Contraction of skeletal muscles

Question 1

agonist

Answer 1

contracting muscle

Question 2

antagonist

Answer 2

relaxing muscle

Question 3

advantage of skeletal muscles being arranged into antagonistic pairs

Answer 3

-muscle only contracts
-2nd muscle requires to reverse the movement caused by the first
-helps maintain posture → contraction of both muscles

Question 4

what’s the cell membrane in muscle cells called?

Answer 4

sarcolemma

Question 5

what’s the endoplasmic reticulum in muscle cells called?

Answer 5

sarcoplasmic reticulum

Question 6

what are myofibrils made up of?

Answer 6

actin and myosin

Question 7

how are muscle cells adapted for their function?

Answer 7

• lots of nuclei
• lots of sarcoplasmic reticulum → mir calcium ions
• lots of mitochondria → more ATP

Question 8

Z line

Answer 8

the end points of a sarcomere

Question 9

M line

Answer 9

the middle of a sarcomere

Question 10

H zone

Answer 10

only contains myosin
shortens during contraction

Question 11

I band

Answer 11

light band only containing actin
shortens during contraction

Question 12

A band

Answer 12

dark bands containing thick myosin filaments AND some overlapping actin
stays the same length during contraction

Question 13

describe the role of calcium ions and ATP in the contraction on myofibrils

Answer 13

1) calcium ions diffuse into myofibrils from the sarcoplasmic reticulum
2) calcium ions cause the movement of tropomyosin
3) causes the exposure of binding sites on actin
4) myosin heads attach to binding sites in actin → crossbridge
5) hydrolysis of ATP cause myosin heads to bend
6) pulls acting molecules along
7) attachment of ATP molecule to myosin head causes myosin to detach from actin

Question 14

which is thicker, myosin or actin?

Answer 14

myosin → thicker
actin → thin