muscle physiology Flashcards
(12 cards)
What are the three types of contractile muscle cells in the human body?
Skeletal, cardiac, and smooth muscle.
What are the key features of skeletal muscle cells?
Multinucleated, striated, voluntary, attached to bones, involved in movement, posture, and metabolism.
What is excitation-contraction coupling in skeletal muscle?
Process by which an action potential triggers Ca²⁺ release from the SR, leading to muscle contraction via the sliding filament model.
Describe the sliding filament model of muscle contraction.
Myosin heads bind actin, pull filaments to shorten sarcomere; requires Ca²⁺ and ATP.
How do red and white skeletal muscle fibers differ?
Red fibers are slow, oxidative, and fatigue-resistant; white fibers are fast, glycolytic, and fatigue quickly.
What is the function of cardiac muscle?
Involuntary, striated muscle responsible for pumping blood through the heart.
What is the excitation-contraction coupling mechanism in cardiac muscle?
Depolarization leads to Ca²⁺ entry via L-type channels, triggering SR Ca²⁺ release (CICR), which activates contraction.
How does cardiac muscle differ from skeletal muscle?
Cardiac muscle has gap junctions, is involuntary, branched, and uses CICR instead of direct DHP-RyR coupling.
What is the function of smooth muscle?
Controls involuntary movements in internal organs like blood vessels, respiratory, GI, and urinary systems.
How does contraction in smooth muscle differ from skeletal muscle?
Smooth muscle uses calmodulin and MLCK instead of troponin; contraction is slower, longer-lasting, and energy-efficient.
What is unique about smooth muscle excitation-contraction coupling?
It can involve second messengers (e.g., IP₃, cAMP, NO) and is initiated by hormones or neurotransmitters as well as voltage changes.
How do the three muscle types compare in contraction mechanism?
All use actin, myosin, ATP, and Ca²⁺; differ in Ca²⁺ source, regulatory proteins, and coupling mechanisms.
