Week 6 - Cardiac Cells Flashcards
(12 cards)
What are the key structural components of cardiomyocytes?
Intercalated discs (desmosomes + gap junctions), sarcolemma, T-tubules, sarcoplasmic reticulum, myofibrils, and abundant mitochondria.
What is the resting membrane potential of a cardiomyocyte?
Approximately -90 mV (inside of the cell is negative).
What mainly creates the resting membrane potential in cardiac cells?
K⁺ leak channels allowing K⁺ to exit the cell, and the Na⁺/K⁺ pump maintaining ion gradients.
What role do gap junctions play in cardiac muscle?
They allow ion flow between cells, enabling synchronized contraction.
How is excitation-contraction (E-C) coupling initiated in cardiac muscle?
By depolarizing current from adjacent cells through intercalated discs.
What triggers calcium release from the SR in cardiac myocytes?
Influx of extracellular Ca²⁺ causes Ca²⁺-induced Ca²⁺ release via ryanodine receptors.
What protein does calcium bind to during cardiac muscle contraction?
Troponin.
What is a key difference in E-C coupling between cardiac and skeletal muscle?
Cardiac muscle requires extracellular Ca²⁺; skeletal muscle does not.
What prolongs the action potential in cardiac myocytes?
L-type voltage-gated Ca²⁺ channels.
Why is the long refractory period important in cardiac muscle?
It prevents tetanus and ensures full contraction and relaxation for proper heart function.
What is tetanus in skeletal muscle?
A sustained contraction due to rapid, repeated stimulation that prevents relaxation.
Why can skeletal muscle experience tetanus but cardiac muscle cannot?
Because skeletal muscle has a short refractory period, while cardiac muscle has a long one.
