenomenon caused by isoproterenol may be regulated by __
Definition
increased intracellular levels of cyclic AMP, the second messenger for many beta actions
Term
The parasympathetic activities of the heart are directed promarily towards __
Definition
SAN, AVN, & atria
Term
The parasympathetic system has very little effect on cardiac __
Definition
ventricular system
Term
Acetylcholine decreases the slow inward current due to calcium influx but more importantly, increased __, thus decreasing the effects of vagal stimulation.
Definition
potassium permeability
Term

increased extra cellular potassium limits he efffect of __ on __ muscles

A. Ach, atrial

B. APM; Purkinje

C. Ach; Purkinje

D. Ach; Ventricular

Definition
D
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