Martini et al. Chapter 9

Study of muscular tissue(mus = mouse, -cle = little)

What are the Muscular Tissues like?Excitability (irritability)ContractilityExtensibilityElasticity

Skeletal* muscle tissue striated & voluntary

studied as the muscular systemCardiac muscle tissue striated & autorhythmicSmooth muscle tissue nonstriated & involuntary

Motion body parts (or substances in body)Stability body parts (or substances in body)Heat production basal metabolic rate & shivering

Skeletal muscles are organsMuscle cells are called “fibers”Nervous tissue -> sensory & motor neuronsBlood vessels (lined by epithelia)Connective tissues wrappers

Each cell/fiber is covered by C.T. endomysium bundles of cells are “fascicles”Fascicles are surrounded by perimysiumWhole muscles are held together by epimysiumTendons or aponeuroses extend from muscles

direct or indirect attachments usu. to boneDeep fascia fills in between musclesSuperficial fascia fills in between muscle & skin

Organ muscleTissue fascicleCell myofiberOrganelle myofibrilChemical myofilament(s)

myosin & actin

Muscle cells are “excited” by nervous tissueA motor neuron stimulates multiple cells Small units are for precise movements Large units are for powerful movements

Muscles have many dif. sized motor unitsPoint of excitement = neuromuscular junction

Distal tips of motor neuron = axon terminalsneurotransmitter (ACh) crosses synaptic cleft

acetylcholine binds to motor end plates of cell

A very long slender cylindrical cellCell membrane = sarcolemmaCytoplasm = sarcoplasmcontaining lots of mitochondria & glycogenmultiple* peripheral nucleimyofibrils: contractile organellesstriated & made of sarcomeressarcoplasmic reticulum: SER filled w/Catransverse tubules: connect sl to sr

Sarcomere: a section of a myofibrilStriations = pattern of myofilaments

thick “myosin” & thin “actin”Z discsA & I bands

H zoneM line

Calcium “frees-up” the myosin headsthey repeatedly “pull actin” toward M-line

Z discs also move toward M-lineI bands & H zone disappearA band length remains constantLack of Ca = relaxed muscle

antagonist can extend sarcomeres

Red/Slow twitch (posture)aerobic: needs oxygen & glucose to make ATPlots of blood, myoglobin & mitochondria

White/Fast Twitch (power)anaerobic: works briefly from stored suppliesless blood, glycogen inclusions

Intermediate Fast Twitch (lower limbs)All muscle have combination of types

HeartShorter branched cells

branched myofibrils = harder to see striations

Intercalated discsLong refractory period, no tetanus

No parallel myofilamentsintermediate filaments maintain cell shape

Single-unit vs. multiunit typessheet all contracts due to gap junctions (stomach)groups of cells are innervated (arrector pili muscles)

Muscle changes throughout lifeDevelopmentDiseases