Anatomy and Physiology - Muscular System Practice Exam

Flashcards covering skeletal muscle anatomy, physiology, innervation, and contraction mechanics based on practice exam questions.

Transverse tubules (T-tubules)

Structures that allow action potentials to propagate deep into the center of skeletal muscle cells.

Sarcomere

The repeating contractile unit of a skeletal muscle fiber.

Rectus abdominis

The abdominal muscle responsible for flexing the trunk and depressing the ribs.

Rotator cuff muscles

A group of muscles including the subscapularis and supraspinatus.

Suprascapular nerve

The nerve that innervates the supraspinatus and infraspinatus muscles.

Levator scapulae

The muscle responsible for scapular elevation.

Motor end plate

The specific part of the sarcolemma that contains acetylcholine receptors.

Triad

A skeletal muscle structure consisting of one transverse tubule and two terminal cisternae.

Terminal cisternae

The specific region of the sarcoplasmic reticulum where calcium ions are stored.

Relaxation phase

The longest phase of a muscle twitch.

Musculocutaneous nerve

The nerve that, if damaged, results in the loss of the ability to flex the elbow and supinate the forearm.

Fusion of myoblasts

The process responsible for the presence of multiple nuclei in skeletal muscle cells.

Gastrocnemius

The muscle responsible for the ability to plantar flex at the ankle.

Motor unit

A functional unit consisting of a single motor neuron, neuromuscular junctions, and muscle fibers.

Tropomyosin

A protein that serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

Thin filaments

Muscle proteins composed of actin, troponin, and tropomyosin, but notably excluding myosin.

Dorsiflexion muscles

Muscles of the foot including the tibialis anterior, extensor hallucis longus, and fibularis tertius.

F-actin

A twisted strand made up of two rows of $G$ actin subunits where myosin heads can bind.

Femoral nerve

The nerve responsible for the innervation and movement of the quadriceps femoris muscle.

Skeletal muscle connective tissue layers

The order from most superficial to deepest: Epimysium, Perimysium, then Endomysium.

Smooth muscle Regulation

Movement that does not use the troponin-tropomyosin complex to regulate cross-bridge activity.

Fascicle

A bundle of muscle fibers wrapped by connective tissue that composes a skeletal muscle.

Latent period

The short period immediately following a stimulus where the neurotransmitter is released, diffuses, and binds to receptors.

Flexor digitorum profundus

A muscle that does not have an origin on the humerus.

Striations

The visible appearance of skeletal muscle resulting from the specific arrangement of actin and myosin.

Third-class lever

A lever system described by the sequence: Load, Effort, Fulcrum ($LEF$).

Isometric contraction

A type of contraction where the muscle cell generates tension but does not shorten.

Optimal length ($L_o$)

The specific length at which a skeletal muscle can generate its maximum tension.

Hamstrings

A muscle group consisting of the biceps femoris, semitendinosus, and semimembranosus.

A band

The letter associated with the dark bands in a sarcomere.

Brachial plexus

A network of nerves formed by the branches of spinal nerve segments $C5-T1$.

Radial nerve

The nerve that innervates the muscles of the posterior arm.

Excitation-contraction coupling

The sequence of events linking a muscle's action potential to changes in skeletal muscle force development.

Skeletal muscle component hierarchy

The order from smallest to largest: Myofibrils, muscle fiber, fascicle, and skeletal muscle.

Troponin function

A protein that binds $Ca^{2+}$, causing tropomyosin to pull away and reveal actin binding spots on the thin filament.