Lecture 2 - Mechanisms of muscle contraction

Question 1

What are the three different types of muscle? [3]

Answer 1

• Smooth muscle
• Cardiac muscle
• Skeletal muscle

Question 2

List the key features of Smooth muscle.

Answer 2

• Mono-nucleated
• Non-striated
• Involuntary control

Question 3

List the key features of Cardiac muscle.

Answer 3

• Mono-nucleated
• Striated and branched
• Involuntary control

Question 4

List the key features of Skeletal muscle.

Answer 4

• Multi-nucleated
• Striated and elongated
• Voluntary control

Question 5

What is a prime mover?

Answer 5

Main muscle producing most of the force during movement

Question 6

What is an antagonist?

Answer 6

Muscles that oppose the prime mover

Question 7

What is an synergist?

Answer 7

Muscles that work with the prime mover

Question 8

What is a fixator?

Answer 8

Muscles that prevent a bone from moving

Question 9

What is a flexor?

Answer 9

Muscles that work to close a joint

Question 10

What is an extensor?

Answer 10

Muscles that work to open a joint

Question 11

What is abduction?

Answer 11

Motion that pulls a structure away from the midline

Question 12

What is adduction?

Answer 12

Motion that pulls a structure towrds the midline

Question 13

What does a muscle contain?

Answer 13

A number of fascicles

Question 14

What do fascicles contain?

Answer 14

A number of muscle fibres

Question 15

What are the two bands within myofibrils?

Answer 15

• Dark band: remains constant length

- Light band: change length when muscle lengthens or shortens

Question 16

What is a sacromere?

Answer 16

Smallest contractile unit in a muscle fibre

Question 17

How many sacromeres are in a muscle fibre?

Answer 17

~20,000

Question 18

What are sarcomeres made from? [3]

Answer 18

• Actin filaments
• Myosin filaments
• Stabilisation and regulation proteins

Question 19

What is the thin filament made form?

Answer 19

• Actin
• Tropomyosin
• Troponin

Question 20

What is the thick filament made from?

Answer 20

Myosin

Question 21

True or False? A sarcomere contract they get larger.

Answer 21

• False

- They get shorter

Question 22

What does the contraction of the sacromeres cause to happen?

Answer 22

The powerstroke

Question 23

What is the state of the sacromere during rest (step1)?

Answer 23

• Ca2+ conc is low
• Myosin heads are ADP-bound
• Actin binding sites are blocked by troponin

Question 24

What is the state of the sacromere during activation (step2)?

Answer 24

• Ca2+ release from cisternae
• Ca2+ binds to troponin
• Exposes actin binding sites
• Cross-bridge is formed

Question 25

What is the state of the sacromere during sliding of filaments (step3)?

Answer 25

• Energy stored in myosin heads is released

- Power stroke

Question 26

What is the state of the sacromere during nyosin detachment (step4)?

Answer 26

• ATP binds to myosin heads making them detach from binding site
• Actin binding sites are empty and can form another cross bridge

Question 27

What is the state of the sacromere during reactivation of myosin (step5)?

Answer 27

• Energy release from ATP > ADP reaction is stored in myosin heads
• High Ca2+ = muscle continues to contract
• Low Ca2+ = myosin heads are unable to form cross-bridge

Question 28

What happens during a low frequency of unintended APs?

Answer 28

Twitching

Question 29

What happens during a high frequency of unintended APs?

Answer 29

Tetani

Question 30

What is concentric contraction?

Answer 30

• Force > Load

- Muscle shortens

Question 31

What is eccentric contraction?

Answer 31

• Force < Load

- Muscle lengthens