Muscle Contraction

Question 1

what does the motor neurone release after the nerve impulse reaches the neuromuscular junction?

Answer 1

acetylcholine

Question 2

what happens when ach binds with receptors in the muscle membrane?

Answer 2

allows sodium to enter

Question 3

what happens once sodium enters?

Answer 3

sodium influx creates an action potential in the sarcolemma

Question 4

what is muscular atrophy?

Answer 4

the weakening and shrinking of the muscle.

Question 5

what is muscle hypertrophy?

Answer 5

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)

Question 6

what makes up a sarcomere?

Answer 6

actin and myosin

Question 7

what is an isomeric contraction?

Answer 7

NO MOVEMENT (eg standing, sitting, posture)

Question 8

what is an isotonic contraction?

Answer 8

produces movement, used in walking

Question 9

what are the anchoring zones of myosin?

Answer 9

M lines

Question 10

what are the anchoring zones of actin?

Answer 10

Z lines

Question 11

what is the region between 2 Z lines called?

Answer 11

sarcomere

Question 12

what happens during muscle contraction?

Answer 12

myosin filaments slide along actin filaments, consuming ATP in the process

Question 13

what does tropomysosin do?

Answer 13

blocks myosin from binding to actin (can be removed by calcium)

Question 14

what are T tubules?

Answer 14

unique to muscle cells, invaginations of the sarcolemma that conduct charge when it is depolarised.

Question 15

what is the function of the sarcoplasmic reticulum?

Answer 15

contains a large store of calcium ions

Question 16

what is the endomysium?

Answer 16

the thin layer of connective tissue that surrounds the muscle fibre

Question 17

what are fascicles?

Answer 17

grouped bundles of muscle fibres

Question 18

what surrounds the fascicles?

Answer 18

connective tissue called perimysium

Question 19

what is the I band?

Answer 19

contains only actin filament

Question 20

what is the A band?

Answer 20

the length of myosin filament which may contain overlapping actin filaments.

Question 21

what is the H zone?

Answer 21

contains only myosin filaments

Question 22

what is the acronym to remember the sarcomere?

Answer 22

MHAIZ

Question 23

what are the 3 different zones of troponin?

Answer 23

I,T,C

Question 24

what is the function of troponin I?

Answer 24

binds to the actin filament

Question 25

what is the function of troponin T?

Answer 25

binds to tropomyosin

Question 26

what is the function of troponin C?

Answer 26

can bind to calcium ions

Question 27

what happens when there is a depolarisation at the neuromuscular junction?

Answer 27

it is conducted down the t-tubules, causing high influx of calcium ions into the sarcoplasm.

Question 28

what are t tubules?

Answer 28

extensions of the cell membrane that penetrate into the centre of the skeletal muscle cardiac muscles.

Question 29

what happens when calcium binds to troponin C?

Answer 29

causes a change in conformation that moves tropomyosin away from the myosin head binding sites of the actin filaments.

Question 30

what happens when the myosin head binds to the actin?

Answer 30

forms a cross link. the power stroke then occurs.

Question 31

what is the power stroke?

Answer 31

myosin heads pivot in a rowing motion moving the actin past myosin towards the M line.

Question 32

what happens when ATP binds to myosin head?

Answer 32

causes it to uncouple from the actin and allows the process to repeat.

Question 33

what happens to the length of the sarcomere during contraction?

Answer 33

it shortens, brings Z lines closer together
-H and I bands shorten
-A band remains the same