7/29/2019 3rd Lecture on Skeletal Muscle Physiology by Dr.roomi
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Skeletal muscle Physiology
By
Dr. Mudassar Ali Roomi (MBBS, M. Phil)
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TETANIZATION:
Definition: Summation ofcontraction/twitchesSustained contraction withoutrelaxation.
Complete tetanus is producedwhen a muscle is stimulated at
a very rapid rate. Example: 60-70 stimuli/sec. Frequency of stimulation at
which complete tetanus isproduced is called tetanizingfrequency.
Muscle tension produced in
complete tetanization is greaterthan that in single muscletwitch.
Clostridium Tetani alphamotor neuron repeateddischarge and tetanus.
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INCOMPLETE & COMPLTE TETANUS
INCOMPLETE Repeated stimuli at a fast
raterelaxation of eachtwitch remainsincomplete incompletetetanus.
COMPLETE
Repeated stimuli at stillhigher raterelaxationphase disappearsaltogether sustained
contraction phase isobtained completetetanus.
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TETANY (increased excitability of motor
nerves)
CAUSES:
Parathyroidectomy (during thyroid surgery) lack of PTHplasma Ca+ level falls signs of neuromuscularhyperexcitability appear.
Alkalosis
plasma proteins behave as anions
bind cationsincluding Ca++decreased ionized calcium hypocalcemia less calcium available in ECF for membrane stabilizationno blocking of sodium channels by calcium cations (negativelycharged on inside) increased excitability of motor nerves tetany.
Hyperventilationhypocapnia (decreased CO2concentration) respiratory alkalosisplasma ionizedcalcium falls carpopedal spasm, a positive Chvostek sign &other signs of tetany).
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SIGNS OF TETANY:
CHVOSTEKS SIGN: Aquick contraction ofipsilateral facial muscles
elicited by tapping overthe facial nerve at theangle of the jaw.
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SIGNS OF TETANY:
TROUSSEAUS SIGN: Aspasm of muscles of theupper extremity thatcause flexion of the
wrist & thumb withextension of fingers. In individuals with mild
tetany with no obviousspasm, trousseaus sign
may be produced byoccluding circulation forfew minutes with a B.Pcuff.
7/29/2019 3rd Lecture on Skeletal Muscle Physiology by Dr.roomi
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TREPPE / STAIRCASE PHENOMENON
Definition: When a muscle isstimulated by maximumstimuli at a frequency lessthan tetanizing frequencyprogressive increase in muscletension with repeated stimuli,
till it becomes constant. If threshold stimuli are applied
so that each stimulus reachesthe muscle when the muscletwitch due to previousstimulus has completedeach successive twitch shows
an increased amplitude till amaximum height is reachedthis is called as staircasephenomenon.
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Ca Gluconate IV Slowly over 20 minutes
Vitamin D
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Mechanism of Treppe
Greater availability of
calcium in sarcoplasm.
Accumulation of
metabolites. Rise in local
temperature.
All these exertbeneficial effect on
contraction.
http://www.google.com.pk/url?sa=i&rct=j&q=TREPPE+/+STAIRCASE+PHENOMENON&source=images&cd=&cad=rja&docid=6emJ-JJJWoOp2M&tbnid=i-czJm70HHDLRM:&ved=0CAUQjRw&url=http://apbrwww5.apsu.edu/thompsonj/Anatomy%20&%20Physiology/2010/2010%20Exam%20Reviews/Exam%203%20Review/CH%2009%20Electromyography.htm&ei=m5gwUeD0OoeTtQbn8YDwCg&bvm=bv.43148975,d.Yms&psig=AFQjCNH7_FsF7BoRvAMLC6VmDm2wfqnSvA&ust=13622256377791537/29/2019 3rd Lecture on Skeletal Muscle Physiology by Dr.roomi
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Muscle Atrophy
Definition of atrophy:decrease in the size of a tissuedue to decrease in size of itscells.
There is weakening andshrinking of a muscle
Mechanism: decrease in theactin, myosin filaments andthe diameter of myofiber.
May be caused by: Immobilization of muscles e.g.
in cases of bed ridden patient
Loss of neural stimulation e.g.in cases of nerve injury
http://www.google.com.pk/url?sa=i&rct=j&q=muscle+atrophy&source=images&cd=&cad=rja&docid=AqsofsIB0346qM&tbnid=pTJIY2s5A5-E9M:&ved=0CAUQjRw&url=http://www.healthcentral.com/diet-exercise/h/how-to-treat-muscle-atrophy.html&ei=_ZwwUf2ZJYjtswaI4oGICQ&bvm=bv.43148975,d.Yms&psig=AFQjCNExsMwmlPGEFFe3WzJBUXCFnrT0ow&ust=13622268070000257/29/2019 3rd Lecture on Skeletal Muscle Physiology by Dr.roomi
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Muscle Hypertrophy
Definition of hypertrophy:
increase in the size of a
tissue due to increase in
size of its cells.
Enlargement of a muscle
More capillaries
More mitochondria
Caused by: Strenuous exercise
Anabolic Steroid hormones
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RIGOR MORTIS:
after deathmuscles of dead body become
rigid rigor mortis.
Its onset depends on:
Temperature: increased temperature rapid
onset.
Activity: Vigorous activity of muscle before
death rapid onset.
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Mechanism of Rigor Mortis
After death ATP is notavailable nodetachment of cross-bridges of myosin from
active site of actinfilaments rigor mortis.
After 16-24 hours rigormortis disappears due to
autolysis of muscleproteins (resulting fromhydrolytic enzymesreleased from lysosomes).
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SIGNIFICANCE of Rigor Mortis
Forensic significance: cangive us a clue about causeof death. In cases of
suicide, the gun or daggeris locked in the hand.
Time since death: it givesus some idea about timesince death. rigor mortis
remains for about 16hours after death. Itdisappears after 16-24 hrsof death.
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SLOW AND FAST MUSCLE FIBERS
http://www.google.com.pk/url?sa=i&rct=j&q=fast+and+slow+muscle+fibers&source=images&cd=&cad=rja&docid=qfnCo3lrwarSmM&tbnid=83bjHxsW5ezvkM:&ved=0CAUQjRw&url=http://www.stmary.ws/highschool/science/humanbio/quarter2/mp2Notes/MuscleTissueNotes.htm&ei=Gik4UZGROsjVsgbypoCoCA&bvm=bv.43287494,d.ZWU&psig=AFQjCNG8kr3imylbPShrh-sX-8_KG1BX1w&ust=13627213731104247/29/2019 3rd Lecture on Skeletal Muscle Physiology by Dr.roomi
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SLOW AND FAST MUSCLE FIBERS
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SOURCES OF ENERGY DURING MUSCLE CONTRACTION
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