Term
What are the 2 cell types found in the myocardium?
Which one is the predominant cell type? |
|
Definition
contractile (predominant)
conductile |
|
|
Term
| Of the 2 cell types in the myocardium, which one can not only propagate the action potential but generate force (contract) in response to the AP? |
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Definition
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Term
| What is the specialized muscle cell in the myocardium that os not involved with generation of force but with the Initiation and propagation of the AP |
|
Definition
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|
Term
| What is the "primary" pacemaker of the heart? |
|
Definition
|
|
Term
| What are the 4 primary characteristics of cardiac cells? |
|
Definition
Automaticity
Excitability
Conductivity
Contractility |
|
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Term
| What is the ability of pacemaker cells to generate their own electrical impulses spontaneously. |
|
Definition
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Term
| What is the ability of ALL cardiac cells to respond to an electrical impulse. |
|
Definition
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|
Term
| What is the ability of ALL cardiac cells to receive an electrical impulse and transmit it to neighboring cardiac cells. |
|
Definition
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Term
| What is – the ability of cardiac myocytes to shorten and cause muscle contraction |
|
Definition
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|
Term
| What two gradients control ion movement (flux)? |
|
Definition
| Concentration and electrical |
|
|
Term
| the resting potential is determined by the potential that’s generated by conductance of what ion? |
|
Definition
| potassium (cell of heart at rest = potassium leak out) |
|
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Term
Is the cell more permeable to K or Na at rest (conductance of K > or < conductance of Na?
Is the resting potential negative or positive? |
|
Definition
K (conductance of K greater)
negative (potassium is negative) |
|
|
Term
When you have an AP, will the cell become more negative or more positive?
What ion channel will open? |
|
Definition
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|
Term
What cardiac action potential will you NOT a fast cardiac action potential?
SA nodal
Atrial cell
Purkinje cell
Ventricular cell |
|
Definition
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Term
True or false
At rest, ventricular and purkinje fibers resting potentials are more stable than atrial myocytes. |
|
Definition
false
At rest in ventricular and atrial myocytes, the resting potential is fairly stable. Not quite so stable in Purkinje fibers |
|
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Term
| From 0-4, what are the phases of the fast cardiac action potential? |
|
Definition
0-depolarization
1-depolarization notch
2-plateu phase
3-repolarization
4-resting phase |
|
|
Term
True or false
There is a phase shift between an action potential and a muscle contraction when superimposed (slight lag between the two) |
|
Definition
True
have to get calcium into the cell so you don’t have instantaneous muscle twitch |
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|
Term
| During phase 4 at rest, the predominant conductance in a ventricular myocyte is what ion? |
|
Definition
K (-80 to -90 mV)
So that drives the resting potential close to the equilibrium potential of K. |
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|
Term
True or false
Ions move across the membrane in response to electrical and concentration gradients |
|
Definition
|
|
Term
| What maintains the ionic gradient in phase 4 (myocyte at rest)? |
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Definition
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|
Term
| Is there low or high Na+ and Ca2+ permeability during phase 4? |
|
Definition
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Term
True or false
during the upstroke, Na channels open very fast (fast activation) but the inactivation is very slow. |
|
Definition
false
FAST ACTIVATION. Channels open (~-70mV) (within 1-2 ms). IMPORTANCE: RAPID DEPOLARIZATON
FAST INACTIVATION. Intrinsic gating mechanism inactivates the channel. IMPORTANCE: REFRACTORINESS |
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Term
Fur the (absolute or relative) refractory period, the h gate remains closed so the cell cannot respond to excitation.
What does this prevent in the cardiac muscle? |
|
Definition
absolute (long refractory period)
tetanic contraction |
|
|
Term
| During what phase do the m and h gates return to their inactive configuration and the Na+ channel can again respond to a wave of excitation? |
|
Definition
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|
Term
What is NOT true about the refractory period?
It allows systole and diastole to occur alternately
It causes tetanic contractions
it is important for pumping blood to the arteries |
|
Definition
it causes tetanic contractions
it PREVENTS tetanic contractions |
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Term
| What are the 2 channels involved with the early depolarization notch (phase 1)? |
|
Definition
voltage-gated Ca2+
Ca2+ activated |
|
|
Term
| The transient, outward current is what phase? |
|
Definition
|
|
Term
| if you alter the repolarization, you can cause a change in the ___________ of the action potential. |
|
Definition
|
|
Term
| During phase 2, what ion enters the cell and what leaves the cell? |
|
Definition
Inward Ca2+ conductance
Outward K+ conductance |
|
|
Term
| Do Ca or Na channels inactivate slowly? |
|
Definition
Ca
(influx of positive Ca is balanced by efflux of positive K) |
|
|
Term
| What are the 2 types of Ca2+ channels? |
|
Definition
|
|
Term
Of the 2 Ca2+ channels, which is more abundant?
Which has a fast inactivation?
Slow inactivation? |
|
Definition
L type
T type (transient)
L type (long lasting) |
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|
Term
True or false:
The L type and T type Ca2+ channels open at the same voltage. |
|
Definition
False
L-type (-10mV) and T-type (-50mV) |
|
|
Term
True or false
There is only 1 type of K channel |
|
Definition
false
there are different types with different biophysical characteristics |
|
|
Term
| The relative abundance of what channel will alter the action potential duration? |
|
Definition
|
|
Term
| Phase 3 begins when the efflux of _____ exceeds the influx of ______ |
|
Definition
|
|
Term
True or false
inwardly rectifying K channels are voltage-dependent |
|
Definition
false
not voltage-dependent (will remain open to set the resting potential back to -90V after depolarization) |
|
|
Term
| During repolarization, what channel is inactivated first? |
|
Definition
Ca channel
(efflux of K+ finally exceeds the influx of Ca2+ = repolarization) |
|
|
Term
True or false
Cells of the SAN, AVN and His-Purkinje system fire spontaneously. Rhythmicity is modulated by channels active at or near threshold. |
|
Definition
|
|
Term
| What is the native pacemaker current that modulates cells of the SAN, AVN, and His purkinje system? |
|
Definition
|
|
Term
I ("funny" current) is (depolarization or hyper polarization) activated?'
Is it selective for Na+, K+, both, or neither?
What is it dependent on? |
|
Definition
hyperpolarization (depolarizing current will drive membrane potential toward threshold)
non-selective for Na+ and K+
cAMP-dependent |
|
|
Term
| What type of action potentials are found in pacemaker cells of the heart? |
|
Definition
| slow response action potentials (SAN and AVN) |
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|
Term
What is NOT a difference between slow response action potentials from fast cardiac action potential?
More depolarized (resting membrane potential)
Phase 0 more steep
Repolarization notch is absent (phase I)
Plateau phase (2) is brief and not flat and cannot be distinguished from phase 3.
Fast Na+ channels absent.
Depolarization achieved by Ca2+ currents |
|
Definition
phase 0 more steep
(phase 0 is LESS steep) |
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|
Term
| What channels are absent in Sinoatrial Node (SAN) and Atrioventricular Node (AVN)? |
|
Definition
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|
Term
| Depolarization achieved by what ion currents in the Sinoatrial Node (SAN) and Atrioventricular Node (AVN)? |
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Definition
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|
Term
In the SA node, what channel conducts an inward current that depolarizes the cell to threshold?
What channel is activated low potentials and contribute to the early depolarization and the AP upstroke (phase 0)?
What channel enhances depolarization and continue phase 0?
As depolarization proceeds, what channel is activated and the cell repolarizes. |
|
Definition
I(f) (funny)
T-type Ca2+
L-type Ca2+
I (k) |
|
|
Term
The AP of Purkinje fibers is similar to what cells?
At what phase does it differ? |
|
Definition
ventricular
Phase 4- membrane potential not stable |
|
|
Term
| Why is the membrane potential at phase 4 for purkinje cells different from ventricular cells? |
|
Definition
| membrane potential is not stable bc it depolarizes automatically (automaticity) due to having I(f) (funny) pacemaker channels (ventricular doesn't have I(f)) |
|
|
Term
| What node is located in the right atrium close to the superior vena cava where the blood is returned back to the atrium? |
|
Definition
|
|
Term
| *What is the sequence of the conduction system of the heart? |
|
Definition
| SA Node _ Atria _ AV Node _ Bundle of His _ Bundle Branches _ Purkinje fibers _ Ventricles |
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|
Term
True or false
SAN cells have an intrinsic ability to initiate an AP |
|
Definition
|
|
Term
True or false
The SAN connects with other elements of the conductile system |
|
Definition
|
|
Term
| What node's rate is 60-100 APs/min? (close to normal HR) |
|
Definition
|
|
Term
| What are the 2 important functions of the AV node? |
|
Definition
relay the wave of depolarization from atria to ventricles (only through AV node because of connective tissue)
Delay spread of excitation (AVN cells conduct slowly) |
|
|
Term
What is the rate of AV nodes?
What is the rate of Purkinje fibers? |
|
Definition
40-60 APs/min
25-40 APs/min |
|
|
Term
| What type of AP conduct very rapidly to spread to all myocardium of the ventricles of the heart at the same time? |
|
Definition
|
|
Term
True or false
If the connection is severed between SA and AV node. AV node will not be able to fire it's action potential. |
|
Definition
False
AV has automaticity. Will fire it's own AP. (same with purkinje fibers but inefficient) |
|
|
Term
| What are the small pores that traverse the extracellular space that allow the movement of both ions and signaling molecules? |
|
Definition
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|
Term
| What allows electrical coupling (enable propagation of the action potential as local currents flow between adjacent cells thereby depolarizing neighboring cell)? |
|
Definition
|
|
Term
| What enables cardiac tissue to behave as a functional syncytium |
|
Definition
|
|
Term
| What is the principal controller of heart rate? |
|
Definition
| autonomic nervous system (sympathetic and parasympathetic) |
|
|
Term
| What molecules of the ANS modulate pacemaker activity, conduction velocity, and contractility? |
|
Definition
|
|
Term
The parasympathetic system is inhibitory or excitatory?
sympathetic? |
|
Definition
ParaSNS is inhibitory (decrease HR)
SNS is excitatory (increase HR) |
|
|
Term
What is the normal heart hart of an adult?
Which branch of ANS predominates here? |
|
Definition
|
|
Term
| If both divisions of the ANS are blocked, what is the remaining heart rate called ? |
|
Definition
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|
Term
| The parasympathetic nervous affects the SAN and AVN through what molecule and receptor? |
|
Definition
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|
Term
In the SAN, ACh will increase or decrease I(f)?
This will increase or decrease the steepness of phase 4 depolarization? |
|
Definition
decrease
decrease (decreases cAMP) |
|
|
Term
In the SAN, ACh will increase or decrease the conductance of Ca?
Will this open or close I(KACh) K+ channels? |
|
Definition
decrease Ca conductance (decrease upstroke)
open channels-makes maximum diastolic potential of SAN cells more negative |
|
|
Term
| In the AVN, ACh slows conduction velocity by inhibiting what? |
|
Definition
I(Ca) - calcium conductance
Becomes more difficult to excite neighboring cells, conduction velocity falls. |
|
|
Term
| The sympathetic nervous system affects the AP with what molecules and receptors? |
|
Definition
| catecholamines via adrenergic receptors |
|
|
Term
| Do catecholamine increase or decrease I(f) currents? |
|
Definition
| increase (increases cAMP) - increases steepness of phase 4 depolarization |
|
|
Term
Do catecholamine increase or decrease I(Ca) in myocardial cells? how?
Does this make the threshold more negative or positive?
Will this have positive or negative chronotropic and ionotropic effects? |
|
Definition
increase - via cAMP activation of PKA
negative
chronotropic and ionotropic effects (increase in intracellular Ca2+ in myocytes enhances contraction) |
|
|
Term
| What 3 ways the SA node can slow the firing rate of its pacemaker? |
|
Definition
1)decrease steepness of depolarization during phase 4 (lengthens time for Vm to reach threshold)
2)maximum diastolic potential can become more negative
3)the threshold for the action potential can become more positive |
|
|
Term
| What is the Standard non-invasive clinical tool to measure the electrical activity of the heart |
|
Definition
| Electrocardiogram (ECG/EKG) |
|
|
Term
| In an ECG, what part of the body acts as a volume conductor? |
|
Definition
|
|
Term
True or false
The movement of action potentials through cardiac myocytes cause minute voltages on the surface of the thorax during an ECG |
|
Definition
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|
Term
| In an ECG, the _________ of the signal detected by surface electrodes depends on the orientation of the electrodes with respect to the electrical field. |
|
Definition
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|
Term
| In an ECG, the ________ of the signal will depend on the mass of tissue. |
|
Definition
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|
Term
| The ECG shows the potential difference between two points - a difference that can only be detected when __________ is changing. |
|
Definition
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|
Term
What is NOT information that can be obtained from the ECG?
Anatomical orientation of the heart
Relative size of the chambers of the heart
Variety of disturbances of rhythm and conduction
The extent, location and progress of ischemic damage to the myocardium
direct information regarding the mechanical activity of the heart
Effects of altered electrolyte concentrations
Influence of drugs |
|
Definition
| The ECG gives no direct information regarding the mechanical activity of the heart! |
|
|
Term
In the ECG, what leads are place in the frontal plane?
What leads are placed in the horizontal plane? |
|
Definition
limbs leads
precordial leads (across rib cage) |
|
|
Term
| Which part(s) of the wave is the sequential atrial depolarization (in response to depolarization of the SA node) |
|
Definition
|
|
Term
| Which part(s) of the wave is the simultaneous ventricular depolarization? |
|
Definition
|
|
Term
| Which part(s) of the wave is the recovery wave/ventricular depolarization? |
|
Definition
|
|
Term
| Which part (s) of the wave is the origin? (probably represents "afterdepolarizations" in the ventricles ) |
|
Definition
|
|
Term
| What is the time interval from onset of atrial depolarization (P wave) to onset of ventricular depolarization (QRS complex) |
|
Definition
|
|
Term
True or false
atrial repolarization is observed on the standard 12-lead ECG |
|
Definition
False
atrial repolarization not observed on the standard 12-lead ECG – masked by QRS |
|
|
Term
What is the duration of ventricular muscle depolarization ?
The period of time between the P wave and the QRS complex. Conduction through the AV node ?
The duration of ventricular depolarization and depolarization ?
The duration of ventricular cardiac cycle (an indicator of ventricular rate)
duration of atrial cycle (an indicator of atrial rate |
|
Definition
QRS duration: duration of ventricular muscle depolarization
PR segment: The period of time between the P wave and the QRS complex. Conduction through the AV node
QT interval: duration of ventricular depolarization and repolarization
RR interval: duration of ventricular cardiac cycle (an indicator of ventricular rate)
PP interval: duration of atrial cycle (an indicator of atrial rate) |
|
|
Term
| When interpreting the ECG, one large box represents how many seconds and mm of amplitude? |
|
Definition
| (5mm) represents 0.2 seconds (200 ms) |
|
|
Term
What is Any change in rhythm from normal sinus rhythm?
What 3 things could be changed? |
|
Definition
Arrhythmia (dysrhythmia)
rate
regularity (one or more beats occurring earlier or later than expected)
sequence |
|
|
Term
What is called when the HR is too fast (>100)?
too slow (<60)? |
|
Definition
too fast = tachyarrhythmia (>100 bpm)
too slow = bradycardia (<60 bpm) |
|
|
Term
| What are the 2 BASIC problems that give rise to cardiac arrhythmias? |
|
Definition
Impulse propagation (altered conduction)
Impulse formation (altered automaticity) |
|
|
Term
| What are the 4 basic types of arrhythmia? |
|
Definition
Arrhythmias of sinus origin
Ectopic rhythms
Conduction blocks
Preexcitation syndromes |
|
|
Term
| What type of arrhythmia follows normal conduction pathways but either too fast, too slow or irregular? |
|
Definition
| Arrhythmias of sinus origin |
|
|
Term
| Why type of arrhythmia is electrical activity arises elsewhere than the sinus node |
|
Definition
|
|
Term
| What type of arrhythmia has normal pacemaker but wave of depolarization encounters unexpected blocks and delays |
|
Definition
|
|
Term
What type of arrhythmia is conduction
bypasses normal pathways through
abnormal (accessory) conduction
pathways (e.g. Wolff-Parkinson-White
syndrome) |
|
Definition
|
|
