Electric Activity of the Heart Flashcards
Which node spreads the impulse from R Atrium to Left atrium?
Sino-atrial node
What is the electrical connection between the atrium and ventricle?
AV node
What ions are found outside the cell?
Na and Ca
Which ion is found in the cell?
K
Describe the 3 states a channel can be in
- open
- closed
- inactivated
Compare the % of specialized cardiac muscle cells
1% autorhythmic and 99% contractile cells in the heart
T/F: Autorhythmic cells can generate action potentials spontaneously
True, they can contract without any outside signal
What is the term when the signal for contraction is originating within the heart itself?
Myogenic
What is another term for the autorhythmic cells?
Pacemaker cells
What makes up the conduction system?
Specialized myocytes: SA node, AV node, His-Purkinje fibers
What is the role of the conduction system?
Initiate and coordinate HB
From where does the contraction travel?
Apex to base
From where does the impulse travel?
Base to apex
Where is the SA node located?
Right atrium, at junction between cranial vena cava and atrium
What is the role of the SA node?
normal pacemaker and initiate the impulse
Atrial depolarization distributes how?
right to left; top to bottom
Where is the AV node located?
Base of the Interventricular septum
What is the role of the AV node?
Only conduction pathway between atria and ventricles
Why is the impulse slowed down in the AV node?
To allow for the atria to contract before the ventricles
If the atrium is beating too fast, what does the AV node do?
Limit the number of impulses conducted to the ventricles
What structure conducts the impulse from AV node to apex of the heart?
Bundle of His
The right bundle branch is isolated from what before the cardiac apex?
Myocytes
Which bundle has connections with the myocytes in the interventricular septum?
Left bundle
Which structure propagates the impulse to the ventricular myocytes?
Purkinje fibers
Which node sets the amount of times the heart will beat?
SA node
What can affect the rate of depolarization?
Autonomic (parasympathetic or sympathetic)
T/F: the Purkinje fibers can take over impulse generation if the SA and AV node fail
True
What is the electrical connection in the intercalated disks called?
Gap junction
Describe the specialized assembling of the conduction systems cells that allow for faster conduction
Wider and contain more gap junctions
How is the electrical impulse in the heart propagated?
In the form of an action potential
T/F Autorhythmic cells have a “flatline”
False, always generating electrical impulses
At rest, the cell is _____________ (electrical description)
polarized
During depolarization (phase 0), Which channels are open?
Sodium only
When Na channels are inactivated, which channels open?
K channels
In the plateau phase, what 2 channels are open?
Ca and K
In the repolarization phase, what is the channel that is closed while K keeps flowing out of the cell?
Ca
What restores equilibrium at the end of repolarization?
Na/K ATPase pump
If you inhibit the Ca ATPase pump, what happens to the muscle contraction?
Strengthens it
The time between the beginning and end of an action potential is:
Refractory period
Why does the refractory period occur?
Because Na channels are inactivated “blocked”
List a role of the refractory period
- prevent repetitive cardiac contractions
What are the 2 types of refractory period?
Absolute and Relative
During which refractory period is an action potential possible if there is a high enough energy stimulus?
Relative
Depolarization = _________ Influx
Rapid Repolarization= ___________ Efflux
Plateau= __________ Influx
Repolarization= Potassium ___________
- Sodium
- Potassium
- Calcium
- Efflux
T/F autorhythmic cells have stable resting membrane potential
False, they have a pacemaker potential
What is the cause of the instability of membrane potentials in autorhythmic cells?
Channels are both permeable to Na and K, which leads to Ca channel opening
In an autorhythmic action potential, which channels open in depolarization?
long-lasting Ca channels
T/F the pacemaker cells has a plateau phase
False
What type of receptor is associated with the sympathetic nerves?
Beta 1 and 2
What will a vagal (parasymp) tone do to HR?
Slows it by decreasing firing of sinus node
How does the adrenergic tone increase HR?
Increase firing (rate of depolarization)
T/F: The sympathetic nervous system can influence cardiomyocytes
True
List some NT associated with Adrenergic tone
Epinephrine
Norepinephrine
Dobutamine
Describe the excitation contraction coupling
Delay between stimulus and contraction
Where does Ca bind to stimulate the contraction of the myocyte
Myofilament
What can you do to make the heart not contract as strongly?
Block Ca
Cardiac contraction depends on what?
Calcium entering the cell
List some sources of intracellular calcium
- Extracellular Ca through voltage-gated channels
- released from Sr through Ca Induced Calcium release
How does dobutamine work as a sympathomimetic drug?
Increases intracellular calcium with ca reuptake from SR
