Introduction to the Muscular System

Comprehensive flashcards covering the components, functions, tissue types, and organization of the human muscular system based on lecture notes.

Muscular System Composition

Consists of three types: skeletal muscle, cardiac muscle, and smooth muscle.

Muscle Weight Percentage

Muscles constitute approximately 40\text{-}50 \text{ %} of the total body weight.

Thermogenesis

The process by which muscular tissue contracts and produces heat as a by-product to maintain body temperature.

Skeletal Muscle

Striated, voluntary muscle attached to bones by tendons, crossing joints to produce whole-body or localized movement.

Cardiac Muscle

Striated, involuntary muscle found in the myocardium that pumps blood; it is self-exciting and highly fatigue resistant.

Smooth Muscle

Non-striated, involuntary muscle found in organ walls (visceral) and blood vessels, adapting sustained contractions like peristalsis.

Sphincters

Valve-like structures formed by ring-like bands of smooth muscle that control the movement of substances in and out of passages.

Myocytes

Also known as muscle fibers; these are the individual muscle cells.

Sarcolemma

The cell membrane of the myocyte.

Sarcoplasm

The cytoplasm of the myocyte.

Myofibrils

Long structures in the sarcoplasm whose arrangement of filaments produces striations.

Intercalated Discs

Structures that connect groups of cardiac muscles, allowing fibers to contract and relax together for pumping action.

Multiunit Smooth Muscle

Found in the iris of the eye and walls of blood vessels; it responds to neurotransmitters and hormones.

Visceral (Single Unit) Smooth Muscle

Found in hollow organ walls; muscle fibers stimulate each other to produce rhythmic motions like peristalsis.

Fascia

Connective tissue that surrounds individual skeletal muscles, separating them from others.

Tendon

A tough cord-like structure that extends from muscle to bone.

Aponeurosis

A tough sheet-like structure that connects muscle to muscle.

Fascicles

Arranged bundles of skeletal muscle fibers bound by connective tissues.

Epimysium

Irregular, dense connective tissue that surrounds individual skeletal muscles and binds fascicles together.

Perimysium

Connective tissue that divides the muscle into sections called fascicles.

Endomysium

Connective tissue made of collagen and reticular fibers that surrounds a muscle fiber and transfers force to tendons.

Mixed Nerve Composition

Nerves supplying muscles are 60 \text{ %} motor (Alpha and Gamma fibers) and 40 \text{ %} sensory.

Muscle Spindles

Stretch receptors within the muscle body that detect changes in length and relay information for proprioception.

Golgi Tendon Organ ($GTO$)

Also called Tendon Spindles; these work reflexively to regulate stiffness and cause the muscle to relax via autogenic inhibition.

Proprioception

The awareness of body position processed by the brain based on information from sensory receptors like muscle spindles.

Agonist (Prime Mover)

The chief muscle responsible for most of a movement through concentric contraction.

Synergist

A muscle that complements the action of the agonist by providing the same but weaker movement or by stabilizing joints.

Fixator

A muscle that stabilizes the origin of the agonist through isometric contraction to ensure efficient action.

Antagonist

A muscle that produces the movement opposite to the agonist.

Parallel Muscles

Muscles with fascicles arranged in the same direction as the long axis; they shorten and grow larger in diameter during contraction.

Convergent Muscles

Muscles where fascicles extend over a broad area and converge on a common attachment site, such as the pectoralis major.

Pennate Muscles

Muscles with fascicles forming a common angle with the tendon (feather-like); they produce less movement but more tension.

Multipennate Muscle

A pennate muscle where fibers pass to the tendon from all sides, or a series of bipennate muscles alongside each other, such as the deltoid.

Axial Division

Muscles that support and position the axial skeleton; they comprise 60 \text{ %} of skeletal muscles.

Appendicular Division

Muscles that support, move, and brace the limbs; they comprise 40 \text{ %} of skeletal muscles.

Bell's Palsy

Paralysis of facial muscles on an affected side caused by injury to the facial nerve ($VII$) or its branches.

Muscles of Mastication

The four muscles used for chewing: Masseter, Medial Pterygoid, Temporalis, and Lateral Pterygoid (mnemonic: Mom Makes Tasty Lasagna).

Belly

The fleshy part of a skeletal muscle.

Raphe

The interdigitation of the tendinous ends of flat muscles.

Platysma

A muscle of the neck and face that depresses the mandible and tenses the skin of the inferior face and neck to convey stress.