CARDIO 3 Flashcards
VENTRICULAR MUSCLE CELL AP how does resting mem potential of ventricular myocyte differ from resting mem potential of slow type AP
flat
VENTRICULAR MUSCLE CELL AP what is required in ventricular myocytes to bring mem potential to threshold
stimulus
VENTRICULAR MUSCLE CELL AP what is resting mem of ventricular myocytes most permeable to
K
VENTRICULAR MUSCLE CELL AP what is resting mem potential of ventricular myocytes close to
K eq potential
VENTRICULAR MUSCLE CELL AP what happens during depol
- Na channels open
- Na moves into cell
VENTRICULAR MUSCLE CELL AP what is rate of depol in ventricular myocytes
fast
VENTRICULAR MUSCLE CELL AP why is depol in ventricular myocytes fast
Na moves into cell fast
VENTRICULAR MUSCLE CELL AP what happens after rapid depol
notch
VENTRICULAR MUSCLE CELL AP what is notch
partial repol
VENTRICULAR MUSCLE CELL AP what is responsible for notch
K channels that open transiently
VENTRICULAR MUSCLE CELL AP what happens after notch
plateau
VENTRICULAR MUSCLE CELL AP what is responsible for plateau
- opening of L type Ca channels (Ca in)
- opening of K channels (K out)
VENTRICULAR MUSCLE CELL AP what happens as plateau continues
- L type Ca channels begin to close
2. more K channels open
VENTRICULAR MUSCLE CELL AP what are 5 phases of ventricular myocyte AP
- resting
- depol
- notch
- plateau
- repol
VENTRICULAR MUSCLE CELL AP what happens to Na permeability when fast voltage gated Na channels close and become inactivated
mem permeability to Na drops
VENTRICULAR MUSCLE CELL AP what K currents correspond to (1) resting (2) notch (3) repol
- resting ==> inward rectifying current
- notch ==> transient outward current
- plateau + repol ==> delayed rectifying current
VENTRICULAR MUSCLE CELL AP what channels correspond to K currents
- resting, inward rectifying current, iK1
- notch, transient outward, ito
- plateau + repol , delayed rectifying, IKr and IKs
VENTRICULAR MUSCLE CELL AP what happens when ito channels open
slight increase in K permeability
VENTRICULAR MUSCLE CELL AP what is the function of IKr channel opening
maintaining plateau
VENTRICULAR MUSCLE CELL AP wha tis the funciton of IKs channel opening
repolarizing
VENTRICULAR MUSCLE CELL AP what is the function of iK1 channels
- setting resting potential
2. maintaining resting potential
VENTRICULAR MUSCLE CELL AP when does iK1 current increase
when returning to resting mem potential (high iK1 permeability)
VENTRICULAR MUSCLE CELL AP when does iK1 current decrease
when depolarizing (low iK1 permeability)
VENTRICULAR MUSCLE CELL AP what is responsible for closing L type Ca channels during plateau phase
ito
VENTRICULAR MUSCLE CELL AP what channel does L type Ca channel close during plateau phase
iK1
what kind of AP in SA node conducing cells
slow
what kind of AP in AV node conducting cells
slow
what is the difference bw SA node conducting cells AP and AV node conducting cell AP
AV node conducting cells take longer to reach threshold
why does SA node set heart rate
reaches threshold potential first
what kind of AP in atrial myocardium contractile cells
fast
what kind of AP in ventricular myocardium contractile cells
fast
how are atrial myocardial contractile cell AP diff from ventricular myocardial contractile cell AP
atria, shorter AP, shorter plateau
ventricles, longer AP, longer plateau
ECG what is first electrical event in conduction pathway
depol of myocytes in SA node
ECG what does P wave represent
depol atria
ECG what does width of P wave represent
how long it takes atrial myocytes to contract
ECG what does QRS complex consist of
- downward deflection (Q)
- upward deflection (R)
- downward deflection (S)
ECG what does QRS complex represent
depol ventricles
ECG what does width of QRS complex represent
how long it takes ventricular myocytes to depol
ECG what does Q represent
wave of depol as AP travels down inter-ventricular septum
ECG what does RS represent
wave of depol as AP travels from apex up
ECG what is happening at same time that ventricle depol
atria repol
ECG what is missing on ECG
- SA node myocyte depol
- AV node myocyte depol
- bundle of his myocyte depol
- bundle branches myocyte depol
- purkinje fibre myocyte depol
- atrial myocyte repol
ECG what does T wave represent
repol ventricles
ECG what is PR interval
- beginning of P wave
- beginning of QRS complex
ECG what does PR interval represent (2)
- atria depol
2. AV delay
ECG what is QT interval
- beginning of QRS complex
- end of T wave
ECG what is QT interval measure of
ventricular AP
ECG what is ST segment
- end of QRS
- start of T
ECG what does ST segment look like
flat
ECG what does ST segment represent
plateau phase of fast AP
what is AV node block
- AV node damage
what is result of AV node block
impair conduction of AP from atria to ventricles
what happens in partial AV node block
every other signal conducted from atria to ventricles
what does partial AV node block look like on ECG
every second wave lacks
- QRS complex
- T wave
what happens in complete AV node block
no signal conducted from atria to ventricles
what does complete AV node look like on ECG
no synchrony bw atria and ventricles
in complete AV node block what part of conducting system generating AP s to stimulate ventricles
bundle of his
what is excitation contraction coupling
process by which arrival of AP at cell mem leads to myocyte contraction
when does extracellular Ca enter myocyte
when L type Ca channels open during plateau phase
what is the function of Ca that enters myocyte during plateau phase
- Ca binds to ryanodine receptors of SR
- SR releases Ca into cyto
(Ca induced Ca release)
what are steps of excitation contraction coupling in cardiac myocyte
- t tubules bring excitation into myocyte
- myocyte increases CA permeability during plateau phase
- Ca enters myocyte through L type Ca channels in sarcolemma and t tubules
- Ca binds to ryanodine receptors
- SR releases Ca into cyto
- Ca concentration in cyto increases
- Ca binds to troponin
- Regulatory complex undergoes conformational change to allow for actin myosin interaction