Muscle Tissue

• What cells have the ability to contract in very small blood vessels?

  Pericytes
• What cells contract in the ducts of exocrine glands?

  Myoepithelial cells
• Which cells exhibit the greatest contractility?


  Muscle cells / myocytes / myoid cells
• What are the functions of muscle tissue?


  • Produce body movements
  • Transport substances in the body
  • Maintenance of posture
  • Heat production
• What is a basic characteristic of muscle tissue?


  Ability to contract
• What does muscle tissue exhibit that allows it to generate action potentials?


  Electrical excitability
• What is the structure of muscle fibers?


  Elongated
• What are the parts of muscle tissue?

  • Sarcolemma: plasma membrane
  • Sarcoplasm: cytoplasm
  • Sarcoplasmic reticulum: smooth ER
  • Sarcosomes: mitochondria
• What is the organization of skeletal muscle?


  Skeletal muscle, fasciculi, muscle fiber, myofibril, myofilament
• What are fasciculi in skeletal muscle?


  Bundles of muscle fibers
• What do myofibrils contain?


  Contractile structures (actin and myosin)
• What are myofilaments?


  Actin or myosin
• What are the characteristics of skeletal muscles?


  • Voluntary
  • Quick and forceful contraction
  • Limited regenerative capacity
  • Attached to bones or skin
• What is the shape of skeletal muscle cells?


  Long and cylindrical
• What is a key feature of skeletal muscle cells?

  Striated
• How many nuclei do skeletal muscle cells have?


  Hundreds (multinucleated)
• Where are the nuclei located in skeletal muscle cells?


  Peripherally
• What is myoglobin?


  An oxygen-binding protein
• What are transverse (T) tubules?


  Tubular invaginations of sarcolemma that transmit action potentials
• What is a TRIAD in skeletal muscle?


  A T-tubule with a pair of terminal cisternae
• What does the sarcoplasmic reticulum contain?


  Calcium
• What is a sarcomere?


  • Fundamental unit within the myofibril
  • Contains contractile proteins (actin and myosin)
  • Contains non-contractile proteins (titin, desmin)
• What are the parts of a sarcomere?


  1. line, A-band, I-band, H-zone, M-line
• What is the function of the Z-line in a sarcomere?


  Links actin filaments
• What does the A-band in a sarcomere represent?

  Extends the length of myosin with overlap of actin
• What is included in the I-band of a sarcomere?


  Only actin
• What is the H-zone in a sarcomere?


  Center of myosin without overlap of actin
• What does the M-line in a sarcomere do?


  Links myosin filaments
• What is the neuromuscular junction?


  • Also known as "motor endplate"
  • Junction between a branch of the axon terminal and a muscle fiber
  • Located near the center of the muscle fiber
  • Neurotransmitter: acetylcholine
• What is a motor unit?


  • Functional unit of skeletal muscle
  • Components:

  1. 1 anterior horn cell (AHC) or motor neuron
  2. 1 nerve fiber or axon
  3. All muscle fibers innervated by the AHC and its axon
• What are the characteristics of cardiac muscles?


  • Involuntary
  • Blood supply is 2x as rich as skeletal muscles
  • Forceful contraction
  • No regenerative capacity
  • Forms the myocardium of the heart
• What is the shape of cardiac muscle cells?


  Short and cylindrical
• What is a key feature of cardiac muscle cells?


  Striated
• How are cardiac muscle cells characterized in terms of branching?


  Bifurcate (branching)
• How many nuclei do cardiac muscle cells have?


  Mononucleated
• Where is the nucleus located in cardiac muscle cells?


  Centrally
• What is a key feature of cardiac muscle cells regarding their cytoplasm?


  More abundant sarcoplasm and more numerous mitochondria
• What are intercalated discs?


  Connections between cardiac muscle cells
• What are the characteristics of smooth muscles?


  • Involuntary
  • Slow and not forceful contraction
  • Can undergo partial contraction for long periods
  • Greater ability to elongate than striated muscles
  • Has regenerative capacity
  • Found in walls of internal organs
• What is the shape of smooth muscle cells?

  Fusiform