Lecture 15

Question 1

Myosin

Answer 1

Thick. Each fibre has tail (structure), myosin head (contains actin binding site to enable power stroke and cross bridging cycling and ATPase site for ATP splitting) and hinge region (what undergoes conformational change)

Question 2

Actin

Answer 2

Thin. Anchored at z-line. titan not involved in active contraction, but, assists with muscle tension.

Question 3

Preventing slipping

Answer 3

Myosin heads dont act simultaneously so whenever theres one bound and then it becomes unbound, there will still be some that are bound

Question 3

the twitch

Answer 3

from a single AP. Discrepancy in the time of AP and time to achieve max contraction as you increase contraction as more Ca is present from SR. takes about 50ms

Question 3

hinge region

Answer 3

tilting of hinge region provides stroking motion and draws each filament, shortening the entire length of the sarcomere and that is called power stroke

Question 3

Force production by skeletal muscle

Answer 3

can be adjusted by;

1)Varying the number of fibres contracting in the muscle: achieved by activating different motor units (activation of one = activating all motor unit muscle fibres)

2) Varying the amount of force developed by each contracting fibre: achieved by selectively recruiting specific motor units which may be large.

Fine control is based off number and size of motor units activated

Question 4

Length-tension relationship

Answer 4

each fibre is able to produce a different force and that is dependent on the initial length of the muscle. When you stretch a muscle beyond resting length, increase passive force within muscle and decreases capacity to achieve active force as you have a decrease in filament overlap

Question 4

Optimal length

Answer 4

L0. Max overlap between filaments as its when you can achieve the most power strokes in synchrony and that will achieve the greatest length (in terms of size)

Question 5

Resting length

Answer 5

length when elastic components are relaxed.