SKELETAL MUSCLES
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SKELETAL MUSCLE TISSUE
NERVOUS TISSUE
BLOOD
DENSE CONNECTIVE TISSUE
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TECHNICALLY, SKELETAL MUSCLE IS NOT AN
INDIVIDUAL CELL BUT A FIBER FORMED BY
THE FUSION OF MANY MYOBLASTS
(EMBRYONIC MUSCLE CELLS).
MULTINUCLEATED
FIBER IS OFTEN CALLED A ‘CELL’
LENGTH: COULD BE MANY CENTIMETERS
LONG: MUCH OF LENGTH OF THE SPECIFIC
MUSCLE IT IS FOUND IN
DIAMETER: 50 µm
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DENSE CONNECTIVE TISSUE
COVERS MUSCLE; A GROUP OF FIBERS AND
INDIVIDUAL FIBERS
◦ EPIMYSIUM: MUSCLE
◦ PERIMYSIUM: FASCICLE
◦ ENDOMYSIUM: INDIVIDUAL FIBER
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IF IT EXTENDS BEYOND THE MUSCLE FIBERS=
TENDON
APONEUROSIS: FIBROUS SHEETS OF FASCIA THAT
CONNECTS TO BONE OR THE FASCIA OF
ANOTHER MUSCLE (ABDOMINAL MUSCLES)
ALLOWS INDIVIDUAL MOVEMENT, CARRIES
BLOOD VESSELS AND NERVES
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DEEP FASCIA
◦ AROUND MUSCLE
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SUBCUTANEOUS FASCIA
◦ FORMS SUBCUTANEOUS LAYER
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SUBSEROUS FASCIA
◦ CONNECTIVE TISSUE LAYERCOVERING THE ORGANS
OF AND LINING THE CAVITIES
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CELL MEMBRANE: SARCOLEMMA
CYTOPLASM: SARCOPLASM
PARTS:
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I BAND
Z LINE
A BAND
M LINE
MYOFIBRILS:
◦ MYOSIN
◦ ACTIN
http://www.comprehensivephysiology.com/WileyCDA/CompPhysArticle/refId-c110050.html
TROPONIN
TROPOMYOSIN
http://jerrybruton.files.wordpress.com/2011/03/parts_of_a_muscle.jpg
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TITIN
SARCOPLASMIC RETICULUM
TRANSVERSE (T) TUBULES
CISTERNAE
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http://www.youtube.com/watch?v=EdHzKYD
xrKc
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ACTIN AND MYOSIN FILAMENTS SLIDE ON
EACH OTHER SHORTENING THE SARCOMERE
AND PULLING ON THE MUSCLES’
ATTACHMENTS
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MOTOR NEURON
◦ CARRY IMPULSE TO EFFECTOR (LIKE MUSCLE)
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SYNAPSE
◦ FUNCTIONAL CONNECTION TO MUSCLE
◦ GAP/SPACE
◦ RELEASES NUEROTRANSMITTERS TO CROSS GAP
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MOTOR END PLATE
◦ SPECIALIZED SECTION OF MUSCLE FIBER MEMBRANE
◦ USUALLY ONE PER MUSCLE FIBER
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MOTOR UNIT
◦ ONE MOTOR NEURON AND ALL THE MUSCLE FIBERS IT
CONNECTS TO
◦ ALL WORK TOGETHER
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ACETYLCHOLINE (Ach)- NEUROTRANSMITTER
FOR MUSCLE CONTRACTION
RELEASED AS NEUROTRANSMITTER FOR
SKELETAL MUSCLE CONTRACTION
DIFFUSES ACROSS SYNAPTIC CLEFT BINDS TO
RECEPTOR
STIMULATES MUSCLE CONTRACTION
SENDS IMPULSE ALONG MUSCLE
http://emedicine.medscape.com/article/1171206-media
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NO CONTRACTION/NO IMPULSE
TROPONIN-TROPOMYOSIN COMPLEX BLOCKS
ACTIVE SITE OF ACTIN
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http://www.blackwellpublishing.com/matthe
ws/myosin.html
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http://www.blackwellpublishing.com/matthe
ws/myosin.html
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IMPULSE TRAVELS ALONG MOTOR NEURON
REACHES AXON TERMINAL CAUSING
NEUROTRANSMITTERS TO RELEASE ACh
Ach BINDS TO RECEPTOR ON MOTOR END
PLATE
DEPOLARIZES MUSCLE FIBER MEMBRANE
MUSCLE IMPULSE/ACTION POTENTIAL MOVES
ALONG SARCOLEMMA IN ALL DIRECTIONS TO
T-TUBULES
CAUSING CISTERNAE OF SARCOPLASMIC
RETICULUM TO RELEASE CALCIUM
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CISTERNAE HOLDS A HIGHER
CONCENTRATION OF CALCIUM THAN
CYTOPLASM (?)
◦ CALCIUM PUMP IN MEMBRANE OF SR
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CALCIUM BINDS TO TROPONIN (WHAT
HAPPENS WHEN SOMETHING FORMS A BOND?)
SHAPE CHANGES (?)
EXPOSES ACTIVE SITES OF ACTIN AND
MYOSIN CROSSBRIDGES CAN BIND TO ACTIVE
SITE
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MYOSIN CROSSBRIDGE BINDS WITH ACTIN
AND BENDS PULLING ACTIN FIBER CLOSER
THEN IT RELEASES, STRAIGHTENS (USING ATP)
AND CAN BIND WITH ANOTHER ACTIVE SITE
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USING ATPase THE CROSSBRIDGES USE ATP
TO GET INTO A COCKED POSITION TO BIND
TO ACTIN AND PULL IT CLOSER SHORTENING
THE SARCOMERE AND THUS THE MUSCLE
USING ANOTHER ATP THE CROSSBRIDGE
RELEASES FROM ACTIN AND THEN GETTING
INTO THE COCKED POSITION ONCE AGAIN
CONTINUES: ?
◦ AS LONG AS NERVE IMPULSES RELEASES ACh
http://www.lab.anhb.uwa.edu.au/mb140/addons/copyright.htm
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NERVE IMPULSE CEASES
ACh?
◦ ACETYLCHOLINESTERASE DECOMPOSES ACh
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Ca?
◦ NOT RELEASED BY CISTERNAE SO PUMP TAKES OVER
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CROSSBRIDGE LINKS BREAK & TROPOMYOSIN
REFORMS SHAPE BLOCKING ACTIVE SITE
MUSCLE FIBER RELAXES
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THICK
2/3 OF PROTEIN
200+ GLOBULAR PROTEINS
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THIN FILAMENT
¼ OF ALL PROTEINS
GLOBULAR PROTEIN
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TROPOMYOSIN
◦ ROD-SHAPED
◦ FILLS IN GROOVE OF ACTIN, BLOCKING ACTIVE SITE
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TROPONIN
◦ ATTACHED TO TROPOMYOSIN
◦ CALCIUM BINDS HERE
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DYSTROPHIN
◦ ATTACHED TO INSIDE OF CELL MEMBRANE
◦ MAKES CELL MEMBRANE STRONGER TO WITHSTAND
CONTRACTION
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ATP
◦ DIRECTLY
◦ A SMALL AMOUNT
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CREATINE PHOSPHATE
◦ 4-6X MORE ABUNDANT THAN ATP
◦ MUST BE CONVERTED TO ATP
◦ SYNTHESIS CONTROLLED BY CREATINE
PHOSPHOKINASE
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RELIES ON CELLULAR RESPIRATION
◦ ONLY A FEW SECONDS WORTH OF ENERGY IN ATP
AND CREATINE PHOSPHATE
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CELLULAR RESPIRATION REQUIRES: ?
◦ OXYGEN
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CARRIED TO CELLS BY: ?
◦ RBC: HEMOGLOBIN
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IN MUSCLES:
◦ MYOGLOBIN
 ATTRACTS O2 MORE
 RED COLOR
 WHY NEEDED?
 MUSCLE CONTRACTION REDUCES BLOOD FLOW
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AT REST: ENERGY SUPPLIED BY AEROBIC RESPIRATION
DURING EXERCISE:
◦ CAN CHANGE GLUCOSE TO: ?
 PYRUVIC ACID  LACTIC ACID = ANAEROBIC THRESHOLD/
LACTIC ACID THRESHOLD
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OXYGEN DEBT IS WHEN LACTIC ACID BUILDS UP
LIVER REFORMS LACTIC ACID INTO GLUCOSE BUT
NEEDS TO HAVE THE OXYGEN REPLENISHED TO DO
THAT
= THE AMOUNT OF OXYGEN NEEDED TO RECONVERT
LACTIC ACID AND REPLACE THE ORIGINAL AMOUNT
OF ATP AND CREATINE PHOSPHATE AND REPLACE
OXYGEN LEVEL OF BLOOD AND TISSUE TO NORMAL
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MUSCLE PRODUCES MORE GLYCOLYTIC
ENZYMES MEANING ?
◦ MORE GLYCOLYSIS
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MORE CAPILLARIES AND MORE
MITOCHONDRIA = ?
◦ MORE AREOBIC RESPIRATION MORE BLOOD
PRODUCTION OF LESS LACTIC ACID SO DOESN’T
AFFECT pH
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LOSES ABILITY TO CONTRACT AFTER PROLONGED
EXERCISE DUE TO:
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LESS BLOOD FLOW ?
 LESS ACh
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ION IMBALANCE ACROSS SARCOLEMMA
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FEELING TIRED
◦ ***MOSTLY FROM INCREASE OF LACTIC ACID WHICH
LOWERS pH AND FIBERS CAN’T RESPOND
CRAMP: SUSTAINED INVOLUNTARY CONTRACTION
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DUE TO DECREASED EXTRACELLULAR ELECTROLYTE
CONCENTRATION
◦ CALCIUM PUMP DOESN’T WORK SO ACTIN & MYOSIN
STAY LOCKED
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FROM?
◦ CELLULAR RESPIRATION ESPECIALLY FROM?
 MUSCLES
 MORE THAN HALF THE ENERGY RELEASED
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CARRIED THROUGHOUT BODY BY?
◦ BLOOD
◦ HOMEOSTASIS MECHANISMS
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THRESHOLD STIMULUS:
◦ THE STRENGTH OF A STIMULUS THAT STARTS AN
IMPULSE
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TWITCH:
◦ PERIOD OF CONTRACTION AND RELAXATION
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LATENT PERIOD:
◦ A PERIOD OF DELAY BEFORE CONTRACTION
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MYOGRAM:
◦ A RECORD OF A CONTRACTION
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LENGTH:
◦ TOO LONG OR TOO SHORT DECREASES CONTRACTION
FORCE
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WHOLE MUSCLE FORCE: DEPENDS ON THE
FREQUENCY AT WHICH INDIVIDUAL MUSCLES
ARE STIMULATED AND HOW MANY FIBERS ARE
CONTRACTING
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SUMMATION:
◦ WHEN THERE ARE MULTIPLE STIMULI OF INCREASING
STIMULATION UNTIL MUSCLE CAN NOT RELAX
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SUSTAINED CONTRACTION:
◦ MUSCLE CAN’T RELAX DUE TO SUMMATION
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TETANIC CONTRACTION:
◦ SUSTAINED CONTRACTION WITH ABSOLUTELY NO
RELAXATION
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?
THE MORE FIBERS IN ONE UNIT THE LESS PRECISE
CONTROL
DIFFERENT MOTOR NEURONS HAVE DIFFERENT
THRESHOLDS SO SOME ARE MORE EASILY
STIMULATED THAN OTHERS
SO VARYING AMOUNT OF CONTRACTION OF
WHOLE MUSCLE
MULTIPLE MOTOR UNIT SUMMATION OR
RECRUITMENT= AN INCREASE IN THE NUMBER OF
MOTOR UNITS INVOLVED IN THE CONTRACTION
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DURING A SUSTAINED CONTRACTION SMALLER
MOTOR UNITS ARE RECRUITED EARLIER AND
LARGER RESPOND LATER BUT MORE FORCEFULLY
(INCREASING STRENGTH)
CONTRACTION IS SMOOTH DUE TO DIFFERENT
MOTOR UNITS BEING RECRUITED AT DIFFERENT
TIMES
TETANIC CONTRACTIONS OCCUR IN SOME OF
THE FIBERS DURING NORMAL CONTRACTIONS
MUSCLE TONE: EVEN AT REST THERE IS SOME
CONTRACTION OF SOME FIBERS
IMPORTANCE:
◦ POSTURE
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ISOTONIC
◦ MUSCLE SHORTENS
◦ CONCENTRIC: SHORTENS
◦ ECCENTRIC: DOESN’T SHORTEN: LESS FORCE
(LAYING DOWN A BOOK)
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ISOMETRIC
◦ ENDS DON’T MOVE
◦ TENSION INCREASES
◦ POSTURE
WHICH OCCURS MOST COMMONLY?
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SLOW TWITCH/ TYPE I
◦ RED FIBERS ?
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MYOGLOBIN
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AEROBIC RESPIRATION
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CAN GENERATE ATP AS FAST AS THEY NEED IT
◦ MANY MITOCHONDRIA ?
◦ HIGH RESPIRATORY CAPACITY
◦ CONTRACT A LONG TIME/ DON’T FATIGUE
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FAST TWITCH/ TYPE IIb
◦ GLYCOLYTIC FIBERS
◦ WHITE FIBERS
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LESS MYOGLOBIN
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LESS CELLULAR RESPIRATION
5ksandcabernets.com/2012/05/fast_twitch-slow_twitch-muscle_fibers/
◦ LESS MITHOCHONDRIA
◦ MORE EXTENSIVE SR
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INTERMEDIATE FIBERS/ TYPE IIa
◦ WHITE FIBERS
◦ FAST TWITCH FATIGUE RESISTANT
◦ FAST SPEED WITH HIGHER OXIDATIVE CAPACITY
www.examiner.com/article/us-olympic-trials-2012-men-s-and-women-s-5000m...
behindtheworkout.com/2012/03/10/
slow-twitch-vs-fast-twitch-know-your
-muscle-fibers/
www.flickr.com/photos/thehappyrower/4083774365/
www.bing.com/images/search?q=fast+speed+muscles+&view
http:/
iupucbio2.iupui.edu/anatomy/Outlines/Martini%204th%20Chapt%209.htm
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BONE AND MUSCLE ACT AS LEVERS
◦ PARTS:
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BAR
PIVOT/FULCRUM
OBJECT TO BE MOVED AGAINST RESISTANCE
FORCE FOR ENERGY FOR MOVEMENT
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FULCRUM BETWEEN OBJECT AND FORCE
◦ SEE-SAW; SCISSORS
◦ RAISING HEAD: FACE IS OBJECT: ATLAS IS FULCRUM:
MUSCLES AT BACK OF HEAD IS THE FORCE
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FULCRUM THEN OBJECT THEN FORCE
◦ WHEELBARROW
◦ STANDING ON TOES: TOES = FULCRUM; BODY =
OBJECT; LEG MUSCLES = FORCE
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OBJECT THEN FORCE THEN FULCRUM
◦ TWEEZERS
◦ RAISING OBJECT IN HAND BY BICEPS: OBJECT IN
HAND; BICEPS PULLS ONE RADIUS; ELBOW=
FULCRUM
http://www.ichristianschool.org/anatomy/images/joints_bones/bonelevr.jpg
SECOND CLASS
SECOND CLASS
THIRD CLASS
SECOND CLASS
THIRD CLASS
THIRD CLASS
FIRST CLASS
FIRST CLASS
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ORIGIN
◦ IMMOVEABLE END OF MUSCLE
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INSERTION
◦ THE END THAT MOVES
http://www.equine-sports-massage.net/images/DeepDigFlexMusc.jpg
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AGONIST/PRIME MOVER
◦ PRIMARY PRODUCER OF MOVEMENT
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SYNERGIST
◦ CONTRACT TO ASSIST THE AGONIST
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ANTAGONIST
◦ RESIST AGONIST’S MOVEMENT AND CAUSE
OPPOSITE MOVEMENT
IF BOTH CONTRACT THE STRUCTURE IS RIGID
SMOOTH MOVEMENT DEPENDS ON RELAXATION OF
ANTAGONISTS
COORDINATED BY THE NERVOUS SYSTEM
http://www.deanza.edu/faculty/mccauley/6a-labs-tissues-01.htm
http://medcell.med.yale.edu/systems_cell_biology/muscle.php
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SHORTER
SINGLE NUCLEUS IN CENTER
ELONGATED, TAPERING ENDS
ACTIN AND MYOSIN FIBERS ARE RANDOMLY
ARRANGED (NOT STRIATED)
LESS DEVELOPED SR
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MULTIUNIT
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VISCERAL/SINGLE UNIT
◦ LESS ORGANIZED
◦ ACT AS SINGLE CELLS
◦ IN IRIS AND BLOOD VESSELS
SHEETS OF SPINDLE SHAPED CELLS
GAP JUNCTIONS
THICK END IS NEAR ANOTHER CELL’S THIN END
WORK AS A UNIT
SOME HAVE RYTHMICITY: A PATTERN OF SPONTANEOUS
REPEATED CONTRACTIONS
◦ EX: PERISTALSIS: CONTRACTION OF LOONGITUDINAL
AND CIRCULAR MUSCLES
◦ FOUND IN HOLLOW ORGANS: OUTER COATS:
LONGITUDINAL; INNER COATS: CIRCULAR
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SIMILARITIES TO SKELETAL
HAS CALMODULIN NOT TROPONIN
CALCIUM COMES MORE FROM
EXTRACELLULAR FLUID
NUEROTRANSMITTERS ACETYLCHOLINE AND
NOREPINEPHRINE AFFECT CONTRACTION:
THEY EACH STIMULATE SOME AND INHIBIT
OTHERS
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WHERE ?
STRIATED
JOINED END TO END
INTERTWINED, 3-D NETWORK ??
SINGLE NUCLEUS
CISTERNAE LESS DEVELOPED =?
◦ STORE LESS Ca
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LARGER T TUBULES
◦ RELEASES MORE CALCIUM MORE QUICKLY
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RELIES MORE ON EXTRACELLULAR CALCIUM
◦ SO CAN CONTRACT LONGER THAN SKELETAL
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INTERCALATED DISCS
◦ GAP JUNCTIONS
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SYNCYTIUM
SELF EXCITING
RHYTHMIC
REFRACTORY PERIOD IS LONGER- AS LONG
AS CONTRACTION = NO SUSTAINED OR
TETANIC CONTRACTIONS
CARDIAC MUSCLE
http://biol251.wikispaces.com/Ch4-Tissues
http://howtoloosebellyfatfast.net/tag/smooth-muscle-cells
http://classes.midlandstech.edu/carterp/Courses/bio110/chap07/chap07.html
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STARTING IN 40’S DECLINES IN:
◦ MYOGLOBIN
◦ ATP
◦ CREATINE PHOSPHATE
DIAMETERS OF SOME MUSCLE FIBERS SHRINK
WALLS OF VEINS THICKEN
BECOME SMALLER, HAVE LESS WATER, LOSE
STRENGTH
CONNECTIVE TISSUE AND ADIPOSE TISSUE
REPLACE SOME MUSCLE TISSUE
BY 80 ½ OF MUSCLE MASS LOST: DUE TO LESS
MOTOR NEURON ACTIVITY
SO REFLEXES SLOW
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EXERCISE HELPS:
◦ COUNTERS THE LESS EFFICIENT O2 DELIVERY
◦ CAN GROW NEW MUSCLE
 RELEASES INTERLEUKIN-6 STIMULATES SATELLITLE CELLS
(STEM CELLS); DIVIDE AND MIGRATE
MAINTAINS FLEXIBILITY OF BLOOD VESSELS KEEPING BLOOD
PRESSURE NORMAL
STRETCHING BEFORE AND AFTER, STRENGTH TRIANING AND
AEROBIC EXERCISE
STRENGTH TRAINING INCREASES MUSCLE MASS DECREASING
FORCE ON JOINTS
AEROBICS IMPROVES O2 USE AND ENDURANCE
STRETCHING INCREASES FLEXIBILITY, DECREASES MUSCLE
STRAIN, IMPROVES BLOOD FLOW
LESS DEPRESSION IN OLDER PATIENTS