MuslcesGroup 4

Classification

Agonist: prime mover

Antagonist: reverses agonist

Synergist: prevents rotation

Fixator: stabilizes the origin of the prime

mover

Naming (LADSNOR!) Direction of the muscle fibers

Ex) transverse, rectus, oblique

Relative size of muscles Ex) major, minor

Location Number and location of origin Shape Action of the muscle

Ex) extensor, flexor

Origin and Insertion

Origin: immovable end

Insertion: movable end

Characteristics

Muscle cells are elongated

Contractions are due to the movement

of microfilaments

Structure (skeletal muscle)

Structure (cont.) From outermost to innermost

Muscle>Fascicles>Muscle fibers>Myofibril>Thick and thin filaments

Fascia>Epimysium>Perimysium>Endomysium

Tissue layers of a skeletal muscle

Fascia: covering the whole muscle

Epimysium: lies beneath the fascia

Perimysium: separates cells of fascicle

Endomysium: separates individual

muscle fibers

Fascicle Collection of muscle fibers Covered by blood vessels and axon of

motor neurons Each muscle fibers is separated by

endomysium It is surrounded by sarcolemma Contains nucleus and sarcoplasmic

reticulum Each muscle fibers is composed of

myofibril

Myofibril & Sarcomere

Sarcomere It is a repeating pattern formed by

striations

Sarcomere (cont.) Troponin: protein that works with

tropomyosin to block muscle contraction until calcium ions are present

Transverse tubule: set of membranous channels that contain extracellular fluid

Smooth muscle It is shorter than skeletal muscle, and

has single centrally located nuclei

It lacks troponin

It alternates between a state of relaxation and contraction

Cardiac muscle Composed of striated cells, containing a

single nucleus

It has a well developed sarcoplasmic reticulum

Its transverse tubule is larger than skeletal muscle’s

Contraction Acetylcholine(ACh) is the

neurotransmitter that contracts skeletal muscles

ACh binds with receptors on the motor endplate, which causes muscle impulse

Calcium ions diffuse from sarcoplasmic reticulum to sarcoplasm and binds to troponin

Contraction (cont.) Tropomyosin moves, which allows actin

and myosin to link Actin is pulled to the center of the

sarcomere, which allows muscle fibers to shorten

Threshold

Respiration

Anaerobic breaks down glucose

and releases ATP

Aerobic requires oxygen to

produce ATP

Oxygen debt

When cellular respiration is not

able to sustain the muscle, lactic

acid diffuses into the blood stream

This creates an oxygen debt, that

must be repaid later

Muscle fatigue

When a muscle loses its ability to

contract

Most likely occurs from

accumulation of lactic acid

Types of contraction