The Sliding Filament Theory Flashcards Preview

A&P I Muscular System Review > The Sliding Filament Theory > Flashcards

Flashcards in The Sliding Filament Theory Deck (12)
Loading flashcards...
1

What happens to the length of the sarcomeres in the contraction

shown above?

The sarcomere shortens as a result of the contraction shown in

the picture.

2

Have the thin and thick filaments shortened because of the

contraction?

Thin (actin) and thick (myosin) filaments have NOT shortened

3

What has happened to the I band?

The I band shortens.

4

What has happened to the H zone?

The H zone disappears (because the actin filaments slide toward

the center of the sarcomere).

5

What has happened to the A band?

There is no change in the appearance of the A band

6

Explain the change or lack of change in the A band

The A band does not change because the myosin filament does not

slide (to the left or right) or shorten during the contraction.

(The sliding of the actin filaments is what causes the sarcomere

to shorten, the I band to shorten, and the H zone to disappear.)

7

Which filament slides toward the center of the sarcomere

during this contraction?

The actin filaments (on the left and right sides of the

sarcomere) slide toward the center of the sarcomere in the

contraction shown.

8

What causes this sliding to occur?

Myosin is responsible for the sliding of the actin filaments.

Myosin heads attach to the actin “beads” and swing, pulling the

actin filaments.

9

Notice that in this contraction the sliding of filaments causes the

sarcomeres to shorten, which shortens the muscle. (For example,

when standing, muscles on top of the thigh shorten to lift your foot

off the ground). What is the more specific name of this contraction?

The general name of this contraction--when sliding of the actin

filaments occurs---is the isotonic contraction. However, the

more specific name for a contraction where sliding of filaments

causes the sarcomeres to shorten, is the concentric contraction.

10

The sliding of filaments can also cause the sarcomeres to lengthen,

which lengthens the muscle. (For example, muscles on top of the thigh

lengthen when you put your foot back on the ground.) What is the

more specific name of this contraction?

An isotonic contraction where the sarcomeres lengthen is called

an eccentric contraction. (The actin filaments are sliding AWAY from

the center of the sarcomere instead of toward it).

11

The sliding of filaments inside the sarcomere does NOT occur in all

types of contractions. What is the contraction called if there is no

sliding of actin at all?

A contraction where sliding does not occur is called an isometric

contraction. Isometric means “Same Length” since the sarcomere

doesn’t shorten (or lengthen) in this contraction

12

In this second type of contraction, where no sliding occurs, what

DOES happen during the contraction?

The myosin heads still attach to actin, which creates tension (a

tightness or tauntness) in the muscle. For this reason an

isometric contraction is also known as a Muscle Tone contraction.

(tone= tension) There is no swinging of the myosin heads or

sliding of actin, just the attachment of myosin to actin. See

#57 for more on Muscle Tone.