LS1130-muscle tissue notes

1) movement-contractions

2) posture+body position-tension

 3) support + shield- visceral organs +internal tissues respectively

4) guard entrances+exits- layers encircle digestive+urinary tract openings

5) maintain body temp.- contractions- energy-heat

6) store nutrient reserves-contractile proteins broken-amino acids-liver synthesises glucose/breakdown a.a- energy release

myosatellite cells: unfused cells, stem cells, repair damaged muscle

tendon definition: bundle of colllagen fibres*

tendon function: attach skeletal muscles to bones

-Where they touch the bone, collagen fibers* extend into bone matrix providing a firm attachment.

-Therfore, contraction of muscles pulls on the attached bones

Muscle contraction needs huge amounts of energy

An extensive vascular network delivers o2 + nutrients and carries away metabolic wastes generated by active skeletal muscles

Skeletal muscles contract only when the central nervous sytem stimulates them

1) enormous

2) multinucleate

genes in these nuclei control production of enzymes and structural proteins required for  contraction

distinctive features of size and multiple nuclei are related

During development: myoblasts fuse, forming individual multinucleate muscle fibers. Each nucleus in a fiber reflects the contribution of a single myoblast.

Some myoblasts do not fuse with developing fibers i.e. myosatellite cells

Sarcolemmma definition: plasma membrane of a muscle fiber

Sarcoplasm definiton: cytoplasm of the muscle fiber

-Sarcolemma has a transmembrane potential (tmp)

-A sudden change in tmp is the 1st step leading to a contraction

-All regions of muscle cell must contract simultaneously therefore contraction signal must spread quickly throughout.

-This signal is conducted through the transverse tublules (T tubules)

Transverse (T) Tubules definiton: narrow tubes  that are continous with the sarcolemma and extend deep into sarcoplasm

-filled with extracellular fluid

-form passageways through muscle fibre

-same properties as sarcolemma

-electrical impules called action potentials which trigger muscle fiber contraction are conducted by the sarcolemma and travel along the T tubules into the cell interior