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Phys. Exam 2 Cardiovacular
exam 2 cardiovascular
45
Physiology
Graduate
10/16/2010

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Term
define equillibrium potential:
Definition
- the electrical potential that directly balances an opposite concentration gradient
Term
calcium and excitation contraction coupling:
Definition
- voltage change> voltage gated calcium channels open> calcium rushes into cell> opens ryanodine receptor channels on SR, more calcium released into cell> contraction
Term
3 things that keep intracellular caclium low:
Definition
- calcium pump- uses ATP to expell calcium
- Na+ Ca++ exchanger- exchanges 1 calcium for 3 sodiums
- SR reuptake
Term
importantance of normal, very negative resting potential (-70 to -90 mV):
Definition
- avoid spontaneous depolarization
- allows more Na+ channels to recover from inactivation
- faster depolarization
- greater amplitude of action potential
- more rapid propogation of action potential
Term
Explain the "fast response" of cardiac action potentials:
Definition
- fast response: Na+ depolarization
- atrial and ventricular contractile cells
- rapidly conducting cells- Purkinje fibers
Term
Explain cardiac action potentials "slow response" :
Definition
- slow response: Ca++ depolarization
- sinoatrial node- pacemaker cells
- atrioventricular node- slowly conducting cells, latent pace maker cells
Term
what node has pace maker cells?
Definition
SA node
Term
what node has slowly conducting fibers aka latent pace makers?
Definition
- AV node
Term
modulators with positive effects on calcium conductance:
Definition
- catecholamines: NE and Epinephrine
- Sympathicomimetic drugs
Term
sympathicomemetic drugs are positive modulators of calcium conductance, how?
Definition
- enhance activation of L-type calcium channels
- enhance reuptake of calcium by SR
Term
Modulators with negative effects on calcium conductance:
Definition
- Calcium channels antagonists
- acetylcholine
Term
How is acetylcholine a negateive modulator for calcium conductance:
Definition
- parasympathetic neurotransmitter
- binds to muscarininc receptors> inhibits adenylyl cyclase> decreases cAMP> decreases activation of L-type calcium channels
- also causes NO release, which stimulates guanylate cyclase to increase cGMP. cGMP decreases activation of L-type calcium channels
Term
calcium channel blockers block the voltage gated calcium channels so there is less intracellular calcium, this decrease force of contraction by decreasing ___.
Definition
- contractility
- used to decrease blood pressure
Term
what are the two types of ligand-gated potassium channels in the heart?
Definition
- ATP-sensitive K+ channel

- Acetylcholine-activated K+ channel
Term
The ATP- sensitive K+channel inhibits electrical activation of the heart by permitting ___ of___ when cytosolic ___ is low. This shortens the ___ phase of the cardiac action potential. Conserves limited myocyte energy during __. This channel is also opened by ___.
Definition
- outflux of potassium
- ATP is low
- plateau
- ischemia
- adenosine
Term
The acetylcholine-activated K+ is opened by ___ stimulation and decreases what three things?
Definition
- vagal stimulation
- decreases resting diastolic potential
- decreases rate of rise of pacemaker potential
- decreases duration of action potential
Term
Slow Response:
If phase 4 of the cardiac action potential is not sufficiently negative, then the fast sodium channels remain closed and the rapid sodium influx cannot occur. Calcium channels are functional and at their threshold begin to open. A slowly deveolping inward calcium current produces a slowly raising phase 0.
Definition
Term
parasympathetic innervation on SA node causes what changes in the pace maker potential:
Definition
- slower rise from a more negative value
- affecting funny sodium channels and transient calcium channels?
Term
sympathetic innervation causes a more rapid ___ depolarization.
Definition
sympathatic innervation causes a more rapid diastolic depolarization
Term
with parasymp on pacemaker potential you reach threshold ____. with sympathetics on pacemaker potential you reach threshold ____.
Definition
- later
- sooner
Term
Also parasymp decreases heart rate by making pacemaker potential reach maximal ___.
Definition
hyperpolarization
Term
The pace maker segment of membrane rises during ___ to reach threshold for sodium channels to open. Only one cell in the SA node has to reach threshold, and then from there on, excitation is conducted by action potentials.
Definition
- diastole
Term
___ not an ___ ___ is conducted.
Definition
Excitation not an action potential is conducted.
Term
put heart tissues in order from fastest conducting to slowest conducting:
Definition
purkinje fibers> atrial and ventricular contractile cells> AV node
Term
factors that influence velocity of conduction:
Definition
1. fast or slow response action potentials
2. negativity of resting potential
3. rate of rise of phase 0
4. degree of depolarization
Term
parasympathetic stimulation slows ___ conduction by opening ___ sensitive ___ channels and by stimulating the release of ___ ____which promotes the formation of ___ which tends to close ___ __ ___.
Definition
- AV
- acetylcholine sensitive K+ channels
- nitric oxide
- cGMP
- cGNP closes L-type calcium channels
Term
sympathetic stimulation increases AV conduction by increasing the ___ ___ ___.
Definition
L-type calcium current
Term
calcium channel antagonists decease the ___ ___ ___ ___ and thus slow __ conduction.
Definition
- L-type calcium current
- AV
Term
Adenosine blocks ___ conduction by inhibiting the ___ ___ ___and by opening ___ ___ ___ ___ causing hyperpolarization.
Definition
- AV
- L-type calcium current
- adenosine sensitive K+channels
Term
Ischemia and other conditions can slow the rate of rise of the ___ ___ action potentials and convert fast response action potentials to slow response action potentials. This occurs when the sodium channels remain ___ and the membrane is depolarized by influx of ___ through___ ___ ___ ___.
Definition
- fast response
- unactivated
- calcium
- slowly opening calcium channels
Term
ischemia alters myocardial _____ of ___ ___ and can decrease efficiency of ___.
Definition
conduction of action potentials
ejection
Term
Ischemia slows the rate of rise of fast response action potentials b/c it stops the ___ ___ which is essential for membrane potential.
Definition
sodium potassium pump
Term
ischemia causes especially slow conduction in the ___.
Definition
ventricles
Term
Ischemia causes loss of intracellular ___ and an elevation of extracelluar ___. This elevates diastolic ___, and thus, the rate of rise and amplitude of action potential ____ and the conduction velocity ___. The duration of action potential is also ___.
Definition
- potassium
- potassium
- diastolic potential
- decrease
- decreases
- decreased
Term
Since sodium channels remain unactivated if the membrane is not polarized, ischemia can make fast action potentials in the slow ones.
Definition
Term
parasympathetic stimulation slows or blocks ___ Conduction.
Definition
AV
Term
pathway for conduction:
Definition
SA node> right atrium> atrial fibers> AV node > AV bundle branches > purkinje cells> around ventricular chambers> contracile cells> contraction
Term
intial wave on an electrocardiogram is the __ wave and is caused by spread of electrical activity in the ___.
Definition
- p
- atria
Term
the QRS complex on an electrocardiogram represents:
Definition
- spread of electrical activity to depolarize left and right ventricles
Term
The electrocardiogram: As the cardiac mass depolarizes time varying differences in ___ ___exist on the body surface. The EKG is a recording of these ___ ____. The electrocardiogram is produced by a ___ of ___ ___ __ (exciation, and then repolarization at different times and places). The EKG is NOT a recording of one action potential.
Definition
- electrical potential
- potential differences
- series of cardiac action potentials
Term
A wave of depolarization APPROACHING a positive electrode will always give a ___ deflection on the EKG. Remember a deflection can positive but descending.
Definition
- POSTIVE
Term
A wave of depolarization MOVING AWAY from a positive electrode will give a ___ delfection. Remember a deflection can be negative and still ascending.
Definition
- negative
Term
The entire surface of a strip of RESTING myocardium is ___charged (relative to the interior of the cells of the fiber) so that no potential difference exists between electrodes A and B. A strip chart recording of this ECG (right) records zero potential difference and so remains at its baseline.
Definition
- positively
Term
look at slides 36-41 of this lecture and be able to interpret EKG.
Definition
Term
events during cardiac action potential during conduction of excitation:
Definition
Ions move parallel to the membrane; Na+ channels open; Ca++ channels open; K+ channels open.
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