Muscle Contraction Flashcards
what does the motor neurone release after the nerve impulse reaches the neuromuscular junction?
acetylcholine
what happens when ach binds with receptors in the muscle membrane?
allows sodium to enter
what happens once sodium enters?
sodium influx creates an action potential in the sarcolemma
what is muscular atrophy?
the weakening and shrinking of the muscle.
what is muscle hypertrophy?
enlargement of muscles due to increased production of organelles. it is the result from very forceful repetitive muscular activity eg weight lifting. (more capillaries, more mitochondria)
what makes up a sarcomere?
actin and myosin
what is an isomeric contraction?
NO MOVEMENT (eg standing, sitting, posture)
what is an isotonic contraction?
produces movement, used in walking
what are the anchoring zones of myosin?
M lines
what are the anchoring zones of actin?
Z lines
what is the region between 2 Z lines called?
sarcomere
what happens during muscle contraction?
myosin filaments slide along actin filaments, consuming ATP in the process
what does tropomysosin do?
blocks myosin from binding to actin (can be removed by calcium)
what are T tubules?
unique to muscle cells, invaginations of the sarcolemma that conduct charge when it is depolarised.
what is the function of the sarcoplasmic reticulum?
contains a large store of calcium ions
what is the endomysium?
the thin layer of connective tissue that surrounds the muscle fibre
what are fascicles?
grouped bundles of muscle fibres
what surrounds the fascicles?
connective tissue called perimysium
what is the I band?
contains only actin filament
what is the A band?
the length of myosin filament which may contain overlapping actin filaments.
what is the H zone?
contains only myosin filaments
what is the acronym to remember the sarcomere?
MHAIZ
what are the 3 different zones of troponin?
I,T,C
what is the function of troponin I?
binds to the actin filament
what is the function of troponin T?
binds to tropomyosin
what is the function of troponin C?
can bind to calcium ions
what happens when there is a depolarisation at the neuromuscular junction?
it is conducted down the t-tubules, causing high influx of calcium ions into the sarcoplasm.
what are t tubules?
extensions of the cell membrane that penetrate into the centre of the skeletal muscle cardiac muscles.
what happens when calcium binds to troponin C?
causes a change in conformation that moves tropomyosin away from the myosin head binding sites of the actin filaments.
what happens when the myosin head binds to the actin?
forms a cross link. the power stroke then occurs.
what is the power stroke?
myosin heads pivot in a rowing motion moving the actin past myosin towards the M line.
what happens when ATP binds to myosin head?
causes it to uncouple from the actin and allows the process to repeat.
what happens to the length of the sarcomere during contraction?
it shortens, brings Z lines closer together
-H and I bands shorten
-A band remains the same
