Topic 6B: Muscles

Question 1

Other names for Skeletal Muscles

Answer 1

• Striated muscle
• Striped muscle
• Voluntary muscle

Question 2

What are tendons?

Answer 2

Skeletal Muscles that are attached to bones

Question 3

What are Ligaments?

Answer 3

• They attach bones to other bones

- hold them together

Question 4

Skeletal Muscles are made up of…

Answer 4

Long Muscle Fibres

Question 5

What are muscle fibres?

Answer 5

large bundles of long cells.

Question 6

The cell membrane of the muscle fibre is called….

Answer 6

sacrolemma

Question 7

When sacrolemma fold inwards and stick the sacroplasm, we call it….

Answer 7

Transverse T Tubules

Question 8

What is the purpose of T Tubules?

Answer 8

Help into spread electrical impulses throughout the sacroplasm so they reach all parts of the muscle fibres

Question 9

A network of internal membranes is called

Answer 9

sacroplasmic reticulum

Question 10

What is the function of the sacroplasmic reticulum?

Answer 10

Stores and releases calcium ions that are need for contraction

Question 11

What organelle is in muscle fibres?

Answer 11

lots of mitrochondria that release ATP for muscle contraction

Question 12

Muscles are multinucleate. What does this mean?

Answer 12

Contain many nucleis

Question 13

What are myofibrils?

Answer 13

• long cylindrical organelles

- they are made up of proteins and are highly specialised

Question 14

Myofibrils contain….

Answer 14

• Thick myofilaments
• Thin myofilaments
• These move past each other to contract

Question 15

If you put a myofibrils under a electron microscope what do you see?

Answer 15

• Dark bands

- Light bands

Question 16

What do dark bands contain?

Answer 16

-Thick myofilaments

Question 17

What do light bands contain?

Answer 17

-Thin myofilaments

Question 18

What are A bands?

Answer 18

Thick myofilaments overlapped with thin myofilaments

Question 19

What I bands?

Answer 19

Thin myofilaments only

Question 20

A myofibrils are made up of short unit called?

Answer 20

sacromeres

Question 21

The end of sacromeres are called?

Answer 21

Z-line

Question 22

What is the middle of the sacromere called?

Answer 22

M-line

Question 23

What is the H-zone?

Answer 23

Contains only myosin filaments

Question 24

Do myofilaments contract?

Answer 24

No they slide over each other

Question 25

Do sacromeres contract?

Answer 25

yes

Question 26

What get shorter when the sarcomere contracts?

Answer 26

• I Bands

- H-Zone

Question 27

What do myosin filaments have structurally?

Answer 27

• Globular heads that are hinged
• binding site for actin
• binding site for ATP

Question 28

What do actin filaments have structurally?

Answer 28

• binding site for myosin heads

- actin-myosin binding sites

Question 29

How are resting muscles maintained?

Answer 29

• actin-myosin binding site blocked by tropomyosin

- can’t slide past each other because of myosin heads cant bind on actin filaments

Question 30

What are muscle contraction triggered by?

Answer 30

An influx of calcium ions

Question 31

What happens when action potential reaches the muscle cells?

Answer 31

• depolarises sacrolemma
• depolarisation spreads down t-tubles to the sarcoplasmic reticulum
• sacroplasmic reticulum releases stores ca2+ into sacroplasm

Question 32

Outline the process of muslce contraction

Answer 32

• ca2 binds to protein on tropomyosin
• changes shape and moves away exposing the actin myosin binding site
• allows myosin head to bend
• forms an actin myosin cross bridge
• enerygy released from ATP causes myosin heads to bind and pull actin filament along in a rowing motion
• Another ATP provides energy for myosin heads to dettach from the actin-myosin cross bridge
• reattaches to a new actin myosin binding site
• cycle repeats as long as calcium ions present

Question 33

What is the role of Ca2+ in muscle contraction?

Answer 33

-Ca2+ binds to protein associated with tropomyosin which makes tropomyosin move away and expose the actin myosin binding site.
-Ca2+ activates the enzyme ATP hydrolase which hydrolyses ATP to provide the energy needed for muscle contraction
-

Question 34

What is the role of ATP in muscle contraction?

Answer 34

• ATP releases energy which makes myosin bend which also pulls actin filaments along in a rowing motion
• Another ATP breaks the actin myosin cross bridge

Question 35

How does muscle contractions stop?

Answer 35

• muscles stop being stimulated
• calcium ions leave the binding site
• by active transport
• back to sacroplasmic reticulum
• causes tropomyosin to move back and block the actin myosin binding site
• sacromeres lengthens again

Question 36

Muscles will only contract if…

Answer 36

Myosin heads are attached to actin filaments

Question 37

What provides the energy for muscle contraction?

Answer 37

ATP and Phosphocreatine (PCr)

Question 38

How is ATP generated in aerobic respiration?

Answer 38

-via oxidative phosphorylation in cells mitrochondria

-

Question 39

How is ATP generated in anaerobic respiration?

Answer 39

-rapidly by glycolysis

Question 40

How is ATP generated in PCr?

Answer 40

• atp made by phosphorylating ADP
• which adds a phosphate group taken from PCr
• only used for short vigorous exercise
• anaerobic processes(no oxygen needed)
• its alactic (doesnt produce lactate)

Question 41

Name the two types of muslce fibres?

Answer 41

slow twitch

fast twitch

Question 42

What are the properties of slow twitch?

Answer 42

• contract slowly
• used for posture
• good for endurance activities eg long distance training
• can work for a long time without being tired
• energy released through aerobic respiration-use of o2
• lots of mitrochondria and blood vessels
• reddich colour-alot of myoglobin

Question 43

What are the properties of fast twitch?

Answer 43

• contract very quickly
• used for fast movements
• good for short bursts of speed and power
• get tired very quickly
• energy released through anaerobic respiration use of glycogen
• Whitish colour because not much myoglobin