Muscle Contractions

Question 1

Different types of muscle

Answer 1

-skeletal
- cardiac
- involuntary

Question 2

Structure and function of skeletal muscle

Answer 2

-striated
-voluntary
-regularly arranged so muscles contract in 1direction
- rapid contraction speed
- short length of contraction
-fibres are tubular and multinucleated

Question 3

Structure and canton of cardiac

Answer 3

• specially striated
• involuntary
• cells branch and interconnect so contractions are simultaneous
• intermediate contraction speed
• intermediate length of contraction
• fibres and branched and uninucleated

Question 4

Structure and function of involuntary mucsles

Answer 4

• non striated
• involuntary
• no regular arrangement so contractions happen in different directions
• slow sped contraction
• long length of contraction
• fibres are spindle shaped and uninucleuated

Question 5

Structure of sarcomere

Answer 5

• Light bands - the region of sarcomere where only actin filaments are present no overlapping. Shortens in contraction
• dark bands- region where actin and myosin overlap
• z line- found at centre of light bands, one z line to another is one sarcomere. Stays the same in contraction
• h zone- lighter region of dark bands where only mysosin is present- h zone shortens in contraction

Question 6

Role of ATP in muscle contraction

Answer 6

1) break the cross bridges between myosin and actin
2) actively transport the Ca2+ ions back to sarcoplasmic reticulum

Energy provided from hydrolysis of ATP to ADP

Question 7

How is muscle contraction initiated

Answer 7

1) when the depolarisation occurs from presynaptic to sarcolemme, the depolarisation travels into muscle fibre which spreads to T- tubules.

2) these are in contact with sarcoplasmic reticulum which contains Ca2+

3) depolarisation causes Ca2+ channels to open allowing Ca2+ to diffuse down conc gradient flooding sarcoplasm with the ions

Question 8

Sliding filament model

Answer 8

1) tropomyeosin molecule prevents myosin head from attaching to actin filament

2) Ca2+ bind to tropomyesoin causing it to detach and causes conformational change

3) now myosin head can attach to actin, changing its angle combing the actin filament as it does forming cross bridges ADP molecule released

4) ATP molecule binds to myosin causing it to detach from acting breaking cross bridges

5) atp hydrolysis provides energy for myosin head to reattach

6) another myosin head attaches further along the actin filament and cycle is repeated