13.10 Sliding filament model

Question 1

what happens to the I-band when contraction occurs?

Answer 1

narrows

Question 2

what happens to the A-band when contraction occurs?

Answer 2

it stays the same

Question 3

what happens to the Z-lines when contraction occurs?

Answer 3

move closer together

so sarcomere becomes smaller

Question 4

what happens to the H-zone when contraction occurs?

Answer 4

narrows

Question 5

relaxed vs contracted sarcomere

Answer 5

Question 6

what is the structure of myosin?

Answer 6

have globular heads which can bind to ATP

Question 7

what is the structure of actin?

Answer 7

have:
troponin
tropomyosin
actin-myosin binding site

Question 8

what does troponin do?

Answer 8

holds tropomyosin over the binding site

releases tropomyosin when a Ca2+ ion binds to it

Question 9

what happens at neuromuscular junction?

Answer 9

SAME AS AT SYNAPSE!!!!

acetylcholine is the neurotransmitter released

Question 10

what happens when the sarcolemma is depolarised?

Answer 10

it causes the sarcoplasmic reticulum to open Ca2+ channels which causes Ca2+ ions to diffuse into the sarcoplasm

Question 11

what do the Ca2+ ions from the sarcoplasmic reticulum do?

Answer 11

they bind to troponin on the actin molecules

Question 12

what does the binding of Ca2+ ions to the troponin do?

Answer 12

causes change in troponin shape which leads to tropomyosin detaching which exposes the myosin-actin binding site

Question 13

what is formed between the myosin head and the binding site?

Answer 13

a cross bridge

Question 14

how does the myosin head pull the actin?

Answer 14

by flexing

Question 15

how is the myosin head detached from the actin?

Answer 15

ADP molecule releases from the head and reacts with P to form ATP

ATP binds to the myosin head which causes the myosin head to detach by breaking the cross bridges

Question 16

how does the myosin head return to normal position?

Answer 16

ATPase hydrolyses the ATP into ADP + P which releases energy which returns the head back to its normal position

Question 17

what does the myosin head do once it returns to it’s normal position?

Answer 17

it binds to a binding site further along the actin filament

cycle is then repeated

Question 18

how does the actin filament return to it’s resting position?

Answer 18

Ca2+ ions leave their binding sites and tropomyosin returns to cover the binding site

the actin filaments slide back to their relaxed positions

Question 19

what ways is ATP generated for muscle contraction to occur?

Answer 19

aerobic respiration
anaerobic respiration
phosphocreatine

Question 20

what is aerobic respiration in muscles used for?

Answer 20

long periods of low-intensity exercise

Question 21

what causes muscle fatigue?

Answer 21

the build up of lactate in muscles due to anaerobic respiration

Question 22

what is anaerobic respiration in muscles used for?

Answer 22

short periods of high-intensity exercise

Question 23

what is aerobic respiration in muscles used for?

Answer 23

long periods of low-intensity exercise

Question 24

what does phosphocreatine do?

Answer 24

provides a reserve supply of phosphate which can combine with ADP to produce ATP