Neuromuscular Physiology Flashcards
sarcolemma
myofibre plasma membrane
sarcoplasm
myofibre cytoplasm
myocyte
muscle cell with one nucleus
myofibre
multinucleated muscle cell
T/F each myofibre spans the length of the muscle
T
each myofibre has at least ___ neuromuscular junction
one
myofibres contain ___________, which are bundles of _____________, made up of the contractile proteins _______ and _______-
myofibrils; myofilaments; actin and myosin
what connects myosin to the Z disc
titin filament
what is the region between two Z lines
sarcomere
where are T tubules located
wrap around each myofibril at the Z disc
where is the sarcoplasmic reticulum
between the T tubule and the surface of the myofibril
describe the structure of myosin filaments
each myosin protein is a homodimer with 2 head groups; many myosin homodimers come together to form a thick filament with many head groups
what are thin filaments composed of (3)
actin, tropomyosin; troponin
____ actin consists of chains of ____ globular actin
F; G
what hides the binding sites for myosin on actin
tropomyosin
what has a high affinity for Ca
troponin
what happens to thin filament in the presence of ca
ca binds troponin -> troponin rotates, moving tropomyosin and exposing the active site on actin -> actin binds myosin
what is the NT for a neuromuscular junction? what is its receptor
Ach; nicotinic AchR
what does Ach binding trigger
influx of Na and local depolarization at the MEP
where does MEP depolarization spread
into T-tubules; stimulates Calcium-triggered calcium release
what happens once the AP reaches the t-tubules
voltage gated Ca channels detect depolarization -> tug on RYR in SR membrane
as an end result, get influx of Ca from both ECF (via Ca channels in the t-tubule) and from the SR (via RYR)
describe the ratchet theory of contraction
myosin head group ATPase cleaves ATP-ADP -> head tilts -> power stroke -> new ATP binds -> actin released -> ATP cleaved into ADP -> etc.
why is creatine important
stored in muscle; converted to phosphocreatine by CK; metabolized to provide phosphate bonds when the muscle needs energy
describe sources of ATP in muscles over time
- phosphocreatine (rapid early contractions for ~30s)
- glycolytic (~1 min)
- anaerobic
white or fast twitch
short contraction times; larger size and more extensive SR; anaerobic metabolism
red or slow twitch
long contraction times; smaller size and less extensive SR; aerobic metabolism
what is responsible for calcium removal after muscle contraction
PMCA, SERCA
visceral sm
single unit; connected via gap junctions; controlled by local stimuli; spontaneous slow waves that trigger AP
multiunit sm
controlled by nervous stimulation (Ach or NE); APs or decremental depolarizations cause contracion
example of visceral sm
enteric NS signalling for peristalsis
example of multiunit sm
piloerector muscle, ciliary muscle
