Muscles

Question 1

What is the calcium sensor in skeletal and cardiac muscle? [1 mark]

Answer 1

Troponin

Question 2

What is the calcium sensor in smooth muscle? [1 mark]

Answer 2

Calmodulin

Question 3

What happens instead of the removal of tropomyosin in smooth muscle? [1 mark]

Answer 3

Myosin Light Chain Kinase is activated

Question 4

What does Myosin Light Chain Kinase (MLCK) do? [2 marks]

Answer 4

• Adds a phosphate group to serine 19 on the light chain of myosin
• This increases the myosin head’s ATPase activity by 1000 times

Question 5

Does smooth muscle have a t-tubule system? [1 mark]

Answer 5

No

Question 6

What receptors does skeletal muscle have? [1 mark]

Answer 6

nAChR

Question 7

What receptors does smooth muscle have to release calcium from their calcium store? [1 mark]

Answer 7

Inositol trisphosphate (IP3)

Question 8

What detects change in voltage in skeletal muscle? [2 marks]

Answer 8

• Dihydropyridine receptors (DHP)

- NOT an ion channel

Question 9

What do ryanodine receptors do? [1 mark]

Answer 9

Release Ca2+

Question 10

What does smooth muscle have instead of troponin? [2 marks]

Answer 10

• Calponin

- Caldesmon

Question 11

Organisation of muscle? [4 marks]

Answer 11

Myofilaments - Myofibrils - Muscle fibres - Muscle fasciculus

Question 12

What is the Z line in a sarcomere? [1 mark]

Answer 12

Where thin filaments attach to the edge

Question 13

What is the M line in a sarcomere? [2 marks]

Answer 13

• The site of attachment for thick filaments

- At the centre

Question 14

What is the I band? [1 mark]

Answer 14

Where thin filaments do not extend, appearing light.

Question 15

What is the A band? [1 mark]

Answer 15

Where thick and thin filaments overlap, appearing dark

Question 16

What are the different types of troponin binding sites?

Answer 16

• Troponin C = calcium binding
• Troponin T = tropomyosin
• Troponin I = actin binding

Question 17

What happens in troponin C for tropomyosin to change shape? [1 mark]

Answer 17

4 Ca2+ ions bind to troponin C

Question 18

What does Ca2+ ATPase do? [1 mark]

Answer 18

Pump Ca2+ back out the cell

Question 19

What is a power stroke? [1 mark]

Answer 19

When ADP and a phosphate group is released

Question 20

What is the affinity for smooth muscle to ATP? [1 mark}

Answer 20

Lower than the affinity for skeletal and cardiac

Question 21

Performance of smooth muscle compared to skeletal muscle? [6 marks]

Answer 21

• Greater shortening in smooth muscle
• Smooth muscle has longer actin
• Lower energy requirement in smooth muscle
• Greater force generation in smooth muscle
• Sustained contraction in smooth muscle

Question 22

What is the latch state? [1 mark]

Answer 22

The capacity of smooth muscle to maintain force for long periods of time