epimysium(fascia) -sheath of connective tissue around a muscle.

perimysium-connective tissue surrounding bundles of skeletal musclefibers. Endomysium-is a wispy layer of areolar connective tissue that ensheaths each individual muscle fiber. 

Muscle fibers(cells)

Fasciculus- a small bundle of nerve or muscle fibers.

Sarcolemma-membranous sheath of a muscle fiber. 

external lamina

consists of hundreds to thousands of muscle cells, plus connective tissue wrappings, blood vessels and nerve fibers;

Covered externally by epimysium

Discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath;

Surrounded by a perimysium

Elongated multinucleate cell; ha a banded (striated) appearance;

Surrounded by the endomysium

Actin filament(thin)-actin, tropomyosin, tryoponin

Myosin(thick)

move the head of the myosin molecule;

Movement of the head causes the actin myofilaments to slide past the myosin myofilament. ADP is released from the myosin head.(3)

the entrance of Ca2+ ion into troponin(protein) located on the actin filament;

when Ca2+ exits, the bridges are uncoupled, relaxin the filaments which lengthen

an increase in the premeability of the sarcoplasmic reticulum to Ca2+ ions;

Ca2+ ions then diffuse from the sarcoplasmic reticulum into the sarcoplasm (2a)

troponin molecules in the actin myofilament;

the troponin molecules bound to G actin molecules are released causing tropomysoin molecules to move exposing active sites on the G actin molecule (3a)

Sequence of events in excitation contraction coupling: 

(1b) Action potential is propagated along

Sequence of events in excitation contraction coupling: 

(2b) Action potential triggers Ca2+ releases from 

Sequence of events in excitation contraction coupling:

(3b) Ca2+ binds to 

troponin;

which changes shape, removing the blocking action of tropomyosin;

Active site exposed

Sequence of events in excitation contraction coupling:

(4b) Contraction

myosin cross bridges alternately attach to actin and detach, pulling the actin filaments toward the center of the sacromere;

release of energy by ATP hydrolysis powers the cycling process

Sequence of events in excitation contraction coupling:

(5b) Removal of Ca2+ by

Sequence of events in excitation contraction coupling:

(6b) Tropomyosin blockage 

restored;

contraction ends and muscle fober relaxes

With the exception of the heart muscle, made up of cardiac muscle, Visceral muscle is composed almost exclusively of

smooth muscle; 

contracts without conscious control:

ex: internal organs such as the stomach, intestine, bladder and blood vessels

small, spindle-shaped cells;

each with one centrally located nucleus

No straitions are visible;

it does NOT contain thick and thin filaments 

Smooth 1:16;

Skeletal 1:2

non-contractile intermediate filaments that attach to 

dark-staining dense bodies that are distributed throughout the cell;

occasionally anchored to the sarcolemma;

Longitudinal layer(runs with the long axis of the organ);

Circular layer(runs around the circumference of the organ)

slow synchronized contraction; the whole sheet responds to a stimulus in unison;

ELECTRICAL COUPLING(of smooth muscles) BY GAP JUNCTIONS

pacemakers cells, and once excited, they act as "drummers" to set the contractile pace for the entire sheet of smooth muscle;

Some can depolarize spontaneously in the absence of stimuli (self-excitatory)

(1) Actin and myosin interct by the sliding filamen mechanism

(2)the final trigger or contractions is a rise in the intracellular calcium ion level

(3) the sliding process is energized by ATP

thick filaments;

skeletal muscle binds to the thin filament

small arterioles and other visceral organs used to maintain a moderate degree of contractions(w/out fatigue);

energy requirement is low, adequate ATP generated to suport contractile activity even in total absence of oxygen; anaerobic pathways

Ex.) when acetylcholine binds to receptors on smooth muscle cells in the bronchiles;

when norepinephine, released by a different type of autonomic fiber, binds to norepinephrine receptors on the same smooth muscle cells, the effect is;

norepinephrine binds to SM in the walls of most blood vessels, the effect is

the smooth muscle contracts strongly, narrowing the bronchioles;

inhibitory and the smooth muscle relaxes, dilating the air passageways;

stimulating and causes th smooth muscle cells to contract and constrict the vessel

Response to sretch:

Stress Relaxation Response