T7L2 How muscles work

Question 1

Name 9 parts of a muscle

Answer 1

Sarcoplasmic reticulum
Myofibril
Sarcomere
Actin
Myosin
A-M binding site
Myosin head
Troponin
Tropomyosin

Question 2

Describe the structure of a muscle

Answer 2

A muscle is made up of bundles of muscle fibres
Each muscle fibre is a multinucleate muscle cell
And within each of these cells are myofibrils - strands of proteins
Which along their length are split into sarcomeres

Question 3

Describe the structure of an individual sarcomere

Answer 3

Encased between z-lines at either end
Thick myosin filaments
Contain mysoin heads
Which bind to troponin receptors
On actin
Unless blocked by tropomyosin protein

Question 4

Explain the sequence of events that occurs for a muscle to contract

Answer 4

Nerve impulse arrives at neurotransmitter junction

Calcium ions are released from sarcoplasmic reticulum

and attach to troponin

causes tropomysoin to move

exposes myosin binding

This allows myosin heads to bind to actin filament

ADP and Pi released

Myosin heads kick forward in a power stroke, pulling the actin filaments closer

This causes the fibre to contract - actin moves over myosin

After contraction ATP binds to myosin head

enzyme ATPase hydrolyses ATP into ADP and inorganic phosphate which causes the myosin heads to move back to their original positions, this is known as the recovery stroke