muscle contraction Flashcards
first step of muscle contraction
AP arrives at synaptic bulb and then the voltage gated Na+ channels open so NA rushes in. membrane potential increases
what happens after the AP arrives at synaptic bulb
voltages gated ca ++ channels open
what happens after voltages gated ca ++ channels ope
ca ++ diffuses in
what happens after ca++ diffuses in
the synaptic vesicles fuse with membrane
what happens when the synaptic vesicles fuse with the membrane
they release their contents into synaptic celft
what occurs after the synaptic vesicles fuse with membrane
Ach is released into the synaptic cleft and then Ach diffuses across synaptic cleft
what does Ach bind to after dissusing across synaptic cleft
binds to membrane receptors on motor end plate
when Ach binds, what opens
ligand gated sodium channels
what happens after ligand gated sodium channels open
na rushes into sarcoplasm
what occurs when na rushes into sarcoplasm
the mem becomes less negative. if there is enough Ach then it will reach threshold and open voltage gated an channels.
what happens after the Na rushes into the sarcoplasm
action potential travels along sarcolemma
What happens after AP travels
the Ach is quickly broken down by AChE. into acetate and choline to be recycled
where do AP travel
along sarcolemma and along t tubule
what does the travelling of AP lead to
excitation, contraction
what is excitation
generation of action potentials
what is contraction
when actins slide past myosin and the muscle shortens
what happens after excitation -contraction of muscle
the ca is releases from sarcoplasmic reticulum and enters the cytoplasm
what happens after ca enters the cytoplasm
it binds troponin
what does troponin do after ca binds it
it pulls tropmyosin away from myosing binding site on actin
what does myosin do after troponin pulls tropomyosin away
it attaches actin and forms cross bridges
what are the 6 steps of the contraction cycle
active site is exposed
myosin attaches to actin and forms a cross bridge
myosin head pivots and pulls actin
release of ADP and Pi
ATP attaches to myosin hed
cross bridge detachment due to ATP
and then myosin is reactivated (through a conformational change of head)
what is the importance of ca++
it binds troponin which them pulls tropomyosin to uncover active site
what does tropomyosin usually cover
the active sites on actin
how long does the contraction cycle continue
until the cytoplasmic ca++ drops of ATP is depleasted
what do you need to detach myosin head
ATP
what type of relationship is there between resistance and speed of contraction
inverse
as sarcomeres shorten, what happens to the muscle
it also shortens
what are the 6 things that mark relaxation
ca ++ concentrations drop
Ca++ detaches from troponin
active sites are re blocked by tropomyosin
contraction cycle ends
what allows ca++ concentrations to drop
they are returned to the SR by Ca++ pumps (which eventually close )
when are active sites reblocked by tropomyosin
during relaxation
what does relaxation do
reduce tension within muscle
what allows a muslce to return to its original length . 3
antagonistic muslce
gravity
very limited elasticity
when does SR release Ca++
when a motor neuron stimulates the muslce fiber
what does free Ca++ in the sarcoplasm trigger
contraction
skeletal muscle fibers shorten as what happens
as thin filaments slide between thick filaments
what type of process is contraction
an active process cuz it consumes lots of atp
what type of process is relaxation and return to resting length
a passive process, uses small amount of ATP.
