Muscle 1

Question 1

How are skeletal muscle fibres created?

Answer 1

In utero by myoblasts

Question 2

What are muscles?

Answer 2

Bundles of fibres encased in connective tissue sheaths

Question 3

What do satellite cells do?

Answer 3

Replace cells after injury

Question 4

What is a sarcomere?

Answer 4

The basic unit of striated muscle tissue

Question 5

After an action potential has been fired in the muscle, calcium ions are released from the

Answer 5

Sarcoplasmic reticulum

Question 6

What do calcium ions bind to?

Answer 6

Troponin on the actin filament

Question 7

What is a skeletal muscle cell

Answer 7

A multinucleate muscle fibre

Question 8

Describe the growth and repair of skeletal muscle

Answer 8

They are formed in utero by mononucleate myoblasts

Their fibre size increases during growth

Myoblasts do not replace cells if damaged

Instead satellite cells replace cells after injury

Question 9

What do tendons do?

Answer 9

Attach muscle to bone

Question 10

Why do muscle fibres undergo hypertrophy?

Answer 10

To compensate when muscle fibres are injured

Question 11

What is meant by hypertrophy?

Answer 11

Increase in size of skeletal muscle

Question 12

Describe what happens during muscle contraction?

Answer 12

Calcium ions released from the sarcoplasmic reticulum bind to troponin

This moves tropomyosin

Myosin (with its ADP + Pi) can then bind to the actin filament

Myosin then unbinds ADP + Pi

ATP then binds to myosin and myosin unbinds from the actin filament

Question 13

Describe what happens to the length of different components during muscle contraction?

Answer 13

Muscle shortens

Sarcomere shortens

Myosin stays the same length

Space between myosin filaments decreases

Space between actin filaments decrease

Question 14

What does tropomyosin do?

Answer 14

Partially covers myosin binding sites on actin,

held in blocking position by troponin

Question 15

What is the motor unit?

Answer 15

Motor neurons + muscle fibres

Question 16

State what is meant by tension

Answer 16

Force exerted by muscle

Question 17

State what is meant by load

Answer 17

Force exerted on muscle

Question 18

Define an isometric twitch

Answer 18

Contraction with constant length (e.g. weightlifting)

Question 19

Define an isotonic twitch

Answer 19

Contraction with shortening length (e.g running)

Question 20

Lengthening means

Answer 20

Contraction with increasing length

Question 21

What causes a twitch?

Answer 21

A single action potential sent to a muscle fibre

Question 22

What is contraction time dependent on?

Answer 22

Calcium ion concentration

Question 23

What is the latent period?

Answer 23

The time before the excitation contraction starts

Question 24

Describe the latent period and contraction event of isometric contraction?

Answer 24

Shorter latent period

Longer contraction event

Question 25

Explain tetanus

Answer 25

A state of EXTENDED contraction via the SUMMATION of action potentials - great level of tension

Question 26

Explain why titanic tension is greater than twitch tension

Answer 26

Calcium ion concentration never gets low enough to allow troponin and tropomyosin to re-block the myosin binding sites

Question 27

What happens as load increases?

Answer 27

Contraction velocity decreases

Distance shortened decreases

Question 28

Describe the length tension relationship

Answer 28

Less overlap of filaments = less tension
Too much overlap of filaments = filaments interfere with each other
Optimal length = muscle length for greatest isometric tension

Question 29

What does movement around a limb require?

Answer 29

2 antagonistic groups of muscles (1 flexes, the other extends)

Question 30

What does the lever system of muscles do?

Answer 30

Amplifies muscle shortening velocity producing increased manoeuvrability