Topic 35 - Muscular Tissue : Molecular basis of muscle contraction

Question 1

muscular contraction is composed of

Answer 1

sarcomes repeats

Question 2

What is it borderd by?

Answer 2

Z lines, with half an isotropin (I) band extending towards A band.

Question 3

What is A band composed of

Answer 3

H band and M line

Question 4

What is actin and where do we find it?

Answer 4

(thin filaments) are found within the Z line

Question 5

What is myosin and where do we find it?

Answer 5

(large and mobile filaments) originate in the A band.

Question 6

Where do we find overlap?

Answer 6

occurs in the A band (outside of H band and A line).

Question 7

Two types of Mulofilaments?

Answer 7

• Thin – F-actin (made up of G-actin) is bound by tropmyosin and troponin complexes.
• Thick – myosin (heavy and light chain dimer) combine to form bipolar structure.

Question 8

Sliding filament: what does it do?

Answer 8

contractions cause muscle shortening and change in muscle width.

Question 9

Sliding filament, steps?

Answer 9

1. ATP allows myosin to undergo conformational change, releases actin.
2. ATP is hydrolyzed, head cocks and filament slides against actin upon myosin binding.
3. Release of P¬I¬ allows for myosin power stroke and tight binding to actin.

Question 10

What is T system?

Answer 10

-t-tubules wrap around two adjacent terminal cisterns of the sarcoplasmic reticulum to form triads, providing calcium. Calcium is required to remove tropomyosin.

Question 11

Requirements for muscle contraction?

• Within the muscle?
• Outside the muscle?

Answer 11

Within the muscle:
•Thick and thin filaments (actin and myosin)
•Sarcoplasmic reticulum and triad (calcium)
•Energy and the enzyme (ATP and myosin head).
Outside the muscle:
•Nerve impulse arriving via the motor endplate (releasing ACh)