Muscular System Notes

Muscle

• organs that are composed of specialized cells that use chemical energy stored in nutrients to contract

Functions of muscles:

• allows person to stand upright

• movement

• digestion and control of waste removal

• affect the rate of blood flow

• holds the skeleton together

• maintenance of normal body temperature

Cardiac muscle tissue

• striated

• involuntary contraction

• heart

Smooth muscle tissue

• involuntary contraction

• contracts slowly + doesn’t fatigue easily

• walls of hollow internal organs

Skeletal muscle tissue

• holds the skeleton together

• striated

• biceps / quads

• voluntary contraction

Action

movement accomplished when a muscle contracts

Origin

the immovable end of the muscle

Insertion

movable end of the muscle

How are skeletal muscles named?

• muscle size

• muscle location

• muscle action

• muscle shape

• # of muscle attachment

• muscle fiber direction

Epimysium

• connective tissue that surrounds the individual skeletal muscle

Perimysium

• layer that surrounds the fascicles

Endomysium

• layer that surrounds the muscle cell/fiber

Fascicles

• bundles of skeletal muscle fibers/cells

Muscle fiber/cell

• single cell that contracts in response to stimulation

• contains myofibrils

Sarcolemma

• cell membrane of a muscle fiber/cell

Sarcoplasmic reticulum

• network of membranous channels that surround each myofibril

• sarcoplasmic reticulum contains a high concentration on calcium ions → helps muscle contraction

Myofibril

• contractile fibers in muscle cells

Actin

• thin protein filament

• double stranded (helix)

Myosin

• think protein filament

• twisted protein strands (crossbridges)

Sarcomere

• functional unit of skeletal muscular contraction

Sliding Filament Model

• cross-bridges of myosin filaments form linkages with actin filament

• when skeletal muscle contracts, individual sarcomere shorten as actin and myosin filaments slide past each other

Muscle tone

• constant state of contraction

• helps to maintain posture

Isotonic contraction

• contraction where movements occur

Isometric contraction

• contraction in which no movement occurs

Muscle twitch

• muscular contraction

Slow twitch muscle fibers

• contraction of lower intensity

• fatigue resistant

• muscle size and strength unchanged

• swimming, long distance running

Fast twitch muscle fibers

• muscle exerts 75% of its maximum tension

• muscle is fatiguable

• muscle diameter increases

• weight-lifting, sprinting

Muscle fatigue

• loss of muscle’s ability to contract

Muscle cramp

• occurs when muscles involuntarily contract and can’t relax

Muscle hypertrophy

• muscle tissue growth that contributes to strength and increases metabolic capability

Muscle atrophy

• muscle fibers shorten over time →muscle weakens

Rigor mortis

• rigidity of death

• cells can’t produce metabolic reactions

  • ATP isn’t produced which is needed by the myofibrils to relax muscles