muscless again

Three muscle types

skeletal cardiac smooth

Skeletal muscle

voluntary striated multinucleated attached to bones

Cardiac muscle

involuntary striated branched heart only

Smooth muscle

involuntary nonstriated walls of organs/vessels

Functions of muscle

movement posture stabilize joints heat production

Properties of muscle

Excitability

respond to stimulus

Contractility

shorten forcibly

Extensibility

stretch

Elasticity

recoil

Connective coverings

Epimysium

around whole muscle

Perimysium

around fascicle

Endomysium

around fiber

Muscle organization

muscle fascicle fiber myofibril myofilaments

Origin

stable attachment

Insertion

movable attachment

Agonist

prime mover

Antagonist

opposes movement

Synergist

assists movement

Contractions

Isometric

tension no movement

Isotonic

movement occurs

Concentric

muscle shortens

Eccentric

muscle lengthens under load

Isokinetic

constant speed contraction

Sliding Filament Theory

Sarcomere

functional contractile unit

Z discs

borders of sarcomere

A band

length of myosin

I band

actin only area

H zone

myosin only center

M line

middle proteins

Thin filament

actin troponin tropomyosin

Thick filament

myosin heads form cross bridges

Neuromuscular junction

neuron meets muscle fiber

Acetylcholine neurotransmitter released at NMJ

Motor unit

one motor neuron + fibers it controls

All or none fiber contracts fully if threshold reached