Chapter 10

Chapter 10 Muscle Tissue (Mostly Skeletal Muscle)

Muscle tissue: skeletal cardiac smooth bones heart “hollow organs”

Muscle tissue: skeletal muscle functions move skeleton maintain balance/posture support soft tissues guard entrances/exits maintain body temp store nutrients

Muscle tissue: muscle contains muscle cells connective tissue nerves (axons) blood vessels

muscle (and connective tissue) surrounded byepimysium subdivided into fascicles surrounded byperimysium fascicles contain myofibers surrounded byendomysium

fig. 10-1

three connective tissues: epimysium perimysium endomysiyum • blend into each other, • and the end of the muscle • blend into the tendon

three connective tissues: contain: blood vessels and nerves that supply the muscle

skeletal muscle voluntary muscle although many are also controlled subconsciously too

skeletal muscle formation and structure

fig. 10-2 myoblast fuse forming large multinucleated cells (myofibers)

myofibers • cell membrane sarcolemma • cytoplasm sarcoplasm • filaments organized into myofibrils • T-tubules (transverse) • -extensions of the sarcolemma • to the interior of the cell • -surround myofibrils

fig. 10-3

sarcoplasmic reticulum (SR) • modified sER • (smooth endoplasmic reticulum) • also surrounds myofibrils • expanded ends called • terminal cisternae • gather and store Ca2+

fig. 10-3 myofibril T tc tc

myofibers: contain myofibrils myofibrils: contain myofilaments thin filaments thick filaments actin myosin

Thin filaments: G actin (globular) F actin (filamentous) • Other components: • Troponin (covers active site) • Tropomyosin • Nebulin

Thin filaments: fig. 10-7b

fig. 10-7a, b

Thick filaments: myosin head tail

Thick filaments: binds to active site on thin filaments fig. 10-7d

fig. 10-7c, d

to here Monday 2/5 lec # 13

fig. 10-6 muscle fascicles myofibers myofibrils thick & thin filaments

fig. 10-4 A band A band I band myosin I band A band Z line Z line actin actin actin actin

from Z line to Z line sarcomere where myosin is A band center of A band M line muscle structure terms where actin isn’t center of A band H zone where myosin isn’t Z line in center I band actin and myosin overlap

T tc tc triad titin

fig. 10-5

when muscle contracts: A band same I band shrinks H zone shrinks Z lines closer overlap increases sliding filament theory

fig. 10-8

The contraction of skeletal m. background physics: tension pull towards compression push away overcome resistance • muscle cells only pull (produce tension) • generate force by getting shorter

OVERVIEW motorneuron AP release nt AP in myofiber release Ca2+ thick/thin interact contraction tension fig. 10-9

control of skeletal muscle motorneurons in CNS synapse with myofiber • neuromuscular junction • aka myoneural junction • aka motor end plate (mep) each myofiber is innervated by a myelinated motorneuron fig. 10-9

neuromuscular junction (nmj) axon terminal with ACh synaptic cleft • postsynaptic membrane • (aka sarcolemma) junctional folds AChR and AChE

fig. 10-10

neuronal AP myofiber AP contraction ? Excitation-Contraction Coupling

myofiber AP (depolarization of sarcolemma) depolarization of the T-tubules • release of Ca2+ • from sacroplasmic reticulum

release of Ca2+ • from sacroplasmic reticulum Ca2+ interacts with troponin (on thin filaments) exposing active site (myosin will now bind)

remember structure: fig. 10-7b fig. 10-5

myosin heads fig. 10-11

Now we are ready for the contraction cycle (almost) fig. 10-7

fig. 10-12

AP AP Ca2+ 2 1 expose active site form cross-bridges fig. 10-12

“POWER STROKE” 3 4 cross bridge detachment re”energize” the myosin fig. 10-12

5 re energize myosin fig. 10-12

As long as Ca2+ is present… power stroke re-energize power stroke re-energize sarcomere shortens ~1%/cycle

tug-of-war energize reach grab pull cross-bridge power stroke release release

tug-of-war repeat cycle reach grab pull release what if everybody released at the same time?

Z line Z line actin myosin sarcomere

Chapter 10

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