Chapter 9 Review APHY 201

Skeletal muscles

Composed of cylindrical, multinucleated muscle fibers derived from myoblasts, linked to bones by tendons at each end of a muscle.

Satellite cells

Undifferentiated stem cells that proliferate and differentiate into myoblasts in response to muscle damage.

Hypertrophy

Increase in size of muscle fibers in response to injury or exercise.

Sarcomeres

Repeating, striated pattern of light and dark bands in skeletal muscle fibers under a microscope.

Thin filaments

Contain actin, troponin, and tropomyosin, anchored to Z lines in a sarcomere.

Thick filament

Made of myosin molecules with cross-bridges that span between thick and thin filaments.

Electrical activation of skeletal muscle fibers

Transmitted via T-tubules interacting with terminal cisternae of the sarcoplasmic reticulum.

Contraction

Activation of force generation in a muscle fiber; relaxation refers to turning off force-generating mechanisms.

Alpha motor neurons

Neurons that innervate skeletal muscle fibers, forming motor units.

Neuromuscular junction

Formed by motor neuron axon branches contacting a muscle fiber at the motor end plate.

Pacemaker Potential

The gradual depolarization of the cell membrane in pacemaker cells, leading to the threshold potential and subsequent action potential initiation.

Effect on Smooth Muscle Cell

The pacemaker potential sets the rhythm for contraction in smooth muscle cells, influencing their spontaneous activity.

Neural Control of Smooth Muscle

Unlike skeletal muscle, smooth muscle activity is primarily regulated by the autonomic nervous system and hormones rather than voluntary control through the somatic nervous system.