A & P - Muscle

Question 1

Answer 1

Skeletal Muscle

Question 2

Parts of Muscle cell

Answer 2

Muscle Fibre Cell

Neuromuscular junction

Myofibril

Sarcomere

Myofilaments

Actin

Myosin

Sacrolemma

Mitochondria

Question 3

Myofibril

Answer 3

Myofibril consists of a chain of repeatig units called sarcomeres with a characteristic pattern of lines, zones and bands.

Question 4

Muscle Movement

Step One

Answer 4

Action potentials arrive at motor end plates, which release the transmitter acetylcholine.

Question 5

Muscle Movement

Step Two

Answer 5

Acetylcholine binds to ligand-gated receptors on the muscle fibre membrane, causing depolarisation.

Question 6

Muscle Movement

Step Three

Answer 6

Depolarisation spreads through the transverse tubules to the sarcoplasmic reticulum which releases Ca^2+ ions.

Question 7

Muscle Movement

Step Four

Answer 7

Ca^2+ ions bind to trponin molecules, which change shape and move tropomyosin away from the binding sites.

Question 8

Muscle Movement

Step Five

Answer 8

Actin-myosin cross-bridges form as the myosin head can now attach to the actin filament

Question 9

Step Six

Muscle Movement

Answer 9

The myosin head bends backwards, pulling the thin filament along.

Myosin attaching and detaching from actin causes the filaments to slide relative to one another.

The movement reduces the sarcomere length (the filaments do not change length).

Question 10

Step Seven

Muscle Movement

Answer 10

The cross-bridge is broken using energy from the hydrolysis of ATP and the myosin head is ‘re-set’. ATPase that does this is located in the myosin heads.