Untitled Quiz

Muscle Types

• Muscle terminology uses similar root words (myo, mys, sacro) that refer to muscles.
• Three types: skeletal, cardiac, and smooth, differing in structure, location, function, and activation.

Skeletal Muscle Tissue

• Has striations (banding patterns).
• Found in skeletal muscles attached to the skeleton.
• Controlled voluntarily.
• Highly adaptable, able to exert varying force.

Cardiac Muscle Tissue

• Also striated, similar to skeletal muscle.
• Located only in the heart.
• Involuntary neural control allows response to bodily needs.

Smooth Muscle Tissue

• Lacks striations.
• Found in the walls of hollow organs.
• Involuntary, controlled by neural and hormonal mechanisms.

Functional Characteristics of Muscle

• Excitability (irritability): Ability to receive and respond to stimuli.
• Contractility: Ability to shorten forcibly.
• Extensibility: Ability to be stretched or extended.
• Elasticity: Ability to recoil and resume resting length.

Muscle Functions

• Producing movement: Muscle moves body parts or materials within the body.
• Maintaining posture: Keeps body upright against gravity.
• Stabilizing joints: Muscle tone reinforces joints.
• Generating heat: Important in regulating body temperature.

Skeletal Muscle Microscopic Anatomy

• A muscle cell is called a muscle fiber.

• Sarcolemma: Muscle fiber's cell membrane.

• Sarcoplasm: Cytoplasm of a large muscle fiber; contains glycogen (stored glucose) and myoglobin (oxygen-binding protein).

• Myofibrils: Dense, rod-like contractile elements within muscle fibers.

• Sarcomeres: Smallest contractile unit within a myofibril; arranged in a repeating series of dark (A bands) and light (I bands) striations.

• Myofilaments: Contractile proteins within sarcomeres.

  • Thick filaments (myosin): Extend throughout the A band; have heads for cross-bridge formation.
  • Thin filaments (actin): Extend across the I band and part of the A band; have active sites for myosin binding.

• Other components: I band, H zone, M line, Z disc, and A band form a repeating pattern.

• Sarcoplasmic reticulum: Elaborate smooth endoplasmic reticulum surrounding myofibrils; regulates calcium levels for muscle contraction.

• T tubules: Elongated tubes that penetrate the cell interior, connecting with sarcoplasmic reticulum at triads and conducting impulses for Ca2+ release.

• Triads: A structure formed by a T tubule and two terminal cisternae, which regulate Ca2+ release for muscle contraction.