Topic 6: Muscular System Part 2

• What type of muscle tissue is cardiac muscle?

  Striated and involuntary
• How many nuclei does each cardiac muscle fiber usually contain?

  One centrally located nucleus
• What connects cardiac muscle fibers?

  Intercalated discs
• What is the primary energy source for cardiac muscle fibers?

  Aerobic cellular respiration
• What types of junctions are found in intercalated discs?

  Gap junctions, adhering junctions, desmosomes
• Where is cardiac muscle tissue located?

  In the heart
• What is the contractility of cardiac muscle tissue influenced by?

  The autonomic nervous system and hormones
• What is the histological feature of cardiac myocytes?

  Joined by intercalated discs
• What do adherens junctions do in cardiac muscle tissue?

  Connect the ends of myocytes
• What is the role of desmosomes in cardiac muscle tissue?

  Prevent separation during contractions
• What do gap junctions allow in cardiac muscle tissue?

  Pathways for ions to pass between cells
• How does depolarization in cardiac tissue differ from skeletal muscle?

  It lasts longer in cardiac tissue
• Where are calcium channels located in cardiac muscle tissue?

  In the T tubule system
• What happens when calcium ions are released in cardiac muscle tissue?

  They bind to channels in the sarcoplasmic reticulum
• What type of muscle tissue is smooth muscle?

  Nonstriated and involuntary
• What additional components do smooth muscle tissues contain?

  Intermediate filaments and dense bodies
• Where is smooth muscle located?

  Walls of hollow viscera and blood vessels
• What do myofibroblasts produce?

  Connective tissue proteins like collagen
• What is the function of dense bodies in smooth muscle?

  Anchor thin filaments in position
• How do intermediate filaments function in smooth muscle contraction?

  Pull the sarcolemma toward the fiber's middle
• How does the duration of contraction in smooth muscle compare to skeletal muscle?

  Longer in smooth muscle
• What is smooth muscle tone?

  A state of continuous partial contraction
• How can smooth muscle fibers be stretched?

  Considerably while retaining contraction ability
• What controls smooth muscle contraction?

  Signals from the autonomic nervous system
• What happens when the stimulus for smooth muscle contraction is removed?

  Cells do not relax immediately
• What is the role of myosin in smooth muscle contraction?

  Continues to bind to actin until calcium falls
• What forms motor units in smooth muscle?

  Varicosities from autonomic neurons
• What is peristalsis in the digestive system?

  Wave-like contraction moving food through the gut
• What happens to skeletal muscle mass as humans age?

  Progressive loss replaced by connective and adipose tissue
• What factors contribute to the decline in muscle strength with aging?

  Decreased physical activity and reflexes
• How do skeletal muscles produce movement?

  By pulling on tendons attached to bones
• What is the origin in muscle attachment?

  The attachment to the stationary bone
• What is the insertion in muscle attachment?

  The attachment to the movable bone
• What is the role of the prime mover (agonist) in muscle action?

  Produces the desired action
• What does the antagonist do in muscle action?

  Produces an opposite action
• What is the function of a synergist muscle?

  Assists the prime mover by reducing unnecessary movement
• What does a fixator do in muscle action?

  Stabilizes the origin of the prime mover
• How many skeletal muscles are there in the human body?

  Over 700
• What are the major descriptive categories for naming skeletal muscles?

  Direction, location, size, shape, action
• What does the term "rectus" mean in muscle naming?

  Parallel to midline