Lecture 5 - Muscle Contraction - Sliding Filaments Flashcards Preview

Second Year - Biomedical Sciences BS22001 > Lecture 5 - Muscle Contraction - Sliding Filaments > Flashcards

Flashcards in Lecture 5 - Muscle Contraction - Sliding Filaments Deck (25)
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1
Q

What does each myosin head have

A

An actin and myosin ATPase

2
Q

What are the three major proteins of the thin filaments

A

Actin, tropomyosin and troponin

3
Q

What structure do the actin molecules make

A

A helix

4
Q

What does tropomyosin do

A

It covers the myosin binding sites on the actin molecules

5
Q

What is troponin composed of

A

Three small spherical subunits

6
Q

What do each of the subunits of troponin bind to

A

One binds to calcium, one binds to actin and one binds to tropomyosin

7
Q

What is the function of troponin (calcium not present)

A

To stabilise the tropomyosin and ensure it is covering the myosin binding sites

8
Q

What occurs to troponin when calcium appears within the cell

A

It undergoes a conformational change and causes the tropomyosin to be removed from the myosin binding site

9
Q

What does the binding of the actin-myosin cross bridge trigger

A

The power stroke

10
Q

Do the myosin heads work together or independantly

A

Independantly

11
Q

What occurs to the thin filaments during contraction

A

The slide inwards over the stationary thick filaments

12
Q

What do the thin filaments pull closer together

A

The Z lines

13
Q

What shortens during contraction

A

Sarcomere

14
Q

What areas within the muscle fibre shorten during contraction

A

The I band, H zone and distances between the Z lines

15
Q

What areas of the muscle fibre remain constant during contraction

A

The A band

16
Q

What is the stiffness of death known as

A

Rigor mortis

17
Q

Why does rigor mortis occur

A

As after death the cyctolic concentration of Ca2+ rises

18
Q

What is not produced during rigor mortis that would allow the muscles to relax

A

ATP

19
Q

How is the contractile process turned off

A

When the Ca2+ returns to the lateral sacs

20
Q

What is the mechanism through which calcium is returned to the lateral sacs

A

The sarcoplasmic reticulum expresses Ca2+-ATPase pumps which actively transport Ca2+ from the cytosol and concentrate it in the lateral sacs

21
Q

What is the time delay between electrical activity and contractile activity known as

A

Latent peroid

22
Q

The time from contraction onset to peak tension is known as

A

The contractile time

23
Q

How long is the contractile time

A

Roughly 50 msec

24
Q

The time from peak tension to relaxation is known as

A

The relaxation time

25
Q

How long is the relaxation itme

A

Roughly 50 msec