Striations (Including A-bands, I-bands, Etc.)

Question 1

What are striations?

Answer 1

Dark and light areas that we see under a microscope.

A-Band-dark areas
I-band-light area

Thick filaments overlap with thin filaments in the A-band.

I-band has thin filaments only

Question 2

Protein filaments

Answer 2

Thick filaments- Myosin
Thin filaments-Actin & troponin

Question 3

What is a z-line?

Answer 3

A meeting of sarcomeres. It is 1 sarcomere (which is a z-line to z-line).

Question 4

What is a sarcomere?

Question 5

What causes striations?

Answer 5

Striations are caused by arrangement of thick and thin filaments within the myofibrils. The length of each myofibril is divided into sarcomeres. A z-line is the meeting of sarcomeres.

Question 6

What happens during muscle contraction in an A-band, I-band, and Z-line?

Answer 6

When a muscle cell contracts, it shortens.
- Distance between the z-line decreases
- I-bands shorten
-A bands move closer together but remain the same length
-An open site is activated for calcium to grab on to.