lecture 4 Flashcards
what is the neuromuscular junction
synaptic connection between motor nerve and muscle
how does the neuromuscular junction work
action potential - axon terminal on nerve release acetylcholine - go into synaptic cleft - bind to receptor on sarcolemma
what is the sarcolemma
muscular membrane
what part of the NS is the motor nerve from
somatic nervous system
how does nicotine interact with receptors
acetylcholine receptors can also be bound by nicotine to open Na channels and cause more AP - addictive because there are a lot of acetylcholine receptors in the body
what does the muscle fibre look like and what are its components
long, multinucleated
actin and myosin surrounded by connective tissue make up the myofibrils, bound by connective tissue to make muscle fibres, bound by connective tissue to make fascicles, many bound by connective tissue to make muscle
describe the AP that travels from the motor neuron to the muscle
acetylcholine - acetylcholine receptor - Na channels open - AP - axon terminal - depolarize sarcolemma - AP spreads via t tubule - muscle - sarcoplasmic reticulum release Ca - Ca for muscle contraction and movement of filaments
what are sarcomeres and what do the repeating sequences look like
thick (myosin) on the inside and 6 thin (actin) on the outside
sliding only happens within each sarcomere
what is at the start and end of a sarcomere
anchor proteins
what other proteins are within a sarcomere
elastic proteins to develop tension
describe the structure of actin
actin molecules - many strung together - two strings make double helix
each molecule has myosin binding site with strip of tropomyosin covering it
troponin (secondary regulatory protein) on some cells to move tropomyosin out of the way
describe the structure of myosin
there is head and tail, two tails intertwine together with heads at opposite ends - many of these come together with heads at staggering formation to form thick filament
at heads, there is ATPase site to bind ATP to make ADP and Pi, there is also actin binding site
low energy = head in
high energy = head out (needed for muscle contraction)
what is the crossbridge formation
binding of filaments at heads for sarcomere to shorten - requires AP and signal from motor neuron
how does caffeine interfere with muscle stimulation
potent stimulator of sarcoplasmic reticulum - releases a lot of Ca - causes you to shake
describe the process of how the filaments bind together
Ca bind to troponin complex - causes tropomyosin to change confirguations and come off of myosin binding sites - heads and myosin binding site come together to form crossbridge formation
