Muscle Anatomy and Physiology - Vocabulary Flashcards (Video Notes)

A comprehensive set of vocabulary flashcards covering the major concepts from the lecture notes: muscle tissue types, anatomy of skeletal muscle, the sliding filament model, neuromuscular junction, excitation-contraction coupling, motor units and twitch physiology, isotonic/isometric contractions, antagonistic muscle pairs, and facial muscles.

Actin

Thin filament in the sarcomere; forms part of the I-band and binds myosin during contraction; regulatory interaction with troponin/tropomyosin.

Myosin

Thick filament with heads that form cross-bridges to pull actin; ATP binding and hydrolysis power the contraction cycle.

Sarcomere

Basic contractile unit of a skeletal muscle between two Z-lines; contains actin and myosin filaments.

Z-line (Z-disc)

Boundary of a sarcomere where thin filaments attach; marks the ends of a sarcomere.

Tropomyosin

Regulatory protein on actin that blocks myosin-binding sites at rest; moved away when Ca2+ binds to troponin.

Troponin

Regulatory complex that binds Ca2+ to reveal actin binding sites for myosin during contraction.

ATP

Adenosine triphosphate; cellular energy currency; hydrolyzed to power the myosin head’s action (ADP and Pi produced).

Calcium (Ca2+)

Ion released from the sarcoplasmic reticulum to trigger contraction by binding troponin.

Sarcoplasmic Reticulum

Organelle that stores and releases Ca2+ in muscle cells; contains Ca2+ pumps and channels.

Sarcolemma

Plasma membrane of a muscle fiber; conducts action potentials and contains t-tubules.

T-tubule

Transverse invaginations of the sarcolemma that propagate action potentials into the muscle fiber to stimulate Ca2+ release.

Neuromuscular Junction

Synapse between a motor neuron and a skeletal muscle fiber; site of acetylcholine signaling.

Acetylcholine (ACh)

Neurotransmitter released at the NMJ; binds receptors on the muscle to initiate depolarization.

Acetylcholine receptor

Ligand-gated Na+ channel on the muscle membrane; binding ACh starts the muscle action potential.

Isotonic contraction

Contraction where the muscle changes length while generating enough force to move a load.

Isometric contraction

Contraction where the muscle develops tension without changing length.

Motor Unit

A single motor neuron and all the muscle fibers it innervates; all fibers respond to one action potential.

Twitch

A muscle fiber’s response to a single action potential; includes latent, contraction, and relaxation phases.

Latent period

Delay after stimulation before force is produced as Ca2+ is released and cross-bridges form.

Contraction phase

Phase where cross-bridges form and the muscle shortens.

Relaxation phase

Phase where Ca2+ is re-sequestered and cross-bridges detach, muscle lengthens.

Temporal summation

Increase in force due to rapid successive stimuli causing more Ca2+ and cross-bridges.

Tetany (tetanic contraction)

Sustained maximal contraction from high-frequency stimulation with no relaxation.

Recruitment

Activation of additional motor units to increase overall muscle force.

Size principle

Small motor units are recruited first; larger units join as stronger force is needed.

Agonist

Prime mover muscle that primarily produces a movement.

Antagonist

Muscle that opposes the action of the agonist, providing control."

Synergist

Muscle that assists the agonist and helps stabilize joints during movement.

Antagonistic pair

Two muscles that perform opposite actions (e.g., flexor vs extensor, abductor vs adductor).

Abductor

Muscle that moves a limb away from the midline.

Adductor

Muscle that moves a limb toward the midline.

Flexor

Muscle that decreases the angle of a joint.

Extensor

Muscle that increases the angle of a joint.

Frontalis

Facial muscle that raises the eyebrows.

Orbicularis oculi

Circular facial muscle that closes the eye (blink).

Orbicularis oris

Muscle surrounding the mouth; controls movements for speech, kissing, and whistling.

Zygomaticus

Facial muscle that raises the corners of the mouth (smile).

Depressor anguli oris

Facial muscle that depresses the corners of the mouth (frown).

Masseter

Jaw elevator; elevates the mandible to close the jaw.

Temporalis

Jaw elevator; assists in closing the jaw; runs to the mandible.

Sternocleidomastoid

Neck muscle that flexes the neck and rotates the head; attaches to sternum, clavicle, and mastoid process.

Trapezius

Large neck/upper back muscle; extends the neck and stabilizes the scapula.

Endomysium

Connective tissue surrounding each individual muscle fiber.

Perimysium

Connective tissue surrounding a fascicle (bundle) of muscle fibers.

Epimysium

Connective tissue surrounding the entire muscle.

Fascicle

Bundle of muscle fibers within a muscle.

Myofibril

Rod-like unit inside a muscle fiber containing sarcomeres.

A-band

Dark band in the sarcomere corresponding to myosin filaments.

I-band

Light band in the sarcomere containing actin filaments; spans Z-lines.

Multinucleated

Characteristic of skeletal muscle fibers; contains many nuclei per cell.

Striated

Appearance of skeletal and cardiac muscles with a banded pattern.

Intercalated discs

Connections between cardiac muscle cells that allow rapid conduction and coordination.

Branching

Cardiac muscle characteristic where cells branch and form a network.

Excitation-contraction coupling

Process by which an action potential leads to Ca2+ release and muscle contraction.