CH. 40- Muscles Bio (Exam 3)

Actin

Thin myofilaments involved in muscle contraction.

Agonist

Muscle that facilitates a specific movement.

Antagonist

Muscle that opposes the action of another.

Dense body

Anchoring point for actin in smooth muscle.

H zone

Region of sarcomere containing only myosin.

I band

Area of sarcomere with actin filaments only.

M line

Center of H zone holding myosin filaments together.

Motor unit

Nerve axon and its innervated muscle fibers.

Myofiber

Individual muscle cell responsible for contraction.

Myofibril

Cytoplasmic structure made of myofilaments.

Myofilament

Filaments in myofibrils, either actin or myosin.

Myosin

Thick myofilaments essential for muscle contraction.

Sarcolemma

Plasma membrane surrounding a muscle cell.

Sarcomere

Basic contractile unit in skeletal muscle.

Sarcoplasmic reticulum

Endoplasmic reticulum in muscle cells for calcium storage.

Triad

Structure formed by T tubule and sarcoplasmic reticulum.

Troponin

Protein regulating actin-myosin interaction via calcium binding.

Tropomyosin

Protein that covers actin binding sites when relaxed.

T Tubule

Inward extension of sarcolemma, interacts with sarcoplasmic reticulum.

Z line

Boundary of sarcomere where actin filaments are anchored.