Module 7

Question 1

what is fascia

how help us

Answer 1

visible connective tiss

distribute stress across structures

Question 2

what is the path of force transmission from muscle to bone (4)

Answer 2

muscle

musculotendinous junction (MTJ)

tendon

bone

Question 3

do all muscle fibres run end to end? exp purpose

Answer 3

no

some attach to endomysium but still end up distibuting force to other fibres and bone. E.g. pennate muscles

Question 4

what does the question “are muscles independent actuators” mean?

what is the answer

Answer 4

can each muscle be activated in isolation

answer?
- no because of neurons connecting to multiple muscles and the connection between muscles

** neurons were not mentioned in this lec

Question 5

arguments for them not being independent actuators

Answer 5

• force measured at proximal and distal tendon sometimes varies (differences decrease when isolated from other muscs)
• change in length of a muscle can change the force length relationship of another muscle.

Question 6

describe the interplay of muscles using the example of two parallel muscles equal in length

Answer 6

if only one is stretched then fascia connecting the two will be pulling more at an angle on one side than the other.

Question 7

Give reasons for why muscles are independent actuators

Answer 7

• in study done on cat, changing joint angle would change the length of gastroct and plantaris, but soleus not change

change length in gastroct not change force prod of soleus

Question 8

describe history dependance on muscles regarding the force-length relationship

describe mechanism

what happens to force if concentrically contracted instead?

Answer 8

after eccentrically contract a muscle it produces more force than it would have if it had had been held static

force = greater than force length relationship suggests

mechanism: titin binds to Ca2+ ions during contraction and this makes it stiffer therefore increasing force production.

Question 9

Describe the three proposed theories of how muscle history dependance works

Answer 9

1. titin does nothing aside from passive stretch (old thinking)
2. Ca2+ minds to titin and makes it stiffer
3. Ca2+ bind to titin to make stiffer and bind to actin