Muscle Physiology

Functions of skeletal muscle

Body movement, maintaining posture, guarding body openings, maintaining body temp., storing nutrients

Epimysium

A fibrous connective tissue layer surrounding the muscle

Fascia

The epimysium is connected/covered by this structure

Fascicles

Divided bundles of muscle fibers

Perimysium

Surrounds each fascicle → blood vessel and nerve supply

Endomysium

ECM of muscle tissue → surrounds each individual muscle fiber

Tendons & Aponeuroses

Areas where connective tissue layers merge at the ends of muscles → connect muscle to bone

Sartorius muscle

Parallel fascicle arrangement

Pectoralis major muscle

Convergent fascicle arrangement

Flexor pollicis longus muscle

Unipennate fascicle arrangement

Rectus femoris muscle

Bipennate fascicle arrangement

Deltoid muscle

Multipennate fascicle arrangement

Orbicularis oculi muscle

Circular fascicle arrangement

Supinator muscle

Spiral fascicle arrangement

Biceps brachii muscle

Fusiform fascicle arrangement

Origin

Remains stable during muscle contraction

Insertion

Moves when the muscle contracts

Action

Movement created when a muscle contracts (ex. flexion of arm)

Agonist

Generate the main force for a movement - prime movement (ex. brachialis)

Synergist

Assist the prime mover by adding extra force or stabilizing joints (ex. biceps brachii)

Antagonist

Oppose the action of the prime mover, providing balance and control (ex. triceps brachii)

Fixator

Stabilize the origin of the prime mover or other body parts to allow efficient movement; no movement

Bones serve as ______ and joints serve as ________

Levers; fulcrums

Myoblasts

Fusion of multiple embryonic cells

Satellite cells

Unfused cells on the periphery of muscle fibers (aid in muscle repair)

Sarcolemma

Plasma membrane

Sarcoplasmic reticulum

Endoplasmic reticulum - wraps myofibrils (stores calcium)

Sarcoplasm

Cytoplasm

Myofibrils

Cylindrical structures that are made up of the proteins involved in muscle contraction

T-tubules

Invaginations of the sarcolemma - dips into the muscle

Terminal cisternae

Enlarged regions of SR around t-tubule

Triad

T-tubule + two terminal cisternae

Contractile proteins

Actin and myosin

Regulatory proteins

Troponin and tropomyosin

Structural proteins

Titin + others

Sarcomeres

The organized contractile units of muscle

Thick filament

Made up of myosin proteins bound together

Thin filament

Mostly actin and regulatory proteins tropomyosin and troponin

Elastic filaments

Composed of a protein called titin - runs through the core of the thick filaments

Sliding-filament mechanism

Where thin filaments slide past the thick filaments