Muscle 1

Question 1

What are the 3 types of muscle?

Answer 1

skeletal, smooth and cardiac

Question 2

Give 2 examples of skeletal muscle.

Answer 2

voluntary muscles, diaphragm

Question 3

Give 2 examples of where you would find smooth muscle.

Answer 3

blood vessels, airways

Question 4

What is a skeletal muscle cell?

Answer 4

a muscle fibre

Question 5

What are skeletal muscle cells formed from in utero? Comment on the nuclei.

Answer 5

multinucleate cells

formed from mononucleate myoblasts

Question 6

What is the repair system of muscle like?

Answer 6

poor. Myoblasts do not replace cells if damaged

Question 7

How can muscle try to repair itself? 2 ways

Answer 7

• cells replaced after injury by satellite cells which differentiate to form new muscle fibres
• other fibres undergo hypertrophy to compensate

Question 8

What are striations in skeletal muscle?

Answer 8

repeating units of structures on muscle fibre myofibrils called sarcomeres

Question 9

What are myofibrils?

Answer 9

clusters of units of many repeating units of sarcomeres inside a muscle cell (fibre)

Question 10

What are myofibrils made up of? (i.e. sarcomeres)

Answer 10

myofilaments such as actin and myosin and titin

Question 11

What is the ‘thick filament’?

Answer 11

myosin

Question 12

What is the ‘thin’ filament?

Answer 12

actin

Question 13

How does the interaction of actin and myosin lead to contraction?

Answer 13

• myosin has lots of ‘heads’ that are capable of binding to sites on actin to form cross bridges
• myosin binds to actin, pulling on the actin filament, shortening the sarcomere
• ATP binds which causes the myosin head to release the actin
• when the ATP is broken down to ADP and Pi again, the myosin head cocks back into the optimum position to bind to actin again

Question 14

What do troponin and tropomyosin do?

Answer 14

• tropomyosin partially covers the myosin binding site on the actin
• troponin holds the tropomyosin in the blocking position

Question 15

How does the interaction of calcium help contraction?

Answer 15

it binds to the troponin causing it to change shape and move the tropomyosin out of the way so that myosin can bind to actin

Question 16

Where is the calcium stored in the muscle fibre?

Answer 16

in the sarcoplasmic reticulum

Question 17

What is the name given to the plasma membrane of a muscle fibre?

Answer 17

sarcolemma

Question 18

What is a T -tubule?

Answer 18

a deep invagination of the sarcolemma

Question 19

What do T-tubules do?

Answer 19

allow depolarisation of the sarcolemma to quickly reach the inside of the muscle cell to allow for voltage gated control of the calcium channels to mediate contraction

Question 20

What is a motor unit?

Answer 20

a motor neurone and the muscle fibres it innervates

Question 21

What is tension?

Answer 21

force exerted BY muscle

Question 22

What is load?

Answer 22

force exerted ON muscle

Question 23

What is isometric contraction?

Answer 23

contraction with constant length e.g weightlifting

Question 24

What is isotonic contraction?

Answer 24

contraction with shortening length e.g running

Question 25

What is lengthening contraction?

Answer 25

contaraction with increasing length e.g sitting down

Question 26

What is a twitch?

Answer 26

When a muscle fibre is stimulated by a single Action potential to cause a brief contraction

Question 27

What does contraction time depend on?

Answer 27

calcium

Question 28

What is latent period when referring to contraction?

Answer 28

time before excitation contraction starts

Question 29

What is tetanus?

Answer 29

sustained muscle contraction due to repeated stimulation of motor units - twitches summate