cardiac muscle Flashcards
what is the function of conductile cells of cardiac muscle? Name the different kinds
- function: rapid spread of electrical signal (action potential) through myocardium
- kinds
- bundle of his
- purkinje fibers
- SA node
- AV node
conducting cells can generate what type of action potentials
spontaneous
what conductile cells are the primary pacemakers
Sinoatrial (SA) node
function of cardiac myocytes
contractile cells: contraction
list the spread of excitation
- SA node: initiates action potential
- spread to atria and AV node
- AV node: slow conduction
- bundle of his and purkinje fibers : fast conduction
![](https://s3.amazonaws.com/brainscape-prod/system/cm/159/728/457/a_image_thumb.jpg?1442768655)
depolarization of ventricular myocardium goes from what level to what level
from endocardium to epicardium
what is conduction velocity
speed of action potential propagation through heart
what conductile cells have the fastest and slowest conduction velocity
slowest: AV node: 0.01-0.05 m/sec
fastest: Bundle of his and purkinje fibers: 2-4 m/sec
what dictates the conduction velocity
- rate of change in membrane potential as a function of time (i.e. upstroke phase of action potential)
- resistance
compare duration of action potentials of cardiac vs skeletal muscle
cardiac AP have a longer duration
![](https://s3.amazonaws.com/brainscape-prod/system/cm/159/730/190/a_image_thumb.gif?1442769634)
compare action potentials between contractile cells and pacemaker cells
- contractile cells: fast AP
- pacemaker cells: slow AP
what is phase 0 of fast action potential
- upstroke, rapid depolarization
- fast inward Na+ current
![](https://s3.amazonaws.com/brainscape-prod/system/cm/159/730/807/a_image_thumb.gif?1442769824)
what is phase 1 of fast action potential
- early repolarization
- activation of K+ channels: K+ moves out
- inactivation gates on Na+ channels close
![](https://s3.amazonaws.com/brainscape-prod/system/cm/159/731/009/a_image_thumb.gif?1442769951)
what is phase 2 of fast action potential
- Plateau phase
- responsible for the very long AP
- due to balance between Ca2+ (L-type channel: inward) current and K+ outward current
- L-type = long lasting: have slower kinetics than “fast” Na+ channels
![](https://s3.amazonaws.com/brainscape-prod/system/cm/159/731/220/a_image_thumb.gif?1442770078)
what is phase 3 of fast action potential
- repolarization
- turn off of Ca2+ current and further increase in K+ current
- K+ current reduced near end of phase 3 because membrane potential closer to K+ equilibrium
![](https://s3.amazonaws.com/brainscape-prod/system/cm/159/731/376/a_image_thumb.gif?1442770154)