Muscular System, Muscle Contraction, Movements, and Joint Articulations

Vocabulary flashcards covering muscle tissue types, organization, cellular physiology, contraction mechanisms, body movements, and joint classifications.

Epimysium

A layer of connective tissue that wraps around the entire muscle.

Perimysium

A layer of connective tissue that wraps around each fascicle.

Endomysium

A layer of connective tissue that wraps around each muscle fiber to protect and reinforce it.

Fascicle

A bundle of muscle fibers.

Tendon

A structure formed by all three connective tissue layers merged together that attaches muscle to the skeleton.

Satellite Cell

A muscle-builder cell whose function is to repair damages.

Smooth Muscle Tissue

Non-striated, involuntary muscle tissue composed of tapered cells with pointed ends and a single nucleus, located in organ walls.

Cardiac Muscle Tissue

Striated, involuntary muscle tissue with branched cells containing $1\text{ to }2$ nuclei, located in the heart.

Skeletal Muscle Tissue

Striated, voluntary muscle tissue composed of long, multinucleated cells attached to the skeleton.

Sarcolemma

The selectively permeable plasma membrane of a muscle cell, composed of a lipid bilayer, proteins, and carbohydrates.

Sarcoplasm

The cytoplasm of a muscle cell.

Sarcoplasmic Reticulum (SR)

The smooth endoplasmic reticulum of a muscle cell that stores $\text{Ca}^{2+}$ signaling ions.

Resting Membrane Potential (RMP)

The electrical charge difference across the resting sarcolemma ($\text{RMP} = -90\text{ mV}$), maintained by the $\text{Na}^+\text{-}\text{K}^+$ pump and $\text{K}^+$ leak channels.

T-tubules

Invaginations of the sarcolemma that deliver electrical signals into the interior of the muscle fiber.

Terminal Cisternae

Expanded end structures of the sarcoplasmic reticulum situated on both sides of T-tubules that store $\text{Ca}^{2+}$.

Sarcomere

The repeating contractile unit of a myofibril bounded by Z discs.

Myosin

The contractile protein composing thick filaments; contains actin-binding and ATP-binding sites, and pulls on actin during contraction.

Actin

The contractile protein in thin filaments that contains myosin-binding sites.

Tropomyosin

A regulatory protein in thin filaments that covers the myosin-binding sites on actin.

Troponin

A regulatory protein in thin filaments containing $\text{Ca}^{2+}$ binding sites that shifts tropomyosin when bound by calcium.

Motor Unit

A single motor neuron together with all the multiple muscle fibers it controls.

Neuromuscular Junction

A type of synapse representing the place of contact or interaction where a motor neuron innervates a muscle cell.

Motor End Plate

The heavily folded region of the sarcolemma equipped with acetylcholine (ACh) receptors.

Synaptic Knob

The terminal expansion of a motor neuron that houses numerous synaptic vesicles filled with acetylcholine (ACh).

Flexion

Movement in the anterior-posterior (sagittal) plane that decreases the angle between bones ("bend").

Extension

Movement in the anterior-posterior (sagittal) plane that increases the angle between bones ("straighten").

Hyperextension

Movement where bones are extended more than $180^\text{ degrees}$.

Abduction

Movement in the lateral-medial (coronal) plane away from the midline.

Adduction

Movement in the lateral-medial (coronal) plane toward the midline.

Circumduction

A cone-shaped movement of a body part.

Dorsiflexion

Foot movement characterized by "digging in heels."

Plantar Flexion

Foot movement characterized by "tiptoeing."

Opposition

Hand movement that brings the thumb toward the tips of the fingers.

Protraction

Forward movement of a body structure.

Retraction

Backward movement of a body structure.

Gomphosis

A fibrous joint described as a "bolt in a socket," exemplified by a tooth in its socket.

Suture

A fibrous joint characterized by "interlocking seams" between flat skull bones that ossifies later.

Syndesmosis

A fibrous joint consisting of a "binding sheet" between bones, such as between the radius and ulna or tibia and fibula.

Synchondrosis

A cartilaginous joint joined by hyaline ("glassy") cartilage.

Symphysis

A cartilaginous joint composed of pads of fibrocartilage, such as the pubic symphysis.

Articular Cartilage

Cartilage covering the bone surfaces in a synovial joint that functions as a shock absorber and protector.

Proprioceptors

Sensory nerves in a joint that report movement, stretch, and body position.

Nociceptors

Sensory nerve endings in a joint that detect painful stimuli.