Muscles

Question 1

How do muscles act?

Answer 1

• muscles act in antagonistic pairs against an incompressible skeleton to create movement
• can be automatic as part of a reflex response or controlled conscious thought

Question 2

Myofibrils?

Answer 2

• made up of fused cells that share a nuclei and cytoplasm (sarcoplasm), and there is a high number of mitochondria
• millions of myofibrils make up muscle fibres

Question 3

Sarcomere?

Answer 3

• two key proteins in myofibrils, myosin and actin, form a sarcomere

Question 4

Sliding filament theory?

Answer 4

1. When an action potential reaches a muscle, it stimulates a response
2. Calcium ions enter and cause the protein tropomyosin to move and uncover the binding sites on actin
3. Whilst ADP is attached to myosin head, myosin heads to actin to form a cross-bridge
4. Angle created in cross-bridge creates tension - actin filament pulled and slides along the myosin. In doing so the ADP molecules are released
5. ATP molecules binds to myosin head and cause shape to change - as a result it detaches from actin

Question 5

ATP and Phosphocreatine?

Answer 5

• active muscles need a high concentration of ATP
• the chemical Phosphocreatine, which is stored in muscles, assists this by providing phosphate to regenerate ATP from ADP

Question 6

Difference in Structure between Slow and Fast twitch fibres?

Answer 6

• Slow twitch fibres - contains large store of myoglobin, a rich blood supply and many mitochondria
• Fast twitch fibres - thicker and more myosin filaments, large store of glycogen, a store of phosphocreatine to help make ATP from ADP, and a high concentration of enzymes involved in aerobic respiration

Question 7

Location of slow and fast twitch fibres

Answer 7

• Slow - calf muscles
• fast - biceps

Question 8

General properties of slow and fast twitch fibres?

Answer 8

• Slow twitch fibres - contract slower and can respire aerobically for longer due to rich blood supply and myoglobin oxygen store. Muscles adapted for endurance work.
• Fast twitch fibres - contract faster to provide short bursts of powerful contraction. Muscles adapted for intense exercise like sprinting or weight lifting.