muscle physiology 1 Flashcards
________ is the the sliding of actin past myosin generates muscle tension
Sliding filament theory
_______ is the smallest contractile unit of a muscle fiber
Sarcomere
compare the bands and lines in a sarcomere (I, A, M, Z)
-I band: light portion made up of actin filaments (thin filament)
-A band: dark portion made up of myosin (thick filament)
-M line: in very middle
-Z line: where two neighboring I bands meet
during a contraction how do the Z lines change?
the distance between the two Z-lines decreases because the Z-line moves toward the H-line
does the length of the A band change during a contraction?
no
does the length of the I band change during a contraction?
yes
Crossbridge linkage between thick and thin filaments are achieved by what two things?
-Chemical and/or electrostatic linkages
-Force generation/ number of bonds between myosin and actin that are made in parallel
______ cross bridges = more force
more
what does in parallel vs in series mean?
-In Parallel: more than one sarcomere is contracting at the same time in different myofibrils. We assume that other myofibers are extending too
-In series: consecutive sarcomeres of one myofibril are contracting. We assume that one myofiber is contracting while others are not
In parallel has ____ chance of producing muscle shortening, while series has _____ chance
GREATER, LESS
Force generation is _____kg/cm2 cross-sectional area of muscle
3-4kg per cm2
Skeletal muscle in males is _____% body weight, while in females muscle is only ____% body weight
40, 32
Edible mussels generate _____ force in shell retractor
15kg/cm2
do males and females generate the same force per cm2?
yes
what is the lever ratio?
power arm of lever : load arm of lever
What does it mean if there is a 1:7 lever ratio?
This means, for every 1cm the muscle (bicep) moves, the hand (or limb attached) will move 7 cm
what is the tension to lift weight formula
Tension to lift weight = (weight)(1/ratio)
Short distance of bicep contraction = ______ mvmt of hand with great speed
large
Forceful exercise produces _______ that results in hypertrophy of myofibers. what does this mean?
hyperplasia of myofibrils
-myofibrils split forming more myofibrils within a myofiber
does hyperplasia of myofibrils create more myofibrils in series or parallel?
parallel
do long-distane runners experience hypertrophy?
no, because they are not exercising their muscles at maximal load
sprinters experience ________ which adds myofibrils in parallel
myofiber hypertrophy
why are bodybuilders so big?
-Muscles are larger due to more blood and interstitial fluid in the muscle and more water/sarcoplasmic fluid in each myofiber (sarcoplasmic hypertrophy)
NOT due to myofibril hyperplasia
Negative mutation of _________ gene can increase muscle mass naturally
myostatin (Gdf8)
________ is the amount of tension that is produced by a muscle as a feature of its length
Length tension
when is max force of a muscle?
when greatest number of crossbridge bonds are made at parallel
Range of muscle length is greatest within____ of 100% resting muscle length
+/-30%
why is muscle not in a constant state of contraction?
because regulator proteins actively inhibit contraction
________ sits on top of myosin binding sites on the actin helix.______ sits on top of tropomyosin
Tropomyosin, Troponin
explain the relaxation/excitement cycle
-No Ca+ = no crossbridge binding, myosin binding site is covered by troponin/tropomyosin complex
-ATP bound to myosin head
-Ca+ enters
-Ca+ binds to troponin
-Troponin rotates on itself and pulls tropomyosin out of the way
-Cross-bridge sites are now exposed
-Binding of Myosin cross bridge to –Actin triggers the power stroke that pulls the thin filament inward during contraction
-During power stroke, ATP hydrolyzed → ADP
Myosin’s ATPase is active when ________
myosin is attached to actin
There are __ heads on each myosin, and __ binding sites on each head
2,2
what are the 2 binding sites on myosin heads?
-Myosin ATPase (where ATP → ADP + Pi)
-Actin binding site
Change of angle from one row to another = wedged ____ (every 3)
40* CCW
