Muscle Structure

Question 1

what is Skeletal/striated/striped muscle ?

Answer 1

these are muscles attached to bones by tendons which contract allowing movement to occur

Question 2

what are the three types of muscle ?

Answer 2

smooth
skeletal
cardiac

Question 3

what is the sarcomere ?

Answer 3

a single contractile unit between the Z-lines

Question 4

why is skeletal muscle striated ?

Answer 4

due the the overlapping thick (myosin) and thin (actin) protien filaments

Question 5

break down the structure of skeletal muscle fibres

Answer 5

Muscle
Fascicles
Muscle fibres
Myofibrils
Myofiliments (actin myosin)

Question 6

What line is actin and what line if myosin attached to?

Answer 6

actin is attached to the Z line and myosin is attached to the M line

Question 7

what are the names of the different lines, zones and bands in the sarcomere?

Answer 7

H zone, A band, M line, Z line, I band

Question 8

what does the H zone consist of and what does it do during contraction?

Answer 8

H zone = myosin only and shortens during contraction because the Z line / sarcomere shorten pushing the actin in further overlapping more of the myosin shown by the A band

Question 9

what does the A band consist of and what does it do during contraction?

Answer 9

overlaped actin and myosin and it stays the same length

Question 10

what does the I band consist of and what does it do during contraction?

Answer 10

actin only and shortens during contraction.

Question 11

what does the sarcomere consist of and what does it do during contraction?

Answer 11

actin and myosin and it shortens during contraction

Question 12

which band appears dark and which band appears light?

Answer 12

I band light and A band dark

Question 13

what is the sliding filament theory?

Answer 13

sarcomere shortens during contractions and thin actin fibres slide over the thick myosin fibres.

Question 14

explain the myosin structure

Answer 14

each has a globular head with ATPase activity, projecting from a fibrous tail

Question 15

explain the process of muscle contraction

Answer 15

• nerve impulse arrives at neuromuscular junction
• wave of depolarisation passes along sarcolemma and t tubules
• calcium channels open and diffuse into the myofibrils in the sarcoplasmic reticulum
• calcuim ions bind to toponin molecules, causing shape change
• this moves tropomyosin, **exposing the myosin binding sites **
• myosin heads form cross bridges to actin
• ADP + Pi released changing the angle of the myosin head back to a relaxed state and myosin molecule rotates pulling the actin past the myosin. this is the **power stroke. **
  -Another ATP molecule binds to the myosin head and this breaks the cross bridges to the acin
• hydrolysis of ATP makes energy available
• THIS SEQUENCE REPEATS UNTIL THE CALCIUM IONS ARE ALL PUMPED BACK INTO THE SARCOPLASMIC RETICULUM

Question 16

what is troponin

Answer 16

part of actin where calcium binds causing tropomyosin to chage shape