Muscles

Question 1

What is in the I band of the sarcomere?

Answer 1

There’s no actin or myosin, just a Z line to section off the sarcomeres.

Question 2

What is in the A band of the sarcomere?

Answer 2

There’s both actin and myosin, and a H zone with the M line within it.

Question 3

What is the first stage of muscle contraction?

Answer 3

Calcium ions are released from the sarcoplasmic reticulum, and they enter the actin filament. They then bin to a protein that’s attached to the tropomyosin and this causes the tropomyosin to move from the binding site.

Question 4

What is the second stage of muscle contraction?

Answer 4

Now that the binding site is no longer blocked, the binding site on the myosin globular head to attach to the actin one, creating an actin-myosin cross bridge.

Question 5

What is the third stage of muscle contraction?

Answer 5

ATP is hydrolysed ( broken down into ADP and an inorganic phosphate ) and the energy released from this is used to move the myosin head in a rowing like motion.

Question 6

What is the fourth stage of muscle contraction?

Answer 6

The ATP binding site is now attached fully to the actin binding site. This causes another ATP molecule to be hydrolysed, and the energy from this is used to break the actin-myosin cross bridge.

Question 7

What is the fifth stage of muscle contraction?

Answer 7

There are no calcium ions in the actin filament, so the tropomyosin moves back in place to block the active site, and the muscle is back to resting.

Question 8

What are the three types of muscle?

Answer 8

Skeletal: you have conscious control over these, they’re long, cylindrical and have many nuclei.
Smooth: this type is within internal organs, you don’t have conscious control over these.
Cardiac: this type is throughout the organs which are part of the cardiac cycle, you don’t have conscious control over these.