Phys 1 Flashcards
What is the state of the Na+ channel in: resting, activated, inactivated?
- Activation gate is closed, inactivation gate is open
- Activation gate is open, inactivation gate is open
- Activation gate is open, inactivation gate is closed
What is the order of the Conduction System?
- Sa Node
- AV Node
- Bundle of His
- Right/Left Bundle Branches
- Purkinje Fibers
The SA Node works to…
create an AP that spreads throughout the atria to elicit their contraction (usually right a little bit ahead of the left)
Atrial myocytes and Ventricular myocytes are…
separated from each other. This means that a depolarization of the SA Node to the atrial myocytes should not spread to the ventral myocytes (AP must go through AV Node to reach ventricular myocytes).
Are Purkinje fibers or myocytes larger? Why does this matter?
- PF
- The PFs/Bundle of His will conduct the AP at a faster rate
*the larger the fiber, the faster the AP transmission
The cells that ____ last are the first to ____.
depolarize, repolarize
How does depolarization/repolarization differ in what layers they move through first/second?
- Depolarization: interior (endo) to exterior (epi)
2. Repolarization: exterior (epi) to interior (endo)
Rank these fastest to slowest for AP Transmission:
AV Node, Atrial/Ventricular muscle, PFs
- PFs
- Atrial/Ventricular muscle
- AV Node
What is the purpose of the delay of the AV Node (why it’s the slowest)?
It allows the atria to have extra time to contract, and to “top off” the ventricles; meaning ventricles reach peak volume of blood
What cells can make an AP? At what pace?
SA Node > AV Node > PFs
What is the RMP of Ventricle? Atrium? SA Node
- -90 +/- -5
- -90 +/- -5
- -65 +/- -5
Na+ (m)
- Ek
- Activated when
- Action
- Phase
- Special Features
- +30mV
- Membrane potential crosses threshold
- Opens
- 0, 1
- Very fast generation of depolarization then automatically closes allowing partial repolarization
K+ (a)
- Ek
- Activated when
- Action
- Phase
- Special Features
- -90mV
- Cell depolarizes
- Opens
- 1
- Very rapid partial repolarization
*Transient outward current
Ca2+
- Ek
- Activated when
- Action
- Phase
- Special Features
- +40mV
- Cell depolarizes
- Opens
- 2, 3
- Slow to open and remains open for a determined amount of time then opens helping with phase 3
*L type
K+ (b)
- Ek
- Activated when
- Action
- Phase
- Special Features
- -90mV
- Cell depolarizes
- Closes
- 2, 3
- Slow to close and remains closed for a determined amount of time then opens helping with phase 3 (special rectifiers)
K+ (c)
- Ek
- Activated when
- Action
- Phase
- Special Features
- -90mV
- Remains open
- Remains open
- 4
- Leak channel which maintains resting potential
Na+ (f)
- Ek
- Activated when
- Action
- Phase
- Special Features
- +30mV
- SA or AV Node depolarize
- Opens
- 4
- Specific to SA/AV Node where it causes slow depolarization during resting phase
Kd
- volatage gated channels
- all phase 3 events involved
*NOT K+ leak channels
What channels did he mention are sensitive to acetylcholine?
Kb channels (has a parasympathetic effect)
Phase 3 is essentially a ____ of phase 1.
reversal
What is equilibrium potential?
it equals a little less than RMP
What phase is the plateau phase?
2 –> purpose is to prolong contraction, and is fundamentally different than skeletal muscle
Conduction velocity usually relates to…
your phase 0 slope
AV Block
AV node damage that further delays conduction
Arrhythmias
Purkinje fiber damage that disrupts the natural conduction and contraction of ventricles
Relative Refractory Period
AP can be generated, but will have an abnormal conduction (phase 0 is tipped to not propogate the next AP at the same speed)
Supranormal Period
the cell is more excitable than normal
Chronotropic
-effect changes rate of depolarization of SA node, and therefore HR
+ –> increased HR
- –> decreased HR (slowed Na+ f channels during phase 4; hyper polarization by increasing outward K+ current via K+ Ach channel)
Dromotropic
-effect is speed of condition
+ –> faster conduction
- –> slower conduction (reduced Ca2+ inward current; increased outward K+ current via K+ Ach)
Inotropic
effect changes the strength of muscular contraction
+ –> heart contracts more forcefully
Lusitropic
effect changes the rate of muscular relaxation
What regions get parasympathetic innervation?
- SA node and AV node
- acetylcholine goes to receptors M2 or M3
- leads to decreased HR
Which has a longer Relative refractory period: neurons or cardiac cells?
cardiac
What is the purpose of the refractor period?
to prevent arrhythmias
