Anatomy: Muscular System Flashcards

Question 1

Define Muscular System.

Accepted Answer

The organ system of skeletal muscles and their tendons that moves the skeleton, maintains posture, stabilizes joints and generates most of the body's heat.

Question 2

Define Skeletal Muscle Tissue.

Accepted Answer

Striated, voluntary muscle tissue made of long, cylindrical, multinucleated cells, usually attached to bones by tendons.

Question 3

Define Cardiac Muscle Tissue.

Accepted Answer

Striated, involuntary muscle found only in the heart wall, made of branched cells with one or two nuclei joined end to end by intercalated discs.

Question 4

Define Smooth Muscle Tissue.

Accepted Answer

Non-striated, involuntary muscle of spindle-shaped cells with a single nucleus, lining the walls of hollow organs such as blood vessels, the gut and the bladder.

Question 5

Define Intercalated Disc.

Accepted Answer

The specialized junction between neighboring cardiac muscle cells, containing desmosomes that hold the cells together and gap junctions that let electrical signals pass directly between them.

Question 6

Define Muscle Fiber.

Accepted Answer

A single skeletal muscle cell: a long, cylindrical, multinucleated cell formed when many embryonic myoblasts fuse together during development.

Question 7

What is Fascicle?

Accepted Answer

A bundle of skeletal muscle fibers wrapped together by perimysium; a whole muscle is built from many fascicles.

Question 8

What is Epimysium?

Accepted Answer

The outer sheath of dense irregular connective tissue that surrounds an entire skeletal muscle and blends into its tendon.

Question 9

What is Perimysium?

Accepted Answer

The connective tissue layer that wraps each fascicle, carrying the blood vessels and nerves that supply the fibers inside it.

Question 10

What is Endomysium?

Accepted Answer

The thin layer of areolar connective tissue surrounding each individual muscle fiber, holding its capillaries and nerve fibers.

Question 11

What is Tendon?

Accepted Answer

A cord of dense regular connective tissue, continuous with a muscle's connective tissue wrappings, that attaches skeletal muscle to bone and transmits its pull.

Question 12

What is Sarcolemma?

Accepted Answer

The plasma membrane of a muscle fiber, which carries the action potential that starts contraction across the cell's surface.

Question 13

Define T Tubules.

Accepted Answer

Transverse tubules: deep inward folds of the sarcolemma that carry the action potential into the interior of the fiber, close to the sarcoplasmic reticulum.

Question 14

Define Sarcoplasmic Reticulum.

Accepted Answer

The specialized smooth endoplasmic reticulum of a muscle fiber that stores calcium ions, releases them to trigger contraction and pumps them back to allow relaxation.

Question 15

What is Myofibril?

Accepted Answer

A long, rod-shaped bundle of contractile protein filaments running the length of a muscle fiber, built from sarcomeres lined up end to end.

Question 16

What is Sarcomere?

Accepted Answer

The smallest functional contractile unit of striated muscle, running from one Z disc to the next and made of overlapping thick and thin filaments.

Question 17

What is Actin?

Accepted Answer

The globular protein that forms the thin filaments of a sarcomere, anchored at the Z disc and carrying binding sites for myosin heads.

Question 18

What is Myosin?

Accepted Answer

The motor protein that forms the thick filaments, with heads that bind actin, split ATP and swivel to pull thin filaments in a power stroke.

Question 19

What is Tropomyosin?

Accepted Answer

A long regulatory protein that winds along the actin filament and, in a resting muscle, covers the sites where myosin heads would bind.

Question 20

What is Troponin?

Accepted Answer

A three-part regulatory protein complex on the thin filament that binds calcium and, when it does, shifts tropomyosin away from actin's myosin-binding sites.

Question 21

Define Sliding Filament Model.

Accepted Answer

The explanation of contraction in which thin filaments slide past thick filaments toward the sarcomere's center, shortening the sarcomere while neither filament changes length.

Question 22

Define Neuromuscular Junction.

Accepted Answer

The synapse where a motor neuron's axon terminal meets a skeletal muscle fiber, releasing acetylcholine onto receptors in the motor end plate.

Question 23

What is Acetylcholine?

Accepted Answer

The neurotransmitter released by motor neurons at the neuromuscular junction; binding to its receptors depolarizes the muscle fiber and starts contraction.

Question 24

Define Excitation-Contraction Coupling.

Accepted Answer

The sequence linking a muscle action potential to contraction: the signal travels down T tubules, calcium is released from the sarcoplasmic reticulum and cross-bridges begin forming.

Question 25

Define Cross-Bridge Cycle.

Accepted Answer

The repeating loop in which a myosin head attaches to actin, performs a power stroke, releases when ATP binds and re-cocks as it splits that ATP.

Question 26

Define Motor Unit.

Accepted Answer

One motor neuron together with all of the skeletal muscle fibers it innervates; when the neuron fires, every fiber in the unit contracts.

Question 27

What is Recruitment?

Accepted Answer

Increasing the force of a whole muscle by activating more motor units, typically small units first and larger ones as more force is needed.

Question 28

Define Muscle Tone.

Accepted Answer

The low level of constant, involuntary contraction in a resting skeletal muscle, produced by small numbers of motor units firing in turn.

Question 29

Define Isotonic Contraction.

Accepted Answer

A contraction in which muscle tension stays roughly constant while the muscle changes length, either shortening (concentric) or lengthening under load (eccentric).

Question 30

Define Isometric Contraction.

Accepted Answer

A contraction in which the muscle develops tension but does not change length, because the load equals or exceeds the force produced.

Question 31

Define Origin and Insertion.

Accepted Answer

The two attachments of a skeletal muscle: the origin is on the bone that stays relatively fixed, and the insertion is on the bone that moves.

Question 32

Define Agonist, Antagonist and Synergist.

Accepted Answer

Roles muscles play in a movement: the agonist (prime mover) produces it, the antagonist opposes it, and a synergist assists the agonist or steadies the joint.