Muscular Systems

• Contractility- ability to shorten forcefully
• Elasticity - ability to return to original length after stretching
• Extensibility- can be stretched beyond its normal resting length and still be able to contract.
• Excitability- capacity to respond to a stimuli
• Sarcolemma: cell membrane: contains transverse tubules ( T tubules)
• T tubules: tube-like inward folds associated with sarcoplasmic reticulum; connects the sarcolemma to terminal cisternae to form a triad.
• Sarcoplasmic Reticulum: a type of smooth ER that surrounds myosin; stores and release Ca2
• Terminal Cisternae: enlarged portion of the sarcoplasmic reticulum; part of triad
• Sarcoplasm: cytoplasm that contains many bundles of myofibrils
• Myofibrils: thread like bundles of protiens that make up muscle fibers
• Myofilaments: protien fibers that make up the myofibrils (Actin and myosin)
• • Actin Myofilaments: are made of actin filaments and myosin filaments
  • actin strands: attachment site for myosin filaments
  • Troponin molecules: binding sites of Ca2+
  • Tropomyosin Filaments: Cover the attachment sites on actin myofilament and binds into troponin that exposes the attachment sites on the actin myofilaments
• Myosin Myofilaments: thick myofilaments: contain myosin heads