Chapter 9

Summary of Muscle Tissue • Muscle _____ = Muscle Cell • Myo, ___, and sarco - prefixes for muscle • Nearly half of body's ____ • Born with total number of muscle _____ you will ever have, but the ______ changes • Transforms chemical energy (ATP) to directed mechanical energy → _______ force • Well ____________ w/ many mitochondria

fiber; mys; mass; cells; width; exerts; vascularized

III. Classifications C. Smooth Muscle 1. Walls of ______ organs 2. Involuntary 3. __ striations 4. Spindle-shaped 5. Uninucleate 6. ____, sustained contractions that do not ____ NOTE: We are only discussing skeletal muscle in this chapter. From here forward EVERYTHING is specific to skeletal muscle!

hollow; no; slow; tire

V. Microanatomy B. Myofibrils 1. Sarcomeres - functional unit • Formed by bundles of ____________ (contractile proteins) • Bordered on each end by _-disc (Z-line) • Alternating ____ (thick) and light (____) bands • Arranged end to end giving ________ appearance

myoglobin; Z; dark; thin; striated

II. Functions A. Movement 1. Of body parts - ________ 2. Pumping _____ - cardiac 3. Peristalsis - ______ B. Maintenance of _______ C. Stabilization of joints - via muscle ____ D. Generation of ____ - shivering E. Additional Functions • Protects organs, forms ______, controls pupil size, "causes goosebumps"

skeletal; blood; smooth; posture; tone; heat; valves

VIII. Contraction of Skeletal Muscle C. Graded Muscle Response 3. Changes in Stimulus Strength a. Multiple Motor Unit ________ -recruiting ________motor units → increased force b. Subthreshold Stimuli - voltage too ___ to stimulate a motor unit c. _________ Stimulus - voltage needed to produce muscle contraction d. Maximal Stimulus - voltage at which ___ motor units have been recruited → maximum force

summation; multiple; low; threshold; all

V. Microanatomy; B. Myofibrils; 1. Sarcomeres f. Memory Tricks • A band is dark band and I band is light band (note 2nd letter) • H zone is only thick filaments and "H" is a thick letter • Z disc zig-zags & borders sarcomere, S is backwards Z • M line is myomesin

...

IX. Energy for Contraction B. Energy for contraction 3. Aerobic Pathway • Yields __ ATP/glucose • Slow process, but makes more ATP/glucose than lactic acid ____________ (e.g., useful during marathon) • Mitochondria use O2 stored in _________ • Fuels: • Simple ______ (glucose, fructose, ________, lactose, pyruvate) • Acetyl-___ (from fatty acid tails) • Glycogen (stored in __________)

32; fermentation; myoglobin; sugars; sucrose; CoA; glycosomes

VII. Physiology of Muscle Fibers E. Excitation-Contraction Coupling • Events connecting the __ to sliding filament model • Takes place between AP __________ and beginning of mechanical activity 1. Transmission along _-tubules - AP travels across sarcolemma & ____ T-tubules → shape change in voltage-__________ proteins in SR → Ca2+ release 2. Ca2+ binds to ________ (2 Ca2+ ions / troponin) causing troponin to roll

AP; initiation; T; down; sensitive; troponin

VII. Physiology of Muscle Fibers B. Definitions 1. Somatic motor neurons - nerve cells __________ skeletal muscle fibers, located in CNS 2. ______________ junction - _____ of neurons enter skeletal muscle and branch, forming the NMJs with each muscle fiber at the motor end plate

activating; neuromuscular; axons

I. Characteristics A. _________ (ability to receive stimulus) / Irritability (ability to _______ to a stimulus) / Responsiveness B. Contractility - generates force via ___________ the functional unit of muscle, the _________ C. ____________ - ability to stretch beyond original length when relaxed D. Elasticity - can return to original shape after ___________

excitability; respond; shortening; sarcomere; contractibility; stretching

V. Microanatomy C. Sarcoplasmic Reticulum (SR) 1. _________, specialized smooth ER 2. Wraps around each _________, connects at H zones 3. Pairs of terminal cisterns form perpendicular _____ channels 4. Stores and releases ______ (Sarc) a. Releases Ca2+ when stimulated by nerve _______ b. When stimulus ends, active transport pumps _______ Ca2+

extensive; myofibril; cross; calcium; impulse; reclaim

VII. Physiology of Muscle Fibers G. Summary 1. Phase 1 - Motor neuron stimulates muscle ______ 2. Phase 2 - Excitation-Contraction Coupling 3. Phase 3 - ________ Filament Model

fibers; sliding

VIII. Contraction of Skeletal Muscle D. Isotonic & Isometric Contractions 2.. Isometric (= same length) a. Force that doesn't ____ load b. ________ lengthens nor shortens c. E.g., pushing against a wall, trying to lift something too heavy

move; neither

VIII. Contraction of Skeletal Muscle D. Isotonic & Isometric Contractions 1. Isotonic (=____ tension) a. Concentric contractions - muscles contract, sarcomeres ______, fibers shorten & muscles do work b. _________ contractions - muscles contract and generate force by _________; involves opposing muscle groups • E.g., ______is concentric but triceps are eccentric

same; shorten; eccentric; lengthening; bicep

V. Microanatomy B. Myofibrils 2. Myofilaments d. Dystrophin • Links actin to integral proteins of __________ which in turn are anchored to ___ • Muscular dystrophy - genetic disorder affecting __________

sarcolemma; ECM; dystrophin

V. Microanatomy A. Specialized Cell Structures 1. __________ - plasma membrane specialized for ______________ 2. Sarcoplasm - cytoplasm specialized b/c contains __________ and myoglobin 3. Glycosome - inclusions/granules of stored _______ to provide readily available source of _______ 4. _________ - inclusion holding O2 (similar to hemoglobin)

sarcolemma; depolarization; glycosomes; glycogen; glucose; myoglobin

VII. Physiology of Muscle Fibers A. To contract: 1. Muscles must be __________ by a nerve impulse 2. Muscle fiber must generate and ________ its own AP along sarcolemma and T tubules 3. AP → _______ in intracellular Ca2+ → sliding filament events → contraction

stimulated; propagate; increase

VII. Physiology of Muscle Fibers B. Definitions 3. ________ Cleft - the _____ between the end of the axon (axon terminal) and the muscle fiber; filled with ECM and lots of _____________ 4. Synaptic Vesicles - vesicles in axon terminal containing _________________ (acetylcholine, ACh)

synpatic; space; glycoproteins; neurotransmitter

III. Classifications A. Skeletal Muscle 1. 40% of body mass so helps maintain body ____ 2. ______ attached to bones and skin 3. __________ (i.e., conscious control) 4. Contract _______; tire easily; powerful 5. Require nervous system ___________ 6. Elongated cells up to __" long 7. _________ (striped) 8. Multi-nucleate (fusion of cells while ______)

temp; organs; rapidly; stimulation; 15; striated; embryo

V. Microanatomy B. Myofibrils 1. Sarcomeres - functional unit d. _ line • Vertical _________ of H zone created by ________ • Myomesin - accessory ________ linking thick filaments in the middle

M; bisection; myomesin; protein

V. Microanatomy B. Myofibrils 1. Sarcomeres - functional unit e. _ disc (Z line) • ________ zig-zagging bisection of I band • ______ of sarcomere • _______ thin filaments

Z; vertical; border; anchors

VIII. Contraction of Skeletal Muscle A. Principles of Muscle Mechanics 1. Muscle tension - force exerted by __________ muscle on an object 2. ____- force exerted by weight of object on contracting muscle • Muscle contraction doesn't always move a load, e.g., _________ 3. _________- muscle exerts force but load is not moved • E.g., trying to move something too heavy 4. Isotonic - muscle exerts force and load is _____

contracting; load; shivering; isometric; moved

IX. Energy for Contraction C. Muscle Fiber Type • Fast vs slow fibers refer to ______activity • Classified by: 1. Speed of __________ - how quickly ATPase hydrolyzes ATP on myosin heads 2. Pathway for forming ATP - whether _____ is using O2 or not a. Slow (IIA) & Fast (I) Oxidative Fibers - ________ pathway, lots of myoglobin & glycosomes (= dark meat) b. Fast ________ Fibers (IIx) - anaerobic pathway, less myoglobin & glycosomes, better CP use (= white meat)

contraction; fiber; aerobic; glycolytic;

VIII. Contraction of Skeletal Muscle B. The Motor Unit 1. A motor neuron and all the muscle fibers it ________ 2. Number of muscle fibers / motor unit _______ • _____ movements have many fibers / unit • Fine movements have ___ fibers / unit 3. Muscle fibers of the same motor unit are _____ out so that stimulation of a single motor unit results in ____ contraction of entire muscle

controls; varies; gross; few; spread; weak

V. Microanatomy B. Myofibrils 1. Sarcomeres - functional unit a. A band (____band) • Where contractile proteins _______ (slight overlap when relaxed); overlap → dark color • Middle of A band is lighter b/c only one ________

dark; overlap; filament

IX. Energy for Contraction B. Energy for contraction (1, 2, and 3 happen in sequential order) 1. ______ Phosphorylation - a phosphate group is transferred directly to ADP from creatine phosphate (CP) • Muscles have 2-3x more __ stored than ATP • ATP + CP stores last __ sec CP + ADP + creatine kinase (enzyme) → 1 ATP + Creatinine

direct; CP; 15

IV. Gross Anatomy C. Attachments 1. ______ (fleshy)—epimysium fused to periosteum of ____ or perichondrium of _________ a. No ligaments b. Large and ____ common c. E.g., ___________, deltoid, __________

direct; bone; cartilage; less; intercostal; temporalis

VI. Sliding Filament Model B. Steps of Muscle Contraction 4. Power Stroke a. Myosin heads ____ and pull thin filaments towards M line b. Myosin stays attached until myosin _____ another ATP c. Myosin heads continue to bind and _______ actin like a ratchet causing contraction (Z disc moves toward M line) d. Contraction achieved by increasing _______ —filament length stays the same. e. Myofibrils _______→ muscle fiber shortens → pulls on __________ → pulls on perimysium → pulls on __________

flex; binds; release; overlap; shorten; endomysium; epimysium

IX. Energy for Contraction A. ATP supplies energy for 1. Cross bridge _________ & detachment 2. Ca2+ pump in __ 3. Muscles have 5-6 sec of stored ___ so must make more CP + ___ + creatine kinase (enzyme) → 1 ATP + Creatinine

formation; SR; ATP; ATP

VII. Physiology of Muscle Fibers D. Action Potential (AP) vs End Plate Potential (EPP) 1. AP uses Na+/K+ _____ • → change in _______ which opens channels allowing more Na+ to enter • → change in voltage which opens more Na+ ________ • AP is propagated down _________ 2. EPP uses ligand gates (for ACh) to ____ Na+ channels • Can't be propagated b/c ACh only in ________cleft 3. AP from _____→ EPP on sarcolemma at synaptic cleft → AP on ____________

gates; voltage; channels; membrane; open; synaptic; gates; sarcolemma

III. Classifications B. Cardiac Muscle 1. Only in _____ 2. ___________ control 3. Striated 4. Uninucleate 5. Cells shorter and _____ than skeletal 6. Branching - branches connected by ____________ discs (desmosomes & gap junctions that ↑ cell communication) 7. Lots of ____________

heart; involuntary; wider; intercalated; mitochondria

VIII. Contraction of Skeletal Muscle C. Graded Muscle Response 2. Changes in Stimulus Frequency • Strength of stimulus stays the same but frequency __________ a. Wave / Temporal Summation - muscle twitch gets stronger with each twitch b/c muscle hasn't fully _______ from previous twitch • Like 3 steps forward, _ steps back, 3 steps forward b. Unfused / Incomplete _______ - frequency of stimuli so fast that it results in a __________ twitch c. Fused / Complete Tetanus - frequency of stimulus allows no time for relaxation so yields ___ muscle tension; less common (like super strength because of adrenaline)

increases; relaxed; 2; tetanus; quivering; max

IV. Gross Anatomy C. Attachments 2. ________—CT wrappings extend beyond muscle for attachment; smaller, more ______, more durable a. Tendon - ____-like dense regular CT attaching muscle to ____ b. ___________- sheet-like dense regular CT attaching muscle to other __ (i.e., cartilage or another muscle) c. Fascia - older term referring to the CT ________ of muscle

indirect; common; rope; bone; aponeurosis; CT; covering

V. Microanatomy D. T Tubules 1. _____________ of sarcolemma (inside continuous w/ECM) 2. Located at A-I band junction 3. Between ends of _________ SR pieces 4. Associate w/ paired ________ cisterns to form triads encircling each sarcomere 5. Allows ______ potential (AP—depolarization of a membrane) to enter cell and cause all sarcomeres to ________ at the same time

invaginations; adjacent; terminal; action; contract

V. Microanatomy B. Myofibrils 1. Sarcomeres - functional unit b. I band (_____ band) • Only thin filaments _______

light; present

IV. Gross Anatomy • Each skeletal muscle is an organ made of ______, CT, adipose, _________ (blood vessels), & nerves A. Nerve & Blood Supply 1. Each muscle served by 1 _______, 1 nerve, and greater than/equal to 1 _____ 2. Enter/exit near central part and branch through connective tissue _______ 3. Every skeletal muscle fiber supplied by nerve ending that controls its ________ 4. Huge nutrient and oxygen need → LOTS of ______

muscle; epithelial; artery; vein; sheaths; activity; waste

V. Microanatomy B. Myofibrils • Organelles w/in ______ fibers, parallel to each other __________; each muscle fiber contains 100's of __________ and each myofibril made of 100's of sarcomeres

muscle; lengthwise; myofibrils

IV. Gross Anatomy B. Connective tissue sheaths • Reinforce whole ______ • Electrical insulation → ________control • ________ to internal 1. _________: outermost; dense irregular CT surrounding entire muscle; often extends beyond muscle to form tendon 2. Perimysium: middle; dense irregular CT surrounding fascicles (groups of muscle fibers) 3. __________: innermost; wispy areolar CT surrounding each muscle fiber

muscle; precise; epimysium; endomysium

V. Microanatomy B. Myofibrils 2. Myofilaments a. Thick Filaments i. 300-400 ______filaments bundled together ii. Each filament made of 2 _____ & 4 light polypeptide chains • Tails are 2 interwoven heavy _____ • Heads are 2 smaller light chains w/ binding sites for _____, ATP and ATPase enzymes; heads point out and toward _ disc at rest • Flexible hinge/neck region between ____ and tail

myosin; heavy; chains; actin; Z; head

VII. Physiology of Muscle Fibers C. Events at Neuromuscular Junction (NMJ) 5. Na+ channels ____- Na+ floods muscle cell (ACh receptors are also Na+ channels) 6. Muscle AP - Na+ generates __ 7. Ach is released from its receptors into the _____ 8. ACh is broken down - muscle fiber _________ acetylcholinesterase (ACh-ase) which splits ACh into 2 pieces 9. Choline is _________ - returned to axon terminal to be used again (acetic acid diffuses—it's easy to make) 10.ACh ___________

open; AP; cleft; releases; recycled; regenerated

VI. Sliding Filament Model A. Summary: during contraction thin filaments slide past thick filaments increasing the _______ of actin and myosin B. Steps of Muscle Contraction 1. Myosin heads bind to ___ 2. ATP hydrolyzed by ______ (energy used to move myosin head) 3. Cross Bridge Formation - attachment of myosin heads to _____

overlap; ATP; ATPase; actin

VII. Physiology of Muscle Fibers C. Events at Neuromuscular Junction (NMJ) 1. Action _________ Arrives - when AP reaches axon terminal it opens voltage gated Ca2+ channels and Ca2+ rushes into terminal 2. ___________ - Ca2+ causes synaptic vesicles to fuse with axon's plasma membrane and exocytose ACh 3. Release of ACh - ACh enters synaptic cleft and diffuses across to sarcolemma 4. ACh binds to ACh receptors on __________

potential; exocytosis; sarcolemma

IX. Energy for Contraction B. Energy for contraction (a, b, and c happen in sequential order) 2. Anaerobic Pathway / Glycolysis • Glucose split into 2 molecules of _______ acid (pyruvate) which makes _ ATP • Pyruvate then converted into ______acid (lactate) • Less efficient use of glucose than _______ pathways but faster ATP production (e.g., useful when sprinting) • Lasts __-40 sec (+ATP + CP = about 1 minute)

pyruvate; 2; lactic; aerobic; 30

VII. Physiology of Muscle Fibers E. Generation of AP • Sarcolemma is polarized at ____ - inside muscle fiber is negative relative to outside 1. EPP - the NMJ is the ___ place depolarization occurs • Receptors bind ACh which ____ ligand-gated channels • Na+ rushes into muscle cell → inside more __________ than out 2. Generation and Propagation • Depolarization at NMJ changes the membrane _________ → adjacent voltage-gated channels ____ → AP on sarcolemma 3. Repolarization • _____ Na+ channels (happens automatically when ACh is removed from receptors) and open K+ channels

rest; 1st; open; positive; potential; open; close

V. Microanatomy B. Myofibrils 1. Sarcomeres - functional unit c. _ zone • Middle of A band, lighter b/c only _____ filament • Lighter color disappears in fully contracted _________

thick; sarcomere

VIII. Contraction of Skeletal Muscle E. Muscle Tone a. Low level contractility in muscle keeping tendons _____ and muscles ready to respond b. Stabilizes _______ c. No movement F. Relaxation a. ACh ______ receptors b. Repolarize membrane c. Return Na+ and K+ using ____ d. Ca2+ returns to SR e. ATP ______cross bridges

tight; joints; leaves; pump; breaks

V. Microanatomy B. Myofibrils 2. Myofilaments c. Elastic Filaments i. Made from polymer of _____ ii. Runs through core of thick filaments anchoring them to _ disc and _ line

titin; Z; M

V. Microanatomy B. Myofibrils 2. Myofilaments b. Thin Filaments i. 2 polymers of actin _______ together ii. 2 regulatory ________ 1. Troponin - triangular, Ca-binding sites, moves tropomyosin away from myosin _______ sites 2. Tropomyosin - long fibrous protein wrapping around actin polymer and _________ myosin binding sites iii. Memory trick: Add "h" to "actin" → "acthin"

twisting; proteins; binding; covering

VII. Physiology of Muscle Fibers F. Excitation-Contraction Coupling 3. Myosin binding site __________ - rolling troponin takes __________ with it, exposing myosin binding sites on actin 4. Myosin binds to _____ - events of sliding filament model now occur as long as sufficient Ca2+ and ATP available • Nervous stimulation ____→ protein channels in SR revert to normal and close (no more Ca2+ released) → SR pumps _______ Ca2+ → Ca2+ leaves troponin which returns to its original _____ → tropomyosin covers binding sites → filaments stop sliding = stop ___________

uncovered; tropomyosin; actin; ends; reclaim; shape; contracting

VIII. Contraction of Skeletal Muscle C. Graded Muscle Response 1. Overview a. Graded = ________ b. Muscle twitch - motor unit response to ______ AP (not typical) c. Graded response achieved by either: i. Changing frequency of stimulating the ____ motor unit(s) ii. Changing ________ of stimulation (i.e., changing the number of motor units recruited)

variable; single; same; strength