L5.2 Heart muscle: specialised structure and function Flashcards Preview

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Flashcards in L5.2 Heart muscle: specialised structure and function Deck (10):
1

Difference b/w physiological and pathological hypertrophy

  • Physiological hypertrophy: Hypertrophy in response to physiological stimuli
  • Pathological hypertrophy: Hypertrophy in response to pathological stimuli (e.g. hypertension)

2

What is the heart muscles arranged in a spiral

allows squeezing of blood up from apex

3

What are intercalated discs

Intercalated discs attaches one myocyte to another

4

What is the ultrastructure of the cardiomyocytes

  • 100microns by 20microns
  • ↑↑[mito] → cardiomyocytes are always contracting
    • More than skeletal muscles
  • Myofilaments: Cardiomyocytes < skeletal muscles

5

Length tension relationship of the cardiomyocytes

  • Frank-starling curve
  • Proportional to myofilament (actin/myosin) overlap
  • ALWAYS on the ascending part of curve (always able to cope with amount of blood)

6

What is the function of the T-tubules

  • Allows integration of the extracellular space into myocyte
    • Allows myocyte to contract at the same time

7

EC coupling of cardiomyocytes

  1. CA ENTERS DURING AP PLATEAU PHASE
    • Ca induced Ca release - unique to cardiac muscle
  2. Triggers release of Ca from SR (binding to RyR)
  3. Ca binds to troponin-C
  4. Cross-bridge cycling
  5. Cell shortens
  6. MOST Ca pumped back into SR (SERCA pumps)
  7. CA EXIT CELL BY NA-CA EXCHANGER & THROUGH SARCOLEMMAL CA PUMPS
    • 3 Na in for every Ca out - unique to cardiac muscle

8

Difference b/w skeletal and cardiac EC coupling

9

What is the fuzzy space?

restricted diffusional region b/w SL & SR

10

Things going wrong in the fuzzy space

  1. Misalignment with RyR & L-type channel
    • Not efficiently stimulating Ca release
  2. L-type channels becomes leaky or hypersensitive to Ca
  3. Space gets wider → ↓effectiveness
    • Disruption in junctophilin (JP2) which is responsible for binding of L-type channels to T-tubules
    • Caused by Ca overload → Activating calpains