Lecture 11 - Cardiac Muscle Physiology Flashcards Preview

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Flashcards in Lecture 11 - Cardiac Muscle Physiology Deck (17):
1

Main features of cardiac muscle?

myogenic, striated, cells electrically coupled, oxidative metabolism, AP triggers internal CA2+ release

2

Cardiac fibroblast function?

secrete and maintain connective tissue fibres

3

Myocyte functions?

majority of heart mass (not cells), contraction, specialised cells (purkinje and nodal cells)

4

Characteristics of cardiac muscle?

striated appearance, ECM containing collagen, intercalated discs containing gap junction, intermediate junctions and desmosomes

5

Cardiac E-C coupling?

AP propagation down t-tubules activating NA channels causing depol leading to CA influx, calcium current activating ryanodine receptors to activate calcium induced calcium release, diffusion into contractile proteins leads to contrction

6

DHPR?

carry inward CA current, AP plateau, trigger E-C coupling, inhibited by SR Ca release, activated by depol >-40mV

7

Targeting DHPR?

stimulated: catecholamines, inhibited: Ca blockers, Mg, low plasma Ca

8

Sarcoplasmic reticulm?

reservoir for intracellular calcium, when load is high increased QE-C coupling through Ca availability

9

SR Ca buffered by?

calsequestrin

10

SR membrane contents?

Ca release channels, SR Ca ATPase

11

Events leading to contraction?

AP from adjacent cell spreads along SL, deopl opens DHPRs, Ca influx opens RyR, Ca ions bind TnC initiating cross-bridge cycle

12

Events causing relxation

Ca reduced and unbinds from TnC, Ca pumped into SR for storage, small amount left for exchange w Na, Na gradient maintained by Na/K ATPase

13

Important transporters for Myocyte relaxation?

SERCA (into cell), SL Ca ATPase (out of cell), SL Na/Ca exchanger (out of cell), Mitochondrial uniporter (into mitochondria)

14

Steady state - if Ca efflux decreases/influx increases?

accumulation in cell, leading to higher SR content and increased extrusion to balance influx

15

SL ATPase effectiveness?

minor contributer, high affinity but slow kinetics - no clinical relevance

16

SL Na/Ca exchanger (electrogenic NCX)?

Reverse mode (Ca entry) follows depol and affects AP plateu, forward mode (Ca out), promoted by repolarization, contributes to Vm

17

Forward mode stimulation?

depends on electrochemical gradient, stimulated by low intra Na, high intra Ca, and -ve membrane potential (reverse mode obviosuly vice versa - charge out)