L8: muscle contraction Flashcards
T/F in a muscle contraction, thick and thin filaments shorten
false - they slide past each other, do not shorten
H band
myosin only portion of sarcomere
M line
line down middle of H band – where myosin separate into different polarities
I band
actin only portion of sarcomere
Z line
line down middle of I band – where actin filaments are anchored
A band
the whole myosin portion of sarcomere, including where it overlaps with actin
these bands of a sarcomere shorten during contraction
H band
I band
this protein anchors myosin to Z lines
titin
titin
anchors myosin filaments to z-lines
this protein lies along actin in the sarcomere and is thought to be a ruler to determine thin filament length
nebulin
nebulin
lies along actin in the sarcomere and is thought to be a ruler to determine thin filament length
a muscle fiber is encased by…
the sarcolemma
a muscle fibril is encased by…
sarcoplasmic reticulum
outline the pathway from motor neuron action potential to actin exposure in skeletal muscle
motor neuron ACh N1 receptor motor end plate sarcolemma t-tubule DHPR dihydropyridine receptor RYR1 ryanodine receptor Ca++ troponin c troponin i troponin t tropomyosin exposed actin
outline the pathway from neuromuscular synapse to exposed actin in cardiac muscle
synapse (cholinergic or adrenergic or other) sarcolemma t-tubule DHPR Ca++ RYR2 Ca++ troponin c troponin i troponin t tropomyosin exposed actin
how is calcium release in skeletal muscle different from calcium release in cardiac muscle?
skeletal - DHPR appears to directly activate the RYR1 channels to release Ca++
cardiac - DHPR releases Ca++, which activates RYR2 to release Ca++
DHCR in skeletal and cardiac muscle contraction is…
dihydropyridine receptor
in skeletal muscle - activates RYR1 Ca++ release
in cardiac muscle - releases Ca++, which binds RYR2 receptors and activates RYR2 Ca++ release
RYR1
ryanodine receptor 1
in skeletal muscle, is directly activated by DHPR protein of t-tuble and releases Ca++
RYR2
ryanodine receptor 2
in cardiac muscle, is activated by the Ca++ released by DHPR in t-tubule to release more Ca++
troponin c
binds calcium, signals troponin i to release actin, which signals troponin t to shift topomyosin and expose actin
troponin i
binds to actin to hold troponin-topomyosin complex in place
between troponin c and t
troponin t
binds tropomyosin, receives signal to shift from troponin c signal to troponin i
how is calcium resequestered into sarcoplasmic reticulum?
Ca++ ATPase pump
what protein buffers Ca++ concentrations in the SR so that more can be stored?
calsequestrin
