Muscle Contraction

Question 1

How long are skeletal muscle cells?

Answer 1

30cm

Question 2

What are skeletal muscle cells made up of and why do they have lots of nuclei?

Answer 2

Lots of myoblasts joined together

Question 3

Why are skeletal and cardiac muscle stripy?

Answer 3

Due to contractile proteins

Question 4

Name the three types of muscle

Answer 4

Skeletal
Cardiac
Smooth

Question 5

How many nuclei does cardiac and smooth muscle cells have?

Answer 5

One

Question 6

Give examples of smooth muscle

Answer 6

Arteries
Gut
Bladder
Reproductive organs

Question 7

Why isn’t smooth muscle stripy?

Answer 7

The contractile proteins aren’t arranged in a logical pattern

Question 8

What is contraction?

Answer 8

The interaction between actin and myosin

Question 9

What is contraction fuelled by?

Answer 9

ATP and Ca2+

Question 10

Whats a group of bundles called in a muscle?

Answer 10

Fascicle

Question 11

What’s the thick strand in muscles?

Answer 11

Myosin

Question 12

What’s the thin strand in muscles?

Answer 12

Actin

Question 13

What’s the I band in muscles comprised of?

Answer 13

Only actin

Question 14

What’s the A band in muscles comprised of?

Answer 14

Only myosin

Question 15

What’s the stuff between two z discs called?

Answer 15

Sarcomere

Question 16

What is the sarcoplasmic reticulum?

Answer 16

Complex, convoluted store of calcium

Question 17

What does troponin C bind to?

Answer 17

Calcium

Question 18

What does troponin T bind to?

Answer 18

Tropomyosin

Question 19

What can block a certain site on actin where myosin would interact?

Answer 19

2 disc formed of alpha actin in

Question 20

What are the two important regions on the myosin head?

Answer 20

Binding domain

ATPase

Question 21

What does the binding domain in a myosin head do?

Answer 21

Interacts with the active cycloactin

Question 22

What does the ATPase in a myosin head do?

Answer 22

Hydrolysed the ATP->ADP

Question 23

What is binding in between myosin and actin?

Answer 23

Myosin cross bridge bonds to an actin molecule

Question 24

What is the power stroke in muscle contraction?

Answer 24

Cross bridge bends, pulling thin myofilament forwards

Question 25

What is detachment in muscle contraction?

Answer 25

Cross bridge detaches at end of power stroke and returns to OG conformation

Question 26

Write out the muscle contraction cycle

Answer 26

Binding, power stroke, detachment, binding (but in more detail)

Question 27

What happens when ATP binds to myosin

Answer 27

Detachment of myosin from actin, cross bridge dissociates

Question 28

What happens when ATP hydrolysis occurs in muscle contraction

Answer 28

Myosin head is cocked

Question 29

What does calcium do in muscle contraction

Answer 29

Binds to troponin which binds to tropomyosin which pulls tropomyosin out the way allowing the myosin and actin to interact

Question 30

What happens to [Ca2+] when nicotinic AchR is bound by an agonist?

Answer 30

Causes massive depolarisation down the T tubules

Question 31

How does the depolarisation happen in the T tubules in skeletal muscle?

Answer 31

DMP proteins that physically interact with a calcium release channel in the sarcoplasmic reticulum (RYR)

Question 32

What does DMP stand for?

Answer 32

Dihydropyridine

Question 33

What does RYR stand for?

Answer 33

Ryanodine receptor

Question 34

How does the depolarisation happen in the T tubules in cardiac muscle?

Answer 34

When the cell is stimulated, the DHP receptor changes conformation alters the RYR causing calcium to be released

Question 35

What does CICR stand for?

Answer 35

Calcium induced calcium release

Question 36

How does smooth muscle contract?

Answer 36

Wring out like a tea towel

Question 37

How does calcium get released in smooth muscle?

Answer 37

Either receptor mediated diffusion or the production of a diffusible messenger called inocytrial disphosphate

Question 38

What is inocytrial disphosphate made from?

Answer 38

A membrane lipid, broken down down through a number of enzyme steps which leads to a calcium release

Question 39

Is there troponin in smooth muscle?

Answer 39

No

Question 40

Does tropomyosin interact with the myosin binding sites in smooth muscle?

Answer 40

No

Question 41

Go draw a table that has skeletal cardiac and smooth along the top and T tubules, arranged myofilaments, calcium sensor and contraction mechanism along the side and fill it out

Answer 41

Skeletal. Cardiac. Smooth T tubules ✅. ✅. ❌ Arranged ✅. ✅. ❌ Myofilaments Calcium troponin. Calmodulin sensor Contraction. Removal of MLCK mechanism. Tropomyosin.